OSA: evaluating and managing perioperative risk Flashcards Preview

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Flashcards in OSA: evaluating and managing perioperative risk Deck (37)
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what should be considered with all overweight patients?

possibility of OSA
-80% of patients with OSA are undiagnosed


describe OSA diagnosis

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


what is a split study of OSA?

diagnosis then CPAP titration


describe apnea hypopnea index (AHI)

number of abnormal respiratory events per hour of sleep


define mild OSA

AHI between 5 and 15 (6-20)


define moderate OSA

AHI between 15 and 30 (21-40)


define severe OSA

AHI > 30 (>40)


how can degree of OSA be determined during patient assessment?

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


what are symptoms of OSA?

-sleep arousal (wakes up a lot during the night)
-loud snoring
-daytime somnolence
-decreased cognition and intellectual function
-concentration and memory problems


what are risk factors for OSA?

-middle age > age 40 (weight gain and loss of muscle tone)
-central abdominal fat distribution
-short mandible


describe the link between OSA and weight

-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


what is the best predictor of OSA risk?

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


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

neck circumference > 16.5 inches


how does OSA affect CRNAs?

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


what are some perioperative complications associated with OSA?

-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


what are most common co morbidities found with OSA?

-cardiovascular disease (CHF, CAD)
-acute MI
-HTN (systemic and pulmonary)
-cerebrovascular disease
-metabolic syndrome
-obesity (probably the cause of co-morbidities)


what results from chronic hypoxemia in OSA?

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


what does polycythemia in OSA lead to ?

-increased risk of ischemic heart disease (IHD) and cerebrovascular disease
-increased SNS tone, cardiac arrhythmias
-increased RVH and LVH


what is the relationship between obesity and airway area?

-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


describe changes in airway physiology in OSA

-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


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

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


what effects do benzodiazepines have on OSA?

-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


what effects do opioids have on OSA?

-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


what inhalation agent is best with OSA?

-earlier return of protective reflexes
-reduced extubation time


what induction agents are effective analgesics in OSA patients?

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


what are the most common treatments of OSA?

-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.


what are the various screening tools for OSA?

-Epworth sleepiness scale
-Snore scale
-Sleep apnea clinical score
-Berlin Questionnaire
-P-SAP score
-ASA checklist


describe the STOP BANG tool

-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


what are the 8 questions in the STOP BANG tool?

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


what are the advantages of the STOP BANG tool?

-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