The effect of althesin (CT 1341) on the oxyhaemoglobin dissociation curve in vitro

Blood from non-smoking donors was incubated with Althesin and the PO2 for half-saturation of haemoglobin at standard pH, PCO2 and temperature (P 50) was measured. The mean P 50 values of blood with blood concentrations of Althesin of 0.14 ml/dl and 0.42 ml/dl were greater (1.14 +/- 0.31 (SEM) mm Hg (P less than 0.005) and 2.22 +/- 0.35 (SEM) mm Hg (P less than 0.001), respectively) than that of control blood. These increases were dose-dependent (P less than 0.05). Erythrocyte 2,3-diphosphoglycerate (2,3-DPG) concentrations were not significantly different between the Althesin-treated and the control blood. Although a decrease in the affinity of haemoglobin for oxygen in vitro in the presence of Althesin was statistically significant, this would have no clinical significance if the drug was being used for the induction of anaesthesia only.