Thoracic epidural analgesia as an adjunct to general anaesthesia for cardiac surgery - Effects on pulmonary mechanics

Background: A lasting impairment of pulmonary function is common after card iac surgery. Pain from the sternotomy may contribute to the impairment. Tho racic epidural analgesia (TEA) can efficiently relieve pain in the postoper ative phase, but may also affect respiratory muscle function if local anaes thetics are used. We examined the effects of TEA on pulmonary function and ventilation at rest, before and after coronary artery bypass graft surgery (CABG). Methods: Thirty patients scheduled for CABG were randomized to receive eith er general anaesthesia alone or general anaesthesia with TEA. Before and af ter the operation the patients were examined by respiratory inductive pleth ysmography and spirometric tests. Results: Before the operation, TEA caused significant reductions in forced vital capacity (FVC), forced expired volume in 1 s (FEV1), maximal inspirat ory (P(I)max) and expiratory (P(E)max) pressure. The rib cage contribution to tidal volume decreased significantly but the co-ordination of the thorac ic and abdominal movements remained essentially unaffected. Minute volume a nd respiratory frequency did not change significantly. On the first postope rative day a decrease in maximal breathing efforts was found in both groups . No differences between the groups in FVC, FEV1 and P(I)max were found, bu t PEmax was significantly greater in the TEA group. Despite the impairment, breathing at rest was largely normal in both groups. Conclusions: A better pain-relief from TEA after CABG may improve the abili ty to cough by a greater expiratory muscle strength. FVC, FEV1, P(I)max and breathing at rest are not affected by TEA after cardiac surgery.