Obesity Flashcards
What is phentermine?
A weight-loss drug (appetite suppressant) that some patients may be on
How is obesity defined?
Weighing 20% more than your ideal body weight
or
BMI > 30 kg/m2
A BMI > ____ is associated with morbidity due to stroke, ischemic heart disease, DM, and certain cancers
30
Obese people have a high incidence of ____ within 30 days of surgery.
PE
More likely to die from it if BMI > 40
New research suggests SQ heparin for 3 weeks after surgery
NPO status for obese patients
Need to be NPO for a longer period of time because they have delayed gastric emptying, increased gastric volume, and lower gastric pH
4 major risk factors for post-op PE
BMI > 30, truncal obesity, venous stasis disease, and OSA or OHS (obesity hypoventilation syndrome)
Respiratory conditions associated with obesity
OSA/OHS
Restrictive lung disease
Pulmonary HTN
CV conditions associated with obesity
HTN Cardiomegaly Ischemic heart disease Cerebrovascular disease PVD DVT HLD Sudden death
Endocrine conditions associated with obesity
DM
Hypothyroidism
Cushing Syndrome
Musculoskeletal conditions associated with obesity
Arthritis of weight bearing joints
Back pain
Malignancies conditions associated with obesity
Colorectal Breast Prostate Uterine Cervical
Resp volume changes associated with obesity
Decreased FRC, ERV, and TV. TV may fall into the range of the closing capacity (cc).
RV is unchanged.
What is closing capacity?
The volume in the lungs at which the alveoli collapse
Obese people should be put to sleep in this position
Reverse-T
What effect does the decreased expiratory reserve volume have?
Faster closure of small airways
What should we try to avoid giving to obese patients?
Muscle relaxants. They do not have a long safe apnea time.
Minute ventilation for obese pts are higher/lower than normal
Higher. Remember that obese people have increased oxygen consumption and CO2 production due to increased body mass/tissue.
Do we want to get PFTs on obese pts?
Not usually.
Changes in PFTs don’t occur until the obesity worsens to the point where they have restrictive lung disease of pulmonary HTN.
What test of pulmonary function do we normally want to get on the obese?
ABG
What will happen if an obese pt has anesthesia induced in the supine position?
Rapid desaturation***
All obese patients should have these on during the case to prevent PE
TEDs and SCDs
Why do obese patients have more strain on their hearts?
Increased CO and expanded blood volume (more tissue). Also, if OSA is present, can cause polycythemia, and increased blood viscosity.
Obese patients have limited reserve for
Hypotension
HTN
Tachycardia
Fluid overload
HLD associated with obesity can lead to
Atherosclerosis -> premature CAD and PVD.
Pancreatitis.
Do we want an EKG for obese patients?
Hell yea!
They probably have enlarged hearts and vascular disease.
Type of heart failure than obesity with OSA causes
Biventricular failure
OSA is characterized by
1) Apnea lasting more than 10 seconds despite resp effort against a closed glottis
2) Hypopnea, and partial or intermittent narrowing/closure of the upper airway during sleep, causing a 4% drop in O2 sat
S/S of OSA
Snoring Decreased SaO2 during sleep Morning HA Impaired concentration Excessive day-time tiredness
How is OSA diagnosed?
At least 5 episodes of hypopnea and/or apnea during 1 hour
5-15 = mild 15-30 = moderate >30 = severe
Risk factors for OSA?
Obese Middle aged Males ETOH Sleep aid drugs Abdominal fat distribution Neck girth ( > 16 for women and > 17 for men)
OSA can result in
Hypercapnea (and resp acidosis during sleep) Hypoxemia and polycythemia Pulmonary and systemic vasoconstriction Pulm and systemic HTN R heart failure
As many as ___-___% of cases of OSA are undiagnosed
80-95%
OHS is also called
Pickwickian syndrome
What causes OHS?
It’s a long-term complication of extreme obesity and OSA
What is OHS?
Different from OSA because in OHS you get CENTRAL apneic events, meaning apnea WITHOUT respiratory effort).
These people even hypoventilate during the day, and tend to have a PaCO2 of 45 even when awake. They lose their hypercarbic drive to breathe.
When should obese people take their aspirin?
Before bed, because more cardiac events occur at night, and this may be related to hypoxia (from their OSA!)
How is OHS characterized?
Obesity Hypercapnia, hypoxemia, and acidosis Pulm HTN R sided HF Daytime hyper-somnolence AIRWAY DIFFICULTY
Why are obese patients at high risk for DVT?
Polycythemia, immobility, and increased intra-abdominal pressure (guessing this causes IVC compression?)
Hepatic considerations for patients with obesity
Fatty liver (will show up on U/S) Abnormal LFTs (will normalize with weight loss, even as little as 5 pounds) Caution with fluorinated volatile anesthetics like halothane (although that's not really used anymore)
What is the single best predictor of problematic intubation for the obese patient?
NECK CIRCUMFERENCE
40cm = 5% chance of difficult airway 60cm = 35% chance
If a patient has a CPAP machine, should they bring it to the hospital?
Yes! Tell them to bring it because we can place it on them in the PACU
Pulmonary tests we want pre-op
CXR (b/c obesity can lead to CHF and cardiomegaly)
Room-air SaO2 (see what their sats are and if they drop while talking)
ABG
PFTs (but remember, only valuable if the patient has restrictive lung disease or pulm HTN like in OHS)
Pre-op CV assessment and tests
Mostly looking for HTN, pulm HTN, and L/R ventricular hypertrophy.
Tests: EKG CXR Echo LV ejection fraction Previous diet aids
Endocrine tests we want pre-op
Fasting BG
HgAlC if diabetic
HgA1C > ___ is poorly controlled
6.5
Do the obese have altered liver function?
Not really. They have fatty livers and elevated LFTs, but have normal clearance in spite of this. Remember though that they will have trouble handing halogenated anesthetics.
Why are those with DM at high risk for cardiac events?
Because it causes atherosclerosis/CAD and can cause silent angina / MIs.
Monitor considerations for the obese
Normal monitors, but make sure that the BP cuff is large enough.
May want to consider an a-line if it’s a longer case.
Positioning considerations
Make sure the table can support the weight (most hold 205kg)
May need 2 tables together
Consider 2 armboards on each side
Protect pressure points
Use the ramp-up to help place them in reverse T!
Problems with the supine position in the obese
Decreased FRC/oxygenation and compression of the IVC and aorta
Which position is generally preferred for the obese, lateral or prone?
Lateral (if surgery permits)
Switching from sitting to supine position causes significant changes in
CO, PAP, and O2 consumption
Aspiration prophylaxis for the obese
Treat pre-op anxiety H2 receptor antagonists Sodium citrate (Bicitra) Metoclopramide (Reglan) Omeprazole (Prilosec)
Should we give PEEP for the obese?
They almost always need PEEP d/t increased respiratory resistance (restrictive lung pattern)
In the obese, CO increases by ____L/min for each kilogram of adipose tissue
.01L/min
This causes an expanded blood volume and increased work load on the heart
The obese have a risk for these diseases that is double the risk of lean people
HTN, DVT, and CAD (presents as angina, MI, and CHF)
Do the obese tolerate fluid boluses ok?
They may not. We may want to try continuous drips instead.
The obese have limited reserve for hypotension, HTN, tachycardia, and fluid overload. They are also at double risk for CAD.
What type of questions should you ask if you suspect your patient may have OSA?
Sleep pattern? Do you snore? HA in the morning? Excessively tired during the day? Difficulty concentrating?
If your patient has been on Ally as a weight loss aid, what should you be aware of?
Decreases fat absorption, so may have low vitamin K and increased bleeding.
Supine positioning may cause compression of the
vena cava
This position allows for the longest safe apnea time
Reverse T
