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Principles II > OSA: evaluating and managing perioperative risk > Flashcards

OSA: evaluating and managing perioperative risk Flashcards

1
Q

what should be considered with all overweight patients?

A

possibility of OSA

-80% of patients with OSA are undiagnosed

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2
Q

describe OSA diagnosis

A
  • gold standard is polysomnography
  • monitors: EEG, airflow, oxygen saturation
  • observes for restlessness and leg movements
  • results use apnea hypopnea index (AHI)
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3
Q

what is a split study of OSA?

A

diagnosis then CPAP titration

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4
Q

describe apnea hypopnea index (AHI)

A

number of abnormal respiratory events per hour of sleep

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5
Q

define mild OSA

A

AHI between 5 and 15 (6-20)

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6
Q

define moderate OSA

A

AHI between 15 and 30 (21-40)

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7
Q

define severe OSA

A

AHI > 30 (>40)

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8
Q

how can degree of OSA be determined during patient assessment?

A

ask for CPAP settings if patient unable to tell you severity of OSA

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9
Q

what are symptoms of OSA?

A
  • sleep arousal (wakes up a lot during the night)
  • loud snoring
  • daytime somnolence
  • fatigue
  • decreased cognition and intellectual function
  • concentration and memory problems
  • headaches
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10
Q

what are risk factors for OSA?

A
  • male
  • middle age > age 40 (weight gain and loss of muscle tone)
  • obese
  • central abdominal fat distribution
  • short mandible
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11
Q

describe the link between OSA and weight

A
  • every 10 kg of weight, risk increases two times
  • 60-70% of OSA patients are obese (BMI > 30)
  • weight loss greatly reduces severity of OSA
  • as BMI increases by 6, OSA risk increases by 4
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12
Q

what is the best predictor of OSA risk?

A
  • waist circumference

- for every 15 cm in WC the risks of OSA increases 4 times

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13
Q

what else is used to predict OSA risk although less effective than WC?

A

neck circumference > 16.5 inches

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14
Q

how does OSA affect CRNAs?

A
  • perioperative pharyngeal obstruction
  • higher postop re-intubation rate
  • difficult mask ventilation and laryngoscopy (difficult intubation 8x more likely)
  • more sensitive to anesthesia drugs
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15
Q

what are some perioperative complications associated with OSA?

A
  • increased length of stay; unplanned ICU admissions
  • most common complication is oxygen desaturation
  • increased pulmonary complications after orthopedic and general surgery d/t increased need of pain meds
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16
Q

what are most common co morbidities found with OSA?

A
  • cardiovascular disease (CHF, CAD)
  • acute MI
  • DM
  • arrhythmias
  • HTN (systemic and pulmonary)
  • cerebrovascular disease
  • metabolic syndrome
  • obesity (probably the cause of co-morbidities)
  • GERD
17
Q

what results from chronic hypoxemia in OSA?

A

-pulmonary vasoconstriction leads to pulmonary HTN which leads to right and left ventricular hypertrophy

18
Q

what does polycythemia in OSA lead to ?

A
  • increased risk of ischemic heart disease (IHD) and cerebrovascular disease
  • increased SNS tone, cardiac arrhythmias
  • increased RVH and LVH
19
Q

what is the relationship between obesity and airway area?

A
  • inverse relationship
  • increased airway resistance/obstruction d/t increased fat which decreases airway patency
  • adipose tissue in all pharyngeal structures/walls is increased
  • pharyngeal muscles relax and airway collapse occurs
20
Q

describe changes in airway physiology in OSA

A
  • even during wakefulness, pharyngeal airway narrower
  • anatomically narrower and more collapsible airways
  • GA and sleep causes depressed neural control mechanisms leading to pharyngeal narrowing and closure (awake have increased neuronal activity and increased pharyngeal muscle tone)
  • higher closure pressures in OSA patients
  • trachea moves caudally up to 1 cm during inspiration
  • longitudinal tension of the airway created
  • reduced total lung capacity adds to instability of upper airway
21
Q

what cycle of events is caused by depression of neural control with sleep onset in OSA patients?

A

1) anatomical imbalance; pharyngeal closure
2) apnea or hypoventilation (decrease O2; increase CO2)
3) increase of chemical stimuli
4) activation of neural control
5) arousal (wakes up gasping for air)
6) pharyngeal opening
7) hyperventilation (blows off CO2; increase O2)
8) reduction in chemical stimuli
9) depression of neural control
10) asleep and cycle restarts

22
Q

what effects do benzodiazepines have on OSA?

A
  • midazolam shown to cause airway obstruction
  • midazolam increases the frequency and duration of apneic events
  • midazolam causes same critical closing pressure that sleep does on the airway
  • can profoundly impair respiration in post op period
  • concurrent use of opioids and benzos increases risk of respiratory depression and airway obstruction
23
Q

what effects do opioids have on OSA?

A
  • increased sensitivity to exogenous opioids d/t recurrent hypoxia
  • opioids exacerbate OSA and prevent arousal
  • concurrent use also with benzos increase the risk of respiratory depression and airway obstruction
24
Q

what inhalation agent is best with OSA?

A

desflurane

  • earlier return of protective reflexes
  • reduced extubation time
25
Q

what induction agents are effective analgesics in OSA patients?

A
  • dexmedetomidine: sedative analgesic; reduces salivary secretions; can be used to reduce opioid requirements
  • ketamine: effective analgesia; less depressant effect on dilating pharyngeal muscle
26
Q

what are the most common treatments of OSA?

A
  • continuous positive airway pressure (CPAP): titrate pressure case by case; noncompliance as high as 50%
  • dental appliances: mandible movement; tongue retention; compliance rate about 60%
  • surgical treatment: range from tonsils, nasal, UP3, maxillary mandibular advancement, etc.
27
Q

what are the various screening tools for OSA?

A
  • STOP BANG
  • Epworth sleepiness scale
  • Snore scale
  • Sleep apnea clinical score
  • Berlin Questionnaire
  • P-SAP score
  • ASA checklist
28
Q

describe the STOP BANG tool

A
  • eight yes/no questions
  • easily administered during pre-anesthesia evaluation
  • stratifies patients into high and low risk OSA (high risk 3 or more yes answers; low risk less than 3 yes answers)
  • patients identified as high risk found to have a higher occurrence of postop complications
  • more valid test
29
Q

what are the 8 questions in the STOP BANG tool?

A

S: snoring- do you snore loudly
T: tired- do you often feel tired or sleepy during the day
O: observed- anyone observed you stop breathing sleep
P: blood pressure- do you have or being treated for HTN
B: BMI- BMI more than 35 kg/m2
A: age- age > 50 y/o
N: neck- neck circumference > 40 cm
G: gender- male

30
Q

what are the advantages of the STOP BANG tool?

A
  • high level of sensitivity and specificity in surgical patients (identifies who does and does not have OSA)
  • if tool ranks as low risk, unlikely to have severe OSA
  • score > or = 6 88% probability of having AHI > 30
  • score of 6.7 or 8 = high probability of severe OSA
  • highest degree of predictability of any tool esp. for moderate to severe OSA
31
Q

describe preoperative management of OSA

A
  • suspect and screen all obese pts. for OSA
  • be aware of comorbid conditions present but undiagnosed (pulm. HTN as high as 20% in OSA)
  • Mallampati class 3 or 4: suspect OSA
  • caution when using pre op Versed
  • be prepared for difficult intubation (cricoid pressure may increase difficulty in OSA)
  • confirm CPAP therapy and brought to facility; consider preop use of OSA severe
32
Q

describe intraoperative management of OSA

A
  • consider regional or local for peripheral surgery
  • regional/neuraxial improves OSA outcomes vs. GA
  • caution in selecting respiratory depressant drugs
  • use muscle relaxant sparingly
  • mild hypercarbia improves tissue oxygenation and perfusion (body use to this state)
33
Q

what are some emergence considerations with OSA?

A
  • extubate fully awake, esp. if difficult intubation
  • fully reverse pt. prior to extubation
  • increase HOB to facilitate patent pharyngeal airway (supine promotes pharyngeal collapse)
  • consider placing nasal airway prior to extubation (nasal airway more effective)
34
Q

describe post op management of OSA

A
  • ASA task force recommends determining post op disposition based on a risk factor scoring system
  • write OSA specific orders if suspected or confirmed
  • use supplemental oxygen; use CPAP if pt. uses at home
  • avoid supine position; increase HOB (supine promotes pharyngeal closure; pharyngeal edema post op increases risk of obstruction)
  • oximetry and/or telemetry if transferred to floor
35
Q

describe the OSA scoring system

A

A) severity of sleep apnea based on sleep study or clinical indications (0-3 pts.)
-none 0; mild 1; moderate 2; severe 3 (subtract a point if use of CPAP; add a point if CO2 > 50)
B) invasiveness of surgery and anesthesia (0-3 pts.)
-superficial under local or block/no sedation- 0
-superficial with mod. sedation or GA- 1
-peripheral with spinal or epidural (mod. sedation)- 1
-peripheral with GA; airway surgery/mod. sed.- 2
-major surgery/airway surgery GA- 3
C)Requirement for post op opioids (0-3 pts.)
-none 0
-low dose oral- 1
-high dose oral/parenteral/neuraxial- 3
D) estimation of risk; total score = A + (higher of B & C) (0-6 pts.)
*overall score of 4 or >- increased risk for perioperative risk
*score of 5 or greater significant risk

36
Q

describe post op discharge of OSA patients

A
  • ASA task force: keep 3 hrs longer
  • most complication occur within 2 hrs. of recovery
  • up to 7 hrs. after last airway obstruction or hypoxemia event in an unstimulating environment
  • educate on home opioid use: anxiety, pain, fragmented and deprived sleep can result in rebound REM sleep (increasing vulnerability to airway obstruction); respiratory depressant effects can last days
  • not good candidates for outpatient surgery
  • if suspected OSA, refer to primary care for evaluation
37
Q

describe ambulatory surgeries with OSA

A
  • use STOP BANG guideline; simple and easy; evidence indicates higher score = higher probability of severe OSA
  • laparoscopic upper abdominal procedures suitable
  • painful ambulatory surgery may not be suitable if unable to control pain with non-opioid analgesia

Principles II (18 decks)

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