Perioperative Management of the Sleep Apnea Patient

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Perioperative Management of the Sleep Apnea
Patient

• Grand Rounds
• June 6, 2007
• Richard Browning, M.D.

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Goals

• Review Incidence
• Define OSA OSH
• Learn how to diagnose
• Understand the pathophysiology
• Develop a plan for pre-, intra- and post-op
  management

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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.

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Causes / Risk Factors

• Obesity, Obesity, Obesity
• Increasing age
• Male gender
• Structural abnormalties
• Tonsillar hypertrophy, nasal pathology
• Alcohol, smoking and family history

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Causes / Risk Factors

• Up to 90 of adult patients with OSA are obese
• OSA parallels the obesity epidemic

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Table 1. Distribution by Age of Categorical
Levels of AHI(AHIApneas Hypopneas/Hour of
Sleep)

• Habitual
• Snoring AHI gt 5
  AHI gt 10 AHI gt 15
• Age (Yrs) () () ()
  ()
• lt25 14 10
  2 0
• 26-50 41 26
  15 0
• gt50 46 61
  50 36

AHI Apnea Hypopnea Index
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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.

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Definition of OSH

• OSH is defined as a decrease in airflow of gt50
  for gt10 seconds, 15 or more times/hour of sleep,
  and often with i in SaO2.

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Anatomy of the Obstructed Airway
Exam Tonsillar Hypertrophy
Oropharynx With Tonsillar Hypertrophy
Normal Oropharynx
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Pediatric Sleep Apnea
Sleep with Sleep Apnea
Childs Enlarged Palatine Adenoidal Tonsils
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Exam Oropharynx
Patient With the Crowded Oropharynx
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Physical Exam
Structural Abnormalities
Guilleminault C et al. Sleep Apnea Syndromes.
New York Alan R. Liss, 1978.
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Airway Anatomy

• 3 collapsible pharyngeal segments
• Nasopharynx, posterior pharynx to soft pallate
• Retroglossal pharynx, uvula to epiglottis
• Retroepiglottal pharynx

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Pathophysiology of Apnea
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Patency

• Depends on pharyngeal dilator muscles which
  stiffen and distend the airway during inspiration.

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Patency

• 3 segments are controlled by
• A. Tensor palatini
• B. Genioglossus
• C. Hyoid bone muscles
• Most important

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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

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What Happens with Normal Sleep?
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Normal Sleep

• 4 to 6 cycles of N-REM sleep followed by REM
  sleep
• 4 stages of N-REM with progressive slowing of EEG

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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

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Normal Sleep

• Progressive decrease in muscle activity and
  resultant increase in upper airway resistance.

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Pathophysiology of Apnea
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Airway Collapse

• Occurs with loss of muscle activity
• Increased subatmospheric pharyngeal pressure
• MRI reveal anterior and lateral wall collapse

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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.

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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

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Obesity Effects Airway Anatomy Adversely

• Therefore, neck obesity is more important than
  generalized obesity in determining risk of OSA.

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Physiologic Consequences of OSA
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Pathophysiology of Sleep Apnea
Awake Small airway neuromuscular compensation
Sleep Onset
Hyperventilate correct hypoxia hypercapnia
Loss of neuromuscular compensation Decreased
pharyngeal muscle activity
Airway opens
Pharyngeal muscle activity restored
Airway collapses
Arousal from sleep
Apnea
Increased ventilatory effort
Hypoxia Hypercapnia
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Clinical Consequences
Sleep Apnea
Sleep Fragmentation Hypoxia/ Hypercapnia
Cardiovascular Complications
Excessive Daytime Sleepiness
Morbidity Mortality
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Diagnosis of OSA

• Clinical
• A. Obesity BMI gt30 Kg/M2
• B. Snoring / Apnea / Arousal
• C. Daytime Sleepiness
• D. Increased Neck Circumference gt42 cm

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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

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AHI

• APNEA Hypopnea Index
• 6-20, 21-50, gt50 per hour Mild, Moderate, Severe
• O2SAT usually reported

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Anesthesia Effect

• Propofol, Thiopental, Opioids, Benzodiazepines,
  NMBs, Inhalational Anesthestics cause pharyngeal
  collapse
• First 3 days are greatest risk for apnea from
  drug-induced sleep

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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

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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

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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

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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

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OSA Severity

• Inpatient vs. Outpatient
• Regional vs. General
• Pre-op Nasal CPAP

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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

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Pain Management

• Regional or local anesthetic technique
• NSAID
• Clonidine / Dex
• IV narcotic, no basal infusion

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Extubation

• High risk, 5 post-extubation obstruction
• Fully reversed, fully awake
• Semi-upright position
• Oral or nasal airway
• Be prepared

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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

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Conclusions

• Increased and severity
• Diagnostic challenge
• Airway management risk
• Post-op challenge for pain, monitoring and
  resource management