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.

Inclusion Criteria:

- Male and female military health care beneficiaries between the ages of 18 and 85
years presenting for elective ambulatory orthopedic surgery at WRNMMC main operating
room.

- American Society of Anesthesiologist physical classification (ASA) I-II

- Scheduled for elective ambulatory orthopedic surgery

- Patients English speaking and capable of providing informed consent.

Exclusion Criteria:

- Patients who are pregnant or breast-feeding at the time of the procedure. Pregnancy
will be ruled out by day of surgery urine human chorionic gonadotropin (HCG) when
appropriate.

- Chronic opioid, benzodiazepine, pregabalin, or other sedating medication users

- Chronic alcohol users (defined by daily or greater use upon standard anesthesia
preoperative interview)

- Patients who require home oxygen use

- Patients who have a tracheostomy

- Patients who decline to participate.