Hlth Ass in Pt with Obesity

Question 0

What is BMI and how do calculate BMI?

Answer 0

BMI is an accepted measure of body habitus that normalizes adiposity for height

BMI= weight (kg) / (Height) (height)

Question 1

What is the formula for ideal body weight?

Answer 1

●Ideal Body Weight
●IBW (male) = 105 lb + 6 lb for each inch > 5 ft.
●IBW (female) = 100 lb + 5 lb for each inch > 5 ft
●IBW useful in calculating some drug doses to avoid toxicity or hemodynamic instability

The broca index can be used to determined IDW:
Height (cm) – 100= ideal weight (Kg) for males
Height (cm) – 100= ideal weight (kg) for females
Ex: a male 6 ft tall (72’’)180cm – 100= 80 kg idea; body
Ideal body weight= BMI of 22-28
Obesity= BMI of 28-35
Morbid obesity= BMI > 35

Question 2

Who is overweight and obesity defined? What are some factors associated with obesity?

Answer 2

1) Overweight defined as BMI of 25-29 kg/m²
–Approximate body weight 20% more than ideal body weight

2) Obesity is defined as BMI > 30 kg/m²
•Associated with deviations in
–anatomic
–physiologic
–biochemical
3) BMI of greater than 30 is associated with morbidity of stroke, ischemic heart disease, diabetes, certain cancers

Question 3

What are some Respiratory changes seen in Obesity?

Answer 3

●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)
●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 4

Do obese patients have an altered response to CO2?

Answer 4

Obesity per se has not been found to decrease the respiratory center’s to CO2. yet 5 to 10% of obese patients experience an apparent decreased ventilatory response to CO2 resulting in this syndromes:

1) Obstructive sleep Apnea Syndrome (OSAS): defined as 30 apneic periods of > 20 secs over 7 hrs
2) Obesity hypoventilation syndrome (OHS): decreased ventilatory response to CO2 and O2 resulting in sleep apnea hypoventilation, hypercapnea, pulm.htn and hypersomnolence. Pickwickian syndrome: symptom include OHS, hypoxemia hypercarbia, pul HTN, polycythemia, and biventricular failure.

Question 5

What is Obesity hypoventilation syndrome (OHS)?

Answer 5

decreased ventilatory response to CO2 and O2 resulting in sleep apnea hypoventilation, hypercapnea, pulm.htn and hypersomnolence. Pickwickian syndrome: symptom include OHS, hypoxemia hypercarbia, pul HTN, polycythemia, and biventricular failure.

Question 6

What are some respiratory Changes and Positioning seen in obesity?

Answer 6

• For the Obese patient Respiratory changes are exaggerated with changes in position
• Supine
• Trendelenbergde-saturation may be seen when anesthesia is induced in
• Rapid recumbent/supine position

Question 7

1) What are some effects of position changes in obesity?

Answer 7

•Deviations in lung volumes lead to
–V/Q mismatch
–hypoxemia
–Increased right to left shunt

Question 8

What are some ABG change seen in obese patients?

Answer 8

ABG change seen in obese patients: the most common alteration is hypoxemia due to V/Q mismatching. Pulmonary perfusion is increased because of Increased CO, circulating blood volume, and pulmonary hypertension. Progressive obesity results in TV resting below closing volum resulting in collapsed airways during tidal respiration and the tendency to undergo oxygen desaturation.

Question 9

What are some effects of obesity on the airway structure?

Answer 9

●Abundant soft tissue in upper airway
●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

What is essential to determine in the pre-op cardiac assessment for obese patients?

Answer 10

●Assessment pre-operatively is essential to determine their cardiac tolerance
●Obese patients have limited reserve for
●hypotension
●hypertension
●tachycardia
●fluid overload

Question 11

What are some Cardiovascular changes seen in obese patients?

Answer 11

1) Cardiac Output is increased by .01L/min for each kilogram of adipose tissue
Results in an increased circulating blood volume
Expanded blood volume can put strain on myocardium
2) Arterial Hypertension risk is twice as high as for lean men and women
3) Risk of CAD is double and presents with angina, CHF, acute MI and sudden death
4) Increased left-sided heart pressures and Left ventricular hypertrophy

Question 12

What are some lipid changes see in obese population?

Answer 12

●Hyperlipidemia is associated with Obesity
Increased LDL cholesterol linked to atherosclerosis
Decreased HDL cholesterol linked to atherosclerosis

●Can lead to :
●Premature coronary artery disease
●Premature vascular disease
●Pancreatitis

Question 13

What are the characteristics of OSA?

Answer 13

Characterized by
●Apnea >10 seconds despite respiratory effort against a closed glottis
●Hypopnea partial or Intermittent closure or narrowing of the upper airway during sleep resulting in a 4% decrease in arterial oxygen saturation
Frequent episodes of apnea during sleep
●oxygen desaturation  
●snoring
●impaired concentration
●morning headache

Question 14

How can you measure the severity of OSA?

Answer 14

•Severity of OSA is measured by Apnea hypoxia index number or Hypopneic episodes
–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

What are some OSA risk factors?

Answer 15

1) Middle age
2) Male
3) Obesity (BMI>30)
4) ETOH use
5) Drug induce sleep aids
6) Abdominal fat distribution
7) Neck girth (41cm)
–>17 inches for men
–>16 inches for women

•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

•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

•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 characteristics results in what?

Answer 16

1) Hypoxemia
2) Right heart failure
3) Hypercapnia
4) Pulmonary and systemic vasoconstriction
5) Polycythemia
6) Respiratory acidosis during sleep
7) Arterial hypoxemia
8) Systemic hypertension
9) Pulmonary hypertension

Question 17

What are some factors associated with OSA you should ask your patients during the pre-op evaluation?

Answer 17

As many as 80 to 95% of patients with OSA are undiagnosed and many patients may present for surgery are in this category

During the Pre-op evaluation patients should be asked about their:
1) Sleeping patterns
2) Snoring
3) Daytime somnolence
4) 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 can you tell me about Obesity Hypoventilation Syndrome (Pickwickian Syndrome) ?

Answer 18

1) Complication of extreme obesity
2) Long term consequence of OSA
3) Airway difficulty
4) Clinically distinct from OSA where you have nocturnal sleep distruption
5) As OHS develops you get nocturnal central apenic events (apnea without resp effort)
–One theory is the loss of the patient’s hypercarbic drive to breathe is due to progressive desensitization of the respiratory centers in nocturnal hypercarbia.
–Gives this syndrome a loss of the central mediated response.

Question 19

What are the characteristics Obesity Hypoventilation Syndrome (Pickwickian Syndrome)?

Answer 19

1) Obesity
2) Hypercapnia
3) Daytime Hyper-somnolence
4) Arterial hypoxemia
5) Pulmonary hypertension
6) Respiratory acidosis
7) Right sided heart failure

•Airway Difficulty

Question 20

What are some GI changes seen in obesity?

Answer 20

1) Gastro-esophogeal reflux
2) Hiatal hernia
3) Increased gastric volume and intra-gastric pressure
4) gastric acidity

The large tissue mass in obese patients increases intr-abdominal and intragastric pressures. Hiatal hernias and gastric reflux are common. Despite an 8 hrs fast 85 to 90% of morbidly obese patients have gastric volumes >25 ml and gastric pH 25ml
pH<2.5 (increased parietal cell secretion)

Question 21

What are some thromboembolic factors related to obesity?

Answer 21

1) Risk of DVT is double that of nonobese patient
2) Polycythemia
3) Increased intra-abdominal pressure
4) Immobility

Question 22

What are some hepatic changes seen with obesity?

Answer 22

1) Fatty liver
2) Abnormal LFTs
3) Fluorinated volatile anesthetics
Obese patients have fatty infiltration of the liver and may have hepatic inflammation, focal necrosis, and cirrhosis. At present no causal relationship between fatty infiltration and cirrhotic changes is known. Hepatic enzymes may be elevated after jejunoileal operations.

Question 23

What are some metabolic changes seen in obesity?

Answer 23

1) Resistant to the effects of insulin
2) Adult onset diabetes
Relationship between obesity and DM: insulin resistant is a prominent feature of both obesity and non-insulin dependent diabetes mellitus (NIDDM). Insulin action in obese patients is impaired by decreasing insulin suppression of hepatic glucose production and decreasing glucose utilization at the muscle. Obese patients are at increased risk for hyperglycemia and hyperinsulinemia.

Question 24

How should you approach an obese patient during the pre-op evaluation?

Answer 24

1) Assess patient in a non-judgemental fashion
2) Emphasis should be on the difficulties obesity presents to the anesthesia provider
3) Discuss the likely post-operative course

Pre-op History: a thorough medical history should include incidence of sleep apnea, snoring, somnolence, and periodic breathing as well as assessment of hypertension, CHF and CAD. Obese pts are inactive and determination of impaired cardiac performance may be difficult. Questions involving symptoms of GERD, hiatal hernia, DM and DVT thrombosis should be asked.

Question 25

What are some factors included in the Airway pre-op evaluation of obese patients?

Answer 25

1) Does patient have a history of previous difficult airway
2) Obstructive sleep apnea
3) Assess ROM of atlantoaxial joint and cervical spine
4) Mouth opening
4) Thyromental distance
5) Interior of the mouth
6) Mallampati classification
7) Neck size single best predictor of problematic intubation (5% with neck circ of 40 cm compared to 35% with a neck circ of 60cm

Physical examination: airway evaluation is important and should include cervical and mandibular range of motion, thyromental distance, and oral airway assessment. Subjective evaluation of chest and neck fat may suggest difficulties with intubation. With potential difficult intubation the patient should be counseled on the procedure and benefits of an awake, sedated fiber-optic intubation. Adequacy of arterial and venous access should be evaluated.

Question 26

What are some primary operative concerns in morbidly obese patients?

Answer 26

1) Airway and ventilatory management: before induction, preparation for a difficult airway should be completed. Fiber-optic bronchopscope, cricothyrotomy equipment etc… should be available. Preoxygenation and denitrogenation are critical. If the airway exam suggests that laryngoscopy and intubation are not problematic, a rapid sequence induction and intubation with cricoid pressure may be used. Otherwise, awake, sedated fiber-optic intubation is the technique of choice. Head elevated position of at least 30 degree may be necessary for induction of anesthesia. Careful attention to airway position before induction may facilitates induction. A wedge under the patient’s shoulder blades combined with good head extensions is helpful. Capnography to ETT placement verification is necessary before auscultation through the thick chest wall can be difficult. Inspired O2 greater than 50% is strongly recommended once intubation is obtained. PEEP is necessary because spontaneous ventilation may predispose the pt to atelectasis and hypoxemia. Increases in TV may worsen oxygenation if high peak pressures impair return of blood to the chest, decrease CO and producing V/Q mismatch.
2) CV management: large BP cuff are used to avoid false readings. A small cuff falsely elevates BP readings, whereas excessively large cuff gives false low readings. Aline may be necessary to follow BP closely and for ABG. CVP to volume status. PA cath are unnecessary unless the patient is undergoing extensive surgery or shows evidence of cardiac or pulmonary disease such as Pulm HTN, and cor pulmonal.
3) positioning. The OR table may be of inadequate width to accommodate obese patient. Care must be taken to protect and pad all pressure points. It may become necessary to secure two operating tables together for extremely obese patients.

Question 27

What are some extubation criteria for obese patients?

Answer 27

Criteria for Extubation for obese patients: 1) awake, alert, and able to sustain a head lift for 5 secs. Muscles relaxants reversed ( sustained tetanus with no post tetanic facilitation of twitches). RR >30. ABG on 40 to 50% oxygen should be equal to or better than preop values; PaO2 >80, PACO2 5 ml/kg lean body weight. Stable hemodynamically.
These are at increased risk for hypoxemia for 4-7 days post-op. suppl Oxy may be necessary. Good pulmonary toilet.

Question 28

What is the relationship between obesity and the biotransformation rate of some anesthetic gas?

Answer 28

Obesity increases the biotransformation rate of some anesthetic gas . With obese patient lipophilic or fat soluble drugs such as benzo, opiods, and barb have an increased volume of distribution and decreased elimination half life, resulting in lower serum concentration and decreased clearance. Except fentanyl which is a lipophilic drug that shows similar pharmacokinetics in obese and nonobese patients.
Hydrophilic or water soluble drugs have similar VD, E ½ time and rates of clearance in obese and nonobese patients.

Question 29

What are some pre-op lab values you should check in obese patients?

Answer 29

1) Hepatic function
2) Albumin level
3) Glucose
4) Consider clotting studies (if risk factors)

Question 30

What are some positioning and monitoring consideration with obese patients?

Answer 30

1) Blood pressure cuff should be appropriate size
2) Venous Access
3) Pulse oximetry
4) ABGs
5) ETCO2
6) Positioning aids

Question 31

What are some positioning considerations with obese patients?

Answer 31

1) Special designed tables or 2 together
2) Ramp Up
3) Regular tables have max weight of approx 205kg
4) Strapping patient carefully
5) Protect pressure points
6) Consider the use of 2 armboards to support entire circumference of arm.
7) Supine compression of vena cava aorta
8) Supine FRC and oxygenation is reduced
9) Changing from sitting to supine causes significant changes in CO, PAP, and O2 consumption
10) Head-Up reverse Trendelenburg provides the longest safe apnea period (SAP)
11) 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 32

What some aspiration prophylaxix you should consider with obese patients?

Answer 32

1) Great risk to morbidly obese patients
2) Pre-operative anxiety
3) Treatment includes
–H2 receptor antagonists
–Sodium Citrate (Bicitra)
–Metoclopramide
–Omeprazole

An obese patient’s increased risk of pulmonary aspiration should be prophylactically treated with H2 receptor antagonist such as cimetidine or ranitidine combined with Reglan