A randomised trial of oral versus intravenous opioids for treatment of pain after cardiac surgery

Cardiac surgery and sternotomy are procedures accompanied by substantial postoperative pain which is challenging to treat. In general, intravenous (IV) opioids are used in the immediate postoperative phase, followed by oral opioids. Oral opioids are easier to use and generally less expensive. Our goal was thus to determine whether a new opioid preparation provides adequate analgesia after sternotomy. In particular, we tested the primary hypothesis that total opioid use (in morphine equivalents) is not greater with oral opioid compared with patient-controlled IV morphine. Our secondary hypothesis was that analgesic efficacy is similar with oral and IV opioids. A total of 51 patients having elective cardiac surgery were enrolled in this study. After rapid postoperative respiratory weaning, the patients were randomised into one of two groups receiving different types of analgesia: oral Targin (a combination of oxycodone-hydrochloride and the opioid antagonist naloxone hydrochloride-dihydrate) or patient-controlled IV morphine. Pain score (visual analogue scale), sedation (Ramsey score), respiratory rate and side effects were assessed at 3, 5, 7, 9 and 11 h after surgery, and every 6 h throughout the third postoperative evening. The total opioid dose in morphine equivalent doses was significantly lower with oral opioid than with IV morphine (adjusted geometric means [95 % confidence interval]: 34 [29; 38] vs. 69 [61; 78] mg, respectively). Pain scores were similar in each group. Analgesic quality was comparable with oral and IV opioids, suggesting that postoperative pain even after very painful procedures can be sufficiently managed with oral opioids.