CURRENT Essentials of Critical Care.pdf

Chapter 1 Monitoring & Support 17■■Obesity, SevereEssential Concepts• Severe obesity (body mass index [BMI]) 28) may be associatedwith increased ICU mortality and complications• Linked directly to obesity-hypoventilation syndrome (OHS), obstructivesleep apnea (OSA), restrictive lung disease• Risk factor for malignancy, heart failure, coronary artery disease,hypertension, diabetes mellitus, glucose intolerance, respiratoryfailure, deep venous thrombosis, pulmonary embolism,nonalcoholic steatohepatitis, decubitus ulcers, hip fractures• Jeopardizes weaning from mechanical ventilation because of increasedbreathing work• Complicates mechanical ventilator settings, drug dosing, nutritionalsupport calculations, fluid and electrolyte replacement• Total body water as proportion of weight falls in obesity(35–40%) compared to 50–60% in nonobese• Extremely obese unable to have CT imaging, cardiac catheterization,angiographyEssentials of Management• Calculate most drug dosages for “ideal weight” estimated fromheight, not actual weight in obese• Dosage of low molecular weight heparin unreliable in obesity• Use ideal weight estimated from height for setting tidal volumeduring mechanical ventilation; eg, 6 mL/kg ideal body weightHigh peak and plateau airway pressures due to non-compliantchest wall (diaphragm) do not increase risk of barotrauma• Most obese patients have normal to low lean body mass; nutritionalsupport important to maintain function; estimate calorie,protein, fluid needs from ideal weight■ PearlTo estimate “ideal” weight in kg: adult men 50 2.7 kg/inch over60 inches tall; adult women 45.5 2.3 kg /inch over 60 inches tall.ReferenceEl-Solh A et al: Morbid obesity in the medical ICU. Chest 2000; 120:1989.[PMID: 11742933]