Detection of Heparin in Salvaged Blood

Abstract

Marketing Manager; Metronic Blood Management; 18501 East Plaza Drive; Parker, Colorado 80124.In Reply:-Dr. Loubser is correct in stating that HPT results with run times longer than 249 s are considered to be invalid in the Hepcon[registered sign] HMS. However, the most common cause for a prolonged run time is inappropriate cartridge selection as opposed to depletion of coagulation factors. Our Heparin Protamine Titration (HPT) is considered to be a quantitative test and performs very reliably even in cases where the fibrinogen is diluted or depleted to levels considered to be physiologically low (e.g., 50 mg/dl). The HPT will typically perform within specification when patients are bleeding due to coagulopathy and is not considered to be an indicator of coagulopathy, only heparin concentration.The HMS will provide a warning if the test has exceeded 249 s. Because the design of the HPT is for use with fresh whole blood (not components or citrated samples), any follow up action recommended assumes the use of a fresh whole blood sample. The HPT cartridge can measure a limited range of possible heparin concentrations. If a user selects the incorrect cartridge range, a channel will usually detect, but with a long run time. This is an indication to repeat the test with another test range. [1]This is rarely an indication of coagulation factor depletion, therefore we do not see it as appropriate to indicate such a state in a warning.Studies from our Sequestra[trademark symbol] and AT 1000[trademark symbol] devices indicate that cell washing generally can remove 90% or more of the residual heparin, plasma, and associated factors from blood, [2]rendering the sample essentially fibrinogen free. This type of sample is not within the scope for which our HPT test was developed.When asked if the HPT will detect heparin in a washed cell pack, we recommend specific methods that provide adequate fibrinogen to obtain a reliable result. One method suggests measuring residual heparin in the patient's blood after the washed product is returned. A second method utilizes PRP or PPP to provide clotting factors for measuring heparin in a cartridge such as our Theracon HPT. Theracon HPTs can measure very low levels of heparin and can be used with a citrated sample.Cynthia A. TaylorMarketing ManagerMedtronic Blood Management; 18501 East Plaza Drive; Parker, Colorado 80124(Accepted for publication June 24, 1997.)