Obesity-Apex Flashcards
According to the national Institute of health, obesity ranks ________ to smoking as a leading cause of preventable death
Obesity
______ _______ is more common than diabetes, cystic fibrosis, and all cancers
Childhood obesity
Each gram of fat provides how many calories of physiologically available energy
9 calories
Each gram of carbohydrate or protein provides how many calories of physiologically available energy
4 calories
What are five diseases that can lead to weight gain/obesity?
Polycystic ovarian syndrome
Cushing’s disease
Hypothyroidism
Depression
Eating disorders
What are two classes of medication’s known to cause weight gain?
Antidepressants
Steroids
What are two genetic conditions that can cause obesity?
Prader-Willi Syndrome
Bardet-Biedl Syndrome
Approximately what percent of Americans are obese?
33%
A terminal consequence of excess Adipost tissue is:
Insulin resistance and information throughout the body
At a post becomes pathological when it releases significant quantities of?
Free fatty acids and cytokines
What kind of fat releases the highest quantities of these insulin resistant inflammatory compounds and appears to pose the most significant health risks?
Visceral fact
What shape is correlated to android obesity?
Apple shaped fat pattern characterized by central or abdominal visceral fat accumulation
Is android obesity, more common in men or women?
Men
What shape is correlated to is gynecoid obesity?
Pear shaped fat pattern. Characterized by gluteal and femoral fat accumulation.
A waist size >40inches for men and >35inches for women is associated with an increased risk of:
Ischemic heart disease
Hypertension
Dyslipidemia
Insulin resistance
Death
Unlike abdominal fat that is metabolically, active, gynecoid fat is metabolically inactive in his primarily used for?
Energy storage
Patient with gynecoid fat accumulation or more likely to develop:
Joint disease in varicose veins
Metabolic syndrome requires at least three of the following signs:
Fasting plasma glucose 100-110
Abdominal obesity (waist >40in. men or >35in. women)
Serum triglyceride level >150
Serum HDL <40 in men or <50 in women
Blood pressure >130/85
The risk of obesity related morbidity increases in ________ proportion to BMI
direct
What is the normal adult BMI?
18.5-24.9
What is adult overweight BMI?
25-29.9
What weight percentile is classified as overweight in children?
85th-94th
What weight percentile is classified as obese in children?
95th-98th
What weight percentile is classified as severely obese in children?
99th
What is the BMI calculation?
BMI= Weight (kg) / Height (m^2)
How do you convert inches to centimeters?
Multiply inches by 2.54 cm
Obesity produces a _________ ventilatory defect
restrictive
How does obesity affect the respiratory system?
Compresses the lungs and reduces lung volume and compliance.
How is lung inflation inhibited by obesity?
- Chest fat compresses, the rib cage and hinders its outward expansion
- Abdominal fat shifts the diaphragm cephalad and compresses the lungs
- Kyphosis in lordosis develop overtime which alters the geometry of the rib cage
What lung volumes and capacities are reduced due to obesity?
Vital capacity
Total lung capacity
Functional Residual Capacity
Expiratory Reserve Volume
What lung volumes are normal or increased in obesity?
Normal Residual Volume
Increased Closing Volume
In an obese patient, general anesthesia causes functional residual capacity to fall by what percent? Compared to a non-obese patient whose FRC is reduced by only ______%.
50% reduction in FRC in obese patients
only 20% reduction in nonobese
What are the respiratory physiological effects of the restrictive ventilatory defect caused by obesity?
Decreased lung compliance
Decreased PaO2, No change in PaCO2
Increase oxygen consumption and CO2 production
A higher oxygen consumption coupled with a smaller FRC predisposes obese patients to what during general anesthesia induction?
Rapid desaturation during apnea
While the obese patient may experience hypoxemia, the PaCO2 is usually normal. why?
High diffusing capacity of CO2 and fear variable characteristics of the carbon dioxide dissociation curve. And elevated PaCO2 signals in pending respiratory failure.
How should minute ventilation be adjusted in obese patients?
Must be increased to maintain normal blood gas tensions.
Because of the extra weight on the chest, wrapped in shallow breathing pattern provides the most energy efficient way to achieve this goal.
[Fat is a metabolic active organ so patients have an increased oxygen consumption in carbon dioxide production.]
What is the optimal title value for a patient with Class 3 obesity?
6-8mL/kg Ideal Body Weight
How should you position the obese patient during induction? why?
Head-elevated laryngoscopy position (HELP)
* The idea is to elevate the head, shoulders, and upper body above the chest.
* You should be able to envision a horizontal line drawn from the sternal notch to the external auditory meatus.
* Creates the most favorable alignment of the oral, pharyngeal and laryngeal axes
How should you pre-oxygenate the obese patient?
Preoxygenate the patient with 100% FiO2 + CPAP 10cmH2O until etO2 exceeds 90%. This will prolong the time before desaturation occurs by 50%.
* Placing the patient in reverse Trendelenburg position, relieves pressure on the thorax and improves FRC. Extubate in this position as well.
What should your FIO2 percent be kept at during anesthetic maintenance to prevent absorption atelectasis?
<80%
What are two ways to recruit collapsed alveoli? And what are the possible side effects of this recruitment?
- Recruitment maneuver (Valsalva). Give a breath to ~40cm H2O and hold for 10s.
A. This may temporarily reduce venous return, blood pressure, and heart rate. - Hold open reexpanded alveoli with PEEP or CPAP 5-10cm H2O.
A. Improves FRC, V/Q matching, and arterial oxygenation.
B. May reduce venous return and cause hypotension
How should you set your ventilator for an obese patient?
Title volume of 6-8mL of ideal body weight. Adjust rate rather than title volume to control PaCO2.
How should you prevent pulmonary aspiration in obese patients?
No data currently illustrates an increased incident of pulmonary aspiration on the basis of BMI alone.
Other risk factors such as GERD or Diabetes should be considered candidate for aspiration prophylaxis and RSI.
Which patients are at highest risk for postoperative hypoxemia?
Patients with obstructive sleep apnea
What are some strategies to maximize postoperative oxygenation both in general and four obese patients?
-CPAP or BiPAP after extubation (especially if the patient uses it at home)
-Elevate the head of the bed to 30°
-Early ambulation
-Control surgical pain (non-opioid and regional anesthesia will minimize respiratory depression)
-Incentive spirometry
When is postoperative hypoxemia most likely to occur in the obese patient?
Immediately after extubation and up to 2-5 days following surgery
Does morbid obesity alone mandate the need for RSI?
No. There’s no data that show an increase incident of pulmonary aspiration on the basis of BMI alone.
How does obesity affect the cardiovascular system?
Increased intravascular volume and high cardiac output lead to:
-increased RV and LV workload
-RV and LV hypertrophy
-RV and LV failure [aka Biventricular Failure)
What variable is responsible for the increase cardiac output in obese patients?
Stroke volume
(Heart rate is usually unchanged in obese patients)
How much does cardiac output increase by for every extra kilogram of fat?
100mL/min
How does heart structure change to accommodate the increase in intravascular volume of obese patients?
The heart dilates to accept the larger incoming venous return volume. It also becomes thicker to compensate for the increased wall stress. Leading to reduction in ventricular compliance and diastolic dysfunction.
Eventually, heart dilates beyond its ability to increase wall thickness leading to systolic dysfunction as well, that can progress to biventricular heart failure.
What finding on TEE may be the most useful confirmation of Pulmonary HTN in obese (and maybe other pts?)?
Tricuspid Regurg
What are some common EKG changes seen in obese patients?
-Low voltage EKG
-Left axis deviation
-Right axis deviation
-QT Prolongation
-Ischemia
-Dysrhythmias
Why might some obese patients have low-voltage EKG?
Caused by the increased distance between the heart and the leads
Why might some obese patients have left axis deviation on EKG?
The stomach push pushes the heart up into the left. Also, there is left ventricular hypertrophy, secondary to volume overload and hypertension.
Why might some obese patients have right axis deviation on EKG?
Right ventricular hypertrophy from obstructive, sleep apnea and volume overload.
Why might some obese patients be more susceptible to arrhythmias?
Can be caused by fatty infiltration of the con conduction system, myocardial hypertrophy, hypoxemia, hypercarbia, obesity, hypoventilation syndrome, and ischemic heart disease.
What body weight should you use to calculate per operative fluid requirements for obese patients? Why?
Lean Body Weight
Obese patients are less tolerant of excessive fluid administration, placing them at risk for fluid overload
As a general rule, what patient weight are water-soluble drug doses calculated with?
Ideal body weight (IBW)
As a general rule, what patient weight are lipid-soluble drug doses calculated with?
Total body weight
The volume of distribution of a drug in the obese patient is altered by:
Increased blood volume
Increase cardiac output
Altered plasma protein binding
Lipid solubility of the drug
How does increase blood volume influence the volume of distribution of a drug in the obese patient?
Requires a higher dose to achieve a given plasma concentration
How does increased cardiac output? influence the volume of distribution of a drug in the obese patient?
Faster drug delivery to the vessel rich group
How does altered plasma protein binding influence the volume of distribution of a drug in the obese patient?
Altered free fractions available
How does the lipid solubility of a drug influence the volume of distribution of a drug in the obese patient?
A large larger fat mass increases the volume of distribution for lipophilic drugs
In the obese patient, which factors are expected to increase? Select two.
MAC
Circulation time
Vd of lipophilic drugs
Vd of hydrophilic drugs
Vd of lipophilic drugs
Vd of hydrophilic drugs
Vd of lipophilic drugs is increased due to larger fat mass and Vd hydrophilic drug drugs is increased due to a larger muscle mass and blood volume
How do you calculate Lean Body Weight?
LBW = IBW x 1.3
Volatile agents are lipophilic, so which agent should be used in the obese population?
Agents with the lowest blood:gas coefficients
(Sevo or Des provide a faster emergence than Iso or propofol)
How is MAC changed by obesity?
Unchanged by obesity
Why is nitrous oxide generally avoided in obese patients?
Because it restricts the maximum FiO2 that can be delivered.
What are three muscles/muscle sets that dilate the upper airway? What are their functions?
Tensor Palatine - opens the nasopharynx
Genioglossus - opens the oropharynx
Hyoid muscle muscles - opens the hypopharynx
Obstructive sleep apnea is defined as?
The cessation of airflow for at least 10 seconds (apnea) with five or more unsuccessful efforts to breathe (obstruction) and a greater than 4% reduction in SaO2
Hypopnea is also a common phenomenon in OSA. It is defined as:
A 50% reduction in airflow for 10 seconds, 15 or more times per hour, and is linked to snoring and decrease oxygen saturation.
What are things that increase the likelihood of patient has OSA?
BMI greater than 30
Abdominal fat distribution
Large neck girth (>17in for men or >16in for women)
USA is an independent risk factor for:
The development of hypertension, cardiovascular morbidity, and death
What is the classic triad of dysfunctional sleep?
- Apnea or snoring with hypopnea during sleep
- Arousal from sleep
- Daytime somnolence
What is the AHI and what are the key values?
AHI = Apnea-Hypopnea Index
Used to quantify the severity of OSA
Mild: 5-15 episodes/hr
Moderate: 15-30 episodes/hr
Severe = >30 episodes/hr
What is the MOST sensitive sign of an anastomotic leak following gastric bypass?
Unexplained tachycardia
An increase in which anthropometric measure correlates BEST with impaired lung function?
A. BMI
B. Height
C. Hip Circumference
D. Waist-Hip Ratio
D. Waist-Hip Ratio
Increased ways to hip ratio (truncal size, increased abdominal circumference, Apple verse pair shape) is correlated with respiratory compromised due to hinder, diaphragmatic movement, poor basil, lung expansion, and peripheral airway closure
What is the most appropriate method to treat hypoxemia from anesthesia induced atelectasis in an obese patient?
Deliver an alveolar recruitment maneuver followed by peep
Which contributes the most to rapid oxygen desaturation during periods of apnea in the obese patient?
A. decreased inspiratory capacity.
B. increased FRC.
C. Increased respiratory system compliance.
D. Tidal volume overlapping with closing capacity.
D. Tidal volume overlapping with closing capacity.
[In obese individuals, especially in the supine position or under anesthesia:
FRC is markedly reduced
→ Due to decreased chest wall compliance and diaphragm being pushed up by abdominal fat
But CC stays the same or increases slightly with age or disease
❗ So what happens?
Closing capacity may exceed FRC
and even overlap with tidal volume]
What anesthetic interaction does the weight management drug Phentermine have?
Tachycardia and HTN
Is an amphetamine variant.
What anesthetic interaction does the weight management drug Locaserin have?
Now off the market notable for its interaction with other serotonin, inhibitors, and risk of serotonin syndrome
What anesthetic interaction does the weight management drug Liraglutide have?
Reduced gastric emptying
Is a GLP – one receptor agonist
Also increases insulin, secretion, decreases glucagon production
What anesthetic interaction does the weight management drug Orlistat have?
Inhibits fat absorption and increases the risk of fat soluble vitamin deficiency
