Comparison of isoflurane and propofol-fentanyl anaesthesia in a swine model of asphyxia

Background. There have been few studies comparing the responseto asphyxia and the effectiveness of typical cardiopulmonaryresuscitation (CPR) using exogenous epinephrine administrationand manual closed-chest compression between total intravenousanaesthesia (TIVA) and inhalational anaesthesia. Methods. Twenty pigs were randomly assigned to two study groupsanaesthetized using either 2% end-tidal isoflurane (n=10) orpropofol (12 mg kg^–1 h^–1)–fentanyl (50 µgkg^–1) (n=10). Asphyxia was induced by clamping the trachealtube until the mean arterial pressure (MAP) decreased to 40%of the baseline value (40% MAP time). The tracheal tube wasdeclamped at that point, and CPR was performed. Haemodynamicparameters and blood samples were obtained before the inductionof asphyxia, at 1-min intervals during asphyxia, and 1, 2, 3,5, 10, 30 and 60 min after asphyxia. Results. TIVA maintained the MAP against hypoxia–hypercapniastress significantly longer than isoflurane anaesthesia (mean(SD) 40% MAP time 498 (95) and 378 (104) s respectively). Inall animals in the isoflurane group, spontaneous circulationreturned within 1 min of the start of CPR. In six of the TIVAanimals, spontaneous circulation returned for 220 (121) s; spontaneouscirculation did not return within 5 min in the remaining fouranimals. Conclusions. Although TIVA is less prone than isoflurane anaesthesiato primary cardiovascular depression leading to asphyxia, TIVAis associated with reduced effectiveness of CPR in which resuscitationbecause of asphyxic haemodynamic depression occurs. Br J Anaesth 2003; 91: 871–7