Acid base status in unanesthetized, unrestrained guinea pigs

Acid-base status of arterial blood was measured in chronically cannulated, unanesthetized, unrestrained guinea pigs. Normal values were: pH = 7.444 +/- 0.032; PaCO2 = 35.7 +/- 4.4; HCO3- = 24.4 +/- 2.8; BE = +0.4 +/- 2.1 (n = 69) and PaCO2 = 91.9 +/- 7.3 (n = 25) (Values are mean +/- S.D.). Induction of light anesthesia with thiopentone caused a respiratory depression (decrease in PaO2) accompanied by respiratory acidosis (increase in PaCO2 and decrease in pH) and a development of slight metabolic acidosis (decrease in base excess and standard bicarbonate). Acid base parameters of guinea pigs are compared to those obtained from rats under identical experimental conditions.