Response

Abstract

We appreciate the comments of Dr Mychaskiw and Dr Dharmavarapu. There is no doubt that the amounts of intravenous opioid and benzodiazepine used in the perioperative period affect extubation time when using intrathecal morphine and that limiting the use of these agents may allow one to realize the combined benefits of early extubation and postoperative analgesia. This is the exact reason why we substantially altered the intraoperative anesthetic (intravenous fentanyl and midazolam) in this second investigation. The amount of intrathecal morphine (10 μg/kg) remained the same because, in our experience, when this amount is used in patients undergoing thoracotomy or abdominal aortic aneurysm resection, extubation can be accomplished in the operating room. Dr Mychaskiw and Dr Dharmavarapu speculate that patients exposed to cardiopulmonary bypass may have decreased postoperative analgesic requirements because of cerebral edema, which may also make them more susceptible to the sedative effects of intrathecal morphine. This represents an interesting proposal deserving investigation. The statements describing their ongoing study are somewhat startling. We frankly find it hard to believe that 5 μg/kg of intrathecal morphine is “adequate for postoperative pain control” in patients undergoing cardiac surgery. Although one could theoretically argue the converse, we do not agree with totally eliminating preoperative and intraoperative intravenous opioids and benzodiazepines. We believe that substantial reduction in these drugs is the answer. The routine “liberal” use of high-dose aprotinin for its anti-inflammatory effects is a practice that does not have support in the established literature and, in fact, may be dangerous.1Cohen DM Norberto J Cartabuke R Ryu G Severe anaphylactic reaction after primary exposure to aprotinin.Ann Thorac Surg. 1999; 67: 837-838Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar, 2Westaby S Katsumata T Editorial: Aprotinin and vein graft occlusion—the controversy continues.J Thorac Cardiovasc Surg. 1998; 116: 731-733Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar Lastly, their statement—“... other studies have also shown the effectiveness of intrathecal morphine at significantly smaller doses.”3Swenson JD Hullander RM Wingler K Leivers D Early extubation after cardiac surgery using combined intrathecal sufentanil and morphine.J Cardiothorac Vasc Anesth. 1994; 8: 509-514Abstract Full Text PDF PubMed Scopus (44) Google Scholar, 4Taylor A Healy M McCarroll M Moriarty DC Intrathecal morphine: One year's experience in cardiac surgical patients.J Cardiothorac Vasc Anesth. 1996; 10: 225-228Abstract Full Text PDF PubMed Scopus (30) Google Scholar—requires comment. Both cited investigations are retrospective in design (eg, no control group, intraoperative baseline anesthetic not standardized), and one investigation involved only 10 patients3Swenson JD Hullander RM Wingler K Leivers D Early extubation after cardiac surgery using combined intrathecal sufentanil and morphine.J Cardiothorac Vasc Anesth. 1994; 8: 509-514Abstract Full Text PDF PubMed Scopus (44) Google Scholar (the other 152 patients4Taylor A Healy M McCarroll M Moriarty DC Intrathecal morphine: One year's experience in cardiac surgical patients.J Cardiothorac Vasc Anesth. 1996; 10: 225-228Abstract Full Text PDF PubMed Scopus (30) Google Scholar). Little can be proved from such studies. The patients in the larger cited retrospective investigation not only received three times the amount of intrathecal morphine (30 μg/kg) as our patients (10 μg/kg), but also 59% of the patients had epidural catheters placed intraoperatively for postoperative analgesia (the most popular technique being continuous morphine infusion).4Taylor A Healy M McCarroll M Moriarty DC Intrathecal morphine: One year's experience in cardiac surgical patients.J Cardiothorac Vasc Anesth. 1996; 10: 225-228Abstract Full Text PDF PubMed Scopus (30) Google Scholar