Modeling Burn Progression Using Comb Burns: The Impact of Thermal Contact Duration on Model Outcomes.

BACKGROUND: Burn progression is a phenomenon that remains poorly characterized. The mechanisms of burn conversion are not completely understood, and consequently, both predictive diagnostic tools and interventions are limited. The rat comb burn model is a commonly used approach to study horizontal burn conversion. However, there is significant variability in how the model is performed. Skin contact duration, comb device heating method, comb heating duration, amount of pressure applied, the weight of the comb, and associated depth of burn are all variables that are heterogeneous in studies utilizing the model. MATERIALS AND METHODS: Here, contact duration was examined to determine the impact the duration of burn delivery has on the conversion of interspaces in this model. Data from multiple experiments consisting of 10, 15, 20, 30, 40, and 45 s comb burns were compiled and assessed. Burns were made using combs heated in a 100°C dry bath and then monitored for 2 d. Interspace viability was assessed by digital and laser doppler imaging and biopsy procurement. RESULTS: Laser Doppler Imaging and viable interspace measurements showed that as burn duration increased, the percentage of the viable interspace and interspace perfusion decreased. Additionally, a contact time of 30 s or greater was required to result in 100% interspace conversion. CONCLUSIONS: These results demonstrate a need to better characterize and potentially standardize the rat comb burn model to reduce variation and maintain it as a valuable tool for controlled studies of the pathophysiology of burn wound progression.

Plasma Ameliorates Endothelial Dysfunction in Burn Injury.

BACKGROUND: A complex inflammatory response mediates the systemic effects of burn shock. Disruption of the endothelial glycocalyx causes shedding of structural glycoproteins, primarily syndecan-1 (SDC-1), leading to endothelial dysfunction. These effects may be mitigated by resuscitative interventions. MATERIALS AND METHODS: Sprague-Dawley rats were used to create small, medium, and large burns and uninjured controls. Three different intravenous resuscitation protocols were applied within each group: Lactated Ringer's (LR) alone, LR plus fresh frozen plasma (FFP), or LR plus albumin. Blood was serially collected, and plasma SDC-1 was quantified with enzyme-linked immunosorbent assay. In one cohort, Evan's Blue Dye (EBD) was administered and quantified in lung by spectrophotometry as a functional assay of vascular permeability. In a second cohort, intact SCD-1 was quantified by immunohistochemistry in lung tissue. Statistical analysis employed two-way analysis of variance with multiple comparisons and Student's t-test. RESULTS: EBD extraction from lung was significantly greater with higher injury severity versus controls. Extraction decreased significantly in large-burn animals with addition of FFP to LR versus LR-only; addition of albumin to LR did not decrease EBD extraction. Plasma SCD-1 increased in injured animals compared with controls, and changes correlated with injury severity in all resuscitation groups (significance, P < 0.05). Lung SCD-1 staining reflected the results in the EBD assay. CONCLUSIONS: Addition of FFP, not of albumin, to post-burn resuscitation diminishes vascular leakage associated with large burns. Addition of colloid does not affect SDC-1 shedding as measured in plasma. Ongoing work will further define pathophysiologic mechanisms and potential therapeutic interventions to mitigate injury and promote repair of the endothelial glycocalyx.