Obesity Flashcards
1
Q
Definition of overweight and obesity?
A
- Overweight Defined: “increased body weight above a standard related to height”
- Obesity Defined: “excessive body weight for the patient’s age, gender and height” (body weight of 20% or more above ideal weight)
- US population:
- 68% overweight
- 33% obese
- 25% of children are obese
2
Q
What is ideal body weight? How do you calculate it?
A
- Ideal Body Weight: weight associated with maximum life expectancy for a given height and gender
- IBW (male) = 105 lb + 6 lb for each inch > 5 ft.
- IBW (female) = 100 lb + 5 lb for each inch > 5 ft
-
Broca’s Index: IBW (kg) = height (cm)-x
- x = 100 males, x = 105 females<<- remember this one
- Miller 8th:
- Male: 50 kg + 2.3 kg for each 2.54 cm (1 in) >152 cm (5 ft)
- Female: 45.5 kg + 2.3 kg for each 2.54 cm (1 in) > 152 cm (5 ft)
- IBW useful in calculating some drug doses to avoid toxicity or hemodynamic instability
- In morbidly obese patients, increasing the IBW by 20% gives an estimate of LBW. In nonobese and nonmuscular individuals, TBW approximates IBW.
3
Q
What is BMI? How do you calculate it?
A
- BMI is an accepted measure of body habitus that normalizes adiposity for height
- Calculation (memorize):
- BMI= weight (kg)/ height2 (m)
- cannot distinguish overweight and overfat as heavily muscular people can easily be classiied as overweight using BMI
- other factors such as age and fat distribution should be taken into consideration, amonth other health predictors that utilize concept of BMI
4
Q
Various BMI stratifications?
A
-
Overweight defined as BMI of 25-29 kg/m²
- Approximate body weight 20% more than ideal body weight
- Obesity is defined as BMI > 30 kg/m²
- Clinically Severe Obese: (formally Morbid Obesity): BMI > 40 kg/m2
- Super-Obese: BMI > 50 kg/m2
- Super-Super Obesity: >60 kg/m2
- BMI > 30 (obese) is associated with increased morbidity related to stroke, ischemic heart disease, HTN, and diabetes
5
Q
Various distributions of body fat?
A
-
Android obesity (android fat distribution)
- Abdominal (central) obesity
- More common in men, higher incidence of metabolic disturbances, increased risk of ischemic heart disease, stroke, diabetes, death
-
Gynecoid obesity (gynecoid fat distribution)
- Fat around hips and buttocks
- More common in females
- Waist circumference & risk of pathophysiology (>102 cm (40”) men or >88 cm (35”) women)
6
Q
What disturbances are associated with obesity
A
- Obstructive sleep apnea/ hypoventilation syndrome
- Restrictive lung disease
- Hypertension
- CAD
- Hyperlipidemia
- Delayed gastric emptying/ GERD
- Type II Diabetes Mellitus
- Gall bladder disease (cholelithiasis)
- Cirrhosis/ Fatty liver disease
- Venous stasis/ Thromboembolic disease
- Degenerative joint/disc disease
- Increased breast, prostate, cervical, uterine, and colorectal cancer
7
Q
Lung volume alterations in obesity?
A
- Chest wall and lung compliance reduced
- Lung volume changes
- Reduced Functional Residual Capacity (FRC)
- Reduced Expiratory reserve volume (ERV)
- RV and CC are not changed
- However….the relationship between FRC and CC is adversely affected
- FEV1 and FVC usually within normal limits
- Reduced Tidal Volume
- TV may fall into the range of the Closing Capacity (CC)
- from added weight of thoracic cage, chest wall and abdomen, which impedes the diaphragm
8
Q
Pulm physio changes in obesity?
A
- Increased pulmonary blood volume
- Increased oxygen consumption and carbon dioxide production
- because of obese pt’s increased body mass, o2 consumption and CO2 production. obese pt must increase MV to compensate
- rapid, shoow breathing to use less energy and prevent fatigue
- High minute ventilation; increased work of breathing
- As obesity worsens you will see lung disease and pulmonary hypertension– > RHF
- (PFTs may remain normal until this occurs)
9
Q
Respiratory alterations in obese patient r/t positioning?
A
- For the obese patient respiratory changes are exaggerated with operative positions
- Supine
- Trendelenberg
- Lateral
- Prone
- Rapid de-saturation may be seen when anesthesia is induced in recumbent/supine position
- sit up as much as possible
- Deviations in lung volumes lead to:
- V/Q mismatch
- hypoxemia
- Increased right to left intrapulmonary shunt
-
PIC:
- upright- obese and nonobese have similar lung volumes but still restrictive in obese
- obese supine - significant decrease in lung volume
-
obese trendelenberg- restrictive physio even wrose
- can cause V/q mismatch, hypoxemia and right ot left intrapulmonary shunt
10
Q
Airway changes in obesity?
A
- TMJ & atlanto-axial joint and cervical spine movement limited by upper thoracic and low cervical fat pads
- Redundant tissue folds in the mouth and pharynx = narrowed upper airway
-
Short, thick neck: measure neck circumference- STRONG predictor of difficult intubation
- 40cm = 5% incidence difficult intubation
- 60cm= 35% incidence difficult intubation
- Fat in suprasternal, presternal, posterior cervical and submental regions- difficult laryngoscopy
- Shortened distance between mandible & sternal fat pads
-
OSA = increase risk of excess pharyngeal tissue on lateral walls
- inverse relationship b/w obesity nf pharyngeal area size
- changes shape of oropharynx into an ellipse with short transverse and long anteroposterior axis
- contribute to airway obstruction
- almost always need OPA to help with mask ventilation
- Creates difficulty maintaining mask airway
- Creates difficult laryngoscopy and intubation
11
Q
Obstructive sleep apnea?
A
- Obesity is an independent risk factor for OSA
- Characterized by
- Apnea >10 seconds total cessation of airflow despite respiratory effort against a closed glottis- rocking horse”
- Hypopnea is 50% reduction in size or number of breaths that lasts at least 10 seconds compared to normal; partial or intermittent collapse of pharyngeal airway during sleep
- Obese pt have airway narrowing d/t excess tissue. decrease in upper airway muscle tone during REM sleep.
- cannot predict OSA on BMI, Neck circumference, PFT or daytime ABG or questionaiires
- 80-90% pt with sleep apnea are undiagnosed
-
Need polysomnography
- apneic-hypopneic index is total number of apneic or hypopneic events (or both) per hour of sleep
-
severity of OSA directly related to magnitude of index
*
12
Q
S/S OSA?
A
- Daytime somnolence
- SNS activation in response to hypoxemia– may aloshave HTN
- Habitual snoring
- interrupted breathing during sleep (apneic spells followed by short gasps, grunts, reuscitative snorting)
- impaired daytime performance
- morning headache
- irritability
- increased neck circumference (>40-42 cm at cricoid cartilage)
13
Q
OSA Risk factors?
A
- Middle age
- Male
- Obesity (BMI>30)
- ETOH use
- Drug induce sleep aids
- Abdominal fat distribution
- Neck girth (41cm)
- >17 inches for men
- >16 inches for women
14
Q
What do apenic episodes of OSA lead to? Severity of OSA?
A
- Frequent episodes of apnea during sleep leads to
- Chronic hypoxia, hypercapnia, pulmonay and systemic vasoconstriction (HTN)
- get lots of SNS activation d/t chronic hypoxemia
- pro-inflammatory state
- get historical info from family member
- Snoring
- Sleep fragmentation/daytime somnolence
- Impaired concentration
- Morning headache
- Chronic hypoxia, hypercapnia, pulmonay and systemic vasoconstriction (HTN)
- Severity of OSA is graded by # of apnea or hypopneic episodes during 1 hour observation
- Mild >5 but ≤15 /hour
- Moderate 15 to 30 /hour
- Severe >30 events/hour
15
Q
What is Pickwickian syndrome (obesity hypoventilation syndrome)
A
- Complication of extreme obesity/ long term OSA
- Extreme obesity (>40 BMI) with:
- hypercapnia
- cyanosis induced polycythemia
- somnolence
- eventual right sided heart failure
- pulmonary HTN
- PCO2 >45 mm Hg in an obese patient without significant COPD is diagnostic
- Clinically distinct from OSA– progression from OSA
-
OSA you have nocturnal sleep disruption
- respiratory effort without ventilation
- OHS you have nocturnal central apneic events (apnea without respiratory effort)
16
Q
Characterization of pickwickian syndrome (obesity hypoventilation syndrome)
A
Characterized by
- Obesity
- Hypercapnia (>45 at RA, daytime– increase monitoring in PACU necessary)
- Daytime hyper-somnolence
- Arterial haypoxemia
- Pulmonary hypertension
- Respiratory acidosis
- Right sided heart failure
- Airway Difficulty
17
Q
CV Alterations in Obesity?
A
- Increased total blood volume
-
Increased Cardiac Output
- Expanded blood volume puts strain on myocardium
-
Increased renin-angiotensin system & SNS activity: HTN (Arterial hypertension risk is twice as high as for lean men and women)
- releated to insulin effects on SNS
- Insulin activated adipocytes to release angiotensinogen, which activates the RAAS pathway, leading to sodium retention and development of HTN
- circulating cytokines may cause damage to and fibrosis of arterial wall, causing arterial stiffness
- Risk of CAD is double and presents with angina, CHF, acute MI and sudden death
-
Increased left-sided heart pressures and left ventricular hypertrophy
- leads to concentric hypertrophy–> first diastolic and then systolic dysfunction
18
Q
Factors to consider preop r/t CV alteration in obesity?
A
- Assessment pre-operatively is essential to determine their cardiac tolerance
- Obese patients have limited reserve for
- hypotension
- hypertension
- tachycardia
- fluid overload
19
Q
Hematologic alterations in obesity?
A
- Polycythemia & Hypercoagulation
-
Thromboembolic Risk
- Risk of DVT is doubles
- Polycythemia leads to increased blood viscosity; increased fibrinogen levels
- Increased intra-abdominal pressure
- Immobility leads to venostasis
20
Q
GI alterations in obesity?
A
- Increased incidence
- Hiatal hernia
- GERD
- Gallbladder disease
- High risk for aspiration pneumonitis
- Greater gastric volumes >25ml related to delayed gastric emptying
- Increased gastric acidity pH<2.5 (increased parietal cell secretion)
- Gastric emptying delays promoted by increased abdominal mass
28
Q
Summary of drug dosing for obese patient?
Propofol?
Succinylcholine?
Roc, vec?
Cis, Atracurium
Fent/sufentanil?
Remi?
Midaz?
Epidural
A
- Propofol
- induction= LBW
- maintenance- TBW
-
Succinylcholine
- Intubation- TBW<— increaesd plasma pseudocholinesterase
- ROC/VEC- LBW both induction and maintenance
- Cisatracurium- TBW
- Atracurium- tbw or lbw
- Fentanyl/Sufentanil
- loading= TBW
- Maintenance- LBW
- Remifentanil
- LOADING- LBW
- Maintenance- LBW
- Midaz- TBW both loading and maintenance
- Epidural- 75% of normal dose
in genearl, NMB exhibit prolonged DOA and recovery in obese patient. use PNS monitor frequently!!
