Oxygen-linked binding of halothane to human adult haemoglobin

The affinity for oxygen of normal human haemoglobin (Hb) solutions was measured in the presence of increasing concentrations of halothane. We observed a maximum increase in P50 of 25% with halothane 40 kPa compared with control (oxygen-argon gas mixtures) indicating the oxygen-linked character of the binding of halothane to the Hb molecule. The effect of halothane on P50 was independent of pH between 7.0 and 8.0 and of chloride concentration between 10 and 100 mmol litre-1. This suggests that halothane-Hb interactions may occur through hydrophobic linkage as occurs with short chain aliphatic hydrocarbons. The oxygen-linked binding of halothane appears of minor importance in altering oxygen binding to Hb in vivo compared with other factors such as chloride ion or 2, 3-DPG.