bstructive sleep apnea (OSA) is an increasingly common
sleep disorder, which is of particular concern to
anesthesiologists because it is associated with increased
perioperative morbidity and mortality. Because OSA
is undiagnosed in an estimated 80 percent of patients,
it is necessary that anesthesia practitioners have
adequate knowledge of the clinical presentation and
diagnosis of OSA. The concerns in patients with OSA
include potential upper-airway obstruction, difficult
tracheal intubation and postoperative respiratory
depression and airway obstruction.
With increasing numbers of surgical procedures performed
on an outpatient basis, there are an increasing number
of patients with OSA scheduled for ambulatory surgery.
The suitability of ambulatory surgery in OSA patients
remains controversial, however. The scientific literature
regarding the perioperative management of OSA patients
is sparse and of limited quality. Recently the Clinical
Practice Review Committee of the American Academy
of Sleep Medicine published its recommendations on
perioperative management of the adult patient with
OSA.1
Most of the recommendations, however, such as high
degree of suspicion, control of the airway throughout
the perioperative period, judicious use of medications
and appropriate monitoring, are too broad and vague
to help the anesthesia practitioner.
At the ASA 2005 Annual Meeting in Atlanta last October,
the ASA House of Delegates approved “Practice
Guidelines for the Perioperative Management of Patients
with Obstructive Sleep Apnea” <www.ASAhq.org/publicationsAndServices/sleepapnea103105.pdf>.
These practice guidelines emphasize that patient selection
for ambulatory surgery should depend upon the severity
of OSA, coexisting diseases, invasiveness of surgery,
type of anesthesia, anticipated postoperative opioid
requirements and adequacy of postdischarge observation.
In addition the ability of the facility to manage
such patients should be taken into consideration.
The facility should have emergency difficult airway
equipment and respiratory care equipment (e.g., nebulizers,
continuous positive airway pressure [CPAP] device,
ventilators) as well as radiology facilities (e.g.,
for portable chest X-ray) and laboratory facilities
(e.g., for blood gas and electrolyte analysis). Furthermore,
transfer arrangements with an inpatient facility should
be in place.
The ASA practice guidelines propose the following
scoring system, which may be used to estimate whether
a patient is at increased perioperative risk of complications
from obstructive sleep apnea. It must be emphasized
that this scoring system is not yet validated and
is meant only as a guide, and clinical judgment should
be used to assess the risk of an individual patient.
A) Severity of sleep apnea based on sleep study
(i.e., apnea-hypopnea index) or clinical indicators
if sleep study not available (i.e., presumptive
diagnosis): None=0; 1=Mild OSA; 2=Moderate OSA;
3=Severe OSA. One point may be subtracted if a
patient has been on CPAP or bi-level positive
airway pressure (BiPAP) prior to surgery and will
be using his/her appliance consistently during
the postoperative period. One point should be
added if a patient with mild or moderate OSA also
has a resting PaCO2> 50 mmHg.
B) Invasiveness of surgical procedure and anesthesia.
Type of surgery/anesthesia: 0=superficial surgery
under local or peripheral nerve block anesthesia
without sedation; 1=superficial surgery with moderate
sedation or general anesthesia or peripheral surgery
with spinal or epidural anesthesia (with no more
than moderate sedation); 2=peripheral surgery
with general anesthesia or airway surgery with
moderate sedation; 3=major surgery under general
anesthesia or airway surgery under general anesthesia.
C) Requirement for postoperative opioids: 0=none;
1=low-dose oral opioids; 3=high-dose oral opioids
or parenteral or neuraxial opioids.
D) Estimation of perioperative risk is based on
the overall score = A + the greater of B or C
points (0-6). Patients with overall score of 4
or greater may be at increased perioperative risk
from OSA. Patients with a score of 5 or greater
may be at significantly increased perioperative
risk from OSA.
Patients who are at significantly increased risk
of perioperative complications (score ≤ 5)
are generally not good candidates for ambulatory
surgery. It is well accepted that patients with
mild OSA undergoing superficial or minor surgical
procedures under local, regional or general anesthesia
as well as expected to have minimal postoperative
opioid requirement may undergo ambulatory surgery.
Preoperative Assessment and Preparation
Development of protocols for adequate preoperative
evaluation of patients with suspected OSA is important.
Although polysomnography remains the gold standard
in the diagnosis of OSA, it may not be always available.
A presumptive diagnosis of OSA can be derived from
abnormal breathing during sleep (i.e., loud snoring
and witnessed apnea), frequent arousals (i.e., periodic
extremity twitching, vocalization, turning and snorting)
and excessive daytime sleepiness as well as a body
mass index of >35 kg/m2,
increased neck circumference (>17 inches for
males and >16 inches for females) and presence
of comorbidities (e.g., systemic hypertension, pulmonary
hypertension, cardiomegaly). These symptoms and
signs, however, do not reliably predict presence
or severity of OSA. Therefore it is essential to
treat patients with presumptive diagnosis of OSA
as if they have severe OSA.
Preoperative optimization with CPAP or BiPAP therapy
should be considered, particularly if OSA is severe.2-4
Patients who use CPAP devices at home should be
advised to bring their devices to the facility for
postoperative use. In addition to CPAP, other treatment
modalities such as corrective surgery, mandibular
advancement devices and oral appliances should be
considered when feasible. It is recommended that
a patient who has had corrective airway surgery
should be assumed to remain at risk for OSA complications
unless the sleep studies and symptoms have normalized.
Intraoperative Management
Although the type and extent of surgery and the
need for postoperative opioids — rather than
the choice of anesthetic technique — appear
to be more important determinants of postoperative
complications,5
local or regional anesthesia should be preferred
whenever possible. For patients requiring moderate
sedation, ventilation should be continuously monitored
using capnography. In patients using CPAP preoperatively,
use of CPAP during moderate sedation may be beneficial.
If deep sedation is required, general anesthesia
(with a secure airway) may be preferable, particularly
for procedures that might mechanically compromise
the airway.
Although OSA patients are at an increased risk of
difficult tracheal intubation, “awake”
tracheal intubation may not always be necessary.
Optimal head and neck positioning (using shoulder
stacking) improve the ease of tracheal intubation.
The decision to perform an “awake” tracheal
intubation may depend upon prior history of difficult
airway, the presence of comorbidities, increased
neck circumference (>17 inches for males and
>16 inches for females) and signs of difficult
intubation (e.g., Mallampati classification III
or IV). If an “awake” tracheal intubation
is planned, sedatives and opioids must be utilized
judiciously.
Because opioids may be associated with pronounced
respiratory depression, patients with OSA benefit
from prophylactic multimodal analgesia techniques
using nonopioid analgesics including local/regional
analgesia, acetaminophen, nonsteroidal anti-inflammatory
drugs/COX-2-specific inhibitors, NMDA antagonists
(e.g., ketamine), steroids and alpha-2 agonists.
Of note, even minimal residual muscle relaxants
can affect the airway muscles and result in airway
obstruction. Therefore residual muscle relaxation
should be reversed.
Extubation should be performed in a semi-upright
position when possible. Importantly, coughing, reflex
movements of the hand moving toward the tracheal
tube and patient sitting up should not be confused
with purposeful movements. The decision to keep
the trachea intubated in the immediate postoperative
period depends upon the severity of OSA and presence
of cardiopulmonary comorbidities and the site (e.g.,
airway surgery) and length of surgery as well as
the difficulty in tracheal intubation and the intraoperative
course.
Postoperative Care
Postoperative complications include airway obstruction,
oxygen desaturation and the need for reintubation
as well as hypertension, dysrhythmias and need for
admission. Although supplemental oxygen may be beneficial
for most patients, it should be administered with
caution as it may reduce hypoxic respiratory drive
and increase the incidence and duration of apneic
episodes. Recurrent hypoxemia may be better treated
with CPAP along with oxygen rather than oxygen alone.
It is recommended that patients who use CPAP preoperatively
should use CPAP postoperatively, as it may reduce
the risk of airway obstruction and respiratory depression.5
CPAP, however, should be used only after patients
are awake and alert. It is necessary that anesthesiologists
familiarize themselves with the use of CPAP devices,
as determination of optimal CPAP setting may be
difficult in patients who have not previously used
CPAP.
Prior to discharge, the oxygen saturation on room
air should return to baseline, and patients should
not become hypoxic or develop airway obstruction
when left undisturbed in the recovery area. It is
observed that most significant postoperative complications
in OSA patients usually occur within two hours after
surgery.6
The ASA “Practice Guidelines for the Perioperative
Management of Patients with Obstructive Sleep Apnea”
suggest that OSA patients be monitored for a median
of three hours longer than their non-OSA counterparts
before discharge from the facility. In addition,
the monitoring should continue for a median of seven
hours after the last episode of airway obstruction
or hypoxemia while breathing room air in an unstimulated
environment. These longer postoperative stays may
be the major limitation of performing ambulatory
surgery in a stand-alone ambulatory surgery center
or office setting. It is important that the postdischarge
instructions emphasize the use of CPAP at home for
patients who use it preoperatively.
Summary
Patients with OSA are at a high risk of perioperative
complications and pose several challenges to the
anesthesiologist, including difficult tracheal intubation
and increased postoperative complications (e.g.,
respiratory obstruction after extubation or respiratory
depression after opioid administration). Because
undiagnosed OSA is common, a focused history and
physical examination can help to identify patients
with OSA.
There is uncertainty regarding scheduling and management
of OSA patients for outpatient surgery. With limited
understanding of their postoperative course, any
recommendations remain speculative. Prudent perioperative
management should be guided by the awareness of
the potential complications based on the severity
of OSA, invasiveness of diagnostic or therapeutic
procedure and requirement of postoperative analgesia.
Nevertheless development of policies and procedures
for acceptable outpatient surgery candidates that
take into consideration the special problems and
risks of OSA are crucial for improved postoperative
outcome. Ambulatory surgical patients with OSA may
not meet criteria for safe home discharge in some
instances. Therefore probable options of admission
should be discussed with the patient prior to surgery.
References:
1. Meoli AL, Rosen CL, Kristo D, et al. Upper-airway
management of the adult patient with obstructive sleep
apnea in the perioperative period —Avoiding
complications. Sleep. 2003; 15:1060-1065.
2. Deutscher R, Bell D, Sharma S. OSA protocol promotes
safer care. APSF Newsletter. 2002; 17:58.
3. Ryan F, Lowe AA, David LI, et al. Magnetic resonance
imaging of the upper airway in obstructive sleep apnea
before and after chronic nasal continuous positive
pressure therapy. Am Rev Respir Dis. 1991;
144:939-944.
4. Rennotte MT, Baele P, Aubert G, Rodenstein DO.
Nasal continuous positive airway pressure in the perioperative
management of patients with obstructive sleep apnea
submitted to surgery. Chest. 1995; 107:367-374.
5. Bryson GL, Chung F, Finegan BA, et al. Patient
selection in ambulatory anesthesia — An evidence-based
review: Part I. Can J Anaesth. 2004; 51:768-781.
6. Terris DJ, Fincher EF, Hanasono MM, et al. Conservation
of resources: Indications for intensive care monitoring
after upper-airway surgery on patients with obstructive
sleep apnea. Laryngoscope. 1998; 108:784-788.
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Girish P. Joshi, M.D., is Professor of Anesthesiology
and Pain Management, University of Texas Southwestern
Medical Center, Dallas, Texas. |
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