Obesity

Question 1

What is the formula for IBW?

Answer 1

IBW (male) = 105 lb + 6 lb for each inch > 5 ft.

IBW (female) = 100 lb + 5 lb for each inch > 5 ft

Question 2

What is the formula for BMI?

Answer 2

BMI= Weight (kg)/ height (m2)

Question 3

What is oversight vs obesity?

Answer 3

Overweight defined as BMI of 25-29 kg/m²
Obese: BMI of greater than 30
Morbidly Obese: BMI of greater than 40
Super- Obese BMI of greater than 50

Question 4

Increased BMI leads to what assessment related risks?

Answer 4

Increased incidence of diabetes and cardiovascular disease
Difficult tracheal intubation
Decreased Pa02
Increased gastric volume
Decreased gastric pH
Increased post-op wound infection
Increased risk of pulmonary embolism
Sudden death
30 day outcomes

Question 5

What are other secondary diseases (disturbances) associated with obesity?

Answer 5

Obstructive sleep apnea
Respiratory Derangements
Systemic hypertension
Ischemic Heart  Disease
CHF
Delayed gastric emptying
Diabetes Mellitus
Hepatobiliary Disease
Thromboembolic Disease
Musculoskeletal Disease
*slide 8

Question 6

What are respiratory changes that occur regarding FRC, ERV, TV?

Answer 6

Lung Volumes are changed due to the physiologic deviations
Functional Residual Capacity (FRC) is reduced
Expiratory reserve volume (ERV) is reduced
Tidal Volume may fall into the range of the Closing Capacity (CC)

Question 7

What are some ventilatory changes regrading CO2 production, minute ventilation, PFTs?

Answer 7

Increased oxygen consumption and carbon dioxide production
High minute ventilation
Reduced chest wall compliance
Increased respiratory resistance-restrictive lung pattern
As obesity worsens you will see lung disease and pulmonary hypertension PFTs may remain normal until this occurs

Question 8

Deviations in lung volumes lead to

Answer 8

V/Q mismatch
hypoxemia
Increased right to left shunt

Question 9

Abundant soft tissue in upper airway can lead to?

Answer 9

Obstruction of the airway
Can impair the mandible and cervical mobility
Creates difficulty maintaining mask airway
Difficult laryngoscopy and Intubation
consider fiberoptic intubation

Question 10

Cardiac Output is increased by ? for each kg of adipose tissue?

Answer 10

0.01L/min

Results in an increased circulating blood volume
Expanded blood volume can put strain on myocardium
Arterial Hypertension risk is twice as high as for lean men and women
Risk of CAD is double and presents with angina, CHF, acute MI and sudden death
Increased left-sided heart pressures and Left ventricular hypertrophy

Question 11

Obese patients have limited reserve for

Answer 11

hypotension
hypertension
tachycardia
fluid overload

Question 12

Obesity does what to your lipid levels?

Answer 12

Hyperlipidemia- leads to premature coronary artery disease and vascular disease, pancreatitis, atherosclerosis.

Question 13

OSA is characterized by what?

Answer 13

1. Apnea >10 seconds despite respiratory effort against a closed glottis
2. Hypopnea partial or Intermittent closure or narrowing of the upper airway during sleep resulting is a 4% decrease in arterial oxygen saturation
   results in: oxygen desaturation, snoring, impaired concentration, morning headache

Question 14

OSA is diagnosed by what?

Answer 14

diagnosed by at least 5 episodes of apnea,  hypopneas,  or both during 1 hour 
Graded as 
Mild  >5 but ≤15 /hour
Moderate 15 to 30 /hour 
Severe >30 events/hour

Question 15

Risk factors for OSA?

Answer 15

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

Question 16

OSA physiologically results in what?

Answer 16

Hypoxemia
Right heart failure
Hypercapnia
Pulmonary and systemic vasoconstriction
Polycythemia
Respiratory acidosis during sleep 
Arterial hypoxemia
Systemic hypertension
Pulmonary hypertension

Question 17

During the pre-op evaluation, patients should be asked about what to determine if the have sleep apnea?

Answer 17

Sleeping patterns
Snoring
Daytime somnolence
High suspicion for OSA in the obese patient
*Preoperative evaluation should focus on identifying patients at risk for OSA and improving associated comorbidities

Question 18

What is Pickwickian syndrome?

Answer 18

Complication of extreme obesity
Long term consequence of OSA
Airway difficulty
Clinically distinct from OSA where you have nocturnal sleep distruption
As OHS develops you get nocturnal central apenic events (apnea without resp effort)

Question 19

What are the characteristics of Pickwickian Syndrome?

Answer 19

Characterized by
Obesity
Hypercapnia
Daytime Hyper-somnolence 
Arterial hypoxemia
Pulmonary hypertension
Respiratory acidosis
Right sided heart failure
Airway Difficulty

Question 20

What are GI effects of Obesity?

Answer 20

Gastro-esophogeal reflux
Hiatal hernia
Increased gastric volume and intra-gastric pressure
gastric acidity
Gastric emptying delays with greater residual volumes, high risk for aspiration, gastric volumes >25ml, pH<2.5 (increased parietal cell secretion)

Question 21

What are Thromboembolic effects of obesity?

Answer 21

Risk of DVT is double that of nonobese patient
Polycythemia
Increased intra-abdominal pressure
Immobility

Question 22

What are hepatic effects of obesity?

Answer 22

Fatty liver
Abnormal LFTs
Fluorinated volatile anesthetics

Look for signs of:

1. Weight loss (even 5 lbs) can reverse the elevated liver enzymes
2. Fatty infiltration (high prevalence of nonalcoholic fatty liver disease)
3. Normal clearance despite often altered histology and LFT’s

Question 23

Metabolic effects of obesity?

Answer 23

Resistant to the effects of insulin
Adult onset diabetes
Fatty tissues are resistant to insulin = glucose intolerance and DM type II
Abnormal serum lipid panels = high prevalence of CAD

Look at:
Fasting Blood Sugar
Diabetes non-insulin or insulin dependent
Does the patient have a history of reflux

Question 24

What questions/exams do you do on the patient with obesity?

Answer 24

Does patient have a history of previous difficult airway
Obstructive sleep apnea
Assess ROM of atlantoaxial joint and cervical spine
Mouth opening
Thyromental distance
Interior of the mouth
Mallampati classification
Neck size single best predictor of problematic intubation (5% with neck circ of 40 cm compared to 35% with a neck circ of 60cm
ask about: Orthopnea, Sleep apnea, Obesity hypoventilation syndrome, Previous history of upper airway obstruction especially regarding a past anesthetic

Question 25

What are some tests/labs you want to look at?

Answer 25

Chest Xray
Room air Sa02
ABG’s
Optimize pulmonary status pre-op
PFT’s
EKG, ECHO, LV EF, cardiac clearance if needed, venous access
*Check for s/s of hypertension, RV/LV hypertrophy, PHTN

Hepatic function
Albumin level
Glucose
Consider clotting studies (if risk factors)

Question 26

What are considerations for positioning the obese patient?

Answer 26

Special designed tables or 2 together
Ramp Up 
Regular tables have max weight of approx 205kg
Strapping patient carefully
Protect pressure points 
Consider the use of 2 armboards to support entire circumference of arm. 
Supine  compression of vena cava aorta 
Supine FRC and oxygenation  is reduced

Question 27

What happens when you change positioning in the obese patient?

Answer 27

Changing from sitting to supine causes significant changes in CO, PAP, and O2 consumption
Head-Up reverse Trendelenburg provides the longest safe apnea period (SAP)
Prone position increases intra-Abd pressure worsens vena cava and aortic compression and decreases FRC
Lateral position is favored over prone if surgery permits

Question 28

What is the aspiration prophylaxis for the obese patient?

Answer 28

Treatment includes
H2 receptor antagonists
Sodium Citrate (Bicitra)
Metoclopramide
Omeprazole