Haemodynamic effects of thoracic epidural anaesthesia during proximal aortic cross-clamping in pigs

Cross-clamping (XC) of the thoracic aorta induces a hyperdynamic circulation proximal to the aortic clamp. In this investigation, the effects of thoracic epidural anaesthesia (TEA) on the haemodynamic response to XC were studied in pigs. Seventeen pigs were anaesthetized with ketamine, and the thoracic aorta was cross-clamped for 30 minutes. In eight of the animals (TEA-group) a thoracic epidural block (3 ml 0.5% bupivacaine) was added to the general anaesthesia. Prior to XC there was a lower heart rate (HR), cardiac output (CO) and mixed venous oxygen saturation (SvO2) in the TEA-group compared to the nine animals with general anasthesia only (control-group). During XC there was an increase in HR, CO, SvO2 and proximal aortic blood pressure (PPROX) in both groups, without differences between groups. Following aortic declamping central venous pressure (CVP), pulmonary artery pressure (PAP) and pulmonary capillary wedge pressure (PCWP) increased in both groups. Fifteen minutes after declamping, one animal in each group died. It was concluded that in this experimental model, TEA combined with general anaesthesia did not modify the haemodynamic response to XC of the thoracic aorta.