Thoracic epidural analgesia started after cardiopulmonary bypass. Adrenergic, cardiovascular and respiratory sequelae

Abstract

The effects of thoracic epidural analgesia started after cardiopulmonary bypass were studied on the subsequent adrenergic, cardiovascular and respiratory responses. Sixteen cardiac surgical patients received either a standardised general anaesthetic (control group) or a standardised general anaesthetic and thoracic epidural analgesia (epidural group). The epidural catheter was sited before surgery and heparinisation. Following discontinuation of cardiopulmonary bypass, patients in the epidural group were given 15 ml bupivacaine 0.5% down the catheter followed by an infusion of bupivacaine 0.375% at 5-8 ml.h-1 after surgery. The control group received an intravenous morphine infusion on completion of surgery. The adrenergic response was assessed by measuring arterial catecholamine concentrations. Respiratory function was determined by spirometry, peak expiratory flow and arterial partial pressure of oxygen while breathing air. Pain scores were also obtained. After cardiopulmonary bypass the increases in catecholamine concentrations were effectively inhibited in the epidural group for the remainder of the study (p < 0.05). Postoperative respiratory function was less impaired in the epidural group, with higher forced expiratory volume in 1 s, forced vital capacity and peak expiratory flow (p < 0.05). Pain scores were also significantly lower in the epidural group (p < 0.05). There were no significant differences in cardiovascular parameters.