THERMOPROTECTIVE MECHANISMS OF IRRIGATION DURING BIPOLAR CAUTERY

Bipolar cautery is routinely used in operations of the head and neck, as well as in other specialties, both for dissection and for achieving hemostasis. Whereas simultaneous irrigation is frequently used to min imize neuronal injury, its effectiveness has not been tested under con trolled conditions. Our objectives in this study were to test the hypo thesis that including irrigation during bipolar cautery is thermoprote ctive and to identify the mechanisms underlying the thermoprotective e ffect. The thermoprotective role of irrigation with bipolar cautery wa s tested in a rat model in which the sciatic nerve was exposed and a I -second stimulus at 40 or 20 watts was applied with bipolar cautery fo rceps placed directly on the nerve in the presence or absence of simul taneous irrigation. We used the Sciatic Functional Index as used to qu antitate the degree of paresis induced. The results showed that simult aneous irrigation reduced the percentage of animals showing paresis. T his effect was significant for animals exposed to 40- and 20-watt caut ery. The mechanism for the reduction in the degree of paresis by irrig ation could not be attributed to a lowering of the maximal temperature achieved after bipolar cautery. Instead, the thermoprotective mechani sm of the irrigation involved an enhanced recovery to basal temperatur es when measured at 15 seconds after nerve stimulation with 40 or 20 w alk. Reducing the power from 40 watts to 20 watts did not significantl y lessen the tissue temperature. The results of this study suggest tha t irrigation done simultaneously with bipolar cautery enhances tempera ture recovery to basal levels and plays a role in thermoprotection aga inst the effects of cautery.