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Perioperative and Anesthesia Management


1

Introduction

Obstructive sleep apnea/hypopnea syndrome (OSAHS) is a growing health care concern with many potentially detrimental consequences and important anesthetic implications. A rise in obesity among the population of the United States corresponds with an upswing in the prevalence of OSAHS. Over the last two decades, the prevalence of OSAHS increased from 26.4% to 33.9% in males and from 13.2% to 17.4% in females. An elevation in the body mass index (BMI) of one standard deviation increases the likelihood of coexisting OSAHS by a factor of four. In the morbidly obese population, the incidence of obstructive sleep apnea (OSA) is approximately 55% in women and 77% in men. Undiagnosed and/or untreated OSA leads to an increased risk of adverse perioperative events, specifically serious pulmonary complications: difficult mask ventilation, difficult direct laryngoscopy or fiber-optic intubations, desaturation and/or airway obstruction, aspiration pneumonia, acute respiratory distress syndrome, or even death.

The airway obstruction in OSAHS patients results from a decrease in the upper airway muscle tone during sleep; airway narrowing due to the deposition of adipose tissue; and resultant increase in size of pharyngeal structures: the uvula, tonsils, tonsillar pillars, tongue, aryepiglottic folds, and the lateral pharyngeal walls ( Fig. 14.1 ). As a result, the shape of the pharynx changes from a long transverse (lateral) and a short anterior–posterior axis into a narrower ellipsoid with a shorter transverse and a longer anterior–posterior axis. This change in shape impairs the action of the anterior pharyngeal airway dilators: the tensor veli palitini, genioglossus, and hyoid muscles ( Fig. 14.2 ).

FIG. 14.1, (A) The action of the most important dilator muscles of the upper airway. The tensor palatine, genioglossus, and hyoid muscles enlarge the nasopharynx, oropharynx, and the laryngopharynx, respectively. (B) Collapse of the nasopharynx at the palatal level, the oropharynx at the glottic level, and the laryngopharynx at the epiglottic level.

FIG. 14.2, The effects of a 5-mm change in the anteroposterior (AP) diameter of the airway on airway cross-sectional area is shown for two equally elliptical airways with different lateral/AP ratios. (A) The lateral/AP ratio = 0.5. (B) The lateral/AP ratio = 2. The lateral dimension of each ellipse was held constant. The solid line represents the starting area (3 cm 2 in both ellipses), and the dotted line represents the area after a 5-mm increase in the AP diameter. The area change is greater in the ellipse with a more lateral orientation (B).

A substantial number of patients seen in the operative units may have undiagnosed and untreated OSAHS. Recent reports have shown that approximately one-quarter of patients undergoing elective surgery have OSAHS, and over 80% of these cases are undiagnosed. High prevalence of undiagnosed OSAHS necessitates utmost vigilance, as well as prevention and early recognition of potentially devastating complications. The inability to intubate the patient, respiratory obstruction after tracheal extubation, and severe respiratory depression and respiratory arrest after the administration of sedatives and narcotics are some of the biggest concerns for anesthesiologists. Gupta et al. compared the occurrence of perioperative complications in OSA ( n = 101) and non-OSA patients ( n = 101) after a hip or knee replacement and reported 39% and 18% complication rates (hypoxemia, hypercapnia, delirium) in the two groups, respectively. These results are corroborated by a number of other large studies, which demonstrate an increased likelihood of perioperative respiratory complications in patients undergoing various types of surgical procedures.

Practice guidelines for the perioperative management of patients with OSAHS published by the American Society of Anesthesiologists (ASA) recommend the use of a scoring system to estimate a risk for perioperative complications from OSAHS, which incorporates three factors: (1) the severity of OSAHS, (2) the invasiveness of the surgery and anesthesia, and (3) the requirement for postoperative opioids ( Table 14.1 ). Patients with an overall score of 5 or greater have an increased risk of perioperative complications.

Table 14.1
Summary of the Recommendations for the Perioperative Care of OSA Patients Developed by the American Society of Anesthesiologists
Adapted from
  • I.

    Preoperative evaluation

  • Collaboration between anesthesiologists and surgeons is advised to develop a perioperative plan for patients with suspected sleep apnea

  • Preoperative evaluation should include a review of past medical records, interview with the patient and/or family, and physical examination

  • Sleep studies should also be reviewed if available

  • II.

    Inpatient/outpatient surgery

Determination should be made after careful assessment of (1) presence of OSA, (2) anatomic and physiologic derangements, (3) comorbidities, (4) nature of surgery, (5) type of anesthesia, (6) need for postoperative opioids, (7) patient's age, (8) adequacy of postoperative monitoring, and (9) capabilities of the outpatient center
  • III.

    Preoperative preparation

  • Careful selection of the intraoperative medications to minimize the risk of respiratory compromise

  • Use local anesthetics or peripheral nerve blocks with or without moderate sedation for superficial procedures

  • Continuous monitoring by capnography of the ventilator status in the presence of moderate sedation due to increased risk of airway obstruction

  • Administer CPAP or oral appliance during sedation in patients previously using the devices

  • Secure airway during general anesthesia and deep sedation

  • Use neuraxial anesthesia (spinal/epidural) for peripheral procedures

  • Extubate after a full reversal of the neuromuscular blockade

  • Extubate in the lateral, semi-upright, or other nonsupine position

  • IV.

    Postoperative management

  • Consider using regional analgesia to avoid using systemic opioids

  • Evaluate risks and benefits of using neuraxial analgesia using opioid only or opioid–local anesthetic mixture versus local anesthetic only

  • Avoid or use with caution continuous background infusions of medication when using patient-controlled analgesia (PCA) with systemic opioids

  • Consider using nonopioid analgesics to reduce the requirement for narcotic medications

  • Exercise caution when combining benzodiazepines and barbiturates, as they increase the risk of respiratory depression

  • Judicious use of supplemental oxygen, as it may also suppress respiratory drive

  • Use CPAP or noninvasive positive pressure ventilation in patients who were using them preoperatively

  • Keep patients in the nonsupine position throughout the recovery process

  • Use continuous pulse oximetry after transfer from the recovery unit into stepdown or telemetry

  • In the event of hypoxemia, frequent, or severe airway obstruction, apply nasal CPAP or noninvasive positive pressure ventilation

  • V.

    Criteria for discharge to unmonitored settings

  • Postpone discharge until patients are no longer at risk of respiratory compromise

  • Monitor the adequacy of oxygen saturation on room air while patient is sleeping

The rate of possible complications varies between different types of anesthesia provided. Memtsoudis et al. assessed perioperative outcomes in 30,024 patients diagnosed with OSAHS who underwent an orthopedic surgery between 2006 and 2010 under neuraxial and/or general anesthesia. The authors found lower rates of perioperative complications (pulmonary and cardiac and need for blood products) and improved postoperative outcomes (mechanical ventilation, intensive care unit [ICU] admission, length and cost of hospitalization) in patients under neuraxial anesthesia (16.0%) compared with general (17.2%) or combined neuraxial-general anesthesia (18.1%) and concluded that the neuraxial anesthesia may be a more beneficial option for patients with OSA. Respiratory compromise can also occur after regional anesthesia as shown by a retrospective study of 206 patients with OSA scheduled for an orthopedic surgery in an outpatient setting, where 34% of the patients experienced hypoxemia postoperatively. Despite those results, Sabers et al. demonstrate that presence of OSA does not increase the risk of adverse events or unforeseen hospital admissions in patients undergoing procedures in the outpatient center. Thus the Society for Ambulatory Anesthesia concluded that patients diagnosed with OSA can be selected for an outpatient procedure if the following criteria are met: comorbid conditions are managed, patients are able to use their continuous positive airway pressure (CPAP) device postoperatively, and the postprocedural pain can be adequately managed with nonopioid medications. After an extensive review of the available scientific literature, the ASA developed specific guidelines and recommendations for the perioperative care of patients diagnosed with OSA ( Table 14.2 ).

Table 14.2
Scoring System for Calculation of Perioperative Risk in Patients With OSAHS ‡
Modified from Gross JB, Bachenberg KL, Benumof JL, et al. American Society of Anesthesiologists Task Force on Perioperative Management: Practice guidelines for the perioperative management of patients with obstructive sleep apnea: a report by the American Society of Anesthesiologists Task Force on perioperative management of patients with obstructive sleep apnea. Anesthesiology 2006;104(5):1081–93, with permission.
  • A.

    Severity of sleep apnea based on sleep study (or clinical indicators if sleep study not available). Point score ______ (0–3). * †

    • 0. None (AHI = 0–5)

    • 1. Mild (AHI = 6–20)

    • 2. Moderate (AHI = 21–40)

    • 3. Severe (AHI > 40)

  • B.

    Invasiveness of the surgery and anesthesia. Point score ______ (0–3).

    • 0. Superficial surgery under local or peripheral nerve block without sedation

    • 1. Superficial surgery with moderate sedation or general anesthesia or peripheral surgery with spinal or epidural anesthesia

    • 2. Peripheral surgery with general anesthesia or airway surgery with moderate sedation

    • 3. Major surgery or airway surgery with general anesthesia

  • C.

    Requirement of postoperative opioids. Point score ______ (0–3).

    • 0. None

    • 1. Low-dose oral opioids

    • 2. High-dose oral, parenteral, or neuroaxial opioids

Estimation of perioperative risk is calculated as follows: Overall score = the score for A plus the greater of the score for either B or C.

* One point may be subtracted if a patient has been on CPAP or noninvasive positive pressure support (NIPPV) before surgery and will be using his or her appliance consistently during the postoperative period.

† One point should be added if a patient with mild or moderate OSAHS also has a resting PaCO 2 greater than 50 mm Hg.

‡ Patients with a score of 5 or 6 may be at significantly increased perioperative risk from OSAHS.

2

Preoperative Assessment of the Patient

Whenever possible, the patient should be evaluated in a preoperative clinic several days before the planned surgery. The evaluation should include a review of the current and previous medical records, an interview of the patient, and a physical examination. Frequently, in the event of an emergency procedure or elective surgeries done in the outpatient centers, an evaluation by an anesthesiologist does not take place until immediately before the procedure. This unfortunately precludes recognition and presurgical management of medical conditions such as sleep apnea.

A careful review of all medical records is very important. Reviewing old medical records can be particularly useful with regard to previous anesthetic history, which may reveal airway difficulties, prolonged emergence, an unusual response to anesthetic agents, and the postoperative course. All coexisting medical conditions and treatments should be noted with special focus on the respiratory and cardiovascular organ systems. Any workup that has been done specific to OSAHS (polysomnographic testing, cardiac and pulmonary studies) should be checked, as it may provide valuable information regarding the severity of the disease. Use of CPAP or mouth appliances for the treatment of OSAHS should be investigated, and patients should be encouraged to bring CPAP equipment with them to the hospital on the day of their surgery.

A detailed history from the patient and bed partner, if possible, helps in the identification of patients with undiagnosed OSAHS. The patient should be asked about the quality of sleep, frequent awakening, energy level in the morning, and daytime sleepiness and fatigue. The bed partner might offer information related to snoring and apneic episodes during the night. Several tools are available to screen the surgical patients for the presence of OSA: the Berlin Questionnaire, ASA Checklist, and STOPBANG. These tools assess presence of snoring, pauses in breathing, arousals, or choking; daytime somnolence manifested by fatigue or drowsiness despite sufficient sleep; high blood pressure; or specific physical characteristics (BMI >35 kg/m 2 , neck circumference >17 inches in men and >16 in women, age, gender, structural abnormalities of the orofacial passages).

Many OSAHS patients have several coexisting diseases due to hypoxic episodes and obesity. A thorough physical examination is critical with a special focus on the physical characteristics such as body habitus, neck thickness, facial features including presence of a beard, mouth opening, and tongue size. The importance of a detailed cardiovascular examination cannot be overemphasized. One should have a low threshold for obtaining an electrocardiogram (ECG) and/or echocardiogram when a suspicion of compromised cardiovascular function arises, and severe cases should be referred to a specialist before an elective surgery. Hypoxic events are associated with several potentially detrimental cardiovascular derangements. For example, patients with moderate to severe OSAHS are nearly three times more likely to have nocturnal cardiac arrhythmias compared with non-OSAHS patients. Systemic hypertension is present in 50% of OSAHS patients and is more prevalent with increasing severity of OSAHS.

Special attention must also be given to the airway of the patient to recognize features predictive of potentially difficult airway management. Frequently, OSA patients have a large tongue and a thick neck, and the probability of a difficult tracheal intubation rises from 5% when the neck circumference is 40 cm to 35% when the neck circumference is 60 cm. Moreover, the commonly seen excessive adipose tissue in the interscapular region (“buffalo hump”) causes misalignment of the oral, pharyngeal, and tracheal axes during direct laryngoscopy. Determining whether tracheal intubation should be performed with the patient awake or under general anesthesia must be individualized on the basis of a methodical, complete airway examination ( Table 14.3 ).

Table 14.3
Components of the Preoperative Airway Physical Examination
Airway Examination Component Nonreassuring Findings
Size of the upper teeth Long incisors
Alignment of maxillary and mandibular incisors during normal jaw closure Maxillary incisors anterior to mandibular incisors (overbite)
Alignment of maxillary and mandibular incisors during voluntary protrusion of mandible Difficulty bringing mandibular incisors anteriorly to maxillary incisors
Extent of mouth opening (distance between open and lower incisors) Less than 3 cm
Visibility of uvula Limited view of the uvula when tongue is protruded with patient in sitting position (Mallampati class III and IV)
Shape of palate Highly arched or very narrow
Appearance and mobility of the oral structures Presence of an oral mass, stiffness, lack of resilience
Thyromental distance Less than three finger breadths (or <6 cm)
Length of neck Short
Thickness of neck Thick (>60 cm)
Range of motion of the cervical spine Diminished flexion or extension of the spine
This table displays some findings of the airway physical examination that may suggest the presence of a difficult intubation. The decision to examine some or all of the airway components shown in this table depends on the clinical context and judgment of the practitioner. The table is not intended as a mandatory or exhaustive list of the components of an airway examination. The order of presentation in this table follows the “line of sight” that occurs during conventional oral laryngoscopy.

2.1

Premedication

Sedatives and narcotics have a propensity to exacerbate the sleep-related apneic episodes and may impair lifesaving arousal in patients with OSAHS. Benzodiazepines and barbiturates preferentially decrease neural input to the upper airway dilating muscles, leading to airway obstruction. Anxiolytic drugs such as midazolam should only be administered when close monitoring of the patient by appropriate personnel is possible. This means that the drug should not be given until the patient is about to enter the operating room for surgery. Narcotic medications specifically are associated with a high risk of respiratory depression. Even small doses of narcotics given intravenously or epidurally can cause severe airway obstruction and apnea. Therefore administration of a combination of sedatives and narcotics can be disastrous. Because of the increased incidence of aspiration of gastric contents, an antacid and/or metoclopramide should be given to decrease the gastric acidity and volume. Glycopyrrolate to reduce oral secretions and dexamethasone to reduce airway edema, nausea, and vomiting are generally administered.

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