Therapeutic effects of repeated immersions in warm chlorhexidine solution on severe frostbite of rabbit feet

The shaved right hind feet of male rabbits weighing 2.5 to 3.0 kg were immersed in −25 °C alcohol to produce experimental severe frostbite. The changes in tissue temperature were recorded by a thermocouple probe inserted subcutaneously.In the first experiment the therapeutic effects of repeated immersion of frostbitten feet in 40 °C 0.1% chlorhexidine (CHX) were observed. The average survival area (ASA) in the untreated control group was 15.6% and in the CHX group, 69.4%. The difference between them is significant.In the second experiment the effects of rapid thawing in 40 °C water when the feet were frozen and the effects of CHX were compared; ASA of both groups (49.0 and 60.4%) was greater than that of the control group (18.6%), but there was no distinct difference between these therapeutic groups.Results of the third experiment demonstrated that repeated immersion in 40 °C water for 6 days was not only useless, but was also harmful (13.6%). At the same time, repeated immersion in 20 °C 0.1% CHX solution was useless as well. Only when the two factors (warmer temperature and CHX) were combined, i.e., repeated immersion in 40 °C rather than 20 °C 0.1% CHX solution were the effects obvious (58.4%).Experiment 4 investigated the relationship between the first immersion time and the therapeutic effects. Results showed that even with the first immersion at 72 hr after thawing, repeated immersion in 40 °C 0.1% CHX solution was still useful; the ASA (53.0%) was greater than that of the control group (17.6%).Experiment 5 concerned the relationship between therapeutic effects and continual days of immersions. The ASA values in control and 1-, 3-, and 6-day groups were 14.2, 36.6, 58.4, and 69.4%, respectively.In the final experiment, the effects of CHX-Cl and CHX-Ac were compared. The ASA values were 71.3 and 77.7%; there was no significant difference between them.All of the above experiments proved that repeated immersions in 40 °C 0.1% CHX solution is a useful therapeutic measure in treatment of severe experimental frostbite of rabbit feet. It is useful even when the first immersion is at 72 hr after thawing of the frozen limbs.