Gerontology & Obesity Flashcards by Allison Beilke

Decreased Propofol requirements for general anesthesia in the elderly

Propofol dose 15% lower in elderly vs young adults

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MAC decrease per decade

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Cardiovascular changes in the elderly

HTN: loss of vascular elasticity
Difficulty increasing cardiac output: Reduced efficacy of beta agonists, endogenous physiological beta blocker, diminished baroreceptor responses
Prolonged circulation time
*Accelerates induction of inhalation agents but decreases onset for IV induction
*Baroreceptor responses respond to vascular tone (increase/decrease HR/BP)

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Pulmonary changes in the elderly

Elastin isn’t replaced by collagen

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Ideal body weight

AKA Broca’s index
-Lowest morbidity and mortality for a given population
= height (cm) - men(100) or women(105)

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Converting inches to centimeters

In x 2.54 = cm

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Lean body weight

TBW - adipose tissue
=IBW x 1.3
-Doesn’t work for nonobese people (TBW=IBW)

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BMI cutoff for obesity and overweight

> 30 obese

>25 overweight (often inaccurate for muscular individuals)

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CV system and obesity (and EBV calculation for obese)

CO increases 0.1L/min for every kg fat gain (d/t increased O2 consumption)
-HR constant, achieved by increased SV
-Greater demand on myocardium -> LV hypertrophy
-Increased total blood volume
EBV=45-50mL/kg (instead of 70)

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Obese non-hypertensive heart adaptation to obesity/HTN

Decrease SVR

Increased blood volume -> eccentric dilated heart

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Obese and uncontrolled HTN heart adaptation to obesity/HTN

Increased blood volume
Mixed eccentric/dilated and concentric/ventricular hypertrophy (wall thickening)
-Will lead to heart failure and pulmonary hypertension
*Wall thickening plus increased blood volume

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Obesity increased risk of hypercoagulability

Increased clotting factors
-Fibrinogen
-Factor VII
-Factor VIII
-vWF
-Plasminogen activator factor
Predisposes to fibrin clot formation
3x risk of developing CAD for every unit change in BMI 
-Obese 50% increased risk of DVT vs nonobese

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Thromboembolic disorders in obese patients

Increased risk of CVA or PE

-Related to prothrombotic and chronic inflammatory state because of excess adipose tissue accumulation

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O2/CO2 changes in obese

Increased O2 consumption and CO2 production

-Maintain normocapnia by increasing MV (rapid shallow breathing) - uses the least amount of energy

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Obesity effect on ERV

Expiratory reserve volume

Decreased
Most sensitive indicator of pulmonary function in obese individuals

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OSA/Hypopnea syndrome in obese patients

Apnea
-Reduction in airflow >10 seconds
->15 episodes/hr of sleep
-Decreased SaO2 >4%
Test
-OPS: Overnight polysomnography
-Inconvenient, a majority of patients are undiagnosed

3 types of sleep apnea

OSA
-Periodic/partial/complete obstruction
-Respiratory efforts but no airflow, produced by excess soft tissue
Central sleep apnea
-No respiratory efforts
Mixed
-Attributes of both OSA/central sleep apnea
-Delayed effort with varying degrees of obstruction
*All associated with decreased O2 levels

STOP Bang

Screening tool for OSA
-Sensitivity of 93%
Snoring
Tiredness
Observed stop breathing
Blood Pressure
BMI>35
Age>50
Neck circumference>40cm
Gender male
High risk = 3+ items
-Refer for sleep testing

Nonalcoholic fatty liver disease (NAFLD)

Increased adipose tissue -> increased intrahepatic triglycerides, impaired insulin activity, release of inflammatory cytokines
-Destruction of hepatocytes and cirrhosis
-Elevated ALT
-Benign form of hepatitis but can lead to HCC, portal HTN
Mortality from liver disease is 1.5-2.5 higher than nonobese

Endocrine/Metabolic disease and obesity

Pancreas: infiltrated with fat -> decreased insulin secretion
Adipocytes: enlarged -> insulin resistance
Abnormal glucose tolerance, hyperglycemia, insulin resistance -> increased wound infection, silent MI
Surgical stress -> adrenal release cortisol -> increased need for insulin
Subclinical hypothyroidism in 25% morbidly obese -> increased TSH levels and possibly TH resistance in tissues

Too small of a BP cuff ___estimates the BP

Overestimates

Pharmacology for obese patients

Water soluble meds based on IBW
Lipid soluble meds based on TBW
Lipophillic drugs have increased volume of distribution (elimination half life is prolonged)
-Benzos and barbiturates : Don’t redose!

Muscle relaxant dosing in obese

Nondepolarizing: Based on IBW (or even lean body weight)
Succinylcholine: Based on TBW (pseudocholinesterase activity is increased in obesity)

Opioid use in obesity

Initial dose is the same but repeat doses are less predictable

Volatile anesthetics in obesity

Sevo/Des: More water soluble, less emergence time | Iso: More lipid soluble, accumulates, increased emergence times

Propofol in obesity

Highly lipophilic, accumulate if TIVA is used - Induction dose based on LBW - Maintenance dose based on TBW, decrease with increased time to avoid accumulating

Volume replacement in obesity

Normally Total body water=60% In obesity=40% Estimated blood volume=45-55mL/kg of actual body weight Avoid rapid infusion of IVF -> CHF

Extubation in obesity

``` Depends on -How easy to BMV -How easy to intubate -Length/type of surgery -Plus all normal considerations If doubtful, leave ETT in place ```

Post op respiratory complications and obesity

Respiratory failure is the most common major postop complication

Post op cardiovascular complications and obesity

Increased 30 day morbidity due to MI -Normal population: 0.1% -Obese: 0.5% Also higher incidence of a fib

DVT/PE in obesity

PE is leading cause of mortality post-op in obese patients | -50% higher rates in obese patients

Restrictive bariatric surgery

Goal=limit food intake VBG: vertical banded gastroplasty (not done anymore) AGB: Laparoscopic adjustable gastric banding -Removable -Shorter hospital stay LSG: Laparoscopic sleeve gastrectomy -Resection of stomach to 20% original size

Combined restrictive/mildly malabsorptive obesity surgery

RYGB: Roux-en-Y gastric bypass - Laparoscopic - Most effective bariatric procedure - Small pouch limits food intake - Distal resected end anastomosed to ilium: small intestinal limb

Combined mildly restrictive/largely malabsorptive obesity surgery

BPD with DS: Biliopancreatic diversion with duodenal switch - Hemigastrectomy to make gastric pouch, connects directly to ilium - Typically done with "super-obese"

Obesity surgery mortality risk score

``` 1 point for each: -BMI>50 -Male -Hypertension -High risk for DVT -Age>45 0-1=Low risk (0.2%) 2-3=Intermediate risk (1.3%) 4-5=High risk (2.4%) ```