Cardiovascular effects of epidural local anaesthetics. Comparison of 0.75% bupivacaine and 0.75% ropivacaine, both with adrenaline.

The cardiovascular effects of 20 ml 0.75% bupivacaine with adrenaline 5 micrograms/ml injected epidurally were compared with those of 20 ml 0.75% ropivacaine with adrenaline. Cardiovascular measurements were performed with a transthoracic electrical bioimpedance monitor. The maximum mean arterial blood pressure decreased significantly from baseline values after both solutions, but the decrease after 20 minutes was more pronounced with bupivacaine (21%) than with ropivacaine (9.6%). Stroke volume increased significantly in both groups (52% for bupivacaine and 29% for ropivacaine). Cardiac output increased significantly from baseline values 2 minutes after epidural administration; the mean of the maximum increase was 64% for bupivacaine and 53% for ropivacaine (NS). The mean of the maximum increase of the ejection fraction was 13% in the bupivacaine group and 9% in the ropivacaine group, but was only significantly different from baseline values following bupivacaine. There was no difference in the onset time or height of the sensory block between the groups. The cardiovascular changes can be ascribed to sympathetic blockade and to systemic absorption of the local anaesthetics and adrenaline.