THE IMPORTANCE OF OSA IDENTIFICATION IN THE BARIATRIC PATIENT

If you look for OSA, you will find it. An estimated 2 to 4 percent of the adult population is said to suffer from symptomatic OSA, and asymptomatic cases (no report of sleepiness) among middle-aged populations are as prevalent as nine percent in women and 24 percent in men.7 Given the increasing rates of obesity (a major risk factor for OSA) in the US, we are likely to see that more and more surgical patients will have OSA, the vast majority undiagnosed. It is important to identify OSA in the surgical patient because it can lead to a plan that can minimize perioperative complications associated with the disorder. First, the airway is the obvious anesthetic concern in patients with OSA. Studies confirm an increased risk of difficult intubation, and excess pharyngeal tissue may lead to difficulties with mask ventilation. More recent data have demonstrated that OSA patients are at risk for major cardiovascular morbidity and mortality, which may certainly impact the perioperative course. Hypertension is common among OSA patients and appears to be related to repeated increased sympathetic tone secondary to oxyhemoglobin desaturation and frequent nocturnal arousals. The increased sympathetic activity surrounding the apneic episodes may also contribute to a documented increase in sudden death at night, more early morning acute coronary events, and an increase in arrhythmias. OSA I an independent risk factor for coronary artery disease, and the hazard ratio for stroke or death is nearly double the normal population, even after adjustment for comorbidities.

THERAPEUTIC OPTIONS FOR OSA

Therapeutic options for OSA include continuous positive airway pressure (CPAP) and related devices, such as bilevel positive airway pressure (BiPAP), oral appliances, or surgery. CPAP is more effective at improving OSA when compared to oral appliances, but may not be different subjectively. The most commonly used oral appliances act by advancing the mandible in order to increase the patency of the upper airway. Oral appliances are probably best suited for patients with mild OSA or those who cannot tolerate CPAP.

IMPORTANCE OF PREOPERATIVE TREATMENT AND SCREENING

Given the perioperative risks associated with OSA, it is important to diagnose and treat OSA preoperatively. Although no studies definitively demonstrate that diagnosing and treating OSA leads to improved surgical outcomes, studies do show that the lack of diagnosis and treatment leads to worse postoperative surgical outcomes. Given the positive systemic changes that occur with successful treatment of OSA, such as improvement in hypertension and nocturnal oxyhemoglobin saturation levels, it appears that CPAP therapy should be initiated as early as possible. Do patients with suspected sleep apnea need to undergo PSG testing, the gold standard for diagnosis of OSA? Given the time and expense involved in such testing and the potential number of patients involved, PSG testing may be more appropriately reserved for those suspected to have OSA. For that subset of patients, an HST sleep study will also allow initiation of therapy, such as CPAP, prior to surgery. The use of newer home-diagnostic HST equipment offers an attractive alternative to traditional laboratory PSG (by both reducing cost and increasing patient comfort), but valid means to conduct such studies do not yet exist.

PERIOPERATIVE CONCERNS: ANESTHESIA

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

POSTOPERATIVE MONITORING

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

CONCLUSION

If not diagnosed or suspected, OSA may place the patient at unnecessary risk postoperatively. Less experienced providers may increase the frequency of administration or the dose of narcotics in an effort to make the patient more comfortable. In the patient with OSA, the result may by respiratory compromise leading to respiratory arrest. In a patient with a difficult airway, or in an offsite location such as radiology, the consequences can be grave. An appreciation of the seriousness of OSA, knowledge of best practices, and team focus on patient safety helps avoid adverse outcomes.OSA is a highly prevalent, frequently undiagnosed, and clinically meaningful medical condition that is particularly perturbed in the perioperative period and can lead to worse surgical outcomes if not recognized and treated. One can screen for possible OSA by employing brief screening tools and conducting focused physical examinations (both outlined in this article) that, if positive, should prompt polysomnography for definitive diagnosis and treatment where possible. The perioperative implications include the need for diagnosis and treatment of previously undiagnosed individuals, airway management, pain control issues, and postoperative monitoring needs. Surgeons, anesthesiologists, and nurses providing care to this patient population need to be fully aware of the risks involved and plan accordingly.

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