Evaluation of Sleep Disordered Breathing Following Ambulatory Surgery

Obstructive sleep apnea (OSA) is a highly prevalent syndrome of upper-airway obstruction and consequent cessation of respiration during sleep. Associated complications include impairment in the cardiovascular and cerebrovascular, neurological and endocrine systems. There is growing concern that the perioperative period may acutely worsen existing OSA or potentially induce sleep disordered breathing in susceptible individuals. Indeed, the presence of OSA has been shown to be an independent risk factor for perioperative complications. The mechanism for this perioperative risk, however, has yet to be fully elucidated.

This study proposes to investigate the relationship between surgical anesthesia and OSA with an observational prospective single-blinded investigation. A sample of 600 adult female and male orthopedic surgery patients scheduled for elective ambulatory orthopedic surgery at WRNMMC will be enrolled. Study subjects shall undergo an unattended Home Sleep Test (HST) the night before surgery followed by surgery and anesthesia as determined by the surgical team unchanged by study participation. Following the surgical procedure and anesthesia, the study subject will undergo a series of two additional HSTs on the first night following surgery and again on post-operative night three and complete a postoperative questionnaire including a validated screening questionnaire and information pertaining to postoperative pain and medication use.

Qualitative and quantitative analysis will be performed on the data. The prevalence in the ambulatory orthopedic population of screening positive with the STOP-BANG questionnaire, a validated Obstructive Sleep Apnea (OSA) screening tool, will be determined as well as the prevalence of OSA diagnosed by the preoperative Home Sleep Test (HST). The analysis of the HST data will be blinded as to OSA status, if known, and screening results using the validated "STOP-BANG" screening questionnaire. There are several additional research questions posed in this observational prospective single-blinded clinical study to determine if OSA, as defined by apnea-hypopnea index (AHI), is a significant factor in adverse events associated with ambulatory orthopedic surgery. First, a study sample size of 600 was selected to provide 82% power to detect a significant difference in unplanned admissions between patients with OSA (estimated at 20% of the surgical orthopedic population) and without OSA. This assumes 10% of patients without OSA experience unplanned admissions compared with 20% of patients with OSA. Other adverse perioperative events to be examined include difficult intubations, upper airway obstruction after extubation, bronchospasm, laryngospasm, arrhythmia such as atrial fibrillation, and need for mechanical ventilation

Additional questions to be examined include if surgery and anesthesia, the specific anesthetic technique, intraoperative sedative use, or postoperative sedative use is associated with any Home Sleep Test (HST) parameter (AHI, Oxygen Desaturation Index (ODI), pulse oximetry (SpO2) nadir, or percentage of time SpO2<90%). Paired t-tests will be used to perform the analyses except for the question of anesthetic technique for which analysis of variance followed by Tukey's post-hoc multiple comparisons will be employed.

Lastly is the clinically relevant question addressing whether there is a difference between patients who screen as high risk for OSA and those who screen as low risk for OSA with regard to pre and postoperative AHI, ODI, SpO2 nadir, or percentage of time SpO2<90%? High- and low-risk patients per the screening instrument will be compared using t-tests for independent samples.

Ultimately understanding the relationship between surgical anesthesia and OSA may be used to risk stratify patients, identify those at an increased risk for perioperative complications, or potentially aid in determining perioperative management plans.