Are i-STAT Results Adversely Affected by an Artificial Blood Substitute In Vivo?

Military Medicine, May 2006 by Estrada, Roy R

The purpose of this study was to determine whether i-STAT measurements on blood treated with hemoglobin-based oxygen carrier-201 (HBOC-201) would provide laboratory test results comparable to those achieved with a known reliable piece of equipment (Radiometer) for swine blood treated with HBOC-201. HBOC-201 is an artificial blood substitute solution being considered for use by medics in the field for the treatment of combat casualties. The i-STAT is a portable compact piece of laboratory equipment used for rapid assessment of blood samples under field conditions, instead of larger, hospital-based, laboratory equipment. Blood from pigs was obtained before and after administration of HBOC-201. The blood was tested with the i-STAT and the Radiometer. No drastic inaccuracy in test results with the i-STAT can be predicted for battlefield casualty care with potential HBOC-201 use, because laboratory results with the i-STAT and Radiometer were comparable with respect to blood testing after the administration of HBOC-201.

Introduction

The Critical Care Aeromedical Transport Team and Expeditionary Medical Support Basic deployable teams use the i-STAT (Abbott Point of Care, East Windsor, New Jersey) ' as the only blood analyzer. If hemoglobin-based oxygen carrier-201 (HBOC-201) (Biopure Corp., Cambridge, Massachusetts)2 is used as an emergency resuscitation adjunct in the field, then it is imperative that the i-STAT, as the only analyzer available, be able to produce test results comparable to those achieved with proven reliable equipment, to ensure the highest-quality patient care possible in the field.

HBOC-201

HBOC-201 is a balanced salt solution containing 13 g/dL polymerized hemoglobin.

Military Implications

Hemorrhage is the main cause of death on the battlefield.3 Civilian trauma is just as seriously affected by hemorrhage,4 in this case associated with trauma and disease, resulting in hemorrhagic shock. The treatment of choice for hemorrhagic shock is volume resuscitation with intravenously administered solutions or blood.5 Use of a product with oxygen-carrying capacity (e.g., blood transfusion) may be beneficial.6 In an effort to alleviate the demands regarding storage, refrigeration, blood shortages, and infectious disease in blood donations, synthetic blood products have been developed.5,6 In particular, Biopure HBOC-201 is being studied by both civilian and military researchers.6 If HBOC-201 is used, then it is essential that any handheld or expedient means of obtaining laboratory results be able to produce test results comparable to those achieved with proven, reliable, laboratory equipment.

Biosensor Technology (i-STAT) for HBOC-201

There is a gap in information regarding the effect of HBOC-201 on laboratory results obtained with the i-STAT. It is possible that HBOC-201 could be administered on the battlefield.5,6 The ability to accurately evaluate patients' laboratory data is necessary for their care. If HBOC-201 alters the accuracy of measurements, then this may limit its use under battlefield conditions.

Oximetric Methods (Radiometer) for HBOC-201

The Radiometer (Radiometer America, Westlake, Ohio) is a standard hospital blood gas analyzer that is different from the i-STAT, in that the i-STAT uses ion-selective electrode (biosensor) technology. Because of the difference in technology, there is a possibility that i-STAT results would not agree sufficiently closely with Radiometer results for blood supplemented with HBOC-201. A method comparison between the i-STAT and ABL700 series Radiometer was performed by Papadea et al.,7 with human blood. The need to use blood for the method comparison was described as necessary beyond controls because of the "matrix effect," which is the fact that blood is heterogeneous and control samples are homogeneous.7 This confounding effect requires blood studies.7 Both the method comparison and the Deming regression (correlation coefficient) indicated that the i-STAT and Radiometer data for blood without HBOC-201 were comparable.7

Other studies reported both clinical (e.g., hemorrhage) and laboratory ramifications of the use of HBOC-201 for laboratory results with standard hospital laboratory equipment such as the Radiometer.8'10 The research on hemorrhage treated with HBOC-201 by McNeil et al.8 resulted in a report of Radiometer laboratory results. That study used the ABL625 Radiometer.8 Hemorrhaged pigs were resuscitated in three groups: HBOC201, lactated Ringer's, or lactated Ringer's followed by shed blood. It revealed no statistically significant difference in the laboratory results obtained with Radiometer testing of the blood of pigs treated with HBOC-201 and those treated with lactated Ringer's solution followed by shed blood.8

Laboratory ramifications were discussed in an in vitro study of human blood that was exposed to increasing concentrations of HBOC-201, measured for calcium with a Radiometer and hemoglobin, chloride, potassium, sodium, and calcium with a CO-oximeter (Chiron Diagnostic Corp.), similar to the Radiometer, by Callas et al.10 That study identified no interference in laboratory values with HBOC-201 concentrations as high as 6.5 g/L.10 However, no study to date has evaluated the i-STAT for the assessment of blood values with HBOC-201.