WO2025239162A1 - Body fluid amount evaluation device and computer program for evaluating body fluid amount - Google Patents

Abstract

This body fluid amount evaluation device comprises a pulse pressure acquisition unit, a first calculation unit, a second calculation unit, and an evaluation unit. The pulse pressure acquisition unit acquires a first pulse pressure of a dialysis patient before returning blood in a dialyzer and a blood circuit, and a second pulse pressure of the dialysis patient at completion of returning the blood. The pulse pressure acquisition unit acquires the first pulse pressure and the second pulse pressure in a plurality of consecutive dialyses of the dialysis patient. The first calculation unit calculates the increase rate of the pulse pressure from the first pulse pressure and the second pulse pressure. The first calculation unit calculates the increase rate of the pulse pressure for each of the plurality of dialyses from the first pulse pressure and the second pulse pressure in each of the plurality of dialyses. The second calculation unit calculates an average value and/or an index that indicates variation of the increase rates of the pulse pressure in the plurality of dialyses. The evaluation unit evaluates the body fluid amount of the dialysis patient on the basis of the average value and/or the index that indicates variation which has been calculated by the second calculation unit.

Description

Body fluid volume evaluation device and computer program for evaluating body fluid volume

This specification relates to technology for evaluating the body fluid volume of a dialysis patient at the end of dialysis.

In dialysis patients, kidney function is lost, so all ingested water accumulates in the body. Excessive water accumulation in the body can lead to edema, high blood pressure, or both. Excess water accumulated in the body is removed through dialysis, but if the volume of bodily fluids decreases excessively during or at the end of dialysis, blood pressure drops. This phenomenon is called dialysis hypotension. When dialysis hypotension occurs, the blood and oxygen supply to various organs decreases, resulting in symptoms specific to each organ caused by an excessive decrease in blood and oxygen supply, such as abdominal discomfort, yawning, sighing, nausea, vomiting, muscle cramps, restlessness, dizziness, loss of consciousness, and anxiety. A state in which the blood and oxygen supply to various organs is excessively reduced is called ischemia of that organ.

In dialysis therapy, the principle is to remove fluid so that the dialysis patient's body fluid volume at the end of dialysis is equal to that of a healthy person with the same body type. To do this, the body fluid volume of a healthy person with the same body type as the dialysis patient must be known. However, there is no way to accurately determine this. Therefore, at present, dry weight is defined by trial and error as the weight at which there is no edema at the end of dialysis, no drop in blood pressure during dialysis, no fatigue after dialysis, and no hypertension when not dialysis (e.g., Charra B, et al: Clinical Determination of Dry Body Weight. Hemodial Int 5: 42-50, 2001.). Water is then removed so that the patient's weight at the end of dialysis is the dry weight.

As mentioned above, during dialysis, fluid is removed from the patient until their weight reaches their dry weight. For this reason, it is necessary to set the dry weight appropriately. However, until now, the only way to know whether the dry weight was appropriate was to observe changes in blood pressure during dialysis and detect the appearance of the clinical symptoms mentioned above.

This specification discloses a technology for optimally evaluating whether a dialysis patient's dry weight is appropriate.

In a first aspect of the technology disclosed in this specification, a body fluid volume evaluation device evaluates the body fluid volume of a dialysis patient at the end of dialysis. The body fluid volume evaluation device includes a pulse pressure acquisition unit, a first calculation unit, a second calculation unit, and an evaluation unit. The pulse pressure acquisition unit acquires a first pulse pressure, which is the pulse pressure of the dialysis patient at the end of dialysis before blood in the dialyzer and blood circuit is returned to the body of the dialysis patient, and a second pulse pressure, which is the pulse pressure of the dialysis patient at the end of blood return. The pulse pressure acquisition unit acquires the first pulse pressure and the second pulse pressure over multiple consecutive dialysis sessions of the dialysis patient. The first calculation unit calculates the rate of increase in pulse pressure from the first pulse pressure and the second pulse pressure. The first calculation unit calculates the rate of increase in pulse pressure for each of the multiple dialysis sessions from the first pulse pressure and the second pulse pressure for each of the multiple dialysis sessions. The second calculation unit calculates at least one index indicating the average value and variation of the rate of increase in pulse pressure over the multiple dialysis sessions calculated by the first calculation unit. The evaluation unit evaluates the body fluid volume of the dialysis patient based on at least one of the average value and the index indicating the variation calculated by the second calculation unit.

If excessive fluid remains in the body even at the end of dialysis, edema will be present at the end of dialysis. In this case, the degree of edema generally parallels the excess amount of body fluid. On the other hand, if the body fluid volume decreases excessively during or at the end of dialysis, dialysis hypotension, post-dialysis fatigue, or both may occur. However, dialysis hypotension and post-dialysis fatigue do not occur with every dialysis session, even if the body fluid deficit remains unchanged. These symptoms may occur in some dialysis sessions, but not in others. This is likely because, although excessive loss of body fluid volume is the cause of these symptoms, factors such as the rate of water removal and physical condition (presence of inflammation in the body) likely make them more likely to appear. Careful observation reveals that the proportion of dialysis sessions in which these symptoms occur increases when the body fluid deficit is large, and conversely, the proportion of dialysis sessions in which these symptoms occur decreases when the body fluid deficit is small.

The compartment in the body where water ingested by dialysis patients accumulates is the extracellular compartment. The compartment from which water is removed by dialysis is also the extracellular compartment. The extracellular compartment is further divided into the intravascular compartment and the interstitial compartment. Blood volume is the sum of the amount of water distributed in the intravascular compartment and the total volume of blood cells. When excess water accumulates in the extracellular compartment, the amount of water distributed in both the intravascular compartment and the interstitial compartment increases. When the amount of water distributed in the intravascular compartment increases, the blood, which consists of water distributed in the intravascular compartment and blood cells, is diluted, and blood volume increases. On the other hand, when water accumulated in the extracellular compartment is removed by dialysis, the water distributed in the intravascular compartment, which is part of the extracellular fluid, decreases. As a result, the blood, which consists of water distributed in the intravascular compartment and blood cells, becomes concentrated, and blood volume decreases.

When excess water accumulates in the body, the amount of water in the interstitial compartment also increases. When the amount of water in the interstitial compartment exceeds a certain level, edema appears. The degree of edema increases in parallel with the excess amount of water accumulated in the interstitial compartment. Meanwhile, when excess water accumulates in the body, the amount of water distributed in the central veins, located immediately upstream of the heart, also increases. As the amount of water distributed in the central veins increases, the amount of blood returning to the heart through the central veins also increases, and as a result, cardiac output, which is the amount of blood pumped from the heart per minute, also increases. Conversely, if the amount of water accumulated in the body decreases excessively, the amount of water distributed in the central veins also decreases. As the amount of water distributed in the central veins decreases, the amount of blood returning to the heart through the central veins also decreases, and as a result, cardiac output also decreases. When cardiac output decreases, the blood and oxygen supply to various organs decreases, resulting in symptoms of ischemia specific to each organ, such as abdominal discomfort, yawning, sighing, nausea, vomiting, muscle cramps, restlessness, dizziness, loss of consciousness, and anxiety.

However, an excessive decrease in the amount of water stored in the body is not the only factor that reduces the amount of water distributed to the central veins. When the amount of blood distributed to the liver increases, the amount of water distributed to the central veins decreases accordingly. In this case, cardiac output decreases in proportion to the decrease in the amount of water distributed to the central veins, reducing the amount of blood and oxygen supplied to various organs, and causing symptoms of ischemia specific to each organ, such as abdominal discomfort, yawning, sighing, nausea, vomiting, muscle cramps, restlessness, dizziness, loss of consciousness, and anxiety. For this reason, the degree of increase in the amount of blood distributed to the liver can be considered a factor that determines whether or not the above symptoms will appear.

The mechanism by which blood volume in the liver increases begins with an excessive decrease in the amount of water retained in the body. An excessive decrease in the amount of water retained in the body reduces the total blood volume. A decrease in total blood volume also reduces the amount of blood distributed to the central veins. A decrease in the amount of blood distributed to the central veins also reduces the amount of blood returning to the heart through the central veins, resulting in a decrease in cardiac output. A decrease in cardiac output reduces the amount of blood and oxygen supplied to the liver. As a result, the liver promotes the breakdown of adenosine triphosphate (ATP), increasing the production of adenosine, a vasodilator (Shinzato T, et al: Role of adenosine in dialysis-induced hypotension. J Am Soc Nephrol 4: 1987-1994, 1994.). Increased adenosine production causes the vasodilatory effect of adenosine to dilate the blood vessels in the liver. When the hepatic blood vessels dilate, the amount of blood distributed to the liver increases, further reducing the amount of blood in the central veins. This theory is supported by the observation that patients who experience dialysis-induced hypotension have increased liver water content (Grant CJ, et al: Effect of ultrafiltration during hemodialysis on hepatic and total-body water: an observational study. BMC Nephrology 19: 356, 2018.).

As mentioned above, the dilation of liver blood vessels that occurs when the blood and oxygen supply to the liver decreases is due to the vasodilatory effect of adenosine. However, because the activity of adenosine degrading enzymes is reduced in dialysis patients, serum adenosine concentrations in dialysis patients are approximately five times higher than in healthy individuals on average. However, the degree of reduction in adenosine degrading enzyme activity varies greatly among dialysis patients, and therefore serum adenosine concentrations also vary greatly among individuals (Guieu R, et al.: Adenosine and hemodialysis in humans. J Investig Med 49: 56-67, 2001.). In addition, interleukin-1, a type of cytokine, is produced when blood comes into contact with the dialyzer membrane and is released from inflammatory sites. When hepatic venular smooth muscle cells are stimulated by interleukin-1, adenosine promotes the production of NO (nitric oxide) in hepatic venular smooth muscle cells (Ikeda U, et al: Adenosine stimulates nitric oxide synthesis in vascular smooth muscle cells. Cardiovasc Res 35:168-174, 1997.). NO has a stronger vasodilatory effect than adenosine. For these reasons, even if the degree of reduction in blood and oxygen supply to the liver is the same, the degree of hepatic vasodilation varies from one patient to the next. Furthermore, even if the degree of hepatic ischemia remains constant within the same patient, the degree of hepatic vasodilation varies from session to session. In other words, if the amount of blood retained in the liver increases due to excessive fluid loss, the amount of blood flowing through the liver will vary from session to session, even if the degree of fluid loss remains constant.

The body fluid volume assessment device disclosed in this specification evaluates a dialysis patient's body fluid volume at the end of dialysis based on the following theory: If the body fluid volume at the end of dialysis decreases excessively, the blood volume in the central vein will decrease. If the blood volume in the central vein decreases, cardiac output will decrease. If cardiac output decreases, the blood supply and oxygen supply to the liver will decrease. If the blood supply and oxygen supply to the liver decrease, the liver's production of the vasodilator adenosine will increase, thereby dilating the blood vessels. As the blood vessels in the liver dilate, the blood volume distributed to the liver increases. If the blood volume distributed to the liver increases, the blood volume in the central vein will decrease by the same amount. If this cycle continues, a considerable amount of blood will be distributed to the liver. If this cycle exists at the end of dialysis, the blood supply and oxygen supply to the liver will increase with the return of blood, causing the cycle to reverse, and the excess blood distributed to the liver will move to the central vein, increasing cardiac output (the total amount of blood pumped by the heart per minute). Incidentally, cardiac output is proportional to stroke volume, which in turn is proportional to pulse pressure (Arumugam R, et al: Relationship between pulse pressure variation and stroke volume variation with changes in cardiac index during hypotension in patients undergoing major spine surgeries in prone position - A prospective observational study. J Anaesthesiol Clin Pharmacol. 38: 553-559, 2022.). Therefore, by examining the rate of increase in pulse pressure associated with blood return, the degree of fluid loss at the end of dialysis can be evaluated.

The rate of increase in pulse pressure reflects the increase in blood volume in the liver before blood return for the following reason: When dialysis is completed, the blood in the dialyzer and blood circuit is returned to the dialysis patient's body. When the blood in the dialyzer and blood circuit is returned to the dialysis patient's body at the end of dialysis, the blood volume in the dialysis patient's body increases. In this case, if the volume of body fluids has not decreased excessively before blood return, the blood volume in the body has not decreased excessively, and a sufficient amount of blood and oxygen is supplied to the liver even before blood return. Therefore, the production of adenosine, which has a vasodilatory effect, does not increase in the liver. Therefore, before blood return, the blood vessels in the liver do not dilate, and the amount of blood distributed to the liver does not increase. In this state, even if the blood supply to the liver increases with blood return, the amount of adenosine produced in the liver does not decrease. Therefore, blood does not transfer from the liver to the central vein with blood return. In other words, if there is not an excess of blood distributed to the liver, the amount of blood pumped per heartbeat (i.e., cardiac output per stroke) does not increase with blood return, nor does pulse pressure. On the other hand, if the blood volume in the body is reduced before blood return, the liver is not supplied with sufficient blood and oxygen at this point, and the liver is in an ischemic state. In an ischemic liver, the production of adenosine, which has a vasodilatory effect, increases. Therefore, the liver's blood vessels dilate, and the amount of blood distributed to the liver increases. In this state, if blood return increases the blood supply to the liver, liver ischemia is alleviated and adenosine production in the liver decreases. When adenosine production in the liver decreases, the liver's blood vessels constrict, thereby reducing the amount of blood distributed to the liver. When the liver's blood volume decreases, blood is transferred from the liver to the central vein to compensate for the decrease. As a result, the amount of blood returned to the heart increases, and cardiac output per stroke increases. Therefore, the rate of increase in stroke volume reflects the increase in the amount of blood distributed to the liver, and the rate of increase in pulse pressure reflects the increase in the amount of blood distributed to the liver.

Incidentally, since stroke volume is proportional to pulse pressure, the rate of increase in stroke volume can be substituted for the rate of increase in pulse pressure, and the variation in the rate of increase in stroke volume can be substituted for the variation in the rate of increase in pulse pressure.

The body fluid volume evaluation device disclosed in this specification comprises a memory unit and a judgment unit. The memory unit stores the average value of the pulse pressure increase rate, an index value for the variation in pulse pressure due to blood return, and the number of times the pulse pressure increase rate exceeds a predetermined value. The judgment unit evaluates the degree of increase in blood volume in the liver before blood return based on these values, and further estimates the excess or deficiency of body fluid volume corresponding to the degree of increase in blood volume in the liver. That is, when the average value of the pulse pressure increase rate is higher than a predetermined first value, the judgment unit determines that excess blood has accumulated in the liver, and therefore the body fluid volume is insufficient. On the other hand, when the average value of the pulse pressure increase rate is lower than a predetermined second value, the judgment unit determines that excess blood has not accumulated in the liver, and therefore the body fluid volume is excessive. Note that the first value is higher than the second value. On the other hand, when the average value of the pulse pressure increase rate is lower than the predetermined first value and higher than the second value, the judgment unit determines that an appropriate amount of blood has accumulated in the liver, and therefore the body fluid volume is appropriate. Furthermore, when the standard deviation, which is an index of variation, is lower than a preset third value, it is determined that there is no excess blood pooling in the liver, and therefore the body fluid volume is excessive. Furthermore, when the number of times that the rate of increase in pulse pressure exceeds a preset value is greater than a preset fourth value (number of times), it is determined that there is excess blood pooling in the liver, and therefore the body fluid volume is insufficient.

The above-mentioned body fluid volume evaluation device determines the degree of increase in blood volume in the liver based on the average value of the rate of increase in pulse pressure over multiple dialysis sessions, the degree of variation in the rate of increase in pulse pressure over multiple dialysis sessions, and the number of times the rate of increase in pulse pressure exceeded a preset value over multiple dialysis sessions, and evaluates the excess or deficiency of body fluid volume corresponding to the degree of increase in blood volume in the liver. Therefore, this body fluid volume evaluation device can accurately determine the excess or deficiency of body fluid volume in a dialysis patient. Note that hereafter, the average value of the rate of increase in pulse pressure over multiple dialysis sessions will be referred to as the average rate of increase in pulse pressure, and the variation in the rate of increase in pulse pressure over multiple dialysis sessions will be referred to as the variation in the rate of increase in pulse pressure.

This specification also discloses a computer program for evaluating the body fluid volume of a dialysis patient at the end of dialysis. The computer program causes a computer to function as a pulse pressure acquisition unit, a first calculation unit, a second calculation unit, and an evaluation unit. The pulse pressure acquisition unit acquires a first pulse pressure, which is the pulse pressure of the dialysis patient at the end of dialysis before blood in the dialyzer and blood circuit is returned to the body of the dialysis patient, and a second pulse pressure, which is the pulse pressure of the dialysis patient at the end of blood return. The pulse pressure acquisition unit acquires the first pulse pressure and the second pulse pressure over multiple consecutive dialysis sessions of the dialysis patient. The first calculation unit calculates the rate of increase in pulse pressure from the first pulse pressure and the second pulse pressure. The first calculation unit calculates the rate of increase in pulse pressure for each of the multiple dialysis sessions from the first pulse pressure and the second pulse pressure for each of the multiple dialysis sessions. The second calculation unit calculates at least one index indicating the average value and variation of the rate of increase in pulse pressure over the multiple dialysis sessions calculated by the first calculation unit. The evaluation unit evaluates the body fluid volume of the dialysis patient based on at least one of the average value and the index indicating the variation calculated by the second calculation unit.

Graph showing the heart rate at the start of blood retransfusion and the heart rate at the end of blood retransfusion. Graphs showing the rate of increase in pulse pressure over multiple consecutive dialysis sessions, where (a) shows a patient in a hydrated state, (b) shows a patient in a normal state (a patient who is neither hydrated nor dehydrated), and (c) shows a patient in a dehydrated state. 1 shows the distribution of the average value and standard deviation value of the increase rate of pulse pressure measured multiple times in the overflow state, the normal state, and the dehydration state, where (a) shows the distribution of the average value and (b) shows the distribution of the standard deviation value. FIG. 1 is a block diagram showing a schematic configuration of a body fluid volume evaluation device according to an embodiment. 10 is a flowchart showing an example of a process for evaluating the hydration status of a dialysis patient at the end of dialysis.

The main features of the embodiments described below are listed below. Note that the technical elements described below are independent technical elements that demonstrate technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

In the technology disclosed in this specification, the body fluid volume evaluation device may include a memory unit. The memory unit may store a first value that is the boundary between the average value of the pulse pressure increase rate when the dialysis patient's body fluid volume is excessive and the average value of the pulse pressure increase rate when the dialysis patient's body fluid volume is appropriate. The memory unit may also store a second value that is the boundary between the average value of the pulse pressure increase rate when the dialysis patient's body fluid volume is appropriate and the average value of the pulse pressure increase rate when the dialysis patient's body fluid volume is insufficient. With this configuration, if the average value of the pulse pressure increase rate is greater than the first value stored in the memory unit, it is possible to determine that the dialysis patient's liver blood volume has increased excessively at the end of dialysis, and therefore that the body fluid volume is insufficient. On the other hand, if the average value of the pulse pressure increase rate is smaller than the second value stored in the memory unit, it is possible to determine that the dialysis patient's liver blood volume has not increased at the end of dialysis, and therefore that the body fluid volume is excessive.

In the technology disclosed in this specification, the body fluid volume evaluation device may further include a memory unit that stores a third value, which is a threshold value for the index of variation in the rate of increase in pulse pressure. With this configuration, if the index of variation in the rate of increase in pulse pressure is smaller than the third value, which is the threshold value (upper limit value) for the index of variation in the rate of increase in pulse pressure stored in the memory unit, it is possible to determine that the blood volume in the dialysis patient's liver has not increased at the end of dialysis, and therefore that the body fluid volume is excessive.

In the technology disclosed in this specification, the index indicating variation may be a standard deviation value.

In the technology disclosed in this specification, the body fluid volume evaluation device may further include a memory unit. The memory unit may store a fourth value that is an upper limit for the percentage of dialysis sessions in which the rate of increase in pulse pressure was higher than a preset value. The memory unit may also store a fifth value that is a lower limit for the percentage of dialysis sessions in which the rate of increase in pulse pressure was higher than a preset value. With this configuration, if the percentage of dialysis sessions in which the rate of increase in pulse pressure was higher than the preset value is higher than the fourth value, it can be determined that the frequency of dialysis sessions in which the blood volume in the liver increased excessively at the end of dialysis was high, and therefore the body fluid volume is insufficient. On the other hand, if the percentage of dialysis sessions in which the rate of increase in pulse pressure was higher than the preset value is lower than the fifth value, it can be determined that the frequency of dialysis sessions in which the blood volume in the liver increased excessively was low, and therefore the body fluid volume is not insufficient or is excessive.

In a second aspect of the technology disclosed in this specification, in the first aspect described above, the body fluid volume evaluation device may further include a memory unit that stores a threshold value for the average value when the dialysis patient's body is in a dehydrated state at the end of dialysis.

In a third aspect of the technology disclosed in this specification, in the first or second aspect described above, the body fluid volume evaluation device may further include a memory unit that stores a threshold value for the index of variation when the dialysis patient's body is in an overflowing state at the end of dialysis.

In a fourth aspect of the technology disclosed in this specification, in any one of the first to third aspects described above, the memory unit may further store a threshold value for the average value when the dialysis patient's body is in a state of overflow at the end of dialysis.

In a fifth aspect of the technology disclosed in this specification, in any one of the first to fourth aspects above, the index indicating the variation may be a standard deviation.

In a sixth aspect of the technology disclosed herein, in the first aspect described above, the bodily fluid volume evaluation device may further include a memory unit that stores a first value that is a threshold value of the average value when the dialysis patient's body is dehydrated at the end of dialysis, a second value that is a threshold value of the average value when the dialysis patient's body is overhydrated at the end of dialysis, and a third value that is a threshold value of the index of variation when the dialysis patient's body is overhydrated at the end of dialysis. The evaluation unit may determine that the dialysis patient's body is dehydrated when the average value is equal to or greater than the first value, determine that the dialysis patient's body is overhydrated when the average value is equal to or less than the second value and the index of variation is equal to or less than the third value, and determine that the dialysis patient's body is neither overhydrated nor dehydrated when the average value exceeds the second value and is less than the first value, or when the average value is equal to or less than the second value and the index of variation exceeds the third value.

With reference to the drawings, the body fluid volume evaluation device 10 according to this embodiment will be described. The body fluid volume evaluation device 10 evaluates whether the blood volume in the liver of a dialysis patient has increased at the end of dialysis based on the rate of increase in pulse pressure associated with the blood return operation performed at the end of dialysis. Evaluating the blood volume in the liver of a dialysis patient at the end of dialysis indirectly evaluates the blood volume in the central vein of the dialysis patient at the end of dialysis, and further evaluates the body fluid volume of the patient.

First, let us explain the central venous blood volume of a dialysis patient at the end of dialysis. As mentioned above, a decrease in body fluid volume leads to a decrease in central venous blood volume. A decrease in central venous blood volume reduces cardiac blood return. A decrease in cardiac blood return reduces cardiac output. A decrease in cardiac output reduces the blood and oxygen supply to the liver. Furthermore, a decrease in blood and oxygen supply to the liver promotes the breakdown of adenosine triphosphate (ATP) in the liver, resulting in the release of adenosine. Adenosine is also known as a vasodilator, and increased release of adenosine dilates hepatic blood vessels, increasing the amount of blood distributed to the liver. This further reduces central venous blood volume and ultimately leads to dialysis hypotension (Shinzato T, et al: Role of adenosine in dialysis-induced hypotension. J Am Soc Nephrol 4: 1987-1994, 1994.). On the other hand, if the body fluid volume does not decrease or if it actually increases, the blood volume in the central vein does not decrease, but rather increases. If the blood volume in the central vein does not decrease, but rather increases, the cardiac blood return volume does not decrease, but rather increases. If the cardiac blood return volume does not decrease, but rather increases, cardiac output does not decrease, but rather increases. If the cardiac output does not decrease, but rather increases, the blood supply and oxygen supply to the liver do not decrease, but rather increase. If the blood supply and oxygen supply to the liver do not decrease, but rather increase, the breakdown of ATP in the liver does not promote, and the release of adenosine does not increase. If the release of adenosine does not increase, the blood vessels in the liver do not dilate, and the volume of blood distributed to the liver does not increase. If the volume of blood distributed to the liver does not increase, the blood volume in the central vein does not decrease, and therefore symptoms such as dialysis hypotension do not occur.

Whether the amount of blood distributed to the liver has increased due to a decrease in the blood and oxygen supply to the liver can be confirmed by administering a small amount of fluid replacement. When the blood and oxygen supply to the liver is decreased, the following cycle occurs: the blood and oxygen supply to the liver decrease, then adenosine production in the liver increases, then the amount of blood distributed to the liver increases, then the blood volume in the central vein decreases, then the cardiac blood return decreases, then cardiac output decreases, and then the blood and oxygen supply to the liver decrease again. This cycle repeats. When this cycle is occurring, if approximately 200 mL of saline is administered, the cycle will reverse as follows: That is, when a small amount of fluid, around 200 mL, is administered, the blood supply and oxygen supply to the liver increase slightly, followed by a slight decrease in adenosine production in the liver, followed by a slight decrease in the amount of blood distributed to the liver, followed by a slight increase in central venous blood volume, followed by a slight increase in cardiac blood return, followed by a slight increase in cardiac output, followed by a further slight increase in the blood supply and oxygen supply to the liver, followed by a slight decrease in liver blood volume, followed by a slight increase in central venous blood volume, followed by a slight increase in cardiac output. This cycle is repeated, ultimately resulting in a significant increase in cardiac output.

After dialysis is completed, approximately 200 mL of blood circulating within the dialyzer and blood circuit of the dialysis machine must be returned to the body. Hereinafter, the process of returning blood circulating within the dialyzer and blood circuit to the body is referred to as "blood return." The time at the end of dialysis, before blood return, is referred to as "before blood return," and the time at which blood return is completed is referred to as "after blood return." Blood return is a special form of fluid replacement. Therefore, if the blood supply and oxygen supply to the liver are reduced, increasing the amount of blood distributed to the liver and thus decreasing the blood volume in the central vein, blood return will increase cardiac output. In contrast, if the blood volume distributed to the liver has not increased, and therefore the blood volume in the central vein has not decreased, blood return will not increase cardiac output. Therefore, by examining whether cardiac output increases with blood return, it is possible to determine whether the amount of blood distributed to the liver has increased. In other words, it is possible to determine whether the amount of body fluid was excessive or insufficient.

Cardiac output is the total volume of blood pumped out by one contraction of the heart per minute. In other words, cardiac output is the product of stroke volume and heart rate per minute. In an experiment on 65 patients, as shown in Figure 1, the heart rate per minute before blood retransfusion was 73.2 ± 15.9 beats/min, while the heart rate per minute after blood retransfusion was 73.1 ± 14.5 beats/min, with no significant difference between the two. In other words, the heart rate does not change before or after blood retransfusion. Therefore, the rate of increase in cardiac output is equal to the rate of increase in stroke volume. Furthermore, since stroke volume is proportional to pulse pressure, the rate of increase in stroke volume is equal to the rate of increase in pulse pressure. Therefore, by examining whether pulse pressure increases due to blood retransfusion, it is possible to evaluate whether blood volume in the liver has increased, thereby determining whether body fluid volume was excessive or insufficient.

We will now explain in more detail the method for evaluating the degree of increase in blood volume distributed to the liver at the end of dialysis. If the dialysis patient's internal blood volume is lower than the appropriate volume before blood return, even if the internal blood volume does not fluctuate, the amount of blood stored in the liver will fluctuate with each dialysis session due to factors such as differences in water removal speed and changes in physical condition. In other words, even if the dialysis patient's body fluid volume does not fluctuate, the amount of blood distributed to the liver will differ with each dialysis session. For this reason, using the rate of increase in stroke cardiac output before and after blood return obtained in a single dialysis session may not accurately evaluate whether the dialysis patient's body fluid volume at the end of dialysis is lower than the appropriate volume. For example, if the dialysis patient's internal blood volume is lower than the appropriate volume and the amount of blood distributed to the liver is increasing, the rate of increase in stroke cardiac output before and after blood return will be larger. Therefore, it is possible to evaluate that the dialysis patient's body fluid volume at the end of dialysis is lower than the appropriate volume. On the other hand, if the dialysis patient's internal blood volume is lower than the appropriate volume but the amount of blood distributed to the liver is small, the rate of increase in stroke cardiac output before and after blood return will not be very large. In this case, the dialysis patient's body fluid volume at the end of dialysis may not be assessed as being lower than appropriate.

Therefore, in this embodiment, whether the amount of blood distributed to the liver of a dialysis patient at the end of dialysis is increased is evaluated based on the multiple increase rates of pulse pressure before and after blood return obtained in multiple dialysis sessions. Here, multiple dialysis sessions refer to multiple consecutive dialysis sessions, and in this embodiment, "multiple dialysis sessions" refers to multiple consecutive dialysis sessions. Furthermore, in multiple consecutive dialysis sessions, dialysis is performed under the same conditions (e.g., the same dry weight). Even if the patient's body fluid volume and blood volume are lower than appropriate in all multiple dialysis sessions, when the increase rates of pulse pressure before and after blood return in multiple dialysis sessions are obtained, the increase rates of pulse pressure before and after blood return may include some that are large and some that are not. This is because the amount of blood distributed to the liver differs for each dialysis session. However, for example, if the patient's body fluid volume and blood volume are lower than appropriate in all multiple dialysis sessions, averaging the increase rates of pulse pressure before and after blood return in multiple dialysis sessions will result in a sufficiently high average value. In other words, by using the average value of the multiple increase rates in pulse pressure before and after blood return obtained over multiple dialysis sessions, it is possible to accurately evaluate the body fluid volume of a dialysis patient at the end of dialysis.

The average value of the rate of increase in pulse pressure associated with blood return over multiple dialysis sessions (hereinafter simply referred to as the "average rate of increase in pulse pressure") can be used when determining the dry weight for the next dialysis session. Specifically, if the average rate of increase in pulse pressure is higher than the upper threshold, the dry weight for the next dialysis session is set higher than the dry weight for the current dialysis session. On the other hand, if the average rate of increase in pulse pressure is lower than the lower threshold, the dry weight for the next dialysis session is set lower than the dry weight for the current dialysis session. Furthermore, if the average rate of increase in pulse pressure is lower than the upper threshold and higher than the lower threshold, the dry weight for the next dialysis session is set the same as the dry weight for the current dialysis session.

The rate of increase in stroke volume is expressed by the following formula 1. Here, Ra indicates the rate of increase in stroke volume before and after blood return, _SV0 indicates the stroke volume before blood return, and _SV1 indicates the stroke volume after blood return.

Stroke volume can be calculated by dividing cardiac output measured directly using, for example, thermodilution by heart rate. However, calculating stroke volume by dividing cardiac output measured directly using thermodilution by heart rate places a significant burden on the medical staff performing the thermodilution measurement and on the dialysis patient themselves. Therefore, in this embodiment, pulse pressure, which is easy to measure and proportional to stroke volume, is used instead of stroke volume. Pulse pressure is the difference between systolic and diastolic blood pressure and may be measured with a sphygmomanometer. In this embodiment, the rate of increase in pulse pressure before and after blood return is used to evaluate whether the amount of blood distributed to the dialysis patient's liver has increased at the end of dialysis, thereby evaluating whether the dialysis patient's body fluid volume at the end of dialysis is appropriate.

As mentioned above, pulse pressure is proportional to stroke volume. Therefore, the rate of increase in pulse pressure before and after blood return can be expressed by the following equation 2. Ra indicates the rate of increase in pulse pressure before and after blood return, _PP0 indicates the pulse pressure before blood return, and _PP1 indicates the pulse pressure after blood return.

By obtaining the pulse pressure before and after blood return, the rate of increase in pulse pressure before and after blood return (hereinafter simply referred to as the "rate of increase in pulse pressure") can be calculated using the formula shown in Equation 2 above. By obtaining the rate of increase in pulse pressure, it is possible to evaluate whether the amount of blood distributed to the dialysis patient's liver at the end of dialysis has increased, and thereby evaluate whether the dialysis patient's body fluid volume at the end of dialysis is appropriate.

When measured with a sphygmomanometer, pulse pressure is the difference between systolic blood pressure and diastolic blood pressure. Therefore, the rate of increase in pulse pressure can also be expressed by the following equation (3). Note that BPs ₀ indicates the systolic blood pressure at the start of blood return, BPd ₀ indicates the diastolic blood pressure at the start of blood return, BPs ₁ indicates the systolic blood pressure at the end of blood return, and BPd ₁ indicates the diastolic blood pressure at the end of blood return.

Figures 2(a) to 2(c) show the rate of increase in pulse pressure over six consecutive dialysis sessions for a dialysis patient. Each of Figures 2(a) to 2(c) shows the change in the rate of increase in pulse pressure for one patient. Figure 2(a) shows a patient who exhibited symptoms of overflow (edema) (hereinafter simply referred to as a "patient with overflow"); Figure 2(b) shows a patient who did not exhibit symptoms of overflow and did not experience dialysis hypotension; and Figure 2(c) shows a patient who experienced dialysis hypotension (hereinafter also referred to as a "patient with dehydration"). Note that the patient in Figure 2(b) who did not exhibit symptoms of overflow and did not experience dialysis hypotension does not require dry weight resetting, and therefore, for ease of explanation, will be referred to below as a "patient with appropriate body fluid volume." In Figures 2(a) to 2(c), the dashed line indicates 0%, and the solid line A parallel to the dashed line indicates the average rate of increase in pulse pressure over six consecutive dialysis sessions.

As shown in Figure 2(a), in patients with overflow, the rate of increase in pulse pressure fluctuated within a narrow range around 0% over the six dialysis sessions. As mentioned above, if the volume of blood in the body before blood return is large, the rate of increase in stroke volume before and after blood return is small. This is because if the volume of body fluids before blood return is large, the volume of blood in the body is also large, which does not reduce the amount of blood and oxygen supplied to the liver. Therefore, the amount of blood distributed to the liver does not increase, and therefore, stroke volume does not increase even with blood return. Incidentally, stroke volume is proportional to pulse pressure. Therefore, in patients with overflow, the rate of increase in pulse pressure before and after blood return fluctuated within a narrow range around 0%. Note that in Figure 2(a), the rate of increase in pulse pressure is negative in the second dialysis session. Physiologically, the rate of increase in pulse pressure cannot be negative; however, because pulse pressure is calculated as the difference between systolic and diastolic blood pressure measured with a conventional cuff-type sphygmomanometer, measurement errors may occur in pulse pressure. The negative pulse pressure increase rate in the second dialysis session can be attributed to measurement error. Furthermore, for patients in an overflow state, the pulse pressure increase rate for all six sessions was roughly 0%, so the standard deviation was also approximately 0%. In summary, for patients in an overflow state, the average pulse pressure increase rate over multiple dialysis sessions is small, and the standard deviation is also small. In other words, if the average pulse pressure increase rate is small and the standard deviation is also small, the dialysis patient's body fluid volume can be determined to be in an overflow state.

As shown in Figure 2 (b), in patients with an appropriate body fluid volume (patients who did not show symptoms of overflow and did not experience dialysis hypotension), the increase rate of pulse pressure over six dialysis sessions varied widely, but the average was approximately 0%. Therefore, in patients with an appropriate body fluid volume, the average increase rate of pulse pressure over multiple dialysis sessions is small and the standard deviation is large. In other words, if the average increase rate of pulse pressure is small and the standard deviation is large, it can be determined that the dialysis patient's body fluid volume is neither overflowing nor dehydrated.

As shown in Figure 2(c), in dehydrated patients, the rate of increase in pulse pressure varied widely over the six dialysis sessions, and the average rate of increase in pulse pressure was approximately 20%, much higher than 0%. This phenomenon is thought to be due to the following reasons: In dehydrated patients, the amount of blood in the body before blood return is small, and therefore cardiac output is reduced. When cardiac output decreases, the amount of blood and oxygen supplied to the liver decreases, and the production of adenosine, which has a vasodilatory effect, increases. Incidentally, adenosine promotes the production of NO, which has a stronger vasodilatory effect than adenosine, in smooth muscle cells of hepatic venules stimulated by interleukin-1 (Ikeda U, et al: Adenosine stimulates nitric oxide synthesis in vascular smooth muscle cells. Cardiovasc Res 35:168-174, 1997.). However, the production rate of interleukin-1 varies depending on many factors, including inflammation, contact of blood monocytes with the dialyzer membrane, endotoxin concentration in the dialysate, and blood flow rate within the dialyzer (Henderson LW, et al.: Hemodialysis hypotension: The interleukin-1 hypothesis. Blood Purif 1: 3-8, 1983). Therefore, when the blood and oxygen supply to the liver is reduced, the liver's blood vessels dilate, increasing the amount of blood distributed to the liver, but the degree of this increase varies from session to session. Consequently, when a patient's body fluid volume is reduced, even if the body fluid volume remains constant, the amount of blood distributed to the liver varies from session to session, resulting in variations in the rate of increase in stroke volume from session to session. Therefore, in dehydrated patients, the mean increase in pulse pressure over multiple dialysis sessions is large, and the standard deviation is also large. In other words, if the average rate of increase in pulse pressure is large and the standard deviation is also large, the dialysis patient's internal fluid status can be determined to be dehydrated.

Next, we will explain the upper and lower thresholds used to determine whether a dialysis patient's body fluid volume state is overhydrated, dehydrated, or neither overhydrated nor dehydrated (for ease of explanation, this may be referred to as an "optimal state") from the average and standard deviation values of the rate of increase in pulse pressure over multiple dialysis sessions. The upper and lower thresholds for the average rate of increase in pulse pressure are the same for all patients. This is for the following reason: When the degree of dehydration is the same, the amount of excess blood that accumulates in the liver is greater for larger patients and less for smaller patients. Therefore, an index of the degree of dehydration common to all patients is the amount of excess blood accumulated in the liver corrected for body size. Meanwhile, the "rate of increase in stroke volume due to blood retransfusion" is the "amount of increase in stroke volume due to blood retransfusion" divided by the stroke volume before blood retransfusion, i.e., the value corrected by the stroke volume before blood retransfusion. The stroke volume before blood return is higher in larger patients and lower in smaller patients. Therefore, the "rate of increase in stroke volume with blood return" is an index obtained by correcting the "amount of increase in stroke volume with blood return" with an index of body size. Incidentally, the "amount of increase in stroke volume with blood return" indicates the amount of excess blood pooling in the liver. From the above, it can be seen that the rate of increase in stroke volume with blood return is an index indicating the degree of dehydration. If this is the case, the upper and lower thresholds indicating the average rate of increase in pulse pressure depend only on the degree of dehydration, not on the patient's physical size. In other words, the upper and lower thresholds indicating the average rate of increase in pulse pressure are the same for all patients. Note that the various thresholds described below are merely examples, and each threshold can be set using a method similar to that described below; the specific values of each threshold are not limited.

24 dialysis patients were divided into an overflow group (6 patients), an appropriate group (11 patients), and a dehydrated group (7 patients). The overflow group consisted of patients who exhibited symptoms of overflow, such as edema. The appropriate group consisted of patients who did not exhibit symptoms of overflow and did not experience dialysis-related hypotension (i.e., patients with appropriate fluid levels or patients who were not clearly overflowed or dehydrated). The dehydrated group consisted of patients who experienced dialysis-related hypotension. For all 24 dialysis patients, systolic and diastolic blood pressures were measured before and after blood reinfusion using a cuff-type sphygmomanometer (a sphygmomanometer that first measures systolic blood pressure, then diastolic blood pressure) in the arm without blood access. The systolic and diastolic blood pressures before and after blood reinfusion were substituted into the equation shown above (Equation 3) to calculate the rate of increase in pulse pressure. Measurements of pulse pressure before and after blood return were performed in six consecutive dialysis sessions, and the rate of increase in pulse pressure was calculated for each dialysis session. The average and standard deviation were then calculated from the six calculated rates of increase in pulse pressure.

As shown in Figures 3(a) and 3(b), in the overflow group, the average increase rate of pulse pressure was 6% or less, and the standard deviation was 6%. All patients in the overflow group and several patients in the appropriate group had an average increase rate of pulse pressure of 6% or less. The average increase rate of pulse pressure was not clearly distinguishable between the overflow group and the appropriate group based on the average increase rate of pulse pressure alone. However, only the overflow group had a standard deviation of 6% or less, while the appropriate and dehydrated groups had standard deviations higher than 6%. Therefore, if the average increase rate of pulse pressure over multiple consecutive dialysis sessions is 6% or less and the standard deviation is 6%, the dialysis patient's internal hydration state can be determined to be overflowing.

Furthermore, in the dehydrated group, the average increase in pulse pressure was 15% or more. In addition to all patients in the dehydrated group, one patient in the appropriate group also had an average increase in pulse pressure of 15% or more, but this one patient in the appropriate group can be considered within the margin of error. Therefore, if the average increase in pulse pressure over multiple consecutive dialysis sessions is 15% or more, the dialysis patient's internal fluid status can be determined to be dehydrated.

If none of the above conditions are met, it can be determined that the condition is appropriate. As mentioned above, "appropriate" here means that the patient is neither clearly overhydrated nor dehydrated, and does not necessarily mean that the amount of fluid in the body of the dialysis patient is appropriate. Specifically, if the average rate of increase in pulse pressure over multiple consecutive dialysis sessions is more than 6% and less than 15%, or if the average rate of increase in pulse pressure is 6% or less and the standard deviation is more than 6%, the condition can be determined to be appropriate (neither overhydrated nor dehydrated).

Next, the configuration of the body fluid volume evaluation device 10 will be described. The body fluid volume evaluation device 10 comprises a calculation unit 12, an input unit 22, and a display unit 24. The calculation unit 12 can be configured, for example, by a computer equipped with a CPU, ROM, RAM, etc. The calculation unit 12 is connected to the input unit 22 and the display unit 24.

)。 English: The calculation unit 12 includes a bodily fluid volume evaluation unit 14 and a judgment unit 20. The bodily fluid volume evaluation unit 14 includes a memory unit 16 and a calculation unit 18. The memory unit 16 stores the pulse pressure before and after blood return obtained from the input unit 22. The memory unit 16 also stores the increase rate of pulse pressure in the last few dialysis sessions (in this embodiment, the last five sessions) obtained from the input unit 22. As described above, the increase rate of pulse pressure stored in the memory unit 16 is the increase rate of pulse pressure in the last few dialysis sessions performed under the same conditions (e.g., dry weight, etc.). The memory unit 16 may also store the pulse pressure before and after blood return in the last few dialysis sessions (performed under the same conditions). The memory unit 16 also stores the increase rate of pulse pressure (or the pulse pressure before and after blood return) in multiple dialysis sessions for each patient. The calculation unit 18 calculates the rate of increase in pulse pressure from the pulse pressure before and after blood return stored in the memory unit 16. The calculation unit 18 also calculates the average value and standard deviation of the rate of increase in pulse pressure for each of multiple dialysis sessions. The judgment unit 20 judges the hydration status of the dialysis patient at the end of dialysis from the average value and standard deviation of the rate of increase in pulse pressure for multiple dialysis sessions calculated by the calculation unit 18.

The input unit 22 accepts instructions and information from the operator. For example, the input unit 22 accepts input of the pulse pressure before and after blood return, and the rate of increase in pulse pressure over the most recent several dialysis sessions. The input unit 22 may also accept input of the pulse pressure before and after blood return over multiple dialysis sessions. The input information is output from the input unit 22 to the calculation unit 12. The display unit 24 displays the judgment result of the judgment unit 20 on the hydration state of the dialysis patient at the end of dialysis. The display unit 24 may also display the average value and standard deviation of the rate of increase in pulse pressure over multiple dialysis sessions calculated by the calculation unit 18.

Next, we will explain the process of evaluating the hydration status of a dialysis patient at the end of dialysis using the body fluid volume evaluation device 10. In this example, the body fluid volume evaluation device 10 uses the pulse pressure before and after blood return in six consecutive dialysis sessions (performed under the same conditions) to calculate the average value and standard deviation of the pulse pressure increase rate, and determines the hydration status of the dialysis patient at the end of dialysis. In this example, the pulse pressure increase rates for the most recent five dialysis sessions are assumed to be stored in the memory unit 16, and the following process is performed after the sixth dialysis session is completed.

First, the calculation unit 12 acquires the pulse pressure before and after blood return for the current (sixth) dialysis session via the input unit 22 (S12). The pulse pressure before blood return is measured before blood is returned at the end of dialysis. The pulse pressure after blood return is measured at the end of blood return. The pulse pressure before and after blood return are measured using a measuring device such as a cuff-type blood pressure monitor or pulse oximeter. The calculation unit 12 stores the acquired pulse pressure before and after blood return in the memory unit 16.

Next, the calculation unit 18 calculates the rate of increase in pulse pressure during this (sixth) dialysis session from the pulse pressure before and after blood return obtained in step S12 (S14). Specifically, the calculation unit 18 calculates the rate of increase in pulse pressure using the formula expressed by Equation 2 or Equation 3 above.

Next, the calculation unit 18 acquires the rate of increase in pulse pressure for the most recent five dialysis sessions stored in the memory unit 16 (S16). Note that the calculation unit 18 may acquire the pulse pressure before and after blood return for the most recent five dialysis sessions, and calculate the rate of increase in pulse pressure for each of the most recent five dialysis sessions.

Next, the calculation unit 18 calculates the average value and standard deviation of the pulse pressure increase rate over six consecutive dialysis sessions using the pulse pressure increase rate calculated in step S14 and the pulse pressure increase rates over the most recent five dialysis sessions obtained in step S16 (S18).

Next, the judgment unit 20 determines whether the average value calculated in step S18 is 6% or less (S20). As described above, if the average value of the rate of increase in pulse pressure over multiple consecutive dialysis sessions is 6% or less, the dialysis patient's internal hydration status can be determined to be in an over-hydration state or an appropriate state. If the average value is 6% or less (YES in step S20), the judgment unit 20 determines whether the standard deviation value calculated in step S18 is 6% or less (S22). As described above, if the average value of the rate of increase in pulse pressure over multiple consecutive dialysis sessions is 6% or less and the standard deviation value is 6% or less, the dialysis patient's internal hydration status can be determined to be in an over-hydration state. If the standard deviation value is 6% or less (YES in S22), the judgment unit 20 determines that the dialysis patient's internal hydration status is in an over-hydration state (S24). The calculation unit 12 then causes the display unit 24 to display an indication that the dialysis patient is in an over-hydration state (S26).

On the other hand, as described above, if the average increase rate of pulse pressure over multiple consecutive dialysis sessions is 6% or less and the standard deviation is greater than 6%, the hydration status of the dialysis patient can be determined to be appropriate. If the standard deviation exceeds 6% (NO in S22), the judgment unit 20 determines that the hydration status of the dialysis patient is appropriate (S30). The calculation unit 12 then causes the display unit 24 to display that the status is appropriate (i.e., not clearly overhydrated or dehydrated) (S32).

Furthermore, if the average value exceeds 6% (NO in step S20), the judgment unit 20 judges whether the average value is 15% or greater (S28). As described above, if the average value of the increase rate of pulse pressure over multiple consecutive dialysis sessions is 15% or greater, the dialysis patient's internal water content can be determined to be dehydrated. If the average value is 15% or greater (YES in S28), the judgment unit 20 judges that the dialysis patient's internal water content is dehydrated (S34). The calculation unit 12 then causes the display unit 24 to display the fact that the patient is dehydrated (S36).

On the other hand, if the average value does not exceed 15% (NO in step S28), the average value will be greater than 6% (NO in step S20) and less than 15%. As described above, if the average value of the rate of increase in pulse pressure over multiple consecutive dialysis sessions is less than 6% and the standard deviation is greater than 6%, the hydration status of the dialysis patient's body can be determined to be appropriate. Therefore, the judgment unit 20 determines that the hydration status of the dialysis patient's body is appropriate (S30), and the calculation unit 12 causes the display unit 24 to display that the status is appropriate (i.e., not clearly overhydrated or dehydrated) (S32).

In this embodiment, the hydration status of a dialysis patient is determined to be overhydrated if the average increase rate of pulse pressure over multiple consecutive dialysis sessions is 6% or less and the standard deviation is 6% or less, but this configuration is not limited to this. As described above, the standard deviation is 6% or less in an overhydrated state, and exceeds 6% in an adequate state and a dehydrated state (see Figure 2(b)). Therefore, the judgment unit 20 may determine that the hydration status of a dialysis patient is overhydrated if the standard deviation is 6% or less, without taking the average value into consideration.

In this embodiment, the hydration status of a dialysis patient at the end of dialysis was evaluated using the rate of increase in pulse pressure over six consecutive dialysis sessions, but this configuration is not limited to this. For example, the hydration status of a dialysis patient at the end of dialysis may also be evaluated from the rate of increase in pulse pressure over three to twelve consecutive dialysis sessions. By using the rate of increase in pulse pressure over three or more consecutive dialysis sessions, it is possible to adequately evaluate the hydration status of a dialysis patient, even if the amount of blood stored in the liver varies with each dialysis session. Furthermore, by using the rate of increase in pulse pressure over 12 or fewer consecutive dialysis sessions, it is possible to avoid an excessively long period between the first and final sessions (up to the 12th session). If the period between the first and final sessions is too long, the dialysis patient's body shape may change, potentially changing their appropriate dry weight. Since 12 consecutive dialysis sessions are often performed over approximately one month, the hydration status of a dialysis patient is unlikely to change significantly. Therefore, it is recommended to evaluate the hydration status of a dialysis patient at the end of dialysis using the rate of increase in pulse pressure over three to 12 consecutive dialysis sessions.

Furthermore, in this embodiment, the standard deviation value of the rate of increase in pulse pressure over multiple consecutive dialysis sessions was calculated, but this configuration is not limited to this. Anything can be done as long as it can show the variation in the rate of increase in pulse pressure over multiple consecutive dialysis sessions; for example, the variance of the rate of increase in pulse pressure over multiple consecutive dialysis sessions may be calculated. Furthermore, in this embodiment, the body fluid volume evaluation unit 14 is provided in the body fluid volume evaluation device 10, but this configuration is not limited to this. For example, the body fluid volume evaluation unit 14 may be provided in a PC separate from the PC in which the judgment unit 20 is provided.

The following points should be noted regarding the body fluid volume evaluation device 10 described in the examples. The body fluid volume evaluation unit 14 in the examples is an example of an "evaluation unit," the calculation unit 18 is an example of a "first calculation unit" and a "second calculation unit," and the input unit 22 is an example of a "pulse pressure acquisition unit."

Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings demonstrate technical utility either alone or in various combinations, and are not limited to the combinations set forth in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of those objectives is itself technically useful.

Claims (7)

An apparatus for evaluating the body fluid volume of a dialysis patient at the end of dialysis,
a pulse pressure acquiring unit that acquires a first pulse pressure, which is the pulse pressure of the dialysis patient at the end of dialysis and before the blood in the dialyzer and the blood circuit is returned to the body of the dialysis patient, and a second pulse pressure, which is the pulse pressure of the dialysis patient at the end of blood return, and that acquires the first pulse pressure and the second pulse pressure during multiple consecutive dialysis sessions of the dialysis patient;
a first calculation unit that calculates an increase rate of pulse pressure from the first pulse pressure and the second pulse pressure, the first calculation unit calculating an increase rate of pulse pressure for each of the plurality of dialysis sessions from the first pulse pressure and the second pulse pressure for each of the plurality of dialysis sessions;
a second calculation unit that calculates at least one of an index indicating an average value and an index indicating a variation in the rate of increase in pulse pressure over the multiple dialysis sessions calculated by the first calculation unit;
a body fluid volume evaluation device comprising: an evaluation unit that evaluates the body fluid volume of the dialysis patient based on at least one of the average value calculated by the second calculation unit and an index indicating the variation. The body fluid volume evaluation device of claim 1 further comprises a memory unit that stores a threshold value for the average value when the dialysis patient's body is in a dehydrated state at the end of dialysis. The body fluid volume evaluation device of claim 1 further comprises a memory unit that stores a threshold value for the index of variation when the dialysis patient's body is in an overflowing state at the end of dialysis. The body fluid volume evaluation device of claim 3, wherein the memory unit further stores a threshold value for the average value when the dialysis patient's body is in an overflowing state at the end of dialysis. The body fluid volume evaluation device of claim 1, wherein the index indicating the variation is a standard deviation. The apparatus further includes a memory unit that stores a first value that is a threshold value of the average value when the dialysis patient's body is in a dehydrated state at the end of dialysis, a second value that is a threshold value of the average value when the dialysis patient's body is in an overhydrated state at the end of dialysis, and a third value that is a threshold value of the index of variation when the dialysis patient's body is in an overhydrated state at the end of dialysis,
The evaluation unit
When the average value is equal to or greater than the first value, it is determined that the dialysis patient is in a dehydrated state;
When the average value is equal to or less than the second value and the index of variation is equal to or less than the third value, it is determined that the dialysis patient is in an overflowing state;
2. The body fluid volume evaluation device of claim 1, which determines that the body of a dialysis patient is neither overhydrated nor dehydrated when the average value exceeds the second value and is less than the first value, or when the average value is equal to or less than the second value and the index of variation exceeds the third value. A computer program for evaluating the body fluid volume of a dialysis patient at the end of dialysis, comprising:
Computer,
a pulse pressure acquiring unit that acquires a first pulse pressure, which is the pulse pressure of the dialysis patient at the end of dialysis and before the blood in the dialyzer and the blood circuit is returned to the body of the dialysis patient, and a second pulse pressure, which is the pulse pressure of the dialysis patient at the end of blood return, and that acquires the first pulse pressure and the second pulse pressure during multiple consecutive dialysis sessions of the dialysis patient;
a first calculation unit that calculates an increase rate of pulse pressure from the first pulse pressure and the second pulse pressure, the first calculation unit calculating an increase rate of pulse pressure for each of the plurality of dialysis sessions from the first pulse pressure and the second pulse pressure for each of the plurality of dialysis sessions;
a second calculation unit that calculates at least one of an index indicating an average value and an index indicating a variation in the rate of increase in pulse pressure over the multiple dialysis sessions calculated by the first calculation unit;
A computer program that functions as an evaluation unit that evaluates the body fluid volume of the dialysis patient based on at least one of the average value and the index indicating the variation calculated by the second calculation unit.