Perioperative Implications of Obstructive Sleep Apnea

by Stephanie B. Jones, MD; Jeffrey M. Ellenbogen, MD; and Daniel B. Jones, MD, FACS

INTRODUCTION

Obstructive sleep apnea (OSA) is a medical condition that leads to significant morbidity and reduced quality of life. Patients with OSA are particularly vulnerable to certain perioperative complications, and the incidence of OSA in the bariatric population may be as high as 77 percent.1 Therefore, the surgeon and bariatric team should routinely screen for OSA as part of the preoperative workup. In this article, we will provide a brief overview of OSA, focusing primarily on the challenges that face surgeons and anesthesiologists in handling these cases. By understanding this disorder, and how it is perturbed in the perioperative period, surgical outcomes may be considerably improved.

OSA is defined by complete cessation (apnea) or marked reduction (hypopnea) of airflow, accompanied by respiratory effort during sleep. The airway compromise results in frequent arousals from sleep, often causing daytime hypersomnolence. OSA also causes transient hypoxemia, which, accompanied by arousals and associated increases in sympathetic tone, can lead to cardiovascular compromise, including chronic hypertension, stroke, and even sudden death.2-4 Clinically, OSA is diagnosed in the sleep laboratory by polysomnography (PSG). The traditional physiologic parameters defining OSA are an apnea-hypopnea index (AHI) greater than five (events per hour), accompanied by excessive daytime sleepiness not accounted for by another cause; or an AHI greater than 10, irrespective of symptoms of sleepiness.5

SCREENING FOR OSA

Subjective screening questionnaires can be helpful in identifying which patients might have OSA; this can include use of the Berlin Questionnaire, looking for evidence of apneas (e.g., snoring), and use of the Epworth Sleepiness Scale, looking for excessive sleepiness.5,6 At the Beth Israel Deaconess Medical Center Obesity Management and Weight Loss Surgery Program, our team asks:

• Are you tired during the day?
• Do your snore?
• Do you wake up several times during the night?
• Does your partner notice if you stop breathing while you sleep?
• Do you fall asleep while driving? • Do you fall asleep while at work?
• Do you have a problem with memory?

There may be poor correlation between the physiologic and subjective markers, which limits the use of questionnaires as sole criteria for diagnosis. A brief, focused, physical examination in the office or at the bedside can be extraordinarily helpful in screening for OSA. One should look for obesity, a compromised airspace patency, or both. Findings that are considered to increase the pretest probability of OSA include a body mass index (BMI) greater than 30Kg/m2; enlarged neck size (>16.5 in men); retrognathia; micrognathia; macroglossia; elongated uvula; narrowed hard palate; low-lying soft palate; and large tonsils—in short, anything that makes the lumen of the upper airway small.

THE IMPORTANCE OF OSA IDENTIFICATION IN THE BARIATRIC PATIENT

If you look for OSA, you will find it. An estimated 2 to 4 percent of the adult population is said to suffer from symptomatic OSA, and asymptomatic cases (no report of sleepiness) among middle-aged populations are as prevalent as nine percent in women and 24 percent in men.7 Given the increasing rates of obesity (a major risk factor for OSA) in the US, we are likely to see that more and more surgical patients will have OSA, the vast majority undiagnosed.

It is important to identify OSA in the surgical patient because it can lead to a plan that can minimize perioperative complications associated with the disorder. First, the airway is the obvious anesthetic concern in patients with OSA. Studies confirm an increased risk of difficult intubation, and excess pharyngeal tissue may lead to difficulties with mask ventilation.8 More recent data has demonstrated that OSA patients are at risk for major cardiovascular morbidity and mortality,9 which may certainly impact the perioperative course. Hypertension is common among OSA patients, and appears to be related to repeated increased sympathetic tone secondary to oxyhemoglobin desaturation and frequent nocturnal arousals.2 The increased sympathetic activity surrounding the apneic episodes may also contribute to a documented increase in sudden death at night, more early morning acute coronary events, and an increase in arrhythmias.4 OSA is an independent risk factor for coronary artery disease, and the hazard ratio for stroke or death is nearly double the normal population, even after adjustment for comorbidities.3,10

THERAPEUTIC OPTIONS FOR OSA

Therapeutic options for OSA include continuous positive airway pressure (CPAP) and related devices, such as bilevel positive airway pressure (BiPAP), oral appliances, or surgery. The Cochrane Collaboration has conducted systematic reviews on all three therapy classes.11-13 Compared to control, CPAP improves objective and subjective sleepiness, several quality of life indicators, depression measures, and hypertension. Compliance can be an issue with CPAP. When higher pressures are needed in order to maintain airway patency (typically defined as >20cm H2O), BiPAP is often used instead of CPAP, in order to reduce expiratory pressure, thereby increasing comfort and increasing compliance. In fact, for any given patient, the same pressure is not needed throughout the night. Newer CPAP devices are incorporating technology that allows for adjustments of the CPAP pressure during the night—so-called “autotitration CPAP,” which adjusts throughout the night (Respironics REMstar Auto, ResMed S8 Vantage). Early anecdotal reports attributed anastomotic leak to entrainment of air into the gastrointestinal tract during postoperative CPAP therapy. This concern has been shown to be unfounded in subsequent studies.14

CPAP is more effective at improving OSA when compared to oral appliances, but may not be different subjectively. The most commonly used oral appliances act by advancing the mandible in order to increase the patency of the upper airway. Oral appliances are probably best suited for patients with mild OSA, or those who cannot tolerate CPAP.

SURGERY OPTIONS FOR OSA

The data on surgery is more difficult to analyze as a class, given the wide variety of procedures performed. Surgery serves to increase the size of the retropalatal space, retrolingual space, or both. No overall significant benefit was found, and many of the studies are based upon case series. A one-time therapy that does not require continuous patient compliance is appealing, but long-term data is lacking. In fact, one must not assume that a patient is cured of sleep apnea following surgery; signs and symptoms of OSA should still be sought if recent testing is not available. But careful selection of patients with particular anatomical abnormalities (e.g., enlarged tonsils or crowded airspace) may yield particularly good candidates for upper-airway surgery. While the goal of surgery is curative, patients should understand that the outcome may simply be a reduction in the required CPAP pressure.

ALTERNATIVE THERAPIES

Alternative therapies for OSA include behavioral modification. The most effective method is weight loss. But this is not feasible for some patients, and not practical for others (not all cases are associated with obesity). Other behavioral changes include modification of position in which one sleeps—OSA tends to be worse in a supine position, which is precisely the position most patients are in during recovery from surgery.

IMPORTANCE OF PREOPERATIVE TREATMENT AND SCREENING

Given the perioperative risks associated with OSA, it is important to diagnose and treat OSA preoperatively. Although no studies definitively demonstrate that diagnosing and treating OSA leads to improved surgical outcomes, studies do show that the lack of diagnosis and treatment leads to worse postoperative surgical outcomes. 15 Given the positive systemic changes that occur with successful treatment of OSA, such as improvement in hypertension and nocturnal oxyhemoglobin saturation levels, it appears that CPAP therapy should be initiated as early as possible. How can patients be screened in the preoperative clinic setting? In 2005, the American Society of Anesthesiologists (ASA) published practice guidelines for the perioperative management of patients with OSA.16 The guidelines include clinical criteria that “suggest the possibility of” OSA. The list includes physical characteristics outlined earlier in this article and signs of apparent airway obstruction, such as frequent snoring and witnessed apneas or gasping for breath during sleep. Those with signs and symptoms suggestive of OSA should then undergo polysomnography (PSG). These criteria have not been validated as a diagnostic tool but represent standard clinical practice. The goal of the task force creating the guidelines was to err on the side of sensitivity, possibly resulting in lower specificity, but allowing for proper caution in perioperative planning. As noted above, validated questionnaires may also be used. The Berlin Questionnaire, for example, was designed for use by primary care providers. In one study of the questionnaire, high risk classification predicted OSA with a sensitivity of 0.86 and specificity of 0.77.6

Do patients with suspected sleep apnea need to undergo PSG testing, the gold standard for diagnosis of OSA? Given the time and expense involved in such testing, and the potential number of patients involved, PSG testing may be more appropriately reserved for those suspected to have OSA. For that subset of patients, a formal sleep study will also allow initiation of therapy, such as CPAP, prior to surgery. The use of newer home-diagnostic equipment offers an attractive alternative to traditional laboratory PSG (by both reducing cost and increasing patient comfort), but valid means to conduct such studies do not yet exist.

FOLLOWING OSA DIAGNOSIS

Once the diagnosis of OSA is confirmed, the patient needs to get fitted and begin using CPAP/ BiPAP at home. Once ideal pressure settings are determined, many patients will report feeling rested and refreshed during the day. However, many patients struggle with the mask (Figure 1) and the noise generated by the machine. The bariatric team needs to reinforce the importance of diagnosis and therapy in order to maximize patient compliance. The patient is also instructed to bring in his or her own sleep apnea mask and machine the day of surgery for postoperative use as patients tend to favor their own equipment.

PERIOPERATIVE CONCERNS: ANESTHESIA

Establishing a diagnosis of OSA in the surgical patient may lead to changes in the anesthetic plan. Nearly all centrally acting anesthetic drugs reduce oropharyngeal tone, increasing the possibility of airway obstruction.17 Similarly, postoperative use of narcotics or benzodiazepines reduces upper-airway tone, thereby unmasking or worsening sleep apnea. OSA patients may be sensitive to even small doses of these medications. Consequently, deep sedation may not be an option, making general anesthesia with a secured airway the safer choice. End tidal carbon dioxide monitoring should be used during sedation to help monitor for obstruction. Placing the patient in the classic “sniffing” position has also been shown to help maintain a patent airway. 18 If alternatives to sedation or general anesthesia exist for a particular procedure, such as a regional nerve block, this option should be considered. If general anesthesia is planned, close attention must be given to the possibility of a difficult intubation, with assistance and airway adjuncts readily available. 19 Patients should be extubated only when fully awake, with their head elevated, and neuromuscular blocking agents fully reversed.20 Oxygen should be administered by mask after extubation, although this might prolong the period before apnea is recognized by a drop in oxygen saturation. Non-opioid analgesics, such as non-steroidal antiinflammatory agents or ketorolac, and analgesic adjuncts such as local anesthetics should be used whenever possible. 19 The goal is to reduce the need for opioids, and consequently the risk of respiratory depression and airway obstruction.

POSTOPERATIVE MONITORING

Little consensus appears in the literature regarding postoperative monitoring of the OSA patient. The ASA guidelines recommend continuous pulse oximetry monitoring until such time that the patient maintains a room air oxygen saturation of 90 percent during sleep. If the patient uses CPAP or another OSA therapy at home, this should be reinitiated as soon as feasible, and with the patient’s own equipment, if possible. For patients undergoing ambulatory surgery, the ASA guidelines are cautious. They recommend that an OSA patient be monitored about three hours longer than a patient without OSA. Furthermore, if airway obstruction or hypoxemia occurs during recovery, they recommend that the patient be monitored for seven hours after the last episode while breathing room air undisturbed. This obviously makes any ambulatory surgery beyond minor peripheral or superficial procedures a near impossibility, especially if the patient requires a general anesthetic. But the ASA closed-claims database seems to support this aggressive treatment approach. After introduction of the ASA difficult airway management guidelines in 1993, there has been a significant drop in death and brain damage suits due to airway management at induction. However, there has been no change during other phases of anesthetic care, including extubation and recovery. 21 If this post-anesthetic phase is perilous for the general population, it can only be more so for the OSA patient. A retrospective study from the Mayo clinic was in fact able to show more serious postoperative complications, unplanned ICU transfers, and longer hospital stays in OSA patients undergoing joint replacements compared to non-OSA case controls.15

CONCLUSION

If not diagnosed or suspected, OSA may place the patient at unnecessary risk postoperatively. Less experienced providers may increase the frequency of administration or the dose of narcotics in an effort to make the patient more comfortable. In the patient with OSA, the result may by respiratory compromise leading to respiratory arrest. In a patient with a difficult airway, or in an offsite location such as radiology, the consequences can be grave. An appreciation of the seriousness of OSA, knowledge of best practices, and team focus on patient safety helps avoid adverse outcomes.

OSA is a highly prevalent, frequently undiagnosed, and clinically meaningful medical condition that is particularly perturbed in the perioperative period and can lead to worse surgical outcomes if not recognized and treated. One can screen for possible OSA by employing brief screening tools and conducting focused physical examinations (both outlined in this article) that, if positive, should prompt polysomnography for definitive diagnosis and treatment where possible. The perioperative implications include the need for diagnosis and treatment of previously undiagnosed individuals, airway management, pain control issues, and postoperative monitoring needs. Surgeons, anesthesiologists, and nurses providing care to this patient population need to be fully aware of the risks involved and plan accordingly.

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