To the Editor
We commend Drs. Ogan and Plevak1 for their excellent review of the obstructive sleep apnea (OSA) syndrome, and the editors for recognizing the importance of the disorder and providing the address of the American Sleep Apnea Association. Below are several further comments regarding this syndrome, with emphasis on patient safety in the perioperative period.
OSA is a surprisingly common disorder occurring in approximately 1-4% of the general population.2 Since more than 50% of these patients may be of normal or only mildly increased weight (<120% ideal body weight),2 other clinical features assume great importance in diagnosing the disorder. The episodes of apnea during sleep are terminated by arousals triggered by the accompanying hypoxemia, and with tens to hundreds of such events per night a state of chronic sleep deprivation results. Accordingly, excessive daytime somnolence is the most consistent symptom and is differentiated from benign “sleepiness” by the patient falling asleep while driving or in the middle of an interesting conversation.
As there have been no clinical trials studying the anesthetic management of OSA patients, recommendations can only be based on our knowledge of the pathophysiology of the disorder and a small number of case reports. As well, most of the available literature has involved only patients with severe forms of the disease; the degree to which such information can be extrapolated to al patients with OSA is not known. The conservative and safest approaches to manage all such patients as if they have severe OSA.
One of the most important characteristics of OSA patients is their exquisite sensitivity to all sedatives.3,4 Being sleep deprived, they may fall asleep with very minimal quantities of any sedatives. Apneas will thereby occur since sleep in these patients is synonymous with apneas. Barbiturates, opioids, and benzodiazepines also have more direct effects, as all been shown to increase the frequency of obstructive apneas compared to the natural sleep state.5 This has been attributed to both a preferential decrease in upper airway muscle tone and a decrease in central respiratory drive.
Based on the above considerations, we do not administer any preoperative sedation to OSA patients outside the operating room. Even in the operating room, sedation is only used when necessary, in minimal effective doses, with full cardiorespiratory monitoring and with immediately available airway management equipment. As well, only easily reversible drugs are administered (i.e., opioids and benzodiazepines) and the appropriate reversal agents are prepared and ready for use. Traditionally, maintenance of anesthesia for OSA patients has been based primarily on inhalational anesthetics to avoid significant residual sedative effects postoperatively. Propofol and remifentanil have become reasonable alternatives, especially for procedures with minimal postoperative pain.
The provision of postoperative analgesia is a particularly challenging aspect of the OSA patient’s management. Certainly, nonsteroidal anti-inflammatory agents and local or regional anesthesia should be used whenever possible. When opioids are necessary, no particular drug or mode of administration has been demonstrated to be clearly superior. A continuous infusion of low-dose remifentanil may be advantageous due to its titratibility. Longer acting opioids administered by intravenous patient-controlled analgesia techniques may be acceptable if a background infusion rate is avoided. Addition of a basal infusion has been demonstrated to increase the risk of respiratory depression in patients without OSA,6 and those with OSA will presumably be similarly affected. A low-dose infusion of intravenous ketamine may be theoretically advantageous due to its relative lack of respiratory depressant effects. However, evidence in decerebrate cats indicates that ketamine preferentially inhibits hypoglossal nerve activity,7 suggesting that it may promote obstructive apneas, especially in the OSA patient. Epidural injections of opioids have been advocated as beneficial due to the lower total doses of medication used,8 however the effects in OSA patients, especially with respect to the potential for delayed respiratory depression, remain essentially unknown.
As noted in Drs. Ogan and Plevak’s article,1 regardless of the technique of postoperative analgesia used, appropriate monitoring for hypoxemia and apneas is imperative. At our institution, all patients with OSA of any severity who have received any opioids or other sedatives in the perioperative period are observed in the PACU or ICU for at least 12 hours after the last dose.
M. Denise Daley, M.D., FRCPC, Assistant professor, peter H. Norman, M.D., FRCPC, Assistant Professor, and Lewis A. Coveler, M.D., Professor, Department of Anesthesiology, Baylor College of Medicine, Houston, TX
1. Ogan OU and Plevak DJ. Anesthesia safety always an issue with obstructive sleep apnea. Anesthesia Patient Safety Foundation Newsletter 1997;12:14-5.
2. Sullivan CE and Issa FG. Obstructive sleep apnea. Clinics in Chest Medicine 1985;6:633-50.
3. Rafferty TD, Ruskis A, Sasaki C and Gee JB. Perioperative considerations in the management of tracheotomy for the obstructive sleep aponea patient. British Journal of Anaesthesia 1980;52:61921.
4. Samuels SI and Rabinov W. Difficulty reversing drug-induced coma in a patient with sleep apnea. Anesthesia and Analgesia 1986;65:1222-4.
5. Robinson RW and Zwillich CW. The effects of drugs on breathing during sleep. Clinics in Chest Medicine 1985;6:603-14.
6. Parker RK, Holtman B, White PF. Effects of a night-time opioid infusion with PCA therapy on patent comfort and analgesic requirements after abdominal hysterectomy. Anesthesiology 1992;76:36-7.
7. Hwang J-C, St. John WM and Bartlett D. Respiratory-related hypoglossal nerve activity: influence of anesthetics. Journal of Applied Physiology 1983;55:785-92.
8. Pellechia DJ, Bretz KA and Barnette RE. Postoperative pain control by means of epidural narcotics in a patient with obstructive sleep apnea. Anesthesia and Analgesia 1987;66:280-2.