Microvascular assessment of burn depth conversion during varying resuscitation conditions.

Conversion of partial- to full-thickness injuries, even after the burning has stopped, remains a significant clinical problem. We developed a rat model with a wide range of burn depths to study this phenomenon by microvascular assessment. Fifty-four male Sprague-Dawley rats weighing 460 g on average were studied. Real-time tissue monitoring of pH, paCO2, and paO2 was achieved by placement of a continuous blood gas monitor transducer in the aorta. Ten, 2-cm x 2-cm burns were created on each animal with milled aluminum templates (100 degrees C) with varying contact times. Conversion of burn depth in these wounds was documented by serial laser Doppler imager scanning over a 5-hour period. Animals received Ringer's lactate resuscitation at 0, 2, 4, 6, and 8 ml/kg/%burn. Serial laser Doppler scanning directly demonstrated progressive loss of perfusion to partial-thickness burns dependent upon the amount of fluid resuscitation. Conversion of partial- to full-thickness burns in this rat model (documented by laser Doppler microvascular assessment) was dependent upon how the animals were resuscitated.