Methods, systems, and kits for the extracorporeal processing of blood

Abstract

Methods, systems, and kits for extracorporeally circulating and processing blood are described. The systems include a pump, a processing unit, and blood drawn return lines for accessing a patient's vasculature. Blood flow through the return line is measured and pump speed controlled to maintain a desired blood flow rate. Alarm conditions can be initiated when expected pump performance differs from that needed to maintain the control point flow rate. By using a ultrasonic flow detector, gas bubbles in the blood flow can be detected.

What is claimed is:  
     
         1 . A method for extracorporeally processing blood, said method comprising: 
 drawing blood from a patient;    pumping the blood with a pump at a predetermined blood flow rate;    measuring an actual blood flow rate delivered by the pump;    comparing the actual blood flow rate with the predetermined blood flow rate; and    adjusting the blood flow rate delivered by the pump.    
     
     
         2 . The method of    claim 1   , further comprising the step of signaling an alarm condition if a difference of a predetermined minimum value exists.  
     
     
         3 . The method of    claim 1   , wherein the actual blood flow rate is directly measured.  
     
     
         4 . The method of    claim 1   , wherein the step of pumping the drawn blood with a pump at a predetermined blood flow rate includes pumping the drawn blood with a pump at a predetermined stroke volume and blood flow rate.  
     
     
         5 . The method of    claim 1   , wherein the drawn blood is pumped at a blood flow rate that corresponds to a theoretical pumped blood flow rate.  
     
     
         6 . The method of    claim 1   , wherein the pump is a peristaltic pump.  
     
     
         7 . The method of    claim 1   , further comprising the step of slowing or stopping pump operation when said difference has said predetermined minimum value.  
     
     
         8 . The method of    claim 1    wherein the measuring step comprises ultrasonically measuring the flow rate using a sensor disposed externally to the blood flow.