Obesity Flashcards
How is BMI calculated?
weight (kg) / height (m)
How can you calculate ideal body weight?
males: 105 + 6lb/in >5 feet
females: 100 + 5lb/in >5 feet
How is obesity defined?
BMI >30 kg/m2
How is overweight defined?
25-29 BMI, or more than 20% greater than IBW
What are some conditions associated with obesity?
OSA, respiratory derangements, systemic HTN, diabetes, ischemic heart disease, CHF, delayed gastric emptying, hepatobiliary disease, thromboembolic disease, musculoskeletal disease
What are the specific risk factors for PE?
truncal obesity
pre-existing vascular disease
obesity hypoventilation syndrome or OSA
BMI >60
How do lung volumes change in obesity?
FRC is reduced
ERV is reduced
Tidal volumes drop to the range of closing capacity (atelectasis)
What are the implications of a decreased FRC in an obese patient?
you have less time for safe apnea
What are some respiratory changes in obesity?
increased O2 consumption and CO2 production high MV reduced chest wall compliance restrictive lung patterns pulmonary HTN and lung disease
How do PFTs change with obesity?
PFTs will actually remain normal until the patient hits severe lung disease or pulmonary HTN
Deviations in lung volume during position changes in the obese patient can lead to…
V/Q mismatch
hypoxemia
increased R to L shunt
How does increased soft tissue around the airway in an obese patient affect the anesthesia provider?
harder to put them in sniffing position
obstruction of the airway
can impair the mandible and cervical mobility
difficulty maintaining mask ventilation
may consider fiberoptic intubation
If a patient needs to be supine but can’t tolerate laying flat because of their obesity, what can you do??
use a wedge that elevates their chest and shoulders to about 25 degrees. this allows for better expansion of the lungs while the abdominal contents are pushed down further
Cardiac output is increased by 0.1L/min per kilogram of extra adipose tissue. How does this effect circulating blood volume?
circulating blood volume will increase to perfuse the extra fat and that will place an extra strain on the myocardium, creating large LVs
In terms of cardiac effects, obese patients have decreased reserves for…
hypotension
hypertension
fluid overload
tachycardia
What are the risk factors for atherosclerosis?
high LDL and low HDL
Hyperlipidemia can lead to….?
premature CAD
pancreatitis
premature vascular disease
How is the severity of OSA measured?
number of hypopneic episodes in one hour OR
apnea hypoxic number in one hour
What are some symptoms of OSA?
daytime sleepiness snoring oxygen desaturation impaired concentration morning headache
What are the risk factors for OSA?
male obese middle age ETOH use drug sleep aids abdominal fat distribution neck girth of >17 for men or >16 for women
What are the effects of OSA?
hypoxemia R sided heart failure hypercapnia pulmonary and systemic vasoconstriction polycythemia respiratory acidosis during sleep
What pre-op questions should you ask a patient who is at risk for OSA?
sleeping patterns
snoring
daytime somnolence
If your patient has obesity hypoventilation syndrome, what are some alternatives you can use to prevent associated symptoms?
observe them overnight if they were intubated
try an epidural or regional block instead of GA
How is OHS different from OSA?
nocturnal central apneic events occur which means that there is apnea without a respiratory effort – patient won’t even try to take deep breaths anymore because of densitization of hypercarbia sensors in the brain
What are the characteristics of Pickwickian syndrome/OHS?
obesity hypercapnia daytime hypersomnolence arterial hypoxemia pulmonary hypertension respiratory acidosis R sided heart failure
What are some GI specific complications associated with obesity?
hiatal hernia GERD delayed gastric emptying increased gastric volume and pressure increased gastric acidity
What are some thromboembolic complications associated with obesity?
polycythemia
doubled risk of DVT
increased intra-abdominal pressure
immobility
What are the risk factors for development of aspiration pneumonitis?
gastric volume >25 mL
gastric pH <2.5 associated with increased parietal cell secretion
What are some preventive measures you can take for a patient at high risk of GI related complications?
order reglan and an anti-reflux drug
What is the best predictor of difficult airway?
neck circumference (>40 in = 35% chance of difficult airway)
What are two pre-op exams/tests all patients should have???
EKG and CXR
Why is it important to ask patients about use of diet aids?
because if patients are on ephedrine based diet products they should have stopped taking them 2 weeks ago… cancel the case??
phen/phen can cause mitral valve problems so they may need to be cardiac cleared 1st
What should blood sugars be before surgery?
400 if puts them at extreme risk for post-op infectious complications and you may have to cancel the case
Which position provides the longest safe apnea period in an obese patient?
head up reverse trendelenburg
What is the problem with placing an obese patient in the prone position?
increases intra-abd pressure, worsens vena cava compression and decreases FRC
**lateral position would be preferred
