Continuous thoracic epidural analgesia versus combined spinal/thoracic epidural analgesia on pain, pulmonary function and the metabolic response following colonic resection.

BACKGROUND

The neuroendocrine response following major surgery has not been previously influenced by either regional anaesthetic techniques or opioid analgesia probably due to insufficient intraoperative afferent neural blockade. In this study we attempted to determine whether significant inhibition of these pathways could be achieved by combining preoperative high spinal anaesthesia with postoperative thoracic epidural anaesthesia. In theory too, there may be additional benefits over perioperative thoracic epidural anaesthesia on pain and pulmonary dysfunction.

METHODS

20 ASA 1-3 patients undergoing elective colonic surgery were studied. Gp 1 (n = 10) received a high spinal intraoperative block to T4 using 6mls of 0.5% bupivacaine plus continuous epidural 0.125% bupivacaine/0.0025% diamorphine. Gp 2 (n = 10) patients received epidural 0.5% bupivacaine block to T4 plus continuous epidural infusion of 0.125% bupivacaine/0.0025% diamorphine. We measured a) plasma glucose and cortisol at 0, 1, 2, 3, 4, 8 and 24 h; b) forced vital capacity (FVC), forced expiratory volume in the first second (FEV1) and peak flow rate (PFR) preoperatively, at 8 and 24 h; c) visual analogue pain scores (VAS 0-10) at rest, cough and mobilisation at 8 and 24 h; d) block height every hour for 12 hours then 3 hourly; e) 24-hour urine volumes for dopamine, adrenaline and noradrenaline f) 24-hour PCA morphine requirements.

RESULTS

The two groups did not differ in age, sex, height, weight, duration of surgery, blood loss or serum albumin. Pain relief was excellent and similar in both groups. The average 24 hour morphine consumption was 10 mg in both groups with no differences in the block height. All the patients had a 30-50% reduction in FEV1, FVC and PFR (P > 0.05). Metabolically, there was no statistical difference between the 2 groups except a higher rise in glucose in Gp1 at 2 and 3 h (P = 0.0312 and 0.014). 24-hour catecholamine studies showed no differences for noradrenaline (P = 0.8), adrenaline (P = 0.47) and dopamine (P = 0.36).

CONCLUSIONS

Thoracic epidural bupivacaine/diamorphine infusion provided excellent postoperative analgesia following colonic surgery. An intraoperative combined spinal/epidural technique conferred no additional benefit on analgesia, pulmonary function and the neuroendocrine response.