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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1

what should be considered with all overweight patients?

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

2

describe OSA diagnosis

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

3

what is a split study of OSA?

diagnosis then CPAP titration

4

describe apnea hypopnea index (AHI)

number of abnormal respiratory events per hour of sleep

5

define mild OSA

AHI between 5 and 15 (6-20)

6

define moderate OSA

AHI between 15 and 30 (21-40)

7

define severe OSA

AHI > 30 (>40)

8

how can degree of OSA be determined during patient assessment?

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

9

what are symptoms of OSA?

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

10

what are risk factors for OSA?

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

11

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

12

what is the best predictor of OSA risk?

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

13

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

neck circumference > 16.5 inches

14

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

15

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

16

what are most common co morbidities found with OSA?

-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

what results from chronic hypoxemia in OSA?

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

18

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

19

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

20

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

21

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

22

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

23

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

24

what inhalation agent is best with OSA?

desflurane
-earlier return of protective reflexes
-reduced extubation time

25

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

26

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.

27

what are the various screening tools for OSA?

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

28

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

29

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

30

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