Monitoring recirculation

A method comprising:

• receiving, by a hemodialysis device, blood from a patient via an arterial line;
• delivering, by the hemodialysis device, blood to the patient via a venous line;
• generating, by the hemodialysis device, a first signal indicative of a first hematocrit level of blood in one of the arterial line or the venous line;
• generating, by the hemodialysis device, a second signal indicative of a second hematocrit level of blood in another of the arterial line or the venous line;
• determining, by the hemodialysis device, a change in blood volume of the patient over time based on the first signal indicative of the first hematocrit level;
• determining, by the hemodialysis device, a threshold blood volume reduction over time for the patient;
• comparing, by the hemodialysis device, the change in the blood volume of the patient over time to the threshold blood volume reduction over time;
• and
• based on the comparison, generating, by the hemodialysis device, an indication of vascular access recirculation, wherein the indication comprises a notification for output, the notification indicative of vascular access recirculation;
• and
• in response to receiving a user input or generating the indication of vascular access recirculation:
• determining, by the hemodialysis device, an extracorporeal blood volume;
• determining, by the hemodialysis device, a blood flow rate through the hemodialysis device;
• based on the extracorporeal blood volume and the blood flow rate through the hemodialysis device, determining, by the hemodialysis device, a transit time for blood from entering the arterial line to exiting the venous line;
• and
• based on the transit time, determining, by the hemodialysis device, a first period of time;
• temporarily increasing, by the hemodialysis device, an ultrafiltration rate for the first period of time;
• after the first period of time, determining a first hematocrit level based on the first signal;
• after the first period of time, determining the second hematocrit level based on the second signal;
• comparing the first and second hematocrit levels;
• and
• determining an amount of vascular access recirculation based on the comparison of the first and second hematocrit levels.

Non-transitory computer-readable storage media comprising instructions, that, when executed by processing circuitry, cause the processing circuitry to:

• determine a change in blood volume of a patient over time based on a first signal indicative of a first hematocrit level of blood from a patient in one of an arterial line or a venous line of a hemodialysis device;
• determine a threshold blood volume reduction over time for the patient;
• compare the change in the blood volume of the patient over time to the threshold blood volume reduction over time;
• and
• based on the comparison, generate an indication of vascular access recirculation, wherein the indication comprises a notification for output, the notification indicative of vascular access recirculation, and
• wherein the instructions cause the processing circuitry to, in response to receiving a user input or generating the indication of vascular access recirculation:
• determine an extracorporeal blood volume;
• determine a blood flow rate through the hemodialysis device;
• based on the extracorporeal blood volume and the blood flow rate through the hemodialysis device, determine a transit time for blood from entering the arterial line to exiting the venous line;
• based on the transit time, determine a first period of time;
• cause the hemodialysis device to temporarily increase an ultrafiltration rate for the first period of time;
• after the first period of time, determine the first hematocrit level based on the first signal;
• after the first period of time, determine a second hematocrit level based on a second signal indicative of a second hematocrit level in another of the arterial line or the venous line;
• compare the first and second hematocrit levels;
• and
• determine an amount of vascular access recirculation based on the comparison of the first and second hematocrit levels.