Blinded observer evaluation of distal skin temperature for predicting lateral infraclavicular block success

BACKGROUND: Changes in digit skin temperature may be used to predict and determine upper limb nerve block success. We investigated whether a temperature difference between the blocked and the nonblocked hands, simply registered by touching the skin of the 5th and 2nd digit was valid and reliable as a diagnostic test for predicting a successful lateral infraclavicular block.

METHODS: Blinded observers investigated temperature difference between the blocked and the nonblocked hands of 40 patients. Sensitivity, specificity, and predictive values of a positive and a negative test were estimated for evaluating the validity of a temperature difference for predicting a successful lateral infraclavicular block defined by sensory and motor block of all 4 major nerves (musculocutaneous, radial, ulnar, and median nerves). κ statistics of interobserver agreement were used for evaluating the reliability of the test.

RESULTS: As a stand-alone test, a temperature difference between the corresponding 2nd and 5th digits of the blocked and the nonblocked hands predicted a successful block with a sensitivity of 92% (95 % confidence interval (CI), 83%-97%) and with a predictive value of a positive test of 95% (CI, 86%-98%). Fleiss κ for multiple observers was 0.74, (CI, 0.61-0.87) for the 5th digit and 0.87 (CI, 0.73-0.998) for the 2nd digit, respectively.

CONCLUSIONS: We found that a qualitative difference in skin temperature between the blocked and nonblocked hands, measured distally on the 2nd and 5th digits, was a valid and reliable diagnostic test for predicting successful lateral infraclavicular block.