Obesity Flashcards
What is the formula for IBW?
IBW (male) = 105 lb + 6 lb for each inch > 5 ft.
IBW (female) = 100 lb + 5 lb for each inch > 5 ft
What is the formula for BMI?
BMI= Weight (kg)/ height (m2)
What is oversight vs obesity?
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
Increased BMI leads to what assessment related risks?
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
What are other secondary diseases (disturbances) associated with obesity?
Obstructive sleep apnea Respiratory Derangements Systemic hypertension Ischemic Heart Disease CHF Delayed gastric emptying Diabetes Mellitus Hepatobiliary Disease Thromboembolic Disease Musculoskeletal Disease *slide 8
What are respiratory changes that occur regarding FRC, ERV, TV?
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)
What are some ventilatory changes regrading CO2 production, minute ventilation, PFTs?
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
Deviations in lung volumes lead to
V/Q mismatch
hypoxemia
Increased right to left shunt
Abundant soft tissue in upper airway can lead to?
Obstruction of the airway
Can impair the mandible and cervical mobility
Creates difficulty maintaining mask airway
Difficult laryngoscopy and Intubation
consider fiberoptic intubation
Cardiac Output is increased by ? for each kg of adipose tissue?
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
Obese patients have limited reserve for
hypotension
hypertension
tachycardia
fluid overload
Obesity does what to your lipid levels?
Hyperlipidemia- leads to premature coronary artery disease and vascular disease, pancreatitis, atherosclerosis.
OSA is characterized by what?
- Apnea >10 seconds despite respiratory effort against a closed glottis
- 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
OSA is diagnosed by what?
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
Risk factors for OSA?
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
OSA physiologically results in what?
Hypoxemia Right heart failure Hypercapnia Pulmonary and systemic vasoconstriction Polycythemia Respiratory acidosis during sleep Arterial hypoxemia Systemic hypertension Pulmonary hypertension
During the pre-op evaluation, patients should be asked about what to determine if the have sleep apnea?
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
What is Pickwickian syndrome?
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)
What are the characteristics of Pickwickian Syndrome?
Characterized by Obesity Hypercapnia Daytime Hyper-somnolence Arterial hypoxemia Pulmonary hypertension Respiratory acidosis Right sided heart failure Airway Difficulty
What are GI effects of Obesity?
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)
What are Thromboembolic effects of obesity?
Risk of DVT is double that of nonobese patient
Polycythemia
Increased intra-abdominal pressure
Immobility
What are hepatic effects of obesity?
Fatty liver
Abnormal LFTs
Fluorinated volatile anesthetics
Look for signs of:
- Weight loss (even 5 lbs) can reverse the elevated liver enzymes
- Fatty infiltration (high prevalence of nonalcoholic fatty liver disease)
- Normal clearance despite often altered histology and LFT’s
Metabolic effects of obesity?
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
What questions/exams do you do on the patient with obesity?
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
What are some tests/labs you want to look at?
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)
What are considerations for positioning the obese patient?
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
What happens when you change positioning in the obese patient?
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
What is the aspiration prophylaxis for the obese patient?
Treatment includes H2 receptor antagonists Sodium Citrate (Bicitra) Metoclopramide Omeprazole
