Children with Burn Injury Have Impaired Cardiac Output during Submaximal Exercise

Abstract

Introduction Burn trauma damages resting cardiac function; however, it is currently unknown if the cardiovascular response to exercise is likewise impaired. We tested the hypothesis that, in children, burn injury lowers cardiac output (Q) and stroke volume (SV) during submaximal exercise. Methods Five children with 49±4% total body surface area (BSA) burned (2 female, 11.7±1 y, 40.4±18 kg, 141.1±9 cm) and eight similar non-burned controls (5 female, 12.5±2 y, 58.0±17 kg, 147.3±12 cm) with comparable exercise capacity (peak oxygen consumption [peak VO2]: 31.9±11 vs. 36.8±8 ml O2·kg·min-1, P=0.39) participated. The exercise protocol entailed a pre-exercise (pre-EX) rest period followed by 3-minute exercise stages at 20 W and 50 W. VO2, heart rate (HR), Q (via non-rebreathing), SV (Q/HR), and arteriovenous O2 difference ([a-v] O2 dif, Q/VO2) were the primary outcome variables. Results Using a 2-way factorial ANOVA (group [G] × exercise [EX]), we found that Q was ∼27% lower in the burned than the non-burned group at 20 W of exercise (burned 5.7±1.0 vs. nonburned: 7.9±1.8 L·min-1) and 50 W of exercise (burned 6.9±1.6 vs. nonburned 9.2 ±3.2 L·min-1) (G × EX interaction, P=0.012). SV did not change from rest to exercise in burned children but increased by ∼24% in the non-burned group (main effect for EX, P=0.046). Neither [a-v] O2 dif nor VO2 differed between groups at rest or exercise, but HR response to exercise was reduced in the burn group (G × EX interaction, P=0.004). When normalized to BSA, SV (index) was similar between groups; however, Q (index) remained attenuated in the burned group (G × EX interaction, P<0.008). Conclusions Burned children have an attenuated cardiovascular response to submaximal exercise. Further investigation of hemodynamic function during exercise will provide insights important for cardiovascular rehabilitation in burned children.

Resting β-Adrenergic Blockade Does Not Alter Exercise Thermoregulation in Children With Burn Injury

“…In addition, something may be difference with children with severe burn injury that are in a hyperadrenergic state. These results are in agreement to are previous work that found attenuated cardiac output during submaximal exercise 16 . Notably, patients with severe burn injury show similar symptoms of heart failure and coronary artery disease, such as exercise intolerance, and resting cardiac dysfunction 34, 35 .…”

“…Given that temperature regulation is disrupted from inadequate core-skin insulation (removal of epidermis, dermis, and subcutaneous tissue) propranolol treatment may increase the risk for heat-related injury by impairing thermoregulation during exercise-heat stress and suppressing cardiac function. Additionally, we have recently shown that cardiac output during submaximal exercise is impaired in severely burned children compared to age matched nonburned children under thermal neutral conditions 16 . Therefore, we designed a study in burned children to determine whether propranolol affects thermoregulatory capacity.…”

Children with severe burns display no sex differences in exercise capacity at hospital discharge or adaptation after exercise rehabilitation training

“…Oxygen uptake and heart rate increase in a linear fashion with exercise intensity. We previously showed that, during submaximal exercise, cardiac output is lower in burned children than nonburned age- and sex-matched children 32 . Additionally, burned children display signs of exercise intolerance and have a lower peak heart rate 32,33 .…”

Burn Injury May Have Age-Dependent Effects on Strength and Aerobic Exercise Capacity in Males

“…We have previously reported that the cardiovascular response to submaximal exercise is diminished in burned children compared with nonburned age-or sex-matched children. 27,28 Thus, burn trauma may have a more pronounced effect in children than adults, and this requires further understanding. Notably, adults have important body morphology characteristics that differ from those of children in early stages of development.…”

“…30 Most importantly, Reynolds et al found that, in children, burn injury causes cardiac failure, particularly left ventricular myocardial depression, and that this outcome that was likewise different from that seen in burned adults. 31 We have recently reported that, during submaximal exercise, burned children have exercise intolerance and attenuated peak heart rate values compared with nonburned age-or sex-matched children 27,28 ; however, this type of investigation has not been conducted in burned adults to date. Relative submaximal heart rate (row A) and peak oxygen uptake (row B) during the first three stages of the modified Bruce exercise in men and boys at discharge (pre-training) and after rehabilitation training (post-training) in men and boys.…”