[Increase in skin surface temperature in spinal anesthesia. Predictive value for probability of surgical tolerance]

Spinal anesthesia causes sympathetic blockade which leads to changes in the local temperature of the skin surface due to hyperemia.

These changes in skin temperature were used in a newly developed method for estimating the level of analgesia. A total of 11 patients who were scheduled for surgical procedures of the lower extremities with symmetrical spinal anesthesia were included in the clinical study. By means of an electronic digital multi-channel body temperature measurement device with eight high precision temperature sensors placed on defined dermatomes, patient skin temperature was continuously measured at 2 s intervals and documented before, during and for 45 min after spinal anesthesia. Simultaneously, a neurological pin-prick test was carried on at regular intervals every 2 min on the defined dermatomes to calculate the correlation between the effects of analgesia and corresponding changes in skin temperature.

The analyzed correlations showed that there is a minimum of 1.05°C temperature difference before and after spinal anesthesia especially on the lower extremities (foot, knee, inguinal) of patient dermatomes. The collected data of varying temperature differences were systematically evaluated using statistical software which led to a deeper understanding of the interdependency between temperature differences at different dermatomes. These interdependencies of temperature differences were used to develop a systematic analgesia level measurement algorithm. The algorithm calculates the skin temperature differences at specified dermatomes to find the accurate level of analgesia and also to find the forward and reverse progresses of analgesia. The developed mathematical method shows that it is possible to predict the level of analgesia up to an accuracy of 95% after spinal anesthesia.

Therefore, it can be concluded that systematic processing of skin temperature data, collected at defined dermatomes can be used as a promising parameter for predicting surgical tolerance. The objective is to improve this experimental method with an extended patient population study.