Obstructive sleep apnea (OSA) is a prevalent. Perioperative Screening for and Management of Patients with Obstructive Sleep Apnea.

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1 Perioperative Screening for and Management of Patients with Obstructive Sleep Apnea Eswar Sundar, MD, Jacqueline Chang, MD, and Gerald W. Smetana, MD Abstract Objective: To provide a comprehensive review of studies related to screening for and perioperative management of patients with possible obstructive sleep apnea (OSA). Methods: We conducted a MEDLINE search for publications related to the incidence and morbidity of OSA, screening for OSA in perioperative patients, effects of anesthesia on OSA and the anesthetic management of patients with OSA. A manual search of bibliographies was undertaken. Results: Anesthesia and surgery are associated with loss of rapid eye movement (REM) sleep and subsequent rebound associated with exacerbation of OSA-related symptoms. Narcotic analgesics, muscle relaxants, and cholinesterase inhibitors also exacerbate OSA. OSA confers higher rates of perioperative airway management difficulties and traditional postoperative pulmonary complications. Available screening tools are described. An algorithm for the postanesthetic management of screen-positive patients that reduces the need for continuous monitoring and continuous positive airway pressure (CPAP) application is proposed. Conclusion: OSA is an important risk factor for perioperative medical complications. While screening tools for OSA in the perioperative populations have methodological deficiencies including high rates of false-positives leading to heavy resource utilization, we recommend their use before major noncardiac surgery. Obstructive sleep apnea (OSA) is a prevalent sleep disorder characterized by recurrent episodes of partial or complete upper airway obstruction during sleep. These obstructions cause low blood oxygen levels and sympathetic activation. Hypoxia varies with the length of the disturbance, lung volume, and the degree of intrapulmonary shunting [1]. The apneas and hypopneas are terminated by arousals that disrupt sleep. Recurrent sleep disruptions result in excessive daytime sleepiness. Loud habitual snoring is a common feature, which signifies the presence of a narrow, floppy airway. The apnea-hypopnea index (AHI) is often used to quantify the severity of OSA. The AHI is a measure of the number of apneas and hypopneas per hour of sleep. By consensus, mild sleep apnea is an AHI of 5 to 15 events per hour, moderate OSA is 15 to 30 events per hour, and severe OSA is greater than 30 events per hour [2]. Medicare guidelines require an AHI of at least 15 or an AHI of 5 to 15 with 2 comorbidities to establish the diagnosis. Comorbidities associated with OSA include cardiovascular disease, heart failure, arrhythmias, hypertension, cerebrovascular disease, metabolic syndrome, obesity, and gastroesophageal reflux [3]. The daytime sleepiness associated with OSA is associated with reduced vigilance and an increased risk of motor vehicle accidents [4]. An AHI of < 5 per hour does not confidently exclude the diagnosis of OSA; repeated sleep studies on consecutive days may be discordant [5]. There is some night-tonight variance in the AHI independent of duration of sleep time. A first-night effect refers to the variance observed with polysomnography (PSG) results between the first night of testing and subsequent testing. Plausible reasons for first-night effect include anxiety, psychiatric disorders, psychoactive medications, alcohol intake, and possibly the age of the patient [5]. The percentage of patients misdiagnosed based on a single-night study may be as high as 43%, but these effects are seen exclusively in the mild end of the OSA spectrum. Prevalence and Risk Factors In the middle-aged population and using an AHI > 5, 24% of men and 9% of women have disordered breath- From the Beth Israel Deaconess Medical Center, Boston, MA. Vol. 18, No. 9 September 2011 JCOM 399

2 Obstructive Sleep Apnea Class 1 Class 2 Class 3 Class 4 Figure 1. Samsoon and Young s modification of the Mallampati classification of the upper airway based on the size of the tongue and pharyngeal structures. Class 1: Tonsillar pillars, fauces, uvula, and soft palate are all visible. Class 2: Tonsillar pillars are hidden while the fauces, uvula, and soft palate are visible. Class 3: Tonsillar pillars, fauces, and uvula are hidden with only the soft and hard palate visible. Class 4: Only hard palate is visible. ing. If the definition also includes daytime sleepiness, then 4% of men and 2% of middle-aged women have OSA [6]. OSA rates increase with age until the age of 65 years at which time the prevalence plateaus [7]. In the Wisconsin Cohort Study, a 10% weight gain was associated with a 6-fold increased risk of OSA [8]. Neck circumference is a strong predictor of sleep apnea. Fatty tissue in the neck causes narrowing of the airway, thus increasing the chances of airway closure during sleep [7]. Rates of OSA are higher among men than women [6,9]. However, women are less likely to report classic symptoms of sleep apnea and therefore may be underdiagnosed. In 1 study, many women with significant sleep apnea did not have symptoms [10]. It is difficult to exclude the diagnosis or grade the severity of OSA in women by history and physical examination findings alone. Rates of OSA differ among ethnic groups. The odds ratio for severe sleep-disordered breathing for African Americans was 2.55 compared with whites, even after adjustment for BMI, sex, and age [2]. The prevalence is higher in selected surgical populations. For example, 70% of patients undergoing bariatric surgery and 60% of those undergoing neurosurgical procedures have OSA [2]. In a study of consecutive women coming in for bariatric surgery and using a cutoff of AHI > 5, 84% of participants had at least mild OSA, and 53% had moderate to severe disease (AHI > 15) [11]. In contrast, a study of 433 patients undergoing general surgery found a 3.2% prevalence of OSA; however, less than half of patients endorsing OSA symptoms agreed to a sleep study, and therefore actual prevalence may have been higher [12]. The great majority of patients (approximately 70% 80%) remain undiagnosed [13]. Effects of Anesthesia and Surgery in OSA Airway Loss of consciousness during general anesthesia or deep sedation is accompanied by an abrupt decrease in upper airway muscle activity and an increase in upper airway collapsibility [14]. The activity of the genioglossus and other extrinsic tongue muscles innervated by the hypoglossal nerve is depressed by sleep or anesthesia through central effects. In a patient with fatty neck deposits or predisposing anatomy (higher Mallampati score) (Figure 1), muscle relaxation due to general anesthesia and deep sedation predisposes to upper airway obstruction [1,4]. The increased resistance of the narrowed airway requires more negative intraluminal pressures, and airway wall compliance is increased at lower calibers [1]. The primary site of collapse within the upper airway during sleep or anesthesia is the velopharynx in 80% of patients [15]. The other common site of collapse is retrolingual. These vulnerable segments correspond to the narrowest levels within the upper airway [1]. 400 JCOM September 2011 Vol. 18, No. 9

3 Intravenous anesthetics increase airway collapsibility. Drugs such as pentothal, propofol, opioids, benzodiazepines, and nitrous oxide may reduce the tone of the pharyngeal musculature that maintains airway patency [16]. Increasing depth of propofol anesthesia increases the collapsibility of the upper airway. This is due in part to profound inhibition of activity of the genioglossus muscle, the major dilator muscle of the upper airway [17]. Muscle relaxants exacerbate the problem as well. Unwarranted use of cholinesterase inhibitors may also inhibit genioglossus activity resulting in airway obstruction [18]. In 1 large series of patients undergoing surgery for OSA, the incidence of failed intubation was 5% compared with 0.05% in the general surgical population [19,20]. Patients with failed intubations are more likely to have OSA [16]. OSA, not body weight itself, predicts difficult direct laryngoscopy [21 23]. Sleep Although anesthesia without surgery in volunteers is usually restorative, sleep is usually disturbed in the postoperative period [24,25]. Anesthesia and surgery abolish rapid eye movement (REM) sleep. The reduction in REM is more pronounced after major surgery [26 29]. Recovery of REM sleep usually occurs in the 2nd or 3rd postoperative day [30,31]. In REM sleep, the neural drive to the pharyngeal muscles is at a minimum, resulting in hypotonia of these muscles. Severity of OSA can be aggravated by REM suppression and subsequent rebound a few days later [1]. REM rebound contributes to hemodynamic instability, myocardial ischemia and infarction, stroke, mental confusion, and wound breakdown. In addition pain disrupts sleep in the immediate postoperative period [1]. In healthy volunteers without pain, opioids suppress both REM and slow-wave sleep [30]. These studies suggest that the stress of surgery and opioids contribute more to the disruption of sleep patterns and REM sleep rebound postoperatively than general anesthesia itself. Hemodynamics Cardiac arrhythmias such as ventricular tachycardia and severe bradycardia occur more commonly among patients with OSA than in the general population. Perioperative massive blood losses or large fluid and electrolyte shifts during surgery are additional predisposing factors for arrhthmias. Atrial fibrillation, atrioventricular nodal block, ventricular ectopy, and nonsustained ventricular tachycardia are also common in patients with OSA [32]. The most frequent dysrhythmia is a sinus bradycardia followed by tachycardia. The extent of slowing correlates with apnea duration and severity of desaturation. The sudden increase in heart rate that occurs after apnea termination is due to the combined effect of decreased vagal parasympathetic tone and increased sympathetic neural activity related to hypoxemia and arousal [31,33]. Perioperative Morbidity Associated with OSA Severe OSA is associated with an increased risk of perioperative morbidity. Oxygen desaturation, arrhythmias, and sleep disruption are the most common complications. However, the true impact of OSA on perioperative morbidity is difficult to study; many patients with OSA remain undiagnosed and untreated. Hence, the prevalence of perioperative complications associated with OSA may be underestimated. Yegneswaran and others from Canada in a case-matched retrospective cohort study reported that the risk of postoperative complications was 44% for subjects with OSA compared with 28% in those without OSA. The vast majority of these excess complications were due to respiratory events. Patients with OSA who were not on home continuous positive airway pressure (CPAP) and required CPAP after surgery had the highest rates of postoperative complications [34]. In another report investigators used data from the National Inpatient Sample (NIS) to compare subjects with OSA with matched controls based on demographic variables using the propensity scoring method. Patients with OSA had higher rates of postoperative pulmonary complications such as pulmonary embolism, aspiration pneumonia, and respiratory failure [33]. Actual complication rates may be higher as the use of administrative databases leads to underreporting of adverse events. However, at least 1 study reports that the severity of OSA does not influence the rate of perioperative complications in patients following bariatric surgery [11]. In a casecontrol study of morbidity after hip or knee arthroplasty, there was a substantial increase in unplanned intensive care unit admission in subjects with OSA [35]. Currently, there is insufficient evidence to support the view that mild OSA increases adverse postoperative outcomes [36,37]. Vol. 18, No. 9 September 2011 JCOM 401

4 Obstructive Sleep Apnea Table 1. Characteristics of Studies Used to Screen for OSA in the Surgical Population Berlin Questionnaire STOP-BANG ASA Checklist P-SAP Study Validating author Chung et al [38] Chung et al [41] Chung et al [38] Ramachandran et al [43] Number of Items 10 questions in 3 categories. No calculated or measured items 8 items including calculated and measured items 14 questions in 3 categories including calculated and measured items 9 items including calculated and measured items and a specialized airway exam Validating test PSG and AHI PSG and AHI PSG and AHI PSG and AHI AHI 5 15 PSAP > 2 PSAP > 6 Sensitivity Specificity PPV NPV Likelihood ratio AHI >15 Sensitivity Specificity PPV NPV Likelihood ratio AHI > 30 Sensitivity Specificity PPV NPV Likelihood ratio Note: Subjects for the Berlin questionnaire, STOP questionnaire, and ASA checklist studies were mostly the same patients, 18 years or older and who were recruited at surgical preoperative clinics in Toronto. Only 211 (8.5%) of all patients who were screened with the ASA checklist, STOP questionnaire, and Berlin questionnaire underwent PSG [38,41]. For P-SAP, the screening test was administered to a general surgical group and a group of surgical patients who happened to have a PSG in the 6 months leading up to surgery. AHI = apnea-hypopnea index; NPV = negative predictive value; PPV = positive predictive value; PSG = polysomnography. Preoperative Screening for OSA Given the risks associated with OSA in the perioperative period, ASA guidelines stress the importance of perioperative diagnosis and management of patients with OSA. The gold standard of diagnosis of OSA and severity grading remains the overnight sleep study, but because of constraints of time, personnel, and cost, it is an impractial screening mechanism for OSA. Many authors have proposed the use of clinical prediction tools to identify patients at risk for having undiagnosed OSA. The most widely studied questionnaires are the Berlin questionnaire [38 40], the STOP and STOP-BANG [41], the American Society of Anesthesiologists (ASA) checklist [38,42], the P-SAP [43], and the SACS [44] (Table 1). Berlin Questionnaire The Berlin questionnaire (Table 2) consists of 10 questions across 3 categories. The Berlin questionnaire and 402 JCOM September 2011 Vol. 18, No. 9

5 Table 2. Berlin Questionnaire Height m Weight Kg Age Male/Female Please choose only 1 correct response to each question. Category 1 Points assignments Points tally 1. Do you snore? a. Yes b. No 1 point for a If you snore: 2. Your snoring is: a. Slightly louder than breathing b. As loud as talking c. Louder than talking d. Very loud can be heard in adjacent rooms 3. How often do you snore? a. Nearly every day b. 3 4 times a week c. 1 2 times a week d. 1 2 times a month e. Never or nearly never 4. Has your snoring ever bothered other people? 1 point for c 1 point for d 1 point for a 1 point for b a. Yes b. No c. Don t know 1 point for a 5. Has anyone noticed that you quit breathing during your sleep? a. Nearly every day b. 3 4 times a week c. 1 2 times a week d. 1 2 times a month e. Never or nearly never Category 1 is positive if total score is 2 or more points 2 points for a 2 points for b Total for Category 1 Category 2 Points assignments Points tally 6. How often do you feel tired or fatigued after your sleep? a. Nearly every day b. 3-4 times a week c. 1-2 times a week d. 1-2 times a month e. Never or nearly never 7. During your waking time, do you feel tired, fatigued or not up to par? a. Nearly every day b. 3 4 times a week c. 1 2 times a week d. 1 2 times a month e. Never or nearly never 8. Have you ever nodded off or fallen asleep while driving a vehicle? 1 point for a 1 point for b 1 point for a 1 point for b a. Yes b. No 1 point for a 9. If you have ever nodded off or fallen asleep while driving a vehicle, how often does this occur? a. Nearly every day b. 3 4 times a week c. 1 2 times a week d. 1 2 times a month e. Never or nearly never Category 2 is positive if total score is 2 or more points Category Do you have high blood pressure? a. Yes b. No c. Don t know Do not score for question 9 Total for Category 2 Category 3 is positive if answer is a Note: High risk of OSA if 2 or more categories scored as positive. Low risk of OSA if 1 or no categories scored as positive. Adapted with permission from reference Vol. 18, No. 9 September 2011 JCOM 403

6 Obstructive Sleep Apnea Table 3. STOP-BANG Scoring Model Circle Yes or No to the following questions: Snoring Do you snore loudly (louder than talking or loud enough to be heard through closed doors)? Tired Do you often feel tired, fatigued, or sleepy during daytime? Yes No Observed apneas Has anyone observed you stop breathing during your sleep? Yes No Blood pressure Do you have or are you being treated for high blood pressure? Yes No BMI BMI more than 35 kg/m 2? Yes No Age Age over 50 yr old? Yes No Neck circumference Neck circumference greater than 40 cm? Yes No Gender Male? Yes No Note: High risk of OSA if answering YES to 3 or more items. Low risk of OSA if answering YES to 2 or fewer items. Adapted with permission from reference 41. Yes No ASA checklist were validated by Chung et al [38] and demonstrated a moderately high level of sensitivity for OSA screening. Chung and colleagues administered the Berlin questionnaire to patients coming for surgery. Less than 10% of patients screened and invited for PSG actually attended PSG and completed the questionnaire; self selection was evident. The authors found similar sensitivities to the ASA questionnaire though specificity, positive predictive value, and negative predictive value were marginally higher with the Berlin questionnaire. The Berlin questionnaire was subsequently tested in patients attending a sleep clinic and correlated with a respiratory distress index. The authors of this retrospective chart review found that at a respiratory distress index cut-off of > 5, the sensitivity and specificity of the Berlin questionnaire were 0.68 and The authors concluded the Berlin questionnaire was not useful in a sleep clinic population [45]. The Berlin questionnaire also has the disadvantage of being lengthy [3,36,38]. STOP and STOP-BANG The STOP questionnaire [41] consists of 4 yes/no questions referring to Snoring, Tiredness, Observed stoppage of breathing during sleep, and blood pressure. The questionnaire was administered to 2467 patients who came to a preoperative clinic. All subjects were invited for overnight PSG; 27.5% of the subjects were classified as high-risk based on the STOP questionnaire. However, only 211 patients (< 8.5% of all patients who took the questionnaire) had overnight sleep studies. The sensitivities of the STOP questionnaire with AHI > 5, > 15, and > 30 as cut-offs were 65.6, 74.3, and 79.5%, respectively. The authors do not provide outcomes for patients who screened low risk on the STOP questionnaire and then subsequently came to the overnight sleep study. Self selection may have played a role, as patients who perceived that they might have sleep apnea may have been more likely to return for sleep studies. Smokers and younger patients were more likely to not attend the sleep study [38]. The STOP-BANG enhancement of the same questionnaire (Table 3) incorporated BMI, age, neck circumference, and gender into the scoring model, with sensitivity increasing to 83.6%, 93%, and 100% at AHI cut-offs of 5, 15, and 30 [41]. STOP-BANG, however, suffers from low specificity: 43% at an AHI of and 37% at an AHI > 30 [36]. Despite this drawback, the STOP-BANG screening tool has one of the lowest falsenegative rates (16%) among screening questionnaires for OSA [36]. The ease of use of this clinical test makes it a user-friendly option for screening for severe OSA in the immediate preoperative period [36]. ASA Checklist The ASA checklist is divided into 3 categories (physical characteristics, OSA symptoms, and somnolence) with 4 to 5 items in each (Table 4). The first section of the scoring system uses signs and symptoms to assess severity of OSA when a formal sleep study is lacking. However, the grading of OSA severity based on clinical features is subject to misclassification and is to some extent arbitrary. A patient is considered high risk if 2 or more categories are scored positive. 404 JCOM September 2011 Vol. 18, No. 9

7 Table 4. American Society of Anesthesiologists (ASA) Checklist Category 1: Predisposing physical characteristics a. BMI 35 b. Neck circumference > 45 cm/17 cm (men) or 40 cm/16 (women) c. Craniofacial abnormalities affecting the airway d. Anatomical nasal obstruction e. Tonsils nearly touching or touching the midline Category 2: History of apparent airway obstruction during sleep a. Snoring loud enough to be heard through closed doors b. Frequent snoring c. Observed pauses in breathing during sleep d. Awakens from sleep with a choking sensation e. Frequent arousals from sleep Category 3: Somnolence a. Frequent somnolence or fatigue despite adequate sleep b. Falls asleep easily in a nonstimulating environment (eg, watching TV, reading, riding in or driving a car) despite adequate sleep c. Parent or teacher comments that child appears sleepy during the day, is easily distracted, is overly aggressive or has difficulty concentrating d. Child often difficult to arouse at usual awakening time If 2 or more items in this category are present, then this category is positive If 2 or more items are present (or 1 item if patient lives alone), then this category is positive If 1 or more items in this category are present, then this category is positive Category result Category result Category result Scoring: High risk of OSA if 2 or more categories are scored positive. Low risk of OSA if 1 or no categories are positive. Adapted with permission from reference 42. The ASA checklist has a lower specificity than the Berlin and STOP questionnaires. The odds ratio to predict milder forms of OSA was also lowest for ASA from among the 3 screening tools [38]. Chung suggests that patients identified as high risk based on the ASA checklist were more likely to have postoperative desaturations. However, in the ASA study a significantly higher number of patients had asthma as compared with patients in Berlin or STOP, and this may have skewed results [38]. P-SAP Prediction models that are derived in high prevalence populations yield higher positive predictive values than when the test is used in a lower risk population. In addition, difficulties are faced by investigators in getting study subjects to undergo PSG [38,41]. Investigators from Ann Arbor, Michigan, approached the issue differently with the P-SAP study. The P-SAP study compares variables present in both a general surgical population and in a surgical population that underwent PSG [43]. The authors performed the study in 2 steps. The first step involved deriving the screening test from a broad spectrum of surgical patients. The second step involved validating the screening test in a set of patients who had undergone overnight sleep study within the 6 months leading up to surgery. The P-SAP score (Table 5) validates 6 of the 8 elements of the STOP-BANG model but differs in that it uses upper airway elements such as high modified Mallampati class (Figure 1) and reduced thyromental distance (Figure 2) and includes type 2 diabetes. Modified Mallampati class is a validated marker of diagnosis and severity of OSA [36]. The P-SAP score has a higher sensitivity than the STOP questionnaire and the ASA checklist. Incidence of postoperative morbidity events was not analyzed as part of this study [43]. SACS Researchers from the Mayo Clinic used the Flemons prediction model [46] to generate a sleep apnea clinical score (SACS) (Table 6) [44]. Patients coming for inpatient surgery were divided into low and high risk Vol. 18, No. 9 September 2011 JCOM 405

8 Obstructive Sleep Apnea Table 5. Perioperative Sleep Apnea Prediction (P-SAP) Score Score 1 point for every item answered yes Points Height m Weight kg Male gender History of snoring Thick neck Mallampati 3 or 4 Hypertension (treated or untreated) Type 2 diabetes (treated or untreated) BMI > 30 Age > 43 Thyromental distance < 4 cm Note: A P-SAP score > 4 has a sensitivity of and a specificity of 0.773, positive predictive value 0.19, and negative predictive value 0.97 for the diagnosis of obstructive sleep apnea. Adapted with permission from reference 43. [44,47]. Combining a preoperative screening tool with intensive PACU observation was useful in predicting postoperative oxygen desaturations on the floor. The authors concluded that a 2-phase process to identify patients at higher risk for perioperative respiratory desaturations and complications may be useful to stratify and manage surgical patients postoperatively. Figure 2. The thyromental distance is the distance between the upper edge of the thyroid cartilage and the bony prominence of the chin with the head in fully extended position. The thyromental distance evaluates the anterior mandibular space. A thyromental distance of > 6.5 cm in the absence of other factors is usually predictive of an easy intubation. A length < 6 cm suggests a receding mandible and as such may be associated with difficulty in lining up the laryngeal axis with the pharyngeal axis during direct laryngoscopy. based on their SACS. Following surgery, patients were monitored in the postanesthesia care unit (PACU) for significant respiratory events (apnea, increased Fio 2 requirement, pain-sedation mismatch, or episodes of desaturation). Both SACS and PACU events were independent predictors of perioperative complications, respiratory complications, and oxygen desaturations Ramachandran et al published a meta-analysis of screening tools for OSA [36]. False-negative rates were substantial with all questionnaires and most clinical prediction models. The Berlin questionnaire, for example, has false-negative rates of 12.8% to 31.1% and a sensitivity and specificity of 69% and 56% in surgical patients [36]. High false-negative rates were also observed with the ASA model (12.3% 27.9%) and STOP questionnaire (20.5% 34.4%) [36,41]. In addition, workup bias in the 3 studies by Chung et al could artificially decrease the false-positive rate. False-positives could significantly increase costs both directly and indirectly because of a prolonged postanesthesia care unit stay as mandated by the ASA guidelines [42]. Around 25% of the general surgical population screens positive for OSA. Widespread use of preoperative screening questionnaires alone may lead to the use of CPAP for patients with milder forms of disease. Given the uncertain benefit of CPAP in patients with mild sleep apnea, and high sensitivity and low specificity of most screening tests, the cost-benefit balance of applying CPAP to all patients screening positive is unclear. This points to the importance of identifying 406 JCOM September 2011 Vol. 18, No. 9

9 Table 6. Flemons Sleep Apnea Clinical Score (SACS) Hypertension Historical question 1 Do you have high blood pressure or have you been told to take medication for high blood pressure? Yes No If you snore, people who have shared or are sharing your bedroom tell you that you snore (pick one answer) Usually (3 5 times a week) Always (every night) Historical question 2 Neck circumference If you gasp or choke in your sleep, the frequency of these symptoms is Usually (3 5) times a week Always (every night) Neck circumference is cm (we will measure you) Not Hypertensive SACS Prediction Chart Hypertensive No historical features One historical feature present Both historical features present Neck circumference, cm No historical features One historical feature present < > Both historical features present Note: Probability of sleep apnea is low if SACS is < 15. Probability of sleep apnea is high if SACS is 15. Adapted with permission from reference 44. a critical outcome measure for defining significant OSA [36]; for example, presence of a certain number of obstructive apneas or desaturations in the immediate recovery period in high-risk patients could further help to triage the large number of screen-positive patients. Optimal Anesthetic Techniques for Patients With OSA There is no definitive evidence supporting one anesthetic technique over another for patients with OSA. Avoiding or minimizing sedative premedication in an unmonitored setting may be prudent [31,48]. The type of surgery (minor versus major, airway versus nonairway, noninvasive versus invasive surgery) is an important predictor of outcome [16]. Patients with sleep apnea are more likely to have difficult airways and hence additional help and instruments like fiberoptic bronchoscopes, bougies, various types of laryngoscope blades and laryngeal mask airway devices should be available [12,48]. Based on expert opinion, patients who use a CPAP at home should use personal CPAP machines during procedures that utilize mild to moderate sedation and do not involve the face or neck. Vol. 18, No. 9 September 2011 JCOM 407

10 Obstructive Sleep Apnea If CPAP cannot be used during sedation, keeping the patient semirecumbent or lateral might minimize the gravity-induced hypotonia of the oral and pharyngeal muscles. An arterial line may be necessary if noninvasive blood pressure monitoring is inaccurate because of the inability of the cuff to conform to the arm, and also measurement of arterial blood gases may assist in optimizing intraoperative ventilation. Sedation and narcotic-based analgesia may exacerbate symptoms of sleep apnea; however, there are no adequately powered studies to guide analgesic therapy of these patients [16]. ASA guidelines recommend regional anesthesia rather than general anesthesia for peripheral surgery [42]. The ASA guidelines, however, remain equivocal regarding whether combined regional and general anesthetics techniques are safer [42]. Excessive use of neostigmine after adequate return of neuromuscular function has been associated with airway collapse [18,49], while inadequate reversal of neuromuscular agents is clearly not desirable. Overenthusiastic use of anticholinesterases may also carry risk. Postoperative Care in the Recovery Area The 2006 ASA guidelines recommend that patients with OSA should be observed for 3 hours longer than a patient who does not have OSA before discharge to an unmonitored area. However, there is no guideline as to how long patients without OSA need to be monitored in the recovery area as discharges and transfers are usually made on the basis of an Alderete s score or some similar modification. If a significant episode of airway obstruction or apnea occurs during the immediate postoperative period, the ASA recommends that postoperative monitoring continue for 7 hours. However, monitoring in the recovery room for that length of time may not be feasible in most community hospitals [42]. The guideline recommends an arterial blood gas to determine if patients with mild or moderate OSA has an arterial Paco 2 of > 50 mm Hg. This may not be possible preoperatively in many ambulatory centers. The consultants suggest that respiratory carbon dioxide monitoring should be used during moderate or deep sedation; however, expiratory carbon dioxide monitoring in patients who are not intubated is subject to dead space artifacts and erroneously low end tidal CO 2 levels. A multimodal approach for analgesia is advocated by some experts. Including drugs like nonsteroidal anti- Table 7. Postanesthetic Complications and Adverse Events Associated with OSA Respiratory Cardiovascular Oxygen desaturation Obstructive apnea Central apnea Atrial fibrillation Tachy-brady arrhythmias Hypertension Pulmonary edema inflammatory drugs, tramadol, ketamine, pregabalin, gabapentin, and dexamethasone in the analgesic regimen can provide beneficial opioid-sparing effect [50] and minimize the opioid-related respiratory depression in OSA patients. For example, postoperative oxygen desaturations were 12 to 14 times more likely to occur in OSA patients receiving postoperative oral or parenteral opioids as compared with those treated with nonopioid analgesic agents [51 53]. Patients who are at high risk of OSA based on screening questionnaires and who have recurrent PACU respiratory events are more likely to have postoperative respiratory complications. Monitored inpatient beds and high dependency are some areas where OSA patients can safely recover. These patients may also require commencement of postoperative PAP therapy [50]. Patients with mild OSA (AHI 5 15) who have undergone minor surgery without recurrent PACU respiratory events and who did not require high doses of oral opioids for analgesia may be discharged home at the discretion of the attending physician [50]. The general consensus is that it is safe to discharge patients after monitored care anesthesia or regional anesthesia if postoperative narcotics will not be required [54,55]. Table 7 lists postanesthetic adverse events that are more likely to occur in patients with OSA compared to patients without OSA. The approach we use in our institution for screening and management is shown in Figure 3. Patients who screen positive for OSA are given a sleep trial. After ensuring that patient is back at baseline or near baseline oxygen requirements and pain control is satisfactory, the patient is left alone and observed for 30 minutes in the recovery room. A patient is deemed to have failed the sleep trial if there are oxygen desaturations of < 90% on 2 or more occasions during JCOM September 2011 Vol. 18, No. 9

11 Patient is deemed OSA screen-positive if he/she has 2 or more of the following: Snoring Witnessed apneas Excessive daytime sleepiness Neck circumference >17.5 in males or >16.5 in females BMI > 30 Known CPAP compliant OSA patient Screen positive for OSA or noncompliant OSA patient General anesthesia MAC, neuraxial or block General anesthesia MAC, neuraxial or block Sleep trial No OSA events Has OSA events or fails sleep trial No OSA events or passes sleep trial Order and page RT for PAP treatment in the PACU after ruling out central apnea and when the patient is back to baseline oxygen requirements. No need for consults. No need for PAP therapy or consults in the PACU Order and page RT for PAP treatment in the PACU after ruling out central apnea and when the patient is back to baseline oxygen requirements. No need for consults. No need for PAP therapy or consults in the PACU Discharge from PACU when patient reaches PAD or PAR criteria On the inpatient floor whenever the patient sleeps apply appropriate PAP treatment as per order for the following: All known OSA patients who are CPAPcompliant (with and without events) Screen-positive patients who fail sleep trial in PACU CPAP-noncompliant OSA patients who fail sleep trial in PACU On the inpatient floor monitor the following patients and consider PAP treatment for the following: Screen-positive patients who pass the sleep trial CPAP-noncompliant patients who pass the sleep trial Rule out central apnea and ensure that patient is back at baseline or near baseline oxygen requirements. Patient must have 1 and either 2 or 3 to declare that the patient has failed the sleep trial. 1. Desaturaion of < 90% on 2 or more occasions during 30 minutes of observation 2. Obstructive apneic episodes 3. Respiratory rate < 8/min Figure 3. The Beth Israel Deaconess Medical Center OSA screening tool and management pathway. Reproduced with permission from Gilmartin G, Dorion S, Sundar E; Beth Israel Deaconess Medical Center OSA Task Force. CPAP = continuous positive airway pressure; MAC = monitored anesthesia care; PACU = postanesthesia care unit; PAD = postanesthesia discharge score; PAP = positive airway pressure; PAR = postanesthesia recovery score; RT = respiratory therapist. Vol. 18, No. 9 September 2011 JCOM 409

12 Obstructive Sleep Apnea minutes of observation. In addition, the patient must have either obstructive apneic episodes or a respiratory rate < 8 breaths/min. Patients who fail the sleep trial are ordered PAP treatment after central apnea is ruled out and when the patient is back to baseline oxygen requirements. Ambulatory surgery patients who screen high risk and subsequently fail the sleep trial are admitted to the hospital and are not permitted to go home on the night of surgery. CONCLUSION OSA is an important risk factor for perioperative morbidity. Its true impact may be vastly underestimated given that many patients coming for surgery remain undiagnosed. The use of screening tools to identify patients at high risk of OSA is important. However many of these screening tools suffer from methodological deficiencies including false-positive results. False-positives may lead to heavy CPAP resource utilization and unnecessary admissions. It is important for physicians to further identify a critical outcome measure for defining OSA, eg, obstructive apneas or desaturations in the immediate recovery period, that could further triage these patients and lead to appropriate care. Corresponding author: Eswar Sundar MD, Dept. of Anesthesiology, BIDMC, 1 Deaconess Rd, CC513, Boston, MA 02215, esundar@bidmc.harvard.edu. Financial disclosures: None. References 1. Hillman DR, Platt PR, Eastwood PR. Anesthesia, sleep, and upper airway collapsibility. Anesthesiol Clin 2010;28: Yaggi HK, Strohl KP. Adult obstructive sleep apnea/hypopnea syndrome: definitions, risk factors, and pathogenesis. Clin Chest Med 2010;31: Seet E, Chung F. Obstructive sleep apnea: preoperative assessment. Anesthesiol Clin 2010;28: Shafazand S. Perioperative management of obstructive sleep apnea: ready for prime time? Cleve Clin J Med 2009;76 Suppl 4:S Mosko SS, Dickel MJ, Ashurst J. Night-to-night variability in sleep apnea and sleep-related periodic leg movements in the elderly. Sleep 1988;11: Young T, Palta M, Dempsey J, et al. The occurrence of sleep-disordered breathing among middle-aged adults. N Engl J Med 1993;328: Duran J, Esnaola S, Rubio R, Iztueta A. Obstructive sleep apnea-hypopnea and related clinical features in a population-based sample of subjects aged 30 to 70 yr. Am J Respir Crit Care Med 2001;163: Young T, Finn L, Peppard PE, et al. Sleep disordered breathing and mortality: eighteen-year follow-up of the Wisconsin sleep cohort. Sleep 2008;31: Redline S, Kump K, Tishler PV, et al. Gender differences in sleep disordered breathing in a community-based sample. Am J Respir Crit Care Med 1994;149: Collop NA, Adkins D, Phillips BA. Gender differences in sleep and sleep-disordered breathing. Clin Chest Med 2004;25: Weingarten TN, Flores AS, McKenzie JA, et al. Obstructive sleep apnoea and perioperative complications in bariatric patients. Br J Anaesth 2011;106: Fidan H, Fidan F, Unlu M, et al. Prevalence of sleep apnoea in patients undergoing operation. Sleep Breath 2006;10: Punjabi NM. The epidemiology of adult obstructive sleep apnea. Proc Am Thorac Soc 2008;5: Hillman DR, Walsh JH, Maddison KJ, et al. Evolution of changes in upper airway collapsibility during slow induction of anesthesia with propofol. Anesthesiology 2009;111: Eastwood PR, Szollosi I, Platt PR, Hillman DR. Collapsibility of the upper airway during anesthesia with isoflurane. Anesthesiology 2002;97: Passannante AN, Tielborg M. Anesthetic management of patients with obesity with and without sleep apnea. Clin Chest Med 2009;30: Eastwood PR, Platt PR, Shepherd K, et al. Collapsibility of the upper airway at different concentrations of propofol anesthesia. Anesthesiology 2005;3: Herbstreit F, Zigrahn D, Ochterbeck C, et al. Neostigmine/ glycopyrrolate administered after recovery from neuromuscular block increases upper airway collapsibility by decreasing genioglossus muscle activity in response to negative pharyngeal pressure. Anesthesiology 2010;113: Esclamado RM, Glenn MG, McCulloch TM, Cummings CW. Perioperative complications and risk factors in the surgical treatment of obstructive sleep apnea syndrome. Laryngoscope 1989;99: Rose DK, Cohen MM. The airway: problems and predictions in 18,500 patients. Can J Anaesth 1994;41(5 Pt 1): Hiremath AS, Hillman DR, James AL, et al. Relationship between difficult tracheal intubation and obstructive sleep apnoea. Br J Anaesth 1998;80: Ezri T, Medalion B, Weisenberg M, et al. Increased body mass index per se is not a predictor of difficult laryngoscopy. Can J Anaesth 2003;50: Benumof JL. Obesity, sleep apnea, the airway and anesthesia. Curr Opin Anaesthesiol 2004;17: Tung A, Mendelson WB. Anesthesia and sleep. Sleep Med Rev 2004;8: Moote CA, Knill RL. Isoflurane anesthesia causes a transient alteration in nocturnal sleep. Anesthesiology 1988;69: JCOM September 2011 Vol. 18, No. 9

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