Obesity
Type of obesity characterized by central or abdominal visceral fat accumulation.
Android Obesity (Apple)
- More common in men
- Waist size > 40 inches for men & > 35 inches for women
- Associated with an increased risk of: ischemic heart disease, HTN, dyslipidemia, insulin resistance, death
The classic presentation of this includes episodes of apnea during sleep without any respiratory effort.
Obesity Hypoventilation Syndrome (OHS)
- OHS is a long-term consequence of untreated OSA
- Over time, the respiratory center in the medulla fails to respond to hypercarbia appropriately
- Diagnostic criteria: BMI > 30, awake PaCO2 > 45, dysfunctional breathing during sleep
- S/S: obesity, hyper somnolence during the day, hypoxemia, hypercarbia, respiratory acidosis
- Respiratory depressant drugs put these pts at high risk of airway obstruction; use approaches that do not impact respiratory drive such as regional anesthesia, NSAIDs, ketamine, dexmedetomidine
Does obesity increase the volume of distribution for lipid-soluble or water-soluble drugs?
Increases the Vd of both
- Vd lipophilic drugs >>>> Vd hydrophilic drugs
- Volatile agents are lipophilic, so agents with the lowest B:G coefficients (des or sevo) should be used, MAC is not affected
- Increased blood volume: requires ^ dose to achieve plasma concentration
- Increased CO: faster drug delivery to vessel rich
- Altered plasma protein binding: altered free fractions available
Two ways to recruit collapsed alveoli.
Recruitment maneuver
- Reopens collapsed alveoli
- Give a breath to 40 cm H2O and hold for 10 seconds
PEEP or CPAP 5-10 cm H2O
- Holds open re-expanded alveoli
- Improves FRC, V/Q mismatch, & arterial oxygenation
** Lungs do not grow in proportion to body mass. Important to give a tidal volume 6-8 mL/kg of ideal body weight
Type of bariatric procedure with gastric reduction and removal of a portion of the small intestine.
Malabsorption
- Limits nutrient absorption
- Risk of vit. K, vit. B12, iron, & folate depletion
Type of obesity characterized by gluteal and femoral fat accumulation.
Gynecoid Obesity (pear)
- More common in women
- Unlike abdominal fat that is metabolically active, this type is metabolically inactive & used for energy storage
- More likely to develop joint disease and varicose veins
- Reduced incidence of non-insulin-dependent diabetes
Classic triad of dysfunctional sleep.
Apnea or snoring with hypopnea during sleep
Arousal from sleep
Daytime somnolence
A patient has a BMI of 36. What class of obesity is this?
Obesity Class 2
- Underweight < 18.5
- Normal 18.5-24.9
- Overweight 25-29.9
- Obesity class 1 30-34.9
- Obesity class 2 35-39.9
- Obesity class 3 (morbid) > 40
The presence of tricuspid regurgitation on TEE may be the most useful confirmation of _________?
Pulmonary Hypertension
- Common EKG changes include:
- Low voltage EKG due to ^ distance b/w heart and leads
- Left & right axis deviation
- QT prolongation
- Ischemia & dysrhythmias
Type of bariatric procedure that limits quantity of food that can be consumed.
Restriction (gastric band/sleeve)
- Least invasive
- Since small intestine left intact, nutrient absorption unaffected
According to the National Institute of Health, what is the leading cause of preventable death in adults?
Smoking
- Adult obesity ranks as the second leading cause
- 1/3 of American adults are obese, and over 30% of children and adolescents are overweight or obese
Defined as the cessation of airflow for at least 10 seconds (apnea) with 5 or more unsuccessful efforts to breathe (obstruction) and a greater than 4% reduction in SaO2.
Obstructive Sleep Apnea (OSA)
- Hypopnea: a 50% reduction in airflow for 10 seconds, 15 or more times per hour, & is linked to snoring and decreased oxygen saturation. Common in OSA
- Incidence of OSA is directly proportional to BMI. Things that ^ the likelihood a pt has OSA: BMI > 30, abdominal fat, large neck girth
- OSA is an independent risk factor for the development of HTN, cardiovascular morbidity, & death due to ANS stimulation
Calculate ideal body weight for a woman who is 5 feet 3 inches tall.
55
- IBW = height (cm) - 100 (men)
- IBW = height (cm) - 105 (women)
- Inches x 2.54 = cm
Does obesity produce an obstructive or restrictive ventilatory defect?
Restrictive
- Compresses the lungs & reduces lung volume and compliance
- v vital capacity, v total lung capacity
- v functional residual capacity - v expiratory reserve volume & normal RV
- ^ closing volume, ^ O2 consumption, ^ CO2 production, ^ work of breathing
What are the 3 most common signs of an anastomotic leak following gastric bypass?
Tachycardia (72%), Fever (63%), Abdominal Pain (54%)
- Unexplained tachycardia, HR > 120 bpm, is the most sensitive sign of a leak
- Other s/s include:shoulder pain (left), pelvic pain, substernal pressure, hypotension
- Roux-en-Y gastric bypass combines restrictive and malabsorption proceeds yielding the best weight loss and improvement of comorbidities
How many calories are required to produce one gram of body fat?
9
- If unused, the body will store these excess calories as adipose
- A gram of carbs provide 4 calories
- A gram of protein provides 4 calories
Diagnosis of this disease requires at least 3 of the following signs:
- Fasting plasma glucose 100-110 mg/dL
- Abdominal obesity
- Serum triglyceride level > 150 mg/dL
- Serum HDL < 40 mg/dL in men & < 50 mg/dL in women
- Blood pressure > 130/85 mmHg
Metabolic syndrome (syndrome X)
- Incorporates several disease states that coincide with obesity
- Cardiovascular risk is 50-60% greater than the general population
A patient weighs 80 kg and stands 74 inches tall. Calculate the BMI to the nearest hundredth.
22.64 kg/m2
- BMI = weight (kg) / height (m2)
- Inches x 0.0254 = m
- Pounds / 2.2 = kg
Cardiac output increases by how much for every extra kg of fat?
100 mL/min
- Increased preload & SV account for the majority of the increase in CO; the HR is usually unchanged
- Increased intravascular volume & a high CO place a higher workload on the myocardium
A norepinephrine and serotonin reuptake inhibitor that acts as an appetite suppressant.
Sibutramine
- Adrenergic overstimulation & serotonin syndrome may occur
- Phentermine is a norepinephrine reuptake inhibitor that acts as an appetite suppressant
Hypertension
- Heart dilates to accept the larger incoming venous return
- Heart becomes thicker to compensate for the increased wall stress
- Both diastolic & systolic dysfunction occur
What is "STOP-BANG" used to predict? What does the S stand for?
Likelihood that a patient has undiagnosed OSA
- Low risk for OSA = < 3 questions answered yes
- 60-70% of pts with OSA remain undiagnosed
- Polysomnography is the definite test for OSA
Snoring
- Tiredness
- Observed apnea
- Pressure (^ BP)
- BMI (> 35)
- Age (> 50)
- Neck circumference (> 40 cm)
- Gender (male)
What drugs should use total body weight for dosing in the obese pt?
a. Remifentanil
b. Rocuronium
c. Cisatracurium
d. Succinylcholine
c & d
- Total body weight: succinylcholine, cisatracurium, atracurium, midazolam, fentanyl (loading dose), sufentanil (loading dose), propofol (maintenance dose)
- Lean body weight: rocuronium, vecuronium, remifenantil, fentanyl (maintenance dose), sufentanil (maintenance dose), propofol (loading dose)
- LBW = IBW x 1.3
The combination of what predisposes the obese pt to oxygen desaturation during apnea?
Small FRC & ^ O2 consumption
- Optimal positioning includes the head-elevated laryngoscopy position (HELP): elevate the head, shoulders, & upper body above the chest
- Preoxygenate pt with 100% FiO2 + CPAP 10 cm H2O until end-tidal O2 exceeds 90% - prolongs time before desaturation by 50%
- Reverse trendelenburg position relived pressure on the thorax and improves FRC
A lipase inhibitor that reversibly binds to lipase and hinders the absorption and digestion of consumed fats.
Orlistat
- Since fat & the vitamins it contains (D,A,K,E) are not absorbed by the gut, they must be supplemented orally
- Insufficient quantities of vitamin K will impair synthesis of clotting factors 2, 7, 9, 10 & cause coagulopathy