Obstructive sleep apnea syndrome in ambulatory surgical patients

AORN Journal,  Sept, 2002  by Yvonne Mull,  Marshall Bedder

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A PSG report is used to determine the severity of OSA syndrome. Patients with sleep disorders are divided into categories indicating low, moderate, or high suspicion of apnea. Patients in the high suspicion category routinely are referred for a PSG before surgical intervention. A sleep disorders center can give a qualified PSG report to the attending physician and anesthesia care provider for review before scheduled surgery is performed. The PSG report includes the apnea-hypopnea index (AHI) as well as the oxygen low point or desaturation index (DI). Apnea is defined as a cessation of breathing for at least ten seconds. Desaturation is defined as a drop in oxygen saturation of at least 4% from baseline for at least six seconds. (2) The AHI is the relation of apneic episodes to hypopnea episodes. The apnea index is the number of apneic events occurring each hour averaged over all hours of sleep and for all body positions. (3) The desaturation index is the number of significant desaturations occurring each hour averaged over all hours of sleep. (4) By most definitions, clinically significant episodes of hypopnea are associated with desaturations; therefore, the DI is used as an approximate indication of hypopneic events.

BACKGROUND

The physiological consequences of obstruction are fairly well understood. Respiratory obstruction leads to hypoxemia, pulmonary artery hypertension, and right-sided heart strain. The underlying cause of tongue or oropharyngeal retrusion and collapse are not well understood. A body of knowledge based largely on observations and experience suggests that general anesthesia exacerbates the obstructive symptomology of patients with OSA. Nevertheless, exacerbation of OSA by anesthesia may manifest itself by postoperative airway obstruction. A number of cases in which patients with OSA syndrome have suffered severe, life-threatening, and sometimes fatal apnea after general anesthesia for a procedure remote to the airway have been observed, as noted by the following scenario. These observations emphasize the importance of perioperative preparation and monitoring of patients with OSA syndrome.

Patient scenario. A patient who presented with sleep apnea underwent general anesthesia for a rotator cuff repair. This patient spent one and one-half hours in the postanesthesia care unit and then was transferred to the nursing unit. The patient's wife was at his bedside and was accustomed to his snoring and periods of apnea. At home, he used nasal continuous positive airway pressure (CPAP) at night. The patient's surgeon made rounds one and one-half hours after the patient's transfer to the floor and, while checking on the patient, was unable to awaken him. Pulse oximetry was performed and showed a reading of 60% oxygen saturation. The patient was transferred to the intensive care unit where he was given supportive measures and made a full recovery. This case could have resulted in an undesirable outcome if immediate intensive corrective measures were not taken. (5)

Obstruction relief. The most commonly performed sleep surgeries (eg, septorhinoplasty, uvulopalatopharyngoplasty, mandibular advancement) do not necessarily provide immediate relief of obstruction, even under the best of circumstances. The anxiety of family members and staff members may be aided through temporary relief with tracheostomy. If this course of action is chosen, it is recommended that the tracheostomy be maintained with a plugged, uncuffed tube during the day. The tube should be unplugged during sleep until a postoperative PSG is performed with the tracheostomy plugged to ascertain the effectiveness of the surgery. Patients with extreme apnea (ie, in excess of 100 events per hour) and associated severe desaturations and cardiac arrhythmias demonstrated on preoperative PSG should be identified as a high-risk group. These patients should not be considered candidates for ambulatory surgery. They would benefit from concurrent tracheostomy, regardless of the proposed sleep surgery.

DIAGNOSING AND EVALUATING SLEEP APNEA

Diagnosing OSA syndrome requires that the perioperative team understand the importance of asking questions that will identify the condition. Questions that reveal unacceptable snoring, either from the patient or from the patient's bed partner; hypertension; daytime somnolence; or obesity all lead to a provisional diagnosis of possible OSA. Formally, OSA syndrome is diagnosed by testing. Often testing is performed at a sleep disorders center. Patients who have undergone testing for OSA will have a PSG report on their chart. This report will include the type of study, results of the test, recommended treatment, regular medications that the patient takes, allergies, smoking history, caffeine history, sleep complaint history, and physical examination. If CPAP was recommended, the report will include mask size and valve pressure.

One method of evaluating patients with sleep apnea is cephalometric analysis. Noninvasive and inexpensive, a cephalometric analysis results in a two-dimensional image of a three-dimensional problem. This analysis, which was developed initially for the study of skeletal landmarks in orthodontics and orthognathic surgery, also allows specific soft tissue outlines and predictions to be performed. Four cephalometric measurements are associated with OSA syndrome. In patients with OSA,