Systems and methods to reduce fluid contamination

Abstract

Methods and systems for determining the concentration of one or more analytes from a sample such as blood or plasma are described. The systems described herein can be configured to withdraw a certain volume of sample from a source of bodily fluid, direct a first portion of the withdrawn sample to an analyte monitoring system and return a second portion of the sample to the patient. The analyte monitoring system can include an automated blood withdrawal system that is configured to withdraw blood from the patient's vasculature at low pressure and/or withdrawal rates so as to reduce or prevent contamination of the withdrawn fluid from the infusion fluids.

1 .- 16 . (canceled) 
     
     
         17 . A method for automatically drawing high quality blood samples to improve periodic blood analysis and reduce contamination risk, the method comprising:
 providing a tube configured to connect to a multi-lumen catheter without leaking, the multi-lumen catheter having an upstream port and a downstream port, each port having an independent lumen not in fluid communication with the other;   positioning the multi-lumen catheter in a patient's vessel such that the lumen of the upstream port opens into the vessel upstream of the lumen of the downstream port;   providing an automated fluid pressure system configured to automatically maintain a low pressure and/or flow rate while drawing blood;   connecting the automated fluid pressure system to the tube such that the system is in fluid communication with the upstream port and blood flow in the patient's vessel; and   using the automated fluid pressure system to periodically draw blood in through the lumen of the upstream port while maintaining a low pressure and/or flow rate, thereby avoiding a reversal of blood flow in the patient's vessel and reducing the risk of contamination of a blood sample.   
     
     
         18 . The method of  claim 17 , wherein infusate is infused into the vessel through the downstream port, the method further comprising reducing the amount of infusate drawn into the lumen of the upstream catheter so that infusate does not cause more than a 20% difference in accuracy of an analyte reading of the blood drawn into the tube as compared to a reading of blood drawn when no infusate is being infused into the vessel. 
     
     
         19 . The method of  claim 17 , wherein the automated fluid pressure system comprises a syringe pump. 
     
     
         20 . The method of  claim 17 , wherein infusate is periodically infused into the vessel through the downstream port, the method further comprising using the automated fluid pressure system to reduce the pressure and/or flow rate of withdrawn blood when infusion of infusate and blood withdrawal occur simultaneously. 
     
     
         21 . The method of  claim 17 , further comprising determining the patient's blood pressure and using the automated fluid pressure system to maintain a withdrawal pressure that is less than the patient's blood pressure, thereby avoiding reversal of blood flow in the vessel. 
     
     
         22 . The method of  claim 17 , further comprising using the automated fluid pressure system to periodically draw blood in through the lumen of the upstream port at a rate that is between 1 mL/minute and 10 mL/minute, thereby maintaining the low pressure below the pressure of blood in the vessel. 
     
     
         23 . The method of  claim 17 , further comprising using the automated fluid pressure system to periodically draw at least 2 ml of blood from the vessel over a draw period that is at least 15 seconds. 
     
     
         24 . The method of  claim 17 , wherein the tube has an inner diameter of between 0.01 inches and 0.04 inches. 
     
     
         25 . The method of  claim 17 , further comprising providing a pressure monitor, the pressure monitor monitoring the pressure at or near the upstream port and providing feedback to the automated fluid pressure system to maintain the low pressure below 99% of the pressure of blood in the vessel. 
     
     
         26 . The method of  claim 17 , wherein the automated fluid pressure system maintains the low pressure between 1 psi and 10 psi.