Opiate Usage in Children with Obstructive Sleep Apnea Syndrome

Abstract

To the Editor: We agree with Sanders et al. (1) that obstructive sleep apnea syndrome, especially in young children, is linked to greater respiratory complications associated with adenotonsillectomy. We differ, however, with the authors’ statements regarding the lack of a relationship between perioperative morphine and those respiratory complications. This conclusion contradicts reports showing that children with severe obstructive sleep apnea syndrome display heightened respiratory sensitivity to intraoperative fentanyl (2) and heightened analgesic sensitivity to postoperative morphine (3). The important parameter that correlated with the opiate sensitivity was the oxygen saturation nadir as a measure of obstructive sleep apnea syndrome severity (3), and not the respiratory disturbance index used by Sanders et al. (1). Although respiratory disturbance index is commonly used to stratify obstructive sleep apnea syndrome levels, and is correlated with the oxygen saturation nadir (4), the saturation nadir is the more reliable indicator of pathophysiology in obstructive sleep apnea syndrome, as it attests to the degree of hypoxemia associated with this syndrome. Brown et al. (3) found a direct correlation between the severity of hypoxemia and the enhanced analgesic morphine sensitivity in children with obstructive sleep apnea syndrome undergoing adenotonsillectomy. This sensitivity is attributed to an alteration of central μ-opioid receptors that results from the recurrent hypox-emia in obstructive sleep apnea syndrome (3,5,6). Perhaps Sanders et al. (1) did not detect any respiratory opiate-related effects, because their use of long-acting morphine during an unspecified duration of surgery precluded a determination of whether the effect of this long-acting opiate lingered from the intraoperative onto the postoperative period. Furthermore, the lack of details provided regarding the total postoperative morphine dose, or of the postsurgical observation period, prevented a precise assessment of the independent effect of morphine on respiratory complications during that period. By contrast, the intraoperative effect of the short-acting fentanyl used by Brown et al. (3) likely did not extend beyond the duration of surgery, thus permitting a precise assessment of the independent effect of the total analgesic morphine dose on respiratory functions during the postoperative recovery period. The heightened opiate sensitivity in young children with obstructive sleep apnea syndrome and hypoxemia undergoing surgery is important. A dismissal of the potential role of opiates in causing perioperative respiratory complications may lead to the continuation of the use of “standard” opiate dosing in vulnerable children. Indeed, in a recent prospective study (5), those children with obstructive sleep apnea syndrome and low oxygen saturation nadir who received half of the postoperative analgesic morphine dose were free from the postoperative respiratory complications previously found in such vulnerable children (7). Karen A. Brown, MD Department of Anesthesiology [email protected] Immanuela Ravé Moss, MD, PhD Department of Pediatrics McGill University McGill University Health Centre/Montreal Children’s Hospital Montreal, Quebec, Canada [email protected] Dr. Sanders does not wish to reply.