Energy requirements

Thermal injury is among the most hypermetabolic conditions encountered in clinical practice, and investigations of metabolism in burn patients have demonstrated energy expenditure increases with the extent of body surface area injured to about 60% total body surface area (TBSA), where increases up to twice the basal energy expenditure (BEE) can occur [55-59].

Factors Influencing Energy Requirements

There are many factors that influence energy expenditure (Table 11.2). Because many critically ill patients are mechanically ventilated and receive sedatives and narcotics for pain control, energy expenditure may be reduced by 24 to 33% [60] with an increase in depth of sedation progressively decreasing resting energy expenditure [61]. In patients with head injuries receiving neuromuscular blockade with pancuronium, energy expenditure was reduced by 20% from 29 kcal/kg to 24 kcal/kg [62]. In pediatric burn patients, oral propranolol, a P-adrenergic receptor blocker, reduced energy expenditure by 25% and improved net muscle protein balance by 82% [63]. P-Blockade also reduces triglyceride-free fatty acid (TG-FFA) cycling from the lipolytic effects of catecholamines [64] and decreases hepatic steatosis by limiting fatty acid delivery [65].

Energy requirements are also affected by temperature changes both internally and externally. Gore [66] reported in a study of 84 burn-injured children, that during febrile episodes, resting energy expenditure (REE)/predicted BEE increased from 1.39 to 1.68 for patients with severe fever (> 40°C) and increased muscle protein

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