Correspondence

Sleep Apnea

N Engl J Med 2003; 348:472-473January 30, 2003

Article

To the Editor:

In his Clinical Practice article (Aug. 15 issue),1 Dr. Flemons discusses several risks associated with obstructive sleep apnea. Recent reports have revealed a number of “unexplained” postoperative cardiopulmonary arrests in surgical patients. All these patients had received parenteral narcotics or sedatives, and in all of them, obstructive sleep apnea was ultimately diagnosed.2

Patients with obstructive sleep apnea are reportedly more sensitive to even minimal doses of sedatives or narcotics than are normal persons. It has been suggested that the administration of these drugs results in decreased pharyngeal muscle tone, which may exacerbate airway obstruction, leading to hypoxia, hypercarbia, arrhythmias, and ultimately, cardiopulmonary arrest.3

There is no national consensus on perioperative care — and specifically, postoperative monitoring — of patients with obstructive sleep apnea, and there is a paucity of clinical data. Should all patients with obstructive sleep apnea who present for ambulatory surgery be admitted, treated with continuous positive airway pressure, monitored, or perhaps even observed in an intensive care unit postoperatively? What perioperative course of action should be taken with patients presenting for ambulatory surgery in whom sleep apnea is undiagnosed but suspected?

Pending answers to these questions, practitioners should keep in mind the potential risks associated with obstructive sleep apnea and consider associated factors (including the severity of obstructive sleep apnea, the surgical procedure, the type of anesthetic, and requirements for postoperative analgesia) in making decisions about management.

Martin Nitsun, M.D.
Glenn S. Murphy, M.D.
Joseph W. Szokol, M.D.
Evanston Northwestern Healthcare, Evanston, IL 60201

3 References

1. 1

   Flemons WW. Obstructive sleep apnea. N Engl J Med 2002;347:498-504
   Full Text | Web of Science | Medline

2. 2

   Sleep apnea and narcotic postoperative pain medication: a morbidity and mortality risk. Vol. 17. No. 2. Winston-Salem, N.C.: APSF Newsletter, Summer 2002.
   

3. 3

   Benumof JL. Obstructive sleep apnea in the adult obese patient: implications for airway management. J Clin Anesth 2001;13:144-156
   CrossRef | Web of Science | Medline

Author/Editor Response

Nitsun and colleagues have identified an important and underappreciated perioperative risk. In patients recovering from anesthesia, the tone of the upper-airway dilating muscles is reduced. This activity is critical for maintaining pharyngeal patency. Studies have shown that patients with obstructive sleep apnea have a greater propensity for pharyngeal closure when they are asleep than do normal persons,1 and such patients are reported to have a high rate of perioperative complications.2 Upper-airway patency is influenced by a complex interaction of neuromuscular factors, craniofacial anatomy, and ventilatory control. Termination of an episode of obstructive apnea depends on an arousal from sleep that increases the activity of pharyngeal dilating muscles. Sedatives or narcotics reduce muscle tone, increasing the likelihood of pharyngeal collapse, and impair potentially life-saving arousal. Collapsibility of the upper airway during sleep has been shown to be correlated with obesity, severe sleep apnea (as indicated by the apnea–hypopnea index), and craniofacial abnormalities,3 and daytime hypercapnia is an indicator of abnormal ventilatory control. These features identify patients at highest risk for life-threatening, perioperative apnea. Factors shown to stabilize the upper airway include mandibular advancement, neck extension, and lateral positioning.4,5 Continuous positive airway pressure is the most effective method of maintaining upper-airway patency and can be expected to prevent most episodes of life-threatening apnea of obstructive origin. Identification of patients at risk, proper preoperative assessment, and perioperative airway management are critical in order to reduce the postoperative risks for patients with sleep apnea.

W. Ward Flemons, M.D.
University of Calgary, Calgary, AB T2N 4N1, Canada
flemons@ucalgary.ca

5 References

1. 1

   Isono S, Remmers JE, Tanaka A, Sho Y, Sato J, Nishino T. Anatomy of pharynx in patients with obstructive sleep apnea and in normal subjects. J Appl Physiol 1997;82:1319-1326
   Web of Science | Medline

2. 2

   Gupta RM, Parvizi J, Hanssen AD, Gay PC. Postoperative complications in patients with obstructive sleep apnea syndrome undergoing hip or knee replacement: a case-control study. Mayo Clin Proc 2001;76:897-905
   CrossRef | Web of Science | Medline

3. 3

   Watanabe T, Isono S, Tanaka A, Tanzawa H, Nishino T. Contribution of body habitus and craniofacial characteristics to segmental closing pressures of the passive pharynx in patients with sleep-disordered breathing. Am J Respir Crit Care Med 2002;165:260-265
   Web of Science | Medline

4. 4

   Isono S, Tanaka A, Nishino T. Lateral position decreases collapsibility of the passive pharynx in patients with obstructive sleep apnea. Anesthesiology 2002;97:780-785
   CrossRef | Web of Science | Medline

5. 5

   Isono S, Tanaka A, Sho Y, Konno A, Nishino T. Advancement of the mandible improves velopharyngeal airway patency. J Appl Physiol 1995;79:2132-2138
   Web of Science | Medline