Children with Burn Injury Have Impaired Cardiac Output during Submaximal Exercise.

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[middle dot]kg[middle dot]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] x 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[middle dot]min-1) and 50 W of exercise (burned 6.9+/-1.6 vs. nonburned 9.2 +/-3.2 L[middle dot]min-1) (G x 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 x 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 x EX interaction, P

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