Efficacy of pre-emptive analgesia and continuous extrapleural intercostal nerve block on post-thoracotomy pain and pulmonary mechanics

Abstract

Objective: Thoracotomy results in severe pain and deleterious changes in pulmonary physiology. The literature suggests that these alterations in pulmonary mechanics are inevitable and can only be minimised but not prevented by effective analgesia. We have re-evaluated this concept and assessed the efficacy of pre-emptive analgesia [preincisional afferent block, premedication with opiate and/or non-steroidal anti-inflammatory drug (NSAID)] in conjunction with postoperative extrapleural continuous intercostal nerve block on postoperative pain and pulmonary function.

Materials and methods: A prospective randomized study was conducted on 56 patients undergoing elective thoracotomy. Subjective pain relief was assessed on a linear visual analogue scale. Pulmonary function was measured on the day before operation and 12 hourly for 48 hours after operation. There were seven patients in each of the eight groups.

Results: The balanced analgesia group comprising preincisional block and premedication with opiate and NSAID (Group 1) had significantly better analgesia, needed less postoperative supplementary analgesics and maintained their preoperative pulmonary function postoperatively irrespective of the nature of the operation. The ranking of importance of the three components of the pre-emptive analgesia as assessed in this study are preincisional block, opiate premedication and premedication with NSAID's. No significant change in plasma levels of cortisol or glucose occurred in Group 1 patients from prior to induction of anaesthesia to 24 hours postoperatively, suggesting effective somatic and sympathetic afferent blockade had been achieved in these patients. There were no complications related to the infusion or the use of NSAID's.

Conclusions: We conclude that a balanced analgesic regime comprising preoperative pain prophylaxis and postoperative maintenance analgesia by NSAID and continuous extrapleural intercostal nerve block will minimise and even reverse the expected decline in lung function after thoracotomy. The postoperative decline in lung function is not obligatory but primarily due to incisional pain and thus is preventable by effective analgesia. An ideal balanced pre-emptive analgesic regime should include preincisional local anaesthetic afferent block and premedication with opiates and a NSAID: