Abstract:Severe burn profoundly affects organs both proximal and distal to the actual burn site. Cardiovascular dysfunction is a well-documented phenomenon that increases morbidity and mortality following a massive thermal trauma. Beginning immediately post-burn, during the ebb phase, cardiac function is severely depressed. By 48 h post-injury, cardiac function rebounds and the post-burn myocardium becomes tachycardic and hyperinflammatory. While current clinical trials are investigating a variety of drugs targeted at reducing aspects of the post-burn hypermetabolic response such as heart rate and cardiac work, there is still a paucity of knowledge regarding the underlying mechanisms that induce cardiac dysfunction in the severely burned. There are many animal models of burn injury, from rodents, to sheep or swine, but the majority of burn related cardiovascular investigations have occurred in rat and mouse models. This literature review consolidates the data supporting the prevalent role that β-adrenergic receptors play in mediating post-burn cardiac dysfunction and the idea that pharmacological modulation of this receptor family is a viable therapeutic target for resolving burn-induced cardiac deficits.
Background
We have reported that a 12-week exercise program is beneficial for the exercise performance of severely burned children. However, it is not known whether the beneficial effects remain at 2 years post burn.
Methods
Severely burned children who received no long-term anabolic drugs were consented to this IRB-approved study. Patients were able to choose between a voluntary exercise program (EX-group) and no exercise (NoEX-group) after discharge from the acute burn unit. Peak torque per lean leg mass (PTLLM), maximal oxygen consumption (VO2max) and percent predicted peak heart rate (%PPHR) were assessed. In addition, BMI percentile (BMI%) and lean body mass index (LBMI) were recorded. Both groups were compared for up to 2 years post burn using mixed multiple analysis of variance, and the level of significance was defined at p<0.05.
Results
One hundred twenty-five patients with a mean age of 12±4 years were analyzed. Demographics between the EX-group (N=82) and NoEX-group (N=43) were comparable. In the EX-group, PTLLM, %PPHR, and VO2max increased significantly with exercise (p<0.01). Between discharge and 12 and 24 months, BMI% increased significantly in the EX-Group (p<0.05) but did not change in the NoEX-group. There were no significant differences between groups in BMI%, LBMI, PTLLM, and VO2max at 24 months post burn.
Conclusions
Exercise significantly improves physical performance of burned children. However, the benefits are limited to early time points and become greatly narrowed with further recovery time. Continued participation in exercise activities or a maintenance exercise program is recommended for exercise-induced adaptations to continue.
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