Using Base Excess
Arterial blood gas analysis was part of everyday intensive care practice for much of the second half of the last century, yet in 2001 considerable differences of opinion and entrenched viewpoints still characterize the evaluation of acid-base disturbances. There are of course relatively non-controversial areas. All agree that in healthy people living near sea-level, the arterial pH will be close to 7.4, and the arterial pCO2 (paCO2) will be close to 40 mmHg. Most define acidemia as arterial pH < 7.35, and alkalemia as pH > 7.45, and agree that in isolated respiratory acidosis, paCO2 exceeds 45 mmHg, and in isolated respiratory alkalosis, paCO2 is less than 35 mmHg. It is also widely understood that metabolic (non-respiratory) acid-base abnormalities are those which manifest on blood gas analysis as a disturbed pH / paCO2 relationship (Fig. 1).
KeywordsBase Excess Metabolic Alkalosis Base Deficit Buffer Base Unmeasured Anion
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