Intraoperative i.v. morphine reduces pain scores and length of stay in the post anaesthetic care unit after thyroidectomy

Editor—Postoperative pain after thyroid surgery may be important especially in the first few hours after surgery.14 The analgesic efficacy of different medications including non-steroidal anti-inflammatory drugs possibly in combination with paracetamol, oral opioids and regional and local anaesthesia, have been described after thyroidectomy.16 We hypothesized that intraoperative i.v. morphine might influence the immediate postoperative pain scores, opioid-related side-effects and length of stay in the postanaesthetic care unit (PACU).

After ethical committee approval, 60 consenting adults ASA I–II undergoing elective total thyroidectomy for multinodular goitre were enrolled into the study. Patients were randomized into two groups: Morphine Group (n=30), and Control Group (n=30). All patients had general anaesthesia with propofol 2.5–4 mg kg–1, and sufentanil 4–5 µg kg–1. Tracheal intubation was performed without using a neuromuscular blocking agent, and anaesthesia was maintained with isoflurane/nitrous oxide/oxygen.

After dissection of the first thyroid lobe, patients received acetaminophen 1 g before administration of the treatment, which consisted, for the control group, of an i.v. injection of saline 10 ml and, for the morphine group, an injection of morphine 0.1 mg kg–1 diluted by an equivalent amount (10 ml) of saline. The treatment was injected by a physician not participating directly in the patient's care, while the anaesthetist in charge of the patient was blinded to the randomization. Inhalational anaesthesia was maintained until the last skin stitch. All patients were extubated in the PACU. Patients were then asked to rate their pain according to a visual analogue scale (VAS, 0–100 mm). When the VAS score was >40, i.v. morphine by titration (2 mg increment, 5 min interval) was started and pain was assessed every 5 min until relief was obtained (VAS <40). The length of stay in the PACU was decided by a physician blinded to the randomization. I.V. acetaminophen was repeated every 6 h for the first 24 h. In the ward, subcutaneous morphine was given every 6 h if the VAS was >40.

Four patients were withdrawn from the study: two for prolonged surgery because of cancer; one because of surgical haematoma requiring drainage; and one for acute respiratory failure attributable to bilateral recurrent laryngeal nerve damage. No patient had delayed extubation or a ventilatory frequency <9 bpm during their stay in the PACU.

The initial mean (SD) postoperative pain scores in the PACU were lower in the morphine group (35 (10) mm) compared with control (55 (15) mm); (P<0.05). The request for morphine, the duration of morphine titration, and the total amount of morphine given in the PACU was less in the morphine group than in the control group (P<0.05). However, the cumulative amount of morphine given (intraoperative + PACU) was not different between groups. The length of stay in the PACU was shorter in the morphine group (103 (30) min) than in the control group (147 (35) min; P<0.05). In the surgical ward, maximum pain scores, and the incidence and amount of morphine required were not different between groups. The incidence of nausea and vomiting during the first 24 h was similar (about 45%) in both groups.

This study shows that morphine given before the end of surgery was effective in controlling postoperative pain in the PACU in patients undergoing thyroidectomy. Morphine requirements, the necessity for morphine titration, and the length of stay in PACU were reduced. However, the incidence of opioid-related side-effects in the PACU and in the surgical ward was unchanged. After thyroid surgery, nausea and vomiting may be related to the surgery itself,7 and postoperative pain confounded by post-intubation sore throat.

In summary, intraoperative use of morphine i.v. 0.1 mg kg–1 is a useful method of decreasing immediate postoperative pain scores and the length of stay in the PACU after total thyroidectomy, without increasing the incidence of opioid-related side-effects.

C. Motamed, J. C. Merle, L. Yakhou, X. Combes, M. Dumerat, J. Vodinh, C. Kouyoumoudjian and P. Duvaldestin

Paris, France

References

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