College of American Pathologists
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September 2001
Raymond D. Aller, MD

Download In Vitro Blood Gas Analyzers Survey

Vendors of commercially available blood gas analyzers have made steady, albeit sometimes slow, progress in adding analytes to the menus of
such devices.

In the early ’80s, these instruments were restricted to pO2, pCO2, and pH. Hemoglobin soon was added. Technologies were introduced in the early ’90s that allowed vendors to add a steady stream of additional analytes.

Many vendors in this arena view themselves as being in the critical care field—if the analyte is not done stat on ICU patients, they don’t add it to the menu. The need for rapid results is just as great in the emergency department, but this area requires a slightly different menu.

In the ER, the blood gases that serve as the genesis of these critical analyte instruments can often be replaced by a pulse oximeter. More important are potassium, calcium, creatinine, alanine aminotransferase, and lipase.

Two years ago, while observing the slow demise of the traditional "med-surg" nursing unit and the shift toward routinely discharging all but the sickest patients to home care, I began to wonder why we still do 24-hour turnaround time procedures in hospital laboratories. What procedures really need to be available in the hospital instead of being provided, with eight-hour turnaround time, by a regional core lab?

This led me to propose, in the August 1999 issue of CAP TODAY (page 48), a minimum menu for a hospital lab. That menu, with a few additions, includes blood gases, glucose, potassium, sodium, total CO2, creatinine, ionized calcium, ALT, alkaline phosphatase, lipase, bilirubin, hemoglobin, WBC, absolute neutrophil count, platelets, PT, PTT, fibrinogen, blood smear, Gram stain, and CSF cell count. Immunoassays include quantitative hCG, troponin, digoxin, phenytoin, RSV, rotavirus, D-dimer, ABO Rh, and red cell antibody screening. Clinical staff in some hospitals also might include lactate, oncotic pressure, ionized magnesium, and TSH. (If you take exception to any of these items or believe that a critical analyte was overlooked, please convey your opinion by sending an e-mail to

This list presumes that specimens can be transported to a regional core laboratory within a two-hour radius for other analyses. The regional core lab would handle such vital analytes as HIV antibody, HBsAg, therapeutic drug monitoring and toxicity, most microbiology, and the 85 or more other chemistries commonly performed.

We urge vendors to move toward critical chemistry instruments that could be teamed with one or perhaps two other devices to encompass this range of analytes. With such an analyzer array, it would be feasible to close down the "big iron" laboratory instruments and provide essential services for a critical care hospital/ER. Until such analyzers are available, however, every hospital, no matter how small, must continue to maintain comprehensive and expensive "big iron" instrumentation.

Pages 36-58 profile 23 in vitro blood gas analyzers from eight vendors. Before purchasing an analyzer, talk to users of these instruments about vendors’ performance claims, instrument reliability, and quality of customer support.

Dr. Aller is vice president for medical affairs and informatics at MDS Laboratory Services (U.S.). He can be reached at