SPRING 2010

Sleep Apnea: Anesthetic Considerations

Dwight Taylor CRNA
Callahan Eye Foundation Hospital

Obstructive sleep apnea (OSA) is a potentially lethal condition in our overweight and obese society with a prevalence of up to 14% in American men and 7% in American women [1]. OSA is clinically defined by multiple episodes of obstructions or mixed apneic events during sleep, loud intermittent or continuous snoring and excessive daytime sleepiness. OSA occurs along a continuum, progressing from snoring and central nervous system (CNS) arousal without apnea to OSA syndrome with more than 5 apneic episodes an hour. Along with obesity or abnormal upper airway anatomy, OSA is associated with hypertension, cardiovascular remodeling, pulmonary hypertension, stroke, transient ischemic attack (TIA), and accumulation of pro-inflammatory cytokines, glucose intolerance and insulin resistance. There is a strong association between OSA and increased mortality rates [2].

Anesthesia providers should remember that OSA patients have altered CNS responses to chemical stimuli, in particular hypoxia and hypercarbia. During sleep, two events occur that impact respiration and ventilation: loss of muscle tone in the pharyngeal musculature and altered control of respiration. Higher CO2 levels and lower O2 levels are necessary to elicit CNS arousal and stimulate breathing in OSA patients. In the context of sleep, arousal is an appropriate response to acute airway obstruction and hypoxemia. However, chronic arousal contributes to the neuropsychological symptoms of OSA. Untreated OSA tends to progress, resulting in a chemoreceptor “reset” which diminishes sensitivity to arousal allowing adverse cardiovascular events to occur.

Not all OSA patients are obese. Patients who demonstrate heavy snoring may have folds of hypertrophied oropharyngeal tissue, macroglossia, or anomalous positioning of the maxilla and mandible. They could also present with neuromuscular factors which affect oropharyngeal muscle tone causing a reduction in ventilatory motor output to upper airway muscles during sleep [3]. Alcohol ingestion may induce signs of airway obstruction as in Charles Dickens’ classic description of Mr. Pickwick who only snored with apneic spells and snorting when he was intoxicated. (The Pickwickian Syndrome was actually named after Joe the Fat Boy in The Pickwick Papers.)

Anesthetic management of OSA patients begins with a thorough pre-operative interview. During the interview, the following information should be requested: are there episodes of abnormal daytime sleepiness, including falling asleep at inappropriate times; have you been told that you “stop breathing” at night; do you awaken tired in the morning; do you have periods of depression, leg swelling, lethargy, loud snoring, memory difficulties, morning headaches, personality changes, poor concentration or restless sleep? [3]. Positive answers to these questions most likely indicate the presence of OSA.

All anesthetics, sedatives, and opioids decrease pharyngeal tone, depress the ventilatory response to hypoxia and hypercarbia, and inhibit arousal responses thereby exacerbating the pre-existing depressed CNS response pattern of the OSA patient [1].  It is especially important to avoid hypercarbia in patients with pulmonary hypertension as this may lead to acute right heart failure.

The ASA Practice Guidelines for the Perioperative Management of Patients with Obstructive Sleep Apnea [4] state that following a general anesthetic, the patient should be fully awake and fully reversed from muscle relaxants prior to extubation. Patients should be in a semi-upright position for extubation and recovery. If moderate sedation is used, ventilation should be continuously monitored via capnography and pulse oximetry. An additional very useful monitor is a precordial stethoscope. One should consider administering CPAP or using an oral appliance during sedation on patients previously treated with these modalities [4]. However, this is rarely possible during ophthalmic surgery
Post-operative pain management in OSA patients using non-steroidal anti-inflammatory agents when acceptable reduces the potential adverse outcomes through an opioid sparing effect [4]. Although the literature is insufficient to evaluate the effects of post-operative supplemental oxygen in patients with OSA, it does support its use in extubated patients during the perioperative period. As it is usually not possible to use CPAP in the immediate post op period following ophthalmic surgery, supplemental oxygen is the key to avoiding hypoxia in OSA patients after eye surgery.

Being mindful of OSA and its ramifications should be an important consideration when interviewing all patients, whether considering general or monitored anesthesia care (MACs). A thorough preoperative interview helps identify patients with possible undiagnosed OSA and may help prevent respiratory complications during and after anesthesia as well as major adverse cardiac events [2].

Perioperative Sleep Apnea Guidelines
Section of Ophthalmic Anesthesia
UAB Department of Anesthesiology

OSA patients that use CPAP should bring their CPAP machines with them to the hospital. Biomed needs to check the machine prior to use in the hospital. We at CEFH have made an exception to this guideline for our cataract patients.

1. Observe in PACU for a minimum of an hour.

2. Note any respiratory obstruction lasting longer than 10 seconds with desaturation to 85%.

3. With each desaturation, add 30 minutes to the PACU time and notify the anesthesiologist.

4. CEFH does not have either CPAP or BiPAP available. Therefore, patients may need to be on supplemental oxygen longer than usual. In addition, the patient’s CPAP machine may not be readily used with the ophthalmic postsurgical dressing.

5. The patients who have not had desaturations may be discharged from the PACU after one hour.

6. At the time of discharge from the PACU, the anesthesiologist will decide the disposition of the patient based on the observation period in the PACU coupled with the severity of the sleep apnea and the patient’s comorbidities. If the patient needs oxygen to maintain saturation, the patient will be admitted to the in-patient unit on continuous pulse oximetry. Some patients may require transfer to another hospital with a higher intensity of care unit for observation. The ASA Guidelines [4] state that patients who have had an episode of desaturation will be monitored an additional seven hours postoperatively. Exceptions to this need to be approved by the attending anesthesiologist.

7. If the patient is suspected to have, but not diagnosed with sleep apnea, he maybe referred to the UAB Sleep/Wake Disorders Center for a sleep evaluation by calling 930-7114.

References

1. Bolden N, Smith CE, Auckley D. Avoiding adverse outcomes in patients with obstructive sleep apnea (OSA): development and implementation of a perioperative OSA protocol. J Clinical Anesthesia 2009; 21: 286-293.

2. Punjabi NM, Caffo BS, Goodwin JL, et al Sleep disordered breathing and mortality: a prospective cohort study. PLoS Med 6(8):e1000132. doi:10.1371/journal.ped.1000132

3. Doyle DJ. Obstructive sleep apnea and the surgical patient: what the anesthesiologist should know. Anesthesiology News Supplement Guide to Airway Management August 2009. Available at www.Anesthesiologynews.com

4. Gross JB, Bachenberg KL, Benumof J, et al. Practice Guidelines for the perioperative management of patients with obstructive sleep apnea: A report by the American Society of Anesthesiologists Task Force on Perioperative management of Patients with Obstructive Sleep Apneas. Anesthesiology, 2006; 104:1081-93.