GI/Obesity Flashcards
Define obesity
20% or more above IBW. Disorder of energy balance.
Diagnosis of metabolic syndrome
Diagnosed when 3 or more of the following are present
1) Abdominal Obesity
- Waist circumference > 102cm in men or 88cm in women
2) High TGs
- > 150mg/dL
3) Low HDL
- 130/85
5) FBS > 110
What is IBW? Definition and calculation
The weight associated with the LOWEST mortality rate for a given height and gender
Use Broca’s Index to calculate:
IBW (kg) = height (cm) - x
Men, x = 100
Women, x = 105
Calculation fro BMI
(weight in kg / height squared in meters)
Degrees of obesity based on BMI
Obesity > 30
Morbid Obesity > 40
Super morbid obesity > 50
BMI > ____ is associated with increased morbidity (3x) due to stroke, CAD, and DM
28
Implications of fat distribution
2 distributions
1) Android (central) obesity / truncal distribution
- Mostly intra-abdominal fat (fat is mostly upper body)
- Presents higher risk in anesthesia
- Higher incidence of CV disease b/c this fat is more metabolically active
- However, because it’s more metabolically active means it’s easier to lose
2) Gynecoid (peripheral) Obesity
- Lower risk in anesthesia
- Located mostly in hips, ass, and thighs
- Less CV disease b/c this tissue is less metabolically active
Respiratory patho in obesity
- Reduced lung and chest wall compliance
- Pulmonary blood volume is increased to perfuse extra adipose tissue
- Polycythemia from chronic hypoxia
- Difficulty breathing in the supine position
This is the only ventilatory parameter that has actually been shown to improve respiratory function in obese patients
PEEP (use 10-12 cmH2O)
Effects of obesity on lung volumes
ERV = 60% of normal
FRC is 80% normal (even worse with anesthesia, normal population, FRC will decrease by 20% with induction of anesthesia, but in the obese, it will decrease by 50%)
VC and TLC are decreased
RV and CC are unchanged. However, because FRC is decreased, TV may fall into the range of CC.
FVC and FEV1 are unchanged.
Metabolic rate is proportional to
body weight
Metabolic rate in obesity
Increased d/t increased body weight. Results in increased O2 consumption and CO2 production (excess fat tissue increases workload).
The body compensates by increasing CO and MV.
PaO2 is usually ___ in obese patients.
Less than predicted on room air. This chronic alteration can lead to pulm HTN and for pulmonale
OSA diagnosis
Involves apneic and hypopneic events.
Apnea = 10 seconds or more of TOTAL airflow cessation despite respiratory effort, resulting in SaO2 drop by 4%
Hypopnea = 10 seconds or more of a 50% or more reduction of airflow, or a reduction significant enough to cause a 4% drop in SaO2.
Apnea-hypopnea index (# events per hour)
> 30 = severe
16-30 = moderate
Peri-op complications associated with OSA
HTN Hypoxia Arrhythmia MI Pulm edema Cognitive impairment Stroke Post-op airway obstruction
What is Obesity Hypoventilation Syndrome
Also called Pickwickian Syndrome
- OSA progression to daytime hypercapnea
- Extreme obesity with hypercapnia, cyanosis, polycythemia, somnolence, and eventual R sided HF and pulm HTN
Diagnostic of obesity hypoventilation syndrome
PaCO2 > 45 in the absence of COPD
This would lead you to investigate further about obesity hypoventilation syndrome
SUPINE SaO2
CV alterations in obestity
- Increased total blood volume
(BF to fat is 2-3mL/100g tissue)
(Overall 50mL/kg for obese person vs. 70mL/kg for normal weight) - Increased renal and splanchnic flow (cause they eatin’ all the time!)
- Increase in CO (2/2 ventricular dilation from increased blood volume), increased SV, and O2 consumption
- Increased SNS and RAAS activity
- LVH from increased body mass to serve, resultant diastolic dysfunction, and eventually pulm edema
- Eventually, this LVH is unable to keep up with body’s demands, resulting in “obesity cardiomyopathy,” causing biventricular failure
On average, BP increases this much per amount of weight gained
Increased of 3-4mmHg SBP and 2mmHg DBP per 10kg of weight gained
Why should we get an EKG in obese patients?
Probably have L or R ventricular hypertrophy, may have CAD, and conduction defects
Risk for arrhythmia 2/2 hypoxia, hypercapnia, CAD, OSA, increased circulating catecholamines, and changes int he myocardium (hypertrophy, etc)
Hematologic changes in obesity
Polycythemia Hyper coagulable state (from increased) - Fibrinogen - Factors 7, 9, and vWF - Plasminogen activator inhibitor-1
GI changes in obesity
- Higher incidence of GERD and hiatal hernia
- Delayed gastric emptying
- Increased gastric residual volume after fasting
- Risk risk of pneumonitis if aspiration occurs
- Normal fasting guidelines can be followed as long as no other GI patho
After fasting, gastric volume and pH are typically
> 25mL
ph