At the University of Texas Medical Branch, Galveston, 25 children (<18 years of age) with acute, severe burns (more than 40% of the total body surface area) were randomized to receive oral propranolol or placebo for at least 2 weeks. All patients had been resuscitated and had initial excision and grafting within 48 hours of admission and were stabilized for at least 5 days prior to entering the study. The dose of propranolol was adjusted to decrease the resting heart rate by 20% from the patient’s baseline. Resting energy expenditure and skeletal muscle protein kinetics were measured before and 2 weeks after initiation of the study.
Patients in each group had similar ages and severity of burn injury. The average dose of propranolol necessary to achieve a 20% decrease in resting heart rate was 1.1 mg/kg every 4 hours. Blood pressure, glucose and temperature did not differ significantly between study groups. Resting energy expenditure (140 kcal/day) and oxygen consumption (25 ml/min) increased in the control group 2 weeks after study initiation. The resting energy expenditure in children who received propranolol decreased (−422 kcal/day, P=.01), as did oxygen consumption (−56 ml/min, P=.002). Children treated with propranolol had net protein synthesis while control patients had net protein breakdown. Children in the 2 treatment groups did not have significant differences in baseline insulin-like growth factor, growth hormone, cortisol, or insulin levels. Changes in these hormone levels during the study did not differ significantly between the treatment groups. The authors conclude that treatment with propranolol attenuates hypermetabolism and reverses muscle-protein catabolism.
Hypermetabolism, secondary to catecholamine mediation, is the hallmark of thermal injury.1,2 The resting energy expenditure can be doubled in patients with burns ≥40% of body surface area resulting in muscle loss. This muscle loss can lead to delay in wound healing, graft loss, ventilator dependence, and other complications, with the potential for increased hospital length of stay. The current strategy used to prevent muscle loss is to administer high-protein, high-calorie nutrition, preferably enterally. Sometimes, parenteral nutrition is needed when enteral nutrition is not sufficient or is not tolerated. The administration of large amounts of protein and carbohydrates can be fraught with complications, which include hyperglycemia, diarrhea, and dehydration.
Other researchers have demonstrated that the heart rate correlates with resting energy expenditure in adults.3 Decreasing the heart rate by 20% from the patients’ baseline significantly reduced the muscle loss in these patients. This study did not evaluate wound healing, wound complications, or hospital length of stay. However, preventing muscle loss should be beneficial in seriously burned children. It is important to note that the administration of propranolol began after the patients were fully resuscitated and had undergone excision of burns with grafting. Blunting the tachycardic response may mask inadequate resuscitation or early sepsis and, therefore, these patients must be carefully monitored.