Cardiovascular support during combined extradural and general anaesthesia

Abstract

We have examined the effect of prophylactic treatment with i.v. fluid 1000 ml, ephedrine 24 mg or methoxamine 4 mg on cardiovascular responses to both extradural and combined extradural and general isoflurane anaesthesia in 45 adult patients undergoing knee arthroplasty. Heart rate (HR) and systemic arterial pressure (AP) were measured using automated oscillotonometry and cardiac output was measured using continuous wave suprasternal Doppler ultrasonography. After lumbar extradural anaesthesia (LEA) there were no significant differences in arterial pressure between treatments, although cardiac index was significantly greater after fluid preloading (mean 4.3 (95% confidence interval 3.7-4.9) litre min-1 m-2) than after ephedrine (3.1 (2.6-3.6) litre min-1 m-2) or methoxamine (2.6 (2.0-3.2) litre min-1 m-2). During combined LEA and general anaesthesia, systolic AP was significantly greater after ephedrine (114 (103-125) mm Hg) than after either preloading (98 (88-107) mm Hg) or methoxamine (97 (89-105) mm Hg). The reduction in AP after induction of general anaesthesia was associated with a decrease in cardiac index after fluid preloading and a decrease in vascular resistance after methoxamine.