Target weight calculation device

Abstract

To properly calculate target weight for stipulating the end of water removal in dialysis.SOLUTION: A target weight calculation device calculates target weight which is weight for becoming a target in ending water removal by dialysis. The target weight calculation device includes: a storage part that can store a target extracellular fluid volume which is an extracellular fluid volume in the target weight; and an operation part that, when a final target extracellular fluid volume is undecided which is the proper extracellular fluid volume of a dialysis patient, operates a target weight in the next dialysis, from a difference between the target extracellular fluid volume in the last dialysis and the extracellular fluid volume after dialysis in the dialysis this time, and from the weight after dialysis in the dialysis this time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present specification relates to a technique for calculating a target weight. [Background technology]

[0002] In dialysis patients, all ingested water accumulates in the body because kidney function has been abolished. Of the compartments in the body where water is distributed, ingested water accumulates in the extracellular compartment. Excess water accumulated in the extracellular compartment is removed by dialysis. When removing excess water accumulated in the extracellular compartment by dialysis, water is removed until the extracellular fluid volume is slightly higher than that of a person with normal renal function. As disclosed in Non-Patent Document 1, the life prognosis is best when water is removed until the extracellular fluid volume of a dialysis patient is estimated to be slightly higher than that of a person with normal renal function. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Wizemann V, et al: The mortality risk of overhydration in haemodialysis patients. Nephrol Dial Transplant 24: 1574-1579, 2009 Summary of the Invention [Problem to be solved by the invention]

[0004] During dialysis, fluid accumulated in the extracellular compartment is removed over several hours until it reaches a volume believed to be slightly greater than the extracellular fluid volume in a person with normal renal function. However, because it is not possible to determine the target volume of extracellular fluid removal, which is slightly greater than the extracellular fluid volume in a person with normal renal function, excessive fluid removal can result in a drop in blood pressure during dialysis. If a drop in blood pressure occurs during dialysis, measures are taken, such as slowing the rate of fluid removal, stopping fluid removal, or administering fluid replacement. However, a drop in blood pressure during dialysis can damage the heart. Repeated drops in blood pressure during dialysis increase the risk of death (Faucon A, et al.: Extracellular fluid volume is associated with incident end-stage kidney disease and mortality in patients with chronic kidney disease. Kidney Int 96: 1020-1029, 2019). Therefore, it is important to prevent repeated drops in blood pressure during dialysis. However, because it is not possible to detect extracellular fluid volumes slightly greater than those of healthy individuals, sometimes the patient is so afraid of a drop in blood pressure that they end fluid removal while leaving enough fluid in the body to cause edema. In such cases, the patient's risk of death increases, so it is necessary to remove fluid only to the point where edema is no longer present. While it is possible to measure or calculate extracellular fluid volume, there was no way to know whether the measured or calculated volume was sufficient to prevent a drop in blood pressure and edema during dialysis.

[0005] As mentioned above, it is possible to estimate or calculate the extracellular fluid volume in the body. However, dialysis patients often have reduced cardiac function, impaired autonomic nervous function, and anemia compared to healthy individuals. Therefore, when attempting to remove fluid during dialysis until the extracellular fluid volume is equal to that of a person with normal renal function, blood pressure often drops before the extracellular fluid volume reaches that of a person with normal renal function. Furthermore, the extracellular fluid volume at which blood pressure drops varies significantly from patient to patient. Therefore, the target extracellular fluid volume for water removal during dialysis varies from patient to patient, and for each patient, the target extracellular fluid volume is often lower than the level at which edema occurs but higher than the level at which blood pressure drops. This extracellular fluid volume has traditionally required repeated trial and error by physicians and other medical professionals.

[0006] This specification discloses a technique for appropriately calculating a target weight, which is the weight to be achieved when water removal by dialysis is terminated. [Means for solving the problem]

[0007] This specification discloses a technology for determining a target post-dialysis extracellular fluid volume based on fluctuations in post-dialysis extracellular fluid volume that accompany fluctuations in fat mass, and for appropriately calculating a target post-dialysis weight, which is the post-dialysis weight corresponding to the target post-dialysis extracellular fluid volume.

[0008] The target weight calculation device disclosed in this specification calculates a target weight, which is the weight to be targeted when water removal by dialysis is completed. The target weight calculation device includes a memory unit capable of storing a target extracellular fluid volume, which is the extracellular fluid volume at the target weight, and a calculation unit that calculates the target weight for the next dialysis session from the difference between the target extracellular fluid volume for the previous dialysis session and the post-dialysis extracellular fluid volume for the current dialysis session, and the post-dialysis weight for the current dialysis session, when the final target extracellular fluid volume, which is the appropriate extracellular fluid volume for the dialysis patient, has not yet been determined.

[0009] To determine the target extracellular fluid volume for fluid removal during dialysis, physicians and other medical professionals often gradually lower the target post-dialysis weight. Once symptoms of post-dialysis fatigue, hoarseness, or a mild drop in blood pressure during dialysis (hereinafter, including mild cases, simply referred to as "blood pressure drop") occur, the target weight is set to a weight slightly higher than the symptoms. However, this method has the problem that the post-dialysis extracellular fluid volume, which is directly related to the drop in blood pressure during dialysis, only decreases while fluctuating. This is because, during the gradual reduction of post-dialysis weight during dialysis, fat mass also increases and decreases, and if the loss of fat is greater than the loss of body weight, the extracellular fluid volume actually increases.

[0010] To determine the target extracellular fluid volume for intradialytic water removal, physicians and other medical professionals often gradually lower the target postdialytic extracellular fluid volume. Once symptoms of postdialytic fatigue or hoarseness, or a drop in blood pressure during dialysis, are detected, the target extracellular fluid volume is set to a slightly higher level. However, when a patient is rapidly losing fat mass due to stress, such as a severe infection or surgery, the rate of fat mass loss may be faster than the rate of postdialytic extracellular fluid loss. In such cases, this method has the problem of not reducing extracellular fluid volume as expected. On the other hand, when a patient is recovering from stress, such as a severe infection or surgery, and therefore gaining fat mass, this method has the problem of reducing extracellular fluid volume more than expected.

[0011] The period between the time when the post-dialysis extracellular fluid volume is measured or calculated during dialysis and the time when the post-dialysis extracellular fluid volume is measured or calculated next during dialysis is defined as the inter-extracellular fluid volume measurement period. The target body weight calculation device disclosed in this specification calculates the target body weight to be used for the inter-extracellular fluid volume measurement period starting from the time when the post-dialysis extracellular fluid volume is measured or calculated during dialysis. When calculating the target body weight for the first time using the target body weight calculation device, the post-dialysis extracellular fluid volume measured or calculated most recently is used as the target extracellular fluid volume up to that point to calculate the target extracellular fluid volume to be used for the inter-extracellular fluid volume measurement period starting from that time. The target body weight is calculated as the post-dialysis body weight at a given target extracellular fluid volume.

[0012] Furthermore, in the target body weight calculation device disclosed in this specification, if the post-dialysis extracellular fluid volume in the current dialysis is greater than the target extracellular fluid volume in the previous dialysis stored in the memory unit, the calculation unit may set the target body weight for the next dialysis to a weight that is less than the post-dialysis weight in the current dialysis by the difference between the post-dialysis extracellular fluid volume in the current dialysis and the target extracellular fluid volume in the previous dialysis, while if the post-dialysis extracellular fluid volume in the current dialysis is equal to or less than the target extracellular fluid volume in the previous dialysis stored in the memory unit, the post-dialysis extracellular fluid volume in the current dialysis may be set to the target extracellular fluid volume in the next dialysis, and the post-dialysis weight in the current dialysis may be set to the target body weight for the next dialysis.

[0013] For example, when there are no signs of a blood pressure drop and no blood pressure drop has occurred during dialysis, and the post-dialysis extracellular fluid volume at the time of measurement or calculation of the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period is greater than the target extracellular fluid volume for the previous inter-extracellular fluid volume measurement period, the calculation unit subtracts the difference between the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period and the target extracellular fluid volume for the previous inter-extracellular fluid volume measurement period from the post-dialysis body weight at the start of the current inter-extracellular fluid volume measurement period, and sets the resulting value as the target body weight for the current inter-extracellular fluid volume measurement period. The reason for this is that, because there were no signs of a blood pressure drop during the previous inter-extracellular fluid volume measurement period and no blood pressure drop occurred during dialysis, the target extracellular fluid volume for the previous inter-extracellular fluid volume measurement period can be considered safe, and therefore it is presumed that it is safe to continue using the target extracellular fluid volume for the previous inter-extracellular fluid volume measurement period as the target extracellular fluid volume for the current inter-extracellular fluid volume measurement period.

[0014] On the other hand, when there are no signs of blood pressure decline and no blood pressure decline has occurred during dialysis, and the post-dialysis extracellular fluid volume at the time of measurement or calculation of the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period is equal to or less than the target extracellular fluid volume used during the previous inter-extracellular fluid volume measurement period, the calculation unit sets the post-dialysis extracellular fluid volume at the time of measurement or calculation of the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period as the new target extracellular fluid volume. In this case, the target body weight to be used during the current inter-extracellular fluid volume measurement period is the post-dialysis body weight during dialysis at the start of the current inter-extracellular fluid volume measurement period. This is because, since there were no signs of blood pressure decline and no blood pressure decline has occurred during dialysis at the start of the current inter-extracellular fluid volume measurement period, it is presumed that the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period can be safely used as the target extracellular fluid volume, even if the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period is equal to or less than the previous target extracellular fluid volume.

[0015] By repeating the above two processes, the target extracellular fluid volume gradually decreases, and eventually, signs of a decrease in blood pressure appear, or a slight decrease in blood pressure occurs during dialysis.

[0016] The reason why the postdialysis extracellular fluid volume at the start of the current inter-measurement period is lower than the previous target extracellular fluid volume is because the postdialysis weight remains constant and the fat mass increases, i.e., the patient becomes overweight, and the increased fat is replaced with extracellular fluid. Setting the postdialysis extracellular fluid volume that is below the previous target extracellular fluid volume as the new target extracellular fluid volume means that the postdialysis weight at the start of the current inter-measurement period is used as the target weight. On the other hand, the reason why the postdialysis extracellular fluid volume at the start of the current inter-measurement period is higher than the previous target extracellular fluid volume is because the postdialysis weight remains constant and the fat mass decreases, i.e., the patient becomes overweight, and the extracellular fluid volume increases by the amount of the fat loss. Therefore, if the previous target extracellular fluid volume is to be used as is, the difference between the post-dialysis extracellular fluid volume at the start of the current extracellular fluid volume measurement interval and the previous target extracellular fluid volume is subtracted from the post-dialysis weight at the start of the current extracellular fluid volume measurement interval, and the resulting value is used as the new target weight.

[0017] In this specification, the above two processes are repeated until a sign of blood pressure decrease or a drop in blood pressure occurs during dialysis. Once a sign of blood pressure decrease or a drop in blood pressure occurs during dialysis, the calculation unit sets the extracellular fluid volume slightly larger than the target extracellular fluid volume at that time as the final target extracellular fluid volume, and at the start of each subsequent extracellular fluid volume measurement period, calculates the target weight so that the post-dialysis extracellular fluid volume at that time matches the final target extracellular fluid volume.

[0018] That is, the target weight calculation device disclosed in this specification may further include an input unit that inputs blood pressure decrease information indicating that a sign of blood pressure decrease has occurred or that blood pressure has decreased during dialysis. The storage unit may store the blood pressure decrease information input to the input unit.

[0019] Furthermore, in the target weight calculation device disclosed in this specification, when blood pressure decrease information is input to the input unit, the calculation unit may calculate, as a final target extracellular fluid volume, a predetermined amount higher than the target extracellular fluid volume in the dialysis performed when the blood pressure decrease information was input. Furthermore, the memory unit may be capable of storing the final target extracellular fluid volume.

[0020] In addition, in the target weight calculation device disclosed in this specification, when the final target extracellular fluid volume is stored in the memory unit, the calculation unit may calculate the target weight for the next dialysis session from the post-dialysis extracellular fluid volume for the current dialysis session, the final target extracellular fluid volume, and the post-dialysis weight for the current dialysis session.

[0021] Furthermore, in the target weight calculation device disclosed in this specification, if the post-dialysis extracellular fluid volume in the current dialysis is greater than the final target extracellular fluid volume stored in the memory unit, the calculation unit may set the target weight for the next dialysis to a weight that is less than the post-dialysis weight for the current dialysis by the difference between the post-dialysis extracellular fluid volume in the current dialysis and the final target extracellular fluid volume, whereas if the post-dialysis extracellular fluid volume in the current dialysis is equal to or less than the final target extracellular fluid volume stored in the memory unit, the calculation unit may set the target weight for the next dialysis to a weight that is more than the post-dialysis weight for the current dialysis by the difference between the final target extracellular fluid volume and the post-dialysis extracellular fluid volume in the current dialysis.

[0022] By using the above configuration, once there are signs of a drop in blood pressure or a drop in blood pressure occurs during dialysis, the target weight can be calculated so that the extracellular fluid volume becomes the final target extracellular fluid volume, and the target weight can be calculated appropriately. [Brief explanation of the drawings]

[0023] [Figure 1] 10 is a flowchart illustrating a method for calculating a target extracellular fluid volume and a final target extracellular fluid volume in this embodiment. [Figure 2]This is a diagram showing a schematic breakdown of a dialysis patient's post-dialysis weight, classified into extracellular fluid volume, fat mass, and other components, and shows a case in which a dialysis patient's fat mass has decreased between the start of the previous extracellular fluid volume measurement period and the start of the current extracellular fluid volume measurement period, when there are no signs of blood pressure drop and no drop in blood pressure has occurred during dialysis. [Figure 3] This is a diagram showing a schematic breakdown of a dialysis patient's post-dialysis weight, classified into extracellular fluid volume, fat mass, and other components, and shows a case in which the fat mass of a dialysis patient has increased between the start of the previous extracellular fluid volume measurement period and the start of the current extracellular fluid volume measurement period, when there are no signs of a drop in blood pressure and no drop in blood pressure has occurred during dialysis. [Figure 4] This is a diagram showing a schematic breakdown of a dialysis patient's weight, broken down into extracellular fluid volume, fat, and other components. It shows a case in which the fat volume of a dialysis patient has decreased between the start of the previous extracellular fluid volume measurement period and the start of the current extracellular fluid volume measurement period, when the target extracellular fluid volume is increased by a predetermined amount to become the final target extracellular fluid volume due to signs of a drop in blood pressure or a drop in blood pressure occurring during dialysis. [Figure 5] This is a diagram showing a schematic breakdown of a dialysis patient's weight, classified into extracellular fluid volume, fat, and other components.The figure shows the extracellular fluid volume when the fat volume of a dialysis patient increases between the start of the previous extracellular fluid volume measurement period and the start of the current extracellular fluid volume measurement period, when the target extracellular fluid volume is increased by a predetermined amount to become the final target extracellular fluid volume due to signs of blood pressure decline or when blood pressure decline occurs during dialysis. [Figure 6] FIG. 1 is a block diagram showing a schematic configuration of a target weight calculation device according to an embodiment. [Figure 7] 10 is a flowchart showing an example of a process for calculating a target weight using a target weight calculation device until a drop in blood pressure occurs. [Figure 8] 10 is a flowchart showing an example of a process for calculating a target weight using a target weight calculation device after a drop in blood pressure occurs. [Figure 9]A figure showing the number of patients who developed edema after dialysis, the number of patients who experienced a drop in blood pressure during dialysis, and the number of asymptomatic patients who did not experience either edema after dialysis or a drop in blood pressure during dialysis before and after the treatment shown in this embodiment was performed. DETAILED DESCRIPTION OF THE INVENTION

[0024] The main features of the embodiments described below are listed below. Note that the technical elements described below are independent technical elements that exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

[0025] The target weight calculation device disclosed in this specification may further include an output unit that outputs the target weight calculated by the calculation unit. With this configuration, the calculated target weight can be output, thereby presenting the target weight of the dialysis patient to medical professionals each time. [Example]

[0026] A target weight calculation device 10 according to this embodiment will be described with reference to the drawings. The target weight calculation device 10 calculates the target weight of a dialysis patient. The target weight is the post-dialysis weight that is targeted when determining the amount of water removal by dialysis. In other words, during dialysis, water removal is performed so that the post-dialysis weight of the dialysis patient matches the target weight.

[0027] First, the method for calculating the target weight in this example will be described. In this example, different methods are used to calculate the target weight depending on whether the patient has not yet shown signs of blood pressure drop, such as post-dialysis fatigue or hoarseness, and has not yet experienced a drop in blood pressure during dialysis, or whether the patient has shown signs of blood pressure drop or has experienced a drop in blood pressure during dialysis.

[0028] In the following description, the term "occurrence of blood pressure decrease" includes not only the occurrence of blood pressure decrease during dialysis but also the occurrence of signs of blood pressure decrease. In addition, in this description, the period from the time when the post-dialysis extracellular fluid volume is measured or calculated during dialysis to the time when the post-dialysis extracellular fluid volume is measured or calculated again is defined as the inter-extracellular fluid volume measurement period.

[0029] If blood pressure has not yet dropped and the post-dialysis extracellular fluid volume at the time of measurement or calculation of the post-dialysis extracellular fluid volume at the start of the current extracellular fluid volume inter-measurement period is greater than the target extracellular fluid volume for the previous extracellular fluid volume inter-measurement period, the difference between the post-dialysis extracellular fluid volume at the start of the current extracellular fluid volume inter-measurement period and the previous target extracellular fluid volume is subtracted from the post-dialysis weight at the start of the current extracellular fluid volume inter-measurement period, and this value is used as the target weight for the current extracellular fluid volume inter-measurement period (i.e., the target weight for the dialysis (next dialysis) performed after the dialysis at the start of the current extracellular fluid volume inter-measurement period (current dialysis) and the target weight for the dialysis performed by the end of the current extracellular fluid volume inter-measurement period).

[0030] On the other hand, if blood pressure has not yet dropped and the post-dialysis extracellular fluid volume at the time of measurement or calculation of the post-dialysis extracellular fluid volume at the start of the current extracellular fluid volume inter-measurement period is less than or equal to the target extracellular fluid volume for the previous extracellular fluid volume inter-measurement period, the post-dialysis weight at the start of the current extracellular fluid volume inter-measurement period is set as the target weight for the current extracellular fluid volume inter-measurement period.

[0031] By repeating these two operations, the target extracellular fluid volume gradually decreases, and eventually, a drop in blood pressure occurs. Once a drop in blood pressure occurs, a volume of extracellular fluid slightly higher than the target extracellular fluid volume at that time is set as the final target extracellular fluid volume, and at the start of each subsequent extracellular fluid volume measurement period, the target weight is calculated so that the post-dialysis extracellular fluid volume matches the final target extracellular fluid volume. Note that while the final target extracellular fluid volume is always constant, the target weight fluctuates with changes in fat mass.

[0032] The final target extracellular fluid volume is a post-dialysis extracellular fluid volume that is slightly higher than the target extracellular fluid volume at which hypotension occurs. Therefore, if water is removed until the post-dialysis extracellular fluid volume reaches the final target extracellular fluid volume, hypotension will not occur. Furthermore, the extracellular fluid volume that causes edema is known to be typically about 2.5 liters higher than the extracellular fluid volume that causes signs of hypotension or hypotension during dialysis (Simon EB: Leg edema assessment and management. Med Surg Nursing 23: 44-53, 2014). Therefore, post-dialysis edema will not occur.

[0033] The method for calculating the target weight in this embodiment will be described in more detail. FIG. 2 shows an example of a process for calculating a target extracellular fluid volume at the start of each inter-extracellular fluid volume measurement period. The target extracellular fluid volume indicates the extracellular fluid volume at the target weight. As shown in FIG. 2, first, the previous target extracellular fluid volume is compared with the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period (S110). The extracellular fluid volume can be measured using an external device (not shown) or the like using a conventionally known impedance method or the like. The post-dialysis extracellular fluid volume may also be calculated using the extracellular fluid volume calculation method disclosed in International Publication No. WO 2019 / 138917 (this calculation method calculates the extracellular fluid volume focusing on uric acid, and therefore is hereinafter also referred to as the "uric acid method"). The extracellular fluid volume is obtained every multiple dialysis sessions (e.g., once a month). In this specification, the interval at which the extracellular fluid volume is measured is defined as the inter-extracellular fluid volume measurement period. When the method of this embodiment is performed for the first time, there is no target extracellular fluid volume for the period between previous extracellular fluid volume measurements, so the most recent post-dialysis extracellular fluid volume measured in the past is provisionally used as the target extracellular fluid volume for the period between previous extracellular fluid volume measurements.

[0034] Next, it is determined whether the post-dialysis extracellular fluid volume at the time of the current extracellular fluid volume measurement is greater than the previous target extracellular fluid volume (S120). If the post-dialysis extracellular fluid volume at the start of the current extracellular fluid volume inter-measurement period is greater than the target extracellular fluid volume for the previous extracellular fluid volume inter-measurement period (YES in step S120), the target extracellular fluid volume for the previous extracellular fluid volume inter-measurement period is set as the target extracellular fluid volume for the current extracellular fluid volume inter-measurement period (S130). In this case, the difference between the post-dialysis extracellular fluid volume at the start of the current extracellular fluid volume inter-measurement period and the target extracellular fluid volume for the previous extracellular fluid volume inter-measurement period is subtracted from the post-dialysis weight at the start of the current extracellular fluid volume inter-measurement period to set the calculated value as the target weight for the current extracellular fluid volume inter-measurement period (see Figure 2). The target weight in this case will be described in detail later.

[0035] On the other hand, if the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period is equal to or less than the target extracellular fluid volume for the previous inter-extracellular fluid volume measurement period (NO in step S120), the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period is set as the new target extracellular fluid volume (S140). In this case, the post-dialysis body weight from dialysis at the start of the current inter-extracellular fluid volume measurement period is set as the target body weight (see Figure 3). The target body weight in this case will be described in detail later.

[0036] When blood pressure has not decreased (NO in step S150), the target weight is set according to steps S110 to S140. That is, the two processes of step S130 and step S140 are repeated until blood pressure decreases. Then, the target extracellular fluid volume gradually decreases, and eventually, blood pressure decreases. When blood pressure decreases, a final target extracellular fluid volume that is a predetermined amount greater than the target extracellular fluid volume at that time is calculated. The predetermined amount is an amount that can be calculated so that the final target extracellular fluid volume is slightly greater than the target extracellular fluid volume at the time when blood pressure decreases. In this embodiment, the predetermined amount is set to 3% of the target extracellular fluid volume at the time when blood pressure decreases. Note that the predetermined amount is not particularly limited and may be a percentage greater than 3% of the target extracellular fluid volume at the time when blood pressure decreases (e.g., 4% or 5%), or a percentage less than 3% of the target extracellular fluid volume at the time when blood pressure decreases (e.g., 2%). Furthermore, the predetermined amount may not be a percentage of the target extracellular fluid volume at the time when blood pressure decreases, but may be a fixed amount. The final target extracellular fluid volume does not change even if the patient's fat mass changes. Thereafter, the body weight corresponding to the final target extracellular fluid volume is calculated and used as the target body weight (see Figures 4 and 5). The target body weight in this case will be described in detail later.

[0037] Referring to FIG. 2, the calculation method for the target body weight in step S130 (when the post-dialysis extracellular fluid volume at the start of the current extracellular fluid volume inter-measurement period is greater than the target extracellular fluid volume for the previous extracellular fluid volume inter-measurement period and the target extracellular fluid volume for the previous extracellular fluid volume inter-measurement period is set as the target extracellular fluid volume for the current extracellular fluid volume inter-measurement period) will be described. FIG. 2 illustrates a case where the fat mass at the start of the current extracellular fluid volume inter-measurement period is less than the fat mass at the start of the previous extracellular fluid volume inter-measurement period, i.e., the patient has lost weight, under the condition that no decrease in blood pressure has occurred. FIG. 2 is a graph that classifies the weight of a dialysis patient into each component, and schematically shows the breakdown of extracellular fluid volume, fat mass, and other components. For ease of explanation, it is assumed that intradialysis was performed during the previous extracellular fluid volume inter-measurement period so that the post-dialysis weight matched the target body weight. Therefore, it is assumed that the post-dialysis weight for the first dialysis session of the current extracellular fluid volume inter-measurement period matches the post-dialysis weight for the previous extracellular fluid volume inter-measurement period. In this case, since water removal was performed during the previous inter-measurement period so that post-dialysis weight matched the target weight, the post-dialysis extracellular fluid volume at the start of the current inter-measurement period is greater than the target extracellular fluid volume during the previous inter-measurement period due to the loss of fat mass.

[0038] However, no hypotension occurred during the previous inter-extracellular fluid volume measurement period. Therefore, even if fluid removal is performed during the current inter-extracellular fluid volume measurement period to maintain the post-dialysis extracellular fluid volume at the same level as the target extracellular fluid volume during the previous inter-extracellular fluid volume measurement period, post-dialysis hypotension is not expected to occur. Therefore, the target extracellular fluid volume during the previous inter-extracellular fluid volume measurement period is continued as the target extracellular fluid volume for the current inter-extracellular fluid volume measurement period, and fluid removal is continued until the post-dialysis extracellular fluid volume matches this target extracellular fluid volume. Theoretically, the post-dialysis weight achieved as a result will be lower than the post-dialysis weight during the first dialysis period during the current inter-extracellular fluid volume measurement period by the difference between the post-dialysis extracellular fluid volume during the first dialysis period and the target extracellular fluid volume during the previous inter-extracellular fluid volume measurement period. In other words, the target weight for the current extracellular fluid volume measurement period is the post-dialysis weight for the first dialysis of the current extracellular fluid volume measurement period minus the difference between the post-dialysis extracellular fluid volume for the first dialysis of the current extracellular fluid volume measurement period and the target extracellular fluid volume for the previous extracellular fluid volume measurement period.

[0039] Next, referring to FIG. 3, we will explain how to calculate the target body weight in step S140 (when the post-dialysis extracellular fluid volume at the start of the current extracellular fluid volume inter-measurement period is equal to or less than the target extracellular fluid volume for the previous extracellular fluid volume inter-measurement period and the post-dialysis extracellular fluid volume at the start of the current extracellular fluid volume inter-measurement period is set as the new target extracellular fluid volume). FIG. 3 illustrates a case where the fat mass at the start of the current extracellular fluid volume inter-measurement period is greater than the fat mass at the start of the previous extracellular fluid volume inter-measurement period, i.e., the patient has gained weight, under the condition that no blood pressure drop has occurred. FIG. 3 is a graph that classifies the weight of a dialysis patient into components, and schematically shows the breakdown of extracellular fluid volume, fat mass, and other components. For ease of explanation, we will assume that intradialysis was performed during the previous extracellular fluid volume inter-measurement period so that the post-dialysis weight matched the target body weight. Therefore, we will assume that the post-dialysis weight at the first dialysis session of the current extracellular fluid volume inter-measurement period matches the post-dialysis weight during the previous extracellular fluid volume inter-measurement period. In this case, since water was removed during the previous inter-extracellular fluid volume measurement period so that the post-dialysis weight matched the target weight, the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period is less than the target extracellular fluid volume during the previous inter-extracellular fluid volume measurement period due to the increase in fat mass.

[0040] Since no hypotension occurred at the start of the current inter-extracellular fluid volume measurement period, it is believed that post-dialysis hypotension will not occur even if water removal is performed until the post-dialysis extracellular fluid volume reaches the post-dialysis extracellular fluid volume during the first dialysis session of the current inter-extracellular fluid volume measurement period. Therefore, from then on, the post-dialysis extracellular fluid volume during the first dialysis session of the current inter-extracellular fluid volume measurement period will be set as the target extracellular fluid volume for the current inter-extracellular fluid volume measurement period, and water will be removed until the post-dialysis extracellular fluid volume matches this target extracellular fluid volume. The resulting post-dialysis weight is theoretically equal to the post-dialysis weight during the first dialysis session of the current inter-extracellular fluid volume measurement period. Therefore, the post-dialysis weight during the first dialysis session of the current inter-extracellular fluid volume measurement period will be set as the target weight.

[0041] Next, with reference to Figures 4 and 5, the method for calculating the target weight in step S160 (after a blood pressure drop occurs) will be described. Figure 4 shows a case where, during an inter-extracellular fluid volume measurement period after a blood pressure drop, the patient's fat mass has increased at the start of the current inter-extracellular fluid volume measurement period compared to the start of the previous inter-extracellular fluid volume measurement period, i.e., the patient is obese. Figure 4 is a graph breaking down the weight of a dialysis patient into components, and schematically shows the breakdown of extracellular fluid volume, fat mass, and other components. For ease of explanation, it is assumed that during the previous inter-extracellular fluid volume measurement periods, intradialysis was performed to ensure that the post-dialysis weight matched the target weight. In other words, it is assumed that the post-dialysis weight for the first dialysis session during the current inter-extracellular fluid volume measurement period was the same as the post-dialysis weight for the previous inter-extracellular fluid volume measurement period. In this case, because the post-dialysis weight was matched to the target weight, the post-dialysis extracellular fluid volume for the first dialysis session during the current inter-extracellular fluid volume measurement period is less than the final target extracellular fluid volume by the amount of the increase in fat mass. Therefore, a new target weight is calculated so that the post-dialysis extracellular fluid volume during the current inter-extracellular fluid measurement period is the same as the final target extracellular fluid volume. In other words, the target weight during the current inter-extracellular fluid measurement period is set to be greater than the post-dialysis weight during the first dialysis session during the current inter-extracellular fluid measurement period by the difference between the final target extracellular fluid volume and the post-dialysis extracellular fluid volume during the first dialysis session during the current inter-extracellular fluid measurement period.

[0042] Figure 5 shows a case where, during an inter-extracellular fluid volume measurement period after a blood pressure drop, the patient's fat mass has decreased at the start of the current inter-extracellular fluid volume measurement period compared to the start of the previous inter-extracellular fluid volume measurement period, i.e., the patient is thin. Figure 5 is a graph showing a dialysis patient's weight categorized by components, and schematically illustrates the breakdown of extracellular fluid volume, fat mass, and other components. For ease of explanation, it is assumed that during the previous inter-extracellular fluid volume measurement period, intradialytic water removal was performed to ensure that post-dialysis weight matched the target weight. That is, it is assumed that the post-dialysis weight for the first dialysis session during the current inter-extracellular fluid volume measurement period matched the post-dialysis weight for the previous dialysis session. In this case, because water removal was performed to ensure that post-dialysis weight matched the target weight, the post-dialysis extracellular fluid volume for the first dialysis session during the current inter-extracellular fluid volume measurement period was greater than the final target extracellular fluid volume by the amount of fat mass reduction. However, from then on, water removal is performed to ensure that post-dialysis extracellular fluid volume matches the final target extracellular fluid volume. Therefore, the resulting post-dialysis weight is less than the post-dialysis weight at the first dialysis session of the current inter-extracellular fluid measurement period by the difference between the post-dialysis extracellular fluid volume at the first dialysis session of the current inter-extracellular fluid measurement period and the final target extracellular fluid volume. In other words, the target weight at the current inter-extracellular fluid measurement period is the post-dialysis weight at the first dialysis session of the current inter-extracellular fluid measurement period minus the difference between the post-dialysis extracellular fluid volume at the first dialysis session of the current inter-extracellular fluid measurement period and the final target extracellular fluid volume.

[0043] Next, the configuration of the target body weight calculation device 10 according to this embodiment will be described. As shown in FIG. 6, the target body weight calculation device 10 includes an arithmetic unit 12 and an interface device 20. The arithmetic unit 12 can be configured, for example, by a computer including a CPU, ROM, RAM, etc. The arithmetic unit 12 is connected to the interface device 20 and acquires information input to the interface device 20. The arithmetic unit 12 includes a memory unit 14 and a calculation unit 16. The calculation unit 16 calculates the target body weight, etc. using the information acquired from the interface device 20. The memory unit 14 stores the target extracellular fluid volume, final target extracellular fluid volume, target body weight, etc.

[0044] The interface device 20 is a display device that provides (outputs) various information calculated by the target body weight calculation device 10 to the operator, and is also an input device that receives instructions and information from the operator. For example, the interface device 20 can display the calculated target extracellular fluid volume, final target extracellular fluid volume, target body weight, etc. to the operator. The interface device 20 can also receive input of blood pressure decrease information. Blood pressure decrease information is information that indicates that a precursor to blood pressure decrease has been observed or that blood pressure decrease has occurred during dialysis.

[0045] Next, the process of calculating a target body weight using target body weight calculation device 10 will be described. Referring to Figure 7, first, the process of calculating a target body weight using target body weight calculation device 10 until a drop in blood pressure occurs will be described. As shown in Figure 7, calculation unit 16 calculates a target body weight based on the target extracellular fluid volume during the previous inter-extracellular fluid volume measurement period (hereinafter simply referred to as the "previous post-dialysis extracellular fluid volume") and the post-dialysis extracellular fluid volume at the start of the current inter-extracellular fluid volume measurement period (hereinafter simply referred to as the "current post-dialysis extracellular fluid volume"), so calculation unit 16 first acquires the current post-dialysis extracellular fluid volume (S14).

[0046] Next, the calculation unit 16 determines whether or not a drop in blood pressure has occurred (S16). When a drop in blood pressure occurs, the medical staff inputs information about the drop in blood pressure to the calculation unit 16 via the interface device 20. The calculation unit 16 determines whether or not the information about the drop in blood pressure has been input from the interface device 20.

[0047] If no decrease in blood pressure has occurred (NO in step S16), the calculation unit 16 determines that water removal has been completed to the current target weight. Then, the calculation unit 16 determines whether the extracellular fluid volume after this dialysis acquired in step S14 is greater than the extracellular fluid volume after the previous dialysis (S18).

[0048] If the extracellular fluid volume after this dialysis is greater than the extracellular fluid volume after the previous dialysis (YES in step S18), the calculation unit 16 calculates the target weight so that it is less than the post-dialysis weight corresponding to the extracellular fluid volume after this dialysis (hereinafter also referred to as the "current target weight") by the difference between the extracellular fluid volume after this dialysis and the extracellular fluid volume after the previous dialysis, as shown in Figure 2 (S20).

[0049] On the other hand, if the extracellular fluid volume after this dialysis is less than or equal to the extracellular fluid volume after the previous dialysis (NO in step S18), the calculation unit 16 calculates the target weight so that it matches the current target weight (S22), as shown in Figure 3.

[0050] Furthermore, if a decrease in blood pressure occurs (YES in step S16), the calculation unit 16 calculates the final target extracellular fluid volume (S24). Specifically, the calculation unit 16 adds a predetermined amount to the extracellular fluid volume after the previous dialysis. In this embodiment, the calculation unit 16 adds 3% of the target extracellular fluid volume when a decrease in blood pressure occurs to the target extracellular fluid volume. Next, the calculation unit 16 stores the final target extracellular fluid volume calculated in step S24 in the memory unit 14 (S26). Next, the calculation unit 16 calculates the target weight so that the extracellular fluid volume becomes the final target extracellular fluid volume (S28). In the current dialysis, a decrease in blood pressure occurred during dialysis (YES in step S16). Therefore, the post-dialysis extracellular fluid volume is a volume that indicates a precursor to a decrease in blood pressure or that will cause a decrease in blood pressure during dialysis. That is, as shown in FIG. 4, the post-dialysis extracellular fluid volume is less than the final target extracellular fluid volume. Therefore, the calculation unit 16 increases the target weight by the difference between the final target extracellular fluid volume and the post-dialysis extracellular fluid volume.

[0051] Once the target weight is calculated in step S20, S22, or S28, the calculation unit 16 stores the calculated target weight in the memory unit 14 (S34). Next, the calculation unit 16 outputs the target weight to the interface device 20 (S36). This allows the calculated target weight, i.e., the target weight for the current inter-extracellular fluid volume measurement period, to be presented to the healthcare professional. The healthcare professional can then perform fluid removal so that the post-dialysis weight for each dialysis session during the current inter-extracellular fluid volume measurement period matches the presented target weight. The target weight for the current inter-extracellular fluid volume measurement period may be output to a medical record or displayed on the monitor of the dialysis machine during each dialysis session during the current inter-extracellular fluid volume measurement period. The target extracellular fluid volume stored in the memory unit 14 is used as the previous target extracellular fluid volume when calculating the target extracellular fluid volume and target weight for the next inter-extracellular fluid volume measurement period from the post-dialysis extracellular fluid volume and post-dialysis weight obtained at the start of the next inter-extracellular fluid volume measurement period.

[0052] Next, with reference to Figure 8, a process for calculating a target weight using target weight calculation device 10 after a drop in blood pressure has occurred will be described. As shown in step S160 above, once a drop in blood pressure has occurred and the final target extracellular fluid volume has been specified, the final target extracellular fluid volume is stored in memory unit 14. In the process of Figure 8, the target weight is calculated using the final target extracellular fluid volume stored in memory unit 14.

[0053] First, the calculation unit 16 acquires the current post-dialysis extracellular fluid volume and post-dialysis body weight (S42). Next, the calculation unit 16 compares the current post-dialysis extracellular fluid volume with the final target extracellular fluid volume stored in the memory unit 14 to determine whether the current post-dialysis extracellular fluid volume is greater than the final target extracellular fluid volume (S44). If the current post-dialysis extracellular fluid volume is greater than the final target extracellular fluid volume (YES in step S44), the calculation unit 16 determines the future target body weight as the value obtained by subtracting the difference between the current post-dialysis extracellular fluid volume and the final target post-dialysis extracellular fluid volume from the current post-dialysis body weight (S46), as shown in FIG. 5. On the other hand, if the final target extracellular fluid volume is greater than the current post-dialysis extracellular fluid volume (NO in step S44), the calculation unit 16 determines the future target body weight as the value obtained by adding the difference between the final target extracellular fluid volume and the current post-dialysis extracellular fluid volume to the current post-dialysis body weight (S48), as shown in FIG. 4. Once the future target weight is calculated in the process of step S46 or 48, the calculation unit 16 stores the calculated target weight in the memory unit 14 (S50) and outputs the target weight to the interface device 20 (S52).

[0054] By executing the processing of Figure 8, even if the post-dialysis extracellular fluid volume begins to deviate significantly from the final target extracellular fluid volume for some reason after a drop in blood pressure has occurred, it is possible to maintain the post-dialysis extracellular fluid volume roughly at the final target extracellular fluid volume by appropriately adjusting the target weight.

[0055] In a test conducted by the inventors, it was confirmed that when water is removed to achieve the target weight calculated by the process shown in this example, it becomes less likely that edema will occur after dialysis or that blood pressure will drop during dialysis.

[0056] In this study, 39 dialysis patients were divided into 12 with post-dialysis edema, 4 with frequent intradialytic hypotension, and 23 with no post-dialysis edema or intradialytic hypotension, i.e., asymptomatic. After four months of treatment with the treatment described in this example, the number of patients with post-dialysis edema decreased to three, and none of the patients with frequent intradialytic hypotension disappeared. The number of asymptomatic patients increased to 36. Furthermore, three dialysis patients who still had post-dialysis edema after four months of treatment with the treatment described in this example were examined. Of these three patients, one had hypoalbuminemia and two had severe autonomic dysfunction. In such patients, edema often occurs even at extracellular fluid volumes slightly higher than the extracellular fluid volume at which blood pressure drops during dialysis. Thus, it was confirmed that the treatment described in this example prevented post-dialysis edema or intradialytic hypotension in most dialysis patients.

[0057] 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 exhibit technical utility alone or in various combinations, and are not limited to the combinations described 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 itself has technical utility. [Explanation of symbols]

[0058] 10: Target weight calculation device 12: Arithmetic device 14: Storage part 16: Arithmetic section 20: Interface device

Claims

1. A target weight calculation device for calculating a target weight, which is a target weight at the time of completing water removal by dialysis, a memory unit capable of storing a target extracellular fluid volume, which is the extracellular fluid volume at a target weight; A target weight calculation device comprising: a calculation unit that calculates the target weight for the next dialysis session from the difference between the target extracellular fluid volume for the previous dialysis session and the post-dialysis extracellular fluid volume for the current dialysis session, and the post-dialysis weight for the current dialysis session, when the final target extracellular fluid volume, which is the appropriate extracellular fluid volume for a dialysis patient, has not been determined.

2. The calculation unit If the post-dialysis extracellular fluid volume in the current dialysis is greater than the target extracellular fluid volume in the previous dialysis stored in the memory unit, the target weight for the next dialysis is set to a weight that is less than the post-dialysis weight in the current dialysis by the difference between the post-dialysis extracellular fluid volume in the current dialysis and the target extracellular fluid volume in the previous dialysis, and A target weight calculation device as described in claim 1, wherein, if the post-dialysis extracellular fluid volume in the current dialysis is equal to or less than the target extracellular fluid volume in the previous dialysis stored in the memory unit, the post-dialysis extracellular fluid volume in the current dialysis is set as the target extracellular fluid volume in the next dialysis, and the post-dialysis weight in the current dialysis is set as the target weight for the next dialysis.

3. The device further includes an input unit for inputting blood pressure decrease information indicating that a sign of blood pressure decrease has occurred or that blood pressure has decreased during dialysis. The target weight calculation device according to claim 1 , wherein the storage unit stores the blood pressure decrease information input to the input unit.

4. The target weight calculation device of claim 3, wherein when the blood pressure drop information is input to the input unit, the calculation unit calculates as a final target extracellular fluid volume a volume of extracellular fluid that is a predetermined amount higher than the target extracellular fluid volume in the dialysis performed when the blood pressure drop information was input.

5. The target body weight calculation device according to claim 4 , wherein the storage unit is capable of storing the final target extracellular fluid volume.

6. A target weight calculation device as described in claim 5, wherein when the final target extracellular fluid volume is stored in the memory unit, the calculation unit calculates the target weight for the next dialysis session from the post-dialysis extracellular fluid volume for the current dialysis session, the final target extracellular fluid volume, and the post-dialysis weight for the current dialysis session.

7. The calculation unit If the post-dialysis extracellular fluid volume in the current dialysis is greater than the final target extracellular fluid volume stored in the memory unit, the target weight for the next dialysis is set to a weight that is less than the post-dialysis weight in the current dialysis by the difference between the post-dialysis extracellular fluid volume in the current dialysis and the final target extracellular fluid volume; A target weight calculation device as described in claim 6, wherein, when the post-dialysis extracellular fluid volume in the current dialysis is equal to or less than the final target extracellular fluid volume stored in the memory unit, the target weight for the next dialysis is set to a weight that is greater than the post-dialysis weight in the current dialysis by the difference between the final target extracellular fluid volume and the post-dialysis extracellular fluid volume in the current dialysis.

8. 8. The target body weight calculation device according to claim 1, further comprising an output unit that outputs the target body weight calculated by the calculation unit.

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