Obesity & Anesthesia Flashcards
How is BMI calculated?
(Weight in lbs / inches ^ 2) x 703
What is IBW? Why does it matter? How is it calculated in men vs women? What is the conversion factor for inches to cm?
It is the weight that a patient who is not overweight would be based on height and sex. It is considered for dosing pharmaceutics as some drugs based on total weight could be detrimental.
Male = height in cm - 100 Female = height in cm - 105
1 inch = 2.54 cm
What is lean body weight? How is it calculated? What is it used for?
Lean body weight is ideal body weight in consideration of lean muscle. It is a compromise between total body weight and ideal body weight for the dosing of pharmaceuticals.
LBW = IBW x 1.3
How does obesity effect the distribution (Vd) of hydrophilic drugs? How does obesity effect the distribution of lipophylic drugs?
Obesity increases the distribution of both water soluble and lipid soluble drugs
How does obesity negatively effect the cardiovascular system?
It increases oxygen demand by increasing the work load of the heart. Furthermore increased risk of CAD my translate to reduced delivery of oxygen to a heart with an increased work load.
Hypertension is common leading to eccentric heart failure and hypertrophy
How does obesity affect the respiratory system?
It leads to a restrictive lung effect reducing TV, TLC, VC, ERV, and FRC
Obesity leads to alveoli collapsing easier and increasing dead space
CO2 production is increased d/t increased metabolism and this leads to an increase in RR
How does general anesthesia affect FRC in the obese compared to those with a normal BMI?
General anesthesia in the obese will reduce FRC by 50% opposed to 20% in those of normal weight.
What is obstructive sleep apnea? How is it assessed? What score is associated with increased risk?
When sleeping excess adipose tissue with decreased airway tone leads to obstruction of the airway and decrease in effective ventilation and delivery of oxygen to the alveoli.
It is assessed via the STOP-BANG questionnaire:
- Snore?
- Tired?
- Observed Apnea?
- Pressure (blood pressure) HTN present?
- BMI high?
- Age?
- Neck Circumference?
- Gender?
If yes is given on >/= 3 then risk of OSA is present
What is “Obesity Hypoventilation Syndrome” or “Pickwickian Syndrome” and what causes it? What other physiological problems can it lead to?
It is a state of hypercapnia (high PaCO2) that results in a wakeful state as a result of obesity, OSA, and dysfunction of the respiratory centers of the body
It can lead to pulmonary hypertension, respiratory acidosis, right heart failure, and polycythemia
What are the 5 indicators of metabolic syndrome? How many must be present to diagnose? What is the concern with metabolic syndrome?
- Waist circumference >40 cm in men, >35 cm in women
- High triglycerides
- HTN
- Blood Glucose >100
- Low HDL
At least 3 of these must be present to diagnose metabolic syndrome
The presences of metabolic syndrome increases cardiovascular risk by 50%
What is the most common indication of anastomotic leak in bariatric surgery? What value is concerning and should be investigated? Wheat are two other common indicators of leak?
Tachycardia
HR > 120 bpm
Fever and Abdominal pain
