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

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AbstrAct

Objective: To provide a comprehensive review of stud-ies related to screening for and perioperative man-agement of patients with possible obstructive sleep apnea (OSA).

Methods: We conducted a MEDLINE search for publi-cations 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 bibliogra-phies 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 exacer-bate OSA. OSA confers higher rates of perioperative airway management difficulties and traditional postop-erative pulmonary complications. Available screening tools are described. An algorithm for the postanes-thetic management of screen-positive patients that reduces the need for continuous monitoring and con-tinuous positive airway pressure (CPAP) application is proposed.

Conclusion: OSA is an important risk factor for peri-operative 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.

O

bstructive sleep apnea (OSA) is a

preva-lent 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. Hy-poxia 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 nar-row, 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]. Medi-care 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 cardiovas-cular disease, heart failure, arrhythmias, hypertension, cerebrovascular disease, metabolic syndrome, obesity, and gastroesophageal reflux [3]. The daytime sleepiness asso-ciated with OSA is assoasso-ciated 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 consecu-tive days may be discordant [5]. There is some night-to-night 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-Perioperative Screening for and Management of

Patients with Obstructive Sleep Apnea

Eswar Sundar, MD, Jacqueline Chang, MD, and Gerald W. Smetana, MD

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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 under-diagnosed. 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 find-ings 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 popula-tions. For example, 70% of patients undergoing bariatric surgery and 60% of those undergoing neurosurgical pro-cedures 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 hypo-glossal 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 in-creased resistance of the narrowed airway requires more negative intraluminal pressures, and airway wall compli-ance is increased at lower calibers [1]. The primary site of collapse within the upper airway during sleep or anesthe-sia 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].

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.

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Intravenous anesthetics increase airway collapsibility. Drugs such as pentothal, propofol, opioids, benzodi-azepines, 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 obstruc-tion [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 reduc-tion in REM is more pronounced after major surgery [26–29]. Recovery of REM sleep usually occurs in the 2ndor 3rdpostoperative 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 contrib-utes to hemodynamic instability, myocardial ischemia and infarction, stroke, mental confusion, and wound breakdown.

In addition pain disrupts sleep in the immediate post-operative 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 opi-oids 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. Peri-operative massive blood losses or large fluid and elec-trolyte shifts during surgery are additional predisposing

factors for arrhthmias. Atrial fibrillation, atrioventricu-lar nodal block, ventricuatrioventricu-lar 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 in-creased sympathetic neural activity related to hypoxemia and arousal [31,33].

PerioPerative Morbidity assoCiated with osa Severe OSA is associated with an increased risk of peri-operative morbidity. Oxygen desaturation, arrhythmias, and sleep disruption are the most common complica-tions. However, the true impact of OSA on periopera-tive 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 con-tinuous positive airway pressure (CPAP) and required CPAP after surgery had the highest rates of postopera-tive 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 compli-cation 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 case-control 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].

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PreoPerative sCreening For osa

Given the risks associated with OSA in the perioperative period, ASA guidelines stress the importance of periop-erative 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 imprac-tial 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 question-naire [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 ques-tions across 3 categories. The Berlin questionnaire and

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

cat-egories. No calculated or measured items

8 items including calculated and measured items

14 questions in 3 catego-ries including calculated and measured items

9 items including calcu-lated and measured items and a special-ized airway exam

Validating test PSG and AHI PSG and AHI PSG and AHI PSG and AHI

PSAP > 2 PSAP > 6 AHI 5–15 Sensitivity 0.69 0.84 0.72 0.95 0.22 Specificity 0.56 0.56 0.38 0.26 0.91 PPV 0.78 0.81 0.72 0.80 0.84 NPV 0.45 0.60 0.38 0.60 0.27 Likelihood ratio 1.56 1.90 1.16 1.28 2.40 AHI >15 Sensitivity 0.79 0.93 0.79 0.97 0.26 Specificity 0.50 0.43 0.37 0.17 0.87 PPV 0.51 0.52 0.45 0.48 0.62 NPV 0.78 0.90 0.73 0.89 0.60 Likelihood ratio 1.58 1.63 1.25 1.16 2.00 AHI > 30 Sensitivity 0.87 1.00 0.87 0.98 0.32 Specificity 0.46 0.37 0.36 0.13 0.85 PPV 0.35 0.31 0.27 0.24 0.38 NPV 0.93 1.00 0.91 0.96 0.82 Likelihood ratio 1.61 1.58 1.35 1.12 2.13

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 screen-ing 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.

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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

1 point for c 1 point for d 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

1 point for a 1 point for b

4. Has your snoring ever bothered other people?

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

2 points for a 2 points for b

Category 1 is positive if total score is 2 or more points 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

1 point for a 1 point for b

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

1 point for a 1 point for b

8. Have you ever nodded off or fallen asleep while driving a vehicle?

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

Do not score for question 9

Category 2 is positive if total score is 2 or more points Total for Category 2 →

Category 3

10. Do you have high blood pressure? a. Yes b. No c. Don’t know

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 38.

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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 specific-ity, positive predictive value, and negative predictive value were marginally higher with the Berlin question-naire. The Berlin questionnaire was subsequently tested in patients attending a sleep clinic and correlated with a respiratory distress index. The authors of this retro-spective 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 0.49. 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 ques-tions referring to Snoring, Tiredness, Observed stoppage of breathing during sleep, and blood pressure. The ques-tionnaire 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 pa-tients (< 8.5% of all papa-tients 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 stud-ies. Smokers and younger patients were more likely to not attend the sleep study [38].

The STOP-BANG enhancement of the same ques-tionnaire (Table 3) incorporated BMI, age, neck cir-cumference, 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 15–30 and 37% at an AHI > 30 [36]. Despite this drawback, the STOP-BANG screening tool has one of the lowest false-negative 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 (physi-cal 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.

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)?

Yes No

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/m2? 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 permis-sion from reference 41.

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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 sug-gests that patients identified as high risk based on the ASA checklist were more likely to have postop-erative 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 ad-dition, 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 under-went 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 ele-ments 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. Modi-fied 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 clini-cal score (SACS) (Table 6) [44]. Patients coming for inpatient surgery were divided into low and high risk

Table 4. American Society of Anesthesiologists (ASA) Checklist

Category 1: Predisposing physical characteristics Category result

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

If 2 or more items in this category are present, then this category is positive

Category 2: History of apparent airway obstruction during sleep Category result

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

If 2 or more items are present (or 1 item if patient lives alone), then this category is positive

Category 3: Somnolence Category result

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 ad-equate sleep

c. Parent or teacher comments that child appears sleepy dur-ing the day, is easily distracted, is overly aggressive or has difficulty concentrating

d. Child often difficult to arouse at usual awakening time

If 1 or more items in this category are present, then this category is positive

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.

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based on their SACS. Following surgery, patients were monitored in the postanesthesia care unit (PACU) for significant respiratory events (apnea, increased Fio2 requirement, pain-sedation mismatch, or episodes of desaturation). Both SACS and PACU events were in-dependent predictors of perioperative complications, respiratory complications, and oxygen desaturations

[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 de-saturations and complications may be useful to stratify and manage surgical patients postoperatively.

Ramachandran et al published a meta-analysis of screen-ing tools for OSA [36]. False-negative rates were sub-stantial with all questionnaires and most clinical predic-tion models. The Berlin quespredic-tionnaire, 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 preop-erative 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 speci-ficity 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

Figure 2. The thyromental distance is the distance between the upper edge of the thyroid cartilage and the bony promi-nence 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. Table 5. Perioperative Sleep Apnea Prediction (P-SAP) Score

Score 1 point for every item answered yes Points Height______ m Weight______ kg

Male gender Yes /No

History of snoring Yes /No

“Thick” neck Yes /No

Mallampati 3 or 4 Yes /No

Hypertension (treated or untreated) Yes /No

Type 2 diabetes (treated or untreated) Yes /No

BMI > 30 Yes /No

Age > 43 Yes /No

Thyromental distance < 4 cm Yes /No

Note: A P-SAP score > 4 has a sensitivity of 0.667 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.

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a critical outcome measure for defining significant OSA [36]; for example, presence of a certain number of obstructive apneas or desaturations in the immedi-ate 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 anes-thetic 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 nonair-way, noninvasive versus invasive surgery) is an important predictor of outcome [16].

Patients with sleep apnea are more likely to have dif-ficult 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.

Table 6. Flemons Sleep Apnea Clinical Score (SACS)

Hypertension Do you have high blood pressure or have you been told to take medication for high blood pressure?

Yes No Historical

ques-tion 1

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

ques-tion 2

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 Neck circumference is _______ cm (we will measure you)

SACS Prediction Chart

Not Hypertensive 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 0 0 1 < 30 0 1 2 0 0 1 30–31 1 2 4 0 1 2 32–33 1 3 5 1 2 3 34–35 2 4 6 1 3 5 36–37 4 6 11 2 4 7 38–39 5 9 16 3 6 10 40–41 8 13 22 5 8 14 42–43 11 18 30 7 12 20 44–45 15 25 42 10 16 28 46–47 21 35 58 14 23 38 48–49 29 48 80 19 32 53 > 49 40 66 110

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.

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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 intraop-erative 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 recom-mend regional anesthesia rather than general anesthesia for peripheral surgery [42]. The ASA guidelines, how-ever, remain equivocal regarding whether combined re-gional 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 neuromus-cular 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 moni-tored 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 im-mediate 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 moder-ate OSA has an arterial Paco2 of > 50 mm Hg. This may not be possible preoperatively in many ambula-tory centers. The consultants suggest that respiraambula-tory 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 CO2 levels.

A multimodal approach for analgesia is advocated by some experts. Including drugs like nonsteroidal anti-

inflammatory drugs, tramadol, ketamine, pregabalin, gabapentin, and dexamethasone in the analgesic regi-men can provide beneficial opioid-sparing effect [50] and minimize the opioid-related respiratory depression in OSA patients. For example, postoperative oxygen de-saturations 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 screen-ing 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 desatu-rations of < 90% on 2 or more occasions during 30

Table 7. Postanesthetic Complications and Adverse Events Associated with OSA

Respiratory Oxygen desaturation

Obstructive apnea Central apnea

Cardiovascular Atrial fibrillation

Tachy-brady arrhythmias Hypertension

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Figure 3. The Beth Israel Deaconess Medical Center OSA screening tool and management pathway. Reproduced with permis-sion 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.

Patient is deemed OSA screen-positive if he/she has 2 or more of the following:

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 oxy-gen 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 oxy-gen 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 CPAP-

compliant (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

BMI > 30 Snoring Witnessed apneas Excessive daytime sleepiness Neck circumference >17.5 in males or >16.5 in females

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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 ad-mitted to the hospital and are not perad-mitted to go home on the night of surgery.

cONcLUsION

OSA is an important risk factor for perioperative mor-bidity. 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 method-ological deficiencies including false-positive results. False-positives may lead to heavy CPAP resource uti-lization 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 Anes-thesiology, BIDMC, 1 Deaconess Rd, CC513, Boston, MA 02215, esundar@bidmc.harvard.edu.

Financial disclosures: None.

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Figure

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
Table 2. Berlin	Questionnaire
Table 3. STOP-BANG	Scoring	Model
Figure 2.	The	thyromental	distance	is	the	distance	between	  the	upper	edge	of	the	thyroid	cartilage	and	the	bony	promi-nence	 of	 the	 chin	 with	 the	 head	 in	 fully	 extended	 position.
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References

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