Obesity Flashcards
1
Q
Definition of Overweight
Definition of obesity
A
- Overweight- increased body weight above a standard related to height
- Obesity- excessive body weight for the patients age, gender, and height
- body weight of 20% or more above ideal weight
- it is a disorder of energy balance
2
Q
Obesity stats
A
- 68% of US population overweight
- 33% obese
- 25% of children are obese
3
Q
Ideal body weight calculation for men
women
A
- men: IBW = 105 lb + 6 lb for each inch >5 ft
- women: IBW = 100lb = 5 lb for each inch >5 ft
- Brocca’s index:
- IBW (kg) = height (cm) -x
- x for men = 100, x for women = 105
- lean body weight is IBW + 20%
4
Q
How do you calculate BMI?
What is the problem with this measurement?
A
- MBI = weight in kg/ height2 (m)
- Does not clearly differentiate between overweight and overfat. Very muscular ppl will be designated overweight/obese even though they are not fat
5
Q
What are the different groupings of BMI?
A
- Overweight = BMI 25-29 kg/m2
- Obese = BMI >30
- Clinically severe Obese = BMI >40
- Super Obese = BMI >50
- Super-Super Obesity = MBI >60
- BMI >30 is associated with increased morbidity related to stroke, ischemic heart disease, HTN, and DM
6
Q
What is the impact of anatomic distribution?
A
- Android obesity- abdominal, central obesity
- more common in men
- higher incidence of metabolic disturbances, ischemic heart disease, stroke, dm, death
- Gynecoid obesity- fat around hips and buttocks
- more common in females
- Waist circumference is directly related to risk of pathophysiology
- >102 cm in men
- >88 cm in women
7
Q
What problems are associated with obesity?
A
- OSA
- RLD
- HTN
- CAD
- hyperlipidemia
- delayed gastric emptying/GERD
- Type II DM
- Gall bladder disease
- Cirrhosis/fatty liver disease
- venous stasis
- degenerative joint/disc disease
- increased breast, prostate, cervical, uterine, and colorectal cancer
8
Q
How does obesity alter the respiratory system?
A
- Reduces chest wall and lung compliance
- reduced FRC- 50%
- reduced ERV
- RV and CC not changed
- relationship btw FRC and CC is adversely effected
- FEV1 and FVC usually WNL
- Reduced TV- may fall into the range of closing capacity
- Increased pulmonary blood volume
- increased O2 consumption and CO2 production
- high MV, increased WOB
- As obesity worsens, you will see lung disease and PHTN but PFTs remain normal until this occurs
9
Q
How does obesity affect the respiratory system in different positions?
A
- Respiratory changes are all exaggerated in different positions
- Rapid desaturation may be seen when anesthesia is induced in recumbent/supine position
- Deviations in lung volumes lead to:
- VQ mismatch-
- hypoxemia
- increased right to left intrapulmonary shunt
- TV overlapping with closing capacity (the small airways will start to close during a normal tidal volume breath)
10
Q
What changes can you expect in securing an airway for an obese patinet?
A
- TMJ and atlanto-axial joint and cervical spine movement is limited by upper thoracic and low cervical fat pads
- Narrowed airway from extra tissue folds in mouth and pharynx
- Short, thick neck- measure it
- 40 cm = 5% incidence of difficult intubation
- 60 cm = 35% incidence of difficutl intubation
- Fat in suprasternal, presternal, posterior cervical and submental regions
- shortened distance between mandible and sternal fat pads
- OSA
- difficult to mask ventilate
- difficult to get a good view on laryngoscopy
11
Q
How is OSA characterized?
A
- Apnea > 10 seconds; total cessation of airflow despite respiratory effort against a closed glottis
- Hypopnea is 50% reduction in size or number of breaths that lasts at least 10 seconds compared to normal
- partial or intermittent collaps of pharyngeal airway during sleep
12
Q
What are the risk factors for OSA?
A
- middle age
- male
- obesity
- ETOH use
- drugs for sleep aids
- abdominal fat distribution
- neck girth 41 cm
- >17 inches for men
- >16 inches for women
13
Q
What problems can OSA lead to?
A
- chronic hypoxia, hypercapnia, pulmonary and systemic HTN
- snoring
- poor sleep leading to daytime somnolence
- impaired concentration
- morning HA
- Right heart failure
- polycythemia and increased blood volume
- respiratory acidosis
14
Q
How is OSA graded?
A
- Severity is graded by # of apnea or hyponeic episodes during 1 hour of observation
- mild = 5 -15/hour
- moderate = 15-30/hour
- severe >30/ hour
15
Q
What is Pickwickian syndrome?
How is it diagnosed?
A
- Obesity hypoventilation syndrome (OHS)
- Complication of extreme obesity/long term OSA
- hypercapnia, cyanosis induced polycythemia, somnolence and eventual right sided heart failure and PHTN
- Doagnosed by PCO2 >45 in an obese pt w/o significant COPD
- Clinically distince from OSA
- OSA you have nocturnal sleep disruption
- OHS you have nocturnal central apneic events (apnea without respiratory effort)
16
Q
How is OHS (Pickwickian syndrome) characterized?
A
- Obesity
- hypercapnia
- daytime hyper-somnolence
- Arterial hypoxemia
- PHTN
- respiratory acidosis
- right sided heart failure
- difficult airway
17
Q
What cardiovasclar alterations would you expect to see in an obese patient?
A
- Increased total blood volume
- increased CO
- higher blood volume puts strain on myocardium
- Risk of CAD is double and presents with angina, CHF, acute MI and sudden death
- Increased RAAS and SNS activity
- arterial HTN risk is twice as high as it is for lean pts
- increased left sided heart pressures and left ventricular hypertrophy
18
Q
What hemotologic alterations would you expect to see in an obese patient?
A
- Polycythemia and hypercoagulation
- Thromboembolic risk
- risk of DVT doubles
- plycythemia leads to increased viscosity and increased fibrinogen levels
- increased intra-abdominal pressure
- immobility leads to venostasis
19
Q
What gastrointestinal alterations would you expect to see in an obese patient?
A
- Increased incidence of Hiatal hernia, GERD, and gallbladder disease
- High risk for aspiration
- greater gastric volumes(>25 ml) d/t delayed gastric emptying
- increased gastric acidity (pH<2.5) d/t increased parietal cell secretion
20
Q
What kind of hepatic alterations would you expect to see in an obese patient?
A
- Fatty infiltration of liver
- inflammation
- cirrhosis
- Abnormal LFTs
- wt loss, even just 5 lbs can reverse the elevated liver enzymes
- caution with fluorinated volatile anesthetics
21
Q
What renal alterations would you expect to see in an obese patient?
A
- increased renal plasma flow and increased GFR
- Increased renal tubular resorption and impaired naturesis secondary to SNS and RAAS
- also physical compression of the kidney
- eventually nephron function can be lost
22
Q
What kind of endocrine alterations would you expect to see in an obese patient?
A
- Obese patients secrete more insulin, but are resistant to the effects of insulin
- develop type 2 dm
- Metabolic syndrome
- presence of at least three of the following signs
- large waiste curcumference
- high triglyceride levels, low levels of HDL
- glucose intolerance
- HTN
- presence of at least three of the following signs
23
Q
What musculoskeletal and CNS changes would you expect to see in an obese patient?
A
- Musculoskeletal
- osteoarthritis and degenerative joint disease
- high weight on joints
- inflammatory response
- osteoarthritis and degenerative joint disease
- CNS
- ANS dysfunction
- peripheral neuropathies
24
Q
Often obese patients have hyperlipidemia. What can this lead to?
A
- Elevated LDL and low HDL is linked to athersclerosis
- Can lead to
- premature CAD
- premature vascular disease
- pancreatitis
25
Q
What alterations in drug pharmacokinetics and metabolism would you expect to see in an obese patient?
A
- Pharmacokinetics:
- increased blood volume and CO
- decreased total body water
- adipose and lean tissue increases
- unpredictable changes in PB
- VOD central compartment unchanged
- metabolism
- Phase 1 (oxidation, reduction, hydrolysis) unaffected
- Phase 2 (glucuronidation, sulfation) enhanced
- Clearance
- Hepatic clearance unchanged even with elevated LFTs
- renal clearance increased d/t increased RBF and GFR
- lipophilic drugs have an increased E1/2t d/t increased Vd
26
Q
How do you calculate lean body mass?
A
- male: 1.1 x TBW- 128x(TBW/Ht)2
- female: 1.07 x TBW - 148 x (TBW/Ht)2
27
Q
How would you adjust the dosing for a weak or moderately lipophillic drug?
A
- add 20% to the IBW
- this will include the extra LBM associated with obesity
28
Q
How would you dose propofol in an obese patient?
A
- induction dose should be based on LBW
- maintenance dose should be based on TBW
29
Q
How should you dose benzos for an obese patient?
A
- (these are highly lipophillic drugs)
- initialdoses based on LBW
- may titrate to TBW
- need larger doses to reach adequate serum concentrations
- Infusions based on LBW
30
Q
How would you dose neuromuscular blocking drugs for an obese patient?
A
- Based on LBW: Roc, Vec, Atracurium, Cisatracurium
- prolonged DOA and recovery
- Pseudocholinesterase activity increases with weight and ECF increases
- dose Succ on TBW
31
Q
How would you dose opioids in an obese patient?
A
- Fentanyl and Sufentanyl: both are highly lipid soluble
- increased Vd and elimination 1/2 life
- dose fentanyl based on LBW (miller says TBW)
- dose sufentanyl on TBW but decrease maintenance to LBW
- Remifentanyl dose based on LBW
32
Q
How would you dose dexmedetomidine in an obese patient?
A
- Use as an adjunct when it is priority to avoid respiratory depression
- 0.2-0.7 mcg/kg/hr, dosed on TBW
33
Q
How would you dose VA for an obese patient?
A
- Metabolism is greater in obese patients which leads to greater increase in inorganic fluoride
- greater incidence of halothane hepatitis
- N2O often avoided to maximize PaO2
34
Q
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