Transcript Document

Perioperative Management of
the Sleep Apnea Patient
Grand Rounds
June 6, 2007
Richard Browning, M.D.
Goals
Review Incidence
Define OSA & OSH
Learn how to diagnose
Understand the pathophysiology
Develop a plan for pre-, intra- and postop management
Incidence
Among middle-aged adults –
4% of men & 2% of women
Estimated that 80-95% are
undiagnosed
Testing increasing 124% every 3 years
Therefore, diagnosis of OSA will
increase 5 to 10-fold over next decade.
Causes / Risk Factors
Obesity, Obesity, Obesity
Increasing age
Male gender
Structural abnormalties
Tonsillar hypertrophy, nasal pathology
Alcohol, smoking and family history
Causes / Risk Factors
Up to 90% of adult patients with OSA
are obese
OSA parallels the obesity epidemic
Table 1. Distribution by Age of Categorical
Levels of AHI*
(AHI=Apneas + Hypopneas/Hour of Sleep)
Age (Yrs)
<25
26-50
>50
Habitual
Snoring
AHI > 5
AHI > 10
(%)
(%)
(%)
(%)
14
41
46
10
26
61
2
15
50
0
0
36
AHI = Apnea Hypopnea Index
AHI > 15
Definition of OSA
OSA is defined as a cessation of airflow
for more than 10 seconds despite
continuing ventilatory effort, 5 or more
times per hour of sleep and a decrease
of more than 4% in SaO2.
Definition of OSH
OSH is defined as a decrease in airflow
of >50% for >10 seconds, 15 or more
times/hour of sleep, and often with i in
SaO2.
Anatomy of the Obstructed Airway
Exam: Tonsillar Hypertrophy
Oropharynx With
Tonsillar Hypertrophy
Normal Oropharynx
Pediatric Sleep Apnea
Sleep with Sleep Apnea
Child’s Enlarged Palatine &
Adenoidal Tonsils
Exam: Oropharynx
Patient With the Crowded Oropharynx
Physical Exam
Structural Abnormalities
Guilleminault C et al. Sleep Apnea Syndromes. New York: Alan R. Liss, 1978.
Airway Anatomy
3 collapsible pharyngeal segments
Nasopharynx, posterior pharynx to soft
pallate
Retroglossal pharynx, uvula to epiglottis
Retroepiglottal pharynx
Pathophysiology of Apnea
Patency
Depends on pharyngeal dilator muscles
which stiffen and distend the airway
during inspiration.
Patency
3 segments are controlled by:
A. Tensor palatini
B. Genioglossus*
C. Hyoid bone muscles
*Most important
Genioglossus Muscle
Activity is phasic with inspiration
Activity decreases with sleep
Almost ceases with REM sleep
Abolished in OSA at onset of APNEA
Increases with arousal
What Happens with
Normal Sleep?
Normal Sleep
4 to 6 cycles of N-REM sleep followed
by REM sleep
4 stages of N-REM with progressive
slowing of EEG
Normal Sleep
Stage 3 and 4 N-REM and REM are very
deep levels of sleep
Progressive generalized loss of muscle
tone
Restorative periods of sleep
Normal Sleep
Progressive decrease in muscle activity
and resultant increase in upper airway
resistance.
Pathophysiology of Apnea
Airway Collapse
Occurs with loss of muscle activity
Increased subatmospheric pharyngeal
pressure
MRI reveal anterior and lateral wall
collapse
Obesity Effects Airway
Anatomy Adversely
Inverse relationship between obesity
and pharyngeal area
Fat deposits in the uvula, tongue,
tonsillor pillars, aryepiglottic folds and
lateral pharyngeal walls.
Obesity Effects Airway
Anatomy Adversely
Increase fat deposits change shape of
pharynx
Decreases efficiency of normal muscle
function
Increase extra-mural pressure
All conspire to increase propensity for
collapse
Obesity Effects Airway
Anatomy Adversely
Therefore, neck obesity is more
important than generalized obesity in
determining risk of OSA.
Physiologic Consequences
of OSA
Pathophysiology of Sleep Apnea
Awake: Small airway + neuromuscular compensation
Sleep Onset
Hyperventilate: correct
hypoxia & hypercapnia
Loss of neuromuscular
compensation
+
Airway opens
Decreased pharyngeal
muscle activity
Pharyngeal muscle
activity restored
Airway collapses
Arousal from sleep
Apnea
Hypoxia &
Hypercapnia
Increased ventilatory
effort
Clinical Consequences
Sleep Apnea
Sleep Fragmentation
Hypoxia/ Hypercapnia
Cardiovascular
Complications
Excessive Daytime
Sleepiness
Morbidity
Mortality
Diagnosis of OSA
Clinical
A.
B.
C.
D.
Obesity BMI >30 Kg/M2
Snoring / Apnea / Arousal
Daytime Sleepiness
Increased Neck Circumference >42 cm
Diagnosis of OSA
Gold Standard is a sleep study
EEG, EOG, Airflow sensors, ETCO2
esophageal pressure, chest and
abdomen movement, submental EMG,
oximetry, BP, EKG
AHI
APNEA – Hypopnea Index
6-20, 21-50, >50 per hour Mild,
Moderate, Severe
O2SAT usually reported
Anesthesia Effect
Propofol, Thiopental, Opioids,
Benzodiazepines, NMBs, Inhalational
Anesthestics cause pharyngeal collapse
First 3 days are greatest risk for apnea
from drug-induced sleep
Surgical Effects
Sleep architecture is disturbed first 3
days
Days 4-6, patients experience REM
sleep rebound
Apnea risk increased for 1 week post-op
Surgical Effects
REM sleep disturbance is surgical stress
related and proportional to magnitude
of surgery
REM rebound may contribute to poor
hemodynamic outcomes from profound
sympathetic activation
OSA Risk Conclusions
Perioperative complications increase
with severity
Anethestic drugs and surgical stress
exacerbate baseline problem
May play significant role in unexplained
MIs, stroke or death
Perioperative Management
Make diagnosis and grade severity
Thorough airway assessment and plan
for intubation to extubation
Plan for pain management
Plan for post-op monitoring
OSA Severity
Inpatient vs. Outpatient
Regional vs. General
Pre-op Nasal CPAP
Airway Assessment
OSA independent factor for difficult
intubation may be as high as 5%
Limited jaw protrusion, abnormal neck
anatomy, obesity, moderate to severe
OSA consider awake intubation
Good topicalization, limit sedatives
Be prepared
Pain Management
Regional or local anesthetic technique
NSAID
Clonidine / Dex
IV narcotic, no basal infusion
Extubation
High risk, 5% post-extubation
obstruction
Fully reversed, fully awake
Semi-upright position
Oral or nasal airway
Be prepared
Monitoring
O2SAT and close observation post-op in
PACU, resume N-CPAP
Inpatients continuous pulse oximetry
monitoring until stable
Outpatients may be discharged if they
meet discharge criteria and the surgical
acuity dictates
Conclusions
Increased # and severity
Diagnostic challenge
Airway management risk
Post-op challenge for pain, monitoring
and resource management