Acute Effects of Burn Injury on Tissue Gas Tensions in the Rabbit

Abstract

Early effects of 10% full-thickness skin burn on subcutaneous tissue P_O2 and P_CO2 levels were studied in anesthetized rabbits. Tissue gas tensions were determined by means of implanted Silastic tonometers in two different areas in each animal—the burn site itself, and an area remote from the injured tissue. Thermal injury resulted in a rapid, progressive decrease of the tissue P_O2 in both locations, with the greatest decrease at the burn site. The minimum P_O2, levels were achieved 3–6 hours post burn. The P_CO2 values increased markedly both in the burn areas and in the distant tissues immediately after the trauma and reached their maximum within 1–3 hours post burn. The greatest accumulation of carbon dioxide occured at the burn site. Six hours after burn the tissue P_CO2 levels had been normalized. During the 6-hour observation period the mean arterial P_O2 of the burned animals increased gradually from 73 to 95 mmHg, while the mean arterial P_CO2 decreased by more than 50% of the original level. The latter effect was probably caused by hyperventilation. Intra-arterial injection of 5 ml of arterial blood from a burned rabbit into a control animal 3 hours post burn induced a significant decrease in cardiac output as well as decline in arterial, intraperitoneal, and tissue P_O2 levels in the control rabbit, probably due to a circulatory depressant factor(s) present in the burn blood. When the same test was carried out one hour post burn or with normal blood, no decrease in oxygen tension occurred.