Effect of steroids or tissue precooling on edema and tissue thermal coagulation after CO2 laser impact

The carbon dioxide laser is frequently used in laryngeal microsurgery. Some surgeons have empirically used preoperative steroids or precooling with ice prior to laser impact to limit the resultant tissue thermal coagulation and/or edema. An animal model was designed to quantitatively test these effects. Depillated areas of rat skin were exposed to a CO2 beam of 1 mm diameter at 15 W for 0.1 sec after either administration of Decadron (0.25 mg/kg) immediately prior to impact or precooling more than 10 degrees C below basal body temperature. Measurement of edema was quantitated as extravasation of Evans's blue dye that had been injected intravenously. Tissue thermal coagulation was measured on hematoxylin and eosin stained histologic sections. In comparison to controls, statistically significant reduction in edema was seen only at the 24 hour time period after laser exposure for the steroid group (P less than .002) but not for the precooling group. Tissue thermal coagulation was significantly smaller for both the steroid and the ice group (P less than .006 and P less than .001, respectively) when compared to controls.