Chapter 23. Evaluation of the Obese Patient

1. Expiratory reserve volume (ERV) is the most sensitive indicator of the effect of obesity on pulmonary function testing.

2. Plasminogen activator inhibitor-1 (PAI-1), secreted by the endothelium, vascular smooth muscle cells, hepatocytes, and adipocytes, is associated with visceral obesity and inhibits the fibrinolytic system. PAI-1 decreases fibrinolysis and increases the risk of coronary artery disease.

3. Gastric emptying may be delayed in obese patients because of increased abdominal mass causing antral distension, gastrin release, and a decrease in pH with parietal cell hypersecretion. However, emptying has been documented to be faster, with high energy content intake such as fat emulsions, but residual volume (RV) is increased because of their larger gastric volume (up to 75% larger). They should follow the same fasting guidelines as nonobese patients.

4. Rhabdomyolysis has been documented in morbidly obese patients undergoing prolonged procedures. Elevations in serum creatinine and creatine phosphokinase (CPK) levels unexplained by other reasons and complaints of buttock, hip, or shoulder pain in the postoperative period should raise the suspicion of rhabdomyolysis.

5. Difficult laryngoscopy and intubation correlates well with increased age, male sex, temporomandibular joint (TMJ) pathology, Mallampati classes 3 and 4, history of obstructive sleep apnea (OSA), and abnormal upper teeth, not the magnitude of body mass index (BMI).

6. Neck circumference has been identified as the single biggest predictor of problematic intubation in morbidly obese patients.

7. Preoxygenation in the head-up or sitting position is more effective and provides the longest safe apnea period (SAP) during induction of anesthesia in obese patients.

8. The head-elevated laryngoscopy position (HELP) position significantly elevates the obese patient's head, neck, upper body, and shoulders above the chest to a point where an imaginary horizontal line can be drawn from the sternal notch to the external ear to better improve laryngoscopy and intubation.

9. Positive end-expiratory pressure (PEEP) is the only ventilatory parameter that has consistently been shown to improve respiratory function in obese subjects, but it decreases venous return, cardiac output, and subsequent oxygen delivery.

10. Postoperative continuous positive airway pressure (CPAP) does not increase the incidence of major anastomotic leakage after gastric bypass surgery despite the theoretical risk of anastomotic injury from pressurized air delivered by CPAP.

The worldwide epidemic status of obesity is a key factor in the increased incidence of type 2 diabetes mellitus and cardiovascular diseases such as high blood pressure, and stroke.1 Obesity is defined as an abnormally high percentage of body weight as fat. Overweight is an increase in weight relative to a standard. Approximately 65%, or 2 of every 3 adults, in the United States are overweight or obese.2

Approximately 85% of the economic burden of obesity can be accounted for by obesity-related diseases (coronary artery disease, stroke, type 2 diabetes mellitus, hypertension, hyperlipidemia) and prescription drugs.3 The anatomic distribution of body fat is associated with varying pathophysiologic consequences. Android (central) obesity is commonly seen in men and associated with increased oxygen consumption and increased incidence of cardiovascular disease with a truncal or upper ...