Effect of alkalimized mepivacaine for epidural anesthesia on the skin temperature and skin blood flow: A mathematical analysis by simulation model.

The changes in skin blood flow after barbiturate injection are predictable based upon changes in skin temperature, assuming that these changes are followed by ramp function of the first-order system composed of blood vessel-tissue-skin. We applied this simulation model to epidural anesthesia, and investigated the analogy between theoretical and measured values using 2% alkalinized and nonalkalinized mepivacaine. During epidural anesthesia, a Laser Doppler flowmeter and a skin temperature probe were used to simultaneously measure skin blood flow and skin temperature. The onset time of increases in skin temperature and blood flow in the alkalinized group was shortened by one-fourth of that of the nonalkalinized group. In the nonalkalinized group, the pattern of changes in skin blood flow could not be predicted using the mathematical model. In the alkalinized group, however, the skin blood flow change was in accord with the theoretical values calculated from the skin temperature. These results indicate that the precise prediction of measured values by the simulation model is dependent on the speed of the sympathetic blockade. Conversely, the response to sympathetic nerve and blood vessels in different conditions can be assessed using this simulation model.