EFFECTS OF PROPOFOL ON PULMONARY AND SYSTEMIC ARTERIAL PRESSURE-FLOW RELATIONSHIPS IN HYPEROXIC AND HYPOXIC DOGS

We have investigated the effects of a continuous infusion (18 mg kg−1 h−1) of the aqueous emulsion formulation of propofol on mean pulmonary arterial (PAP)/cardiac output (Q) and mean systemic arterial pressure (SAP)/Q relationships in 15 intact pentobarbitone-anaesthetized dogs subjected to hyperoxia (F1O2, 0.4) and hypoxia (F1O2 0.1). Five-point PAP/Q and SAP/Q plots were obtained by opening an arterio-venous femoral fistula or by step wise inflations of an inferior vena cava balloon. Over the range of Q studied (2–5 litre min−1), hypoxia increased PAP in eight dogs (“responders”) and did not affect PAP in seven others (“non-responders”). Hypoxia pulmonary vasoconstriction (HPV) was restored in non-responders by the administration of acetylsalicylic acid (ASA) 1 g i.v. Hypoxia did not affect SAP over the range of Q studied in the responders or in the non-responders treated with ASA. Propofol had no effect on hyperoxic or on hypoxic PAP at all values of Q either in responders or in non-responders with HPV restored by ASA. Propofol did not change Q at uncontrolled flow, but decreased SAP at the lowest Q (2 and 3 litre min−1) during hyperoxia and at all values of Q during hypoxia. The systemic vascular effects were the same in animals of both groups, treated with ASA or not. We conclude that propofol does not influence pulmonary vascular tone and does not inhibit HPV, but reduces systemic vascular tone when venous return or oxygenation is decreased. The haemodynamic response to propofol was not affected by cyclo-oxygenase inhibition.