Postburn Blood Flow, Edema, and Survival of the Hairy Mouse Ear After Scald Injury at Different Temperatures

Abstract

In one group (a) one ear of NMRI hairy mice was scalded in water at 36°C, 39°C, 42°C, 45°C, 48°C, 51°C, 52°C, 53°C, 54°C, 57°C, and 60°C for 20 s, using a new dip burn model, for evaluation of edema formation 2 h postburn. In another group of mice (b) one ear was scalded in the 45°C-60°C interval and the ear studied in a vital microscope repeatedly for 4 days. In a third group (c), one ear was scalded in the 36°C-60°C interval and the microcirculatory flow was recorded by a laser Doppler flowmeter (1 Df) for a period of 2 h postburn. In a fourth group of animals (d) one ear was scalded at 53°C or 54°C. In some animals the ear was then cooled in 8°C water or saline for 30 min. Others were treated preburn with cimetidine, Ketanserin, indomethacin or methylprednisolone. Edema was determined in group (a) by wet-dry weight measurements of punch biopsies from both the burned and the contralateral unburned ear and expressed as an increase in tissue water content. The long-term effect was determined by observing the survival of the ears (groups b and d); the area of necrosis was expressed as a percentage of the totai area of the ear. Significant edema was formed in ears immersed in 48°C to 60°C water with a maximum after 53°C burns. No increased tissue water content of the contralateral unburned ear (remote edema) was found. Using 1Df, significantly reduced blood flow was recorded only after a 60°C scald, starting 15 min postburn and continuing through the 2 h observation period. In the vital microscope blood flow seemed to have stopped within 2 h after a 60°C scald, within 6 and 4 h after 54°C and 57°C scalds, respectively, within 8 h after a 53°C scald, and within 8–24 h after a 52°C scald. After 51°C scalds, all ears survived completely whereas ears burned at 52°C necrotized to approximately 50% within 4 days, to 75%–100% after a 53°C scald, and completely after 54°C burns. The pharmacological pretreatment or the postburn cooling had no effect on the survival of the ears.