Thermographic temperature measurement compared with pinprick and cold sensation in predicting the effectiveness of regional blocks.
Galvin EM, Niehof S, Medina HJ, Zijlstra FJ, van Bommel J, Klein J, Verbrugge SJ. Department
of Anesthesiology, Erasmus University Medical Center, Rotterdam, The Netherlands.

We designed this study to evaluate the usefulness of thermographic temperature measurement
with an infrared camera, compared with patient response to cold and pinprick, as a means of
assessing the success or failure of axillary blockades. Axillary blocks were performed on 25
patients undergoing surgery on the hand or forearm using a nerve stimulator technique with
mepivacaine 1.5%. Pinprick and cold sensation were assessed on the operative site at 5-min
intervals for 30 min. A thermographic image of the operative limb was recorded at similar time
intervals. Thermographic images of the unblocked limb were taken before block placement and at
30 min. Temperature values at the operative site and unblocked limb were calculated from the
thermographic images. Results revealed that thermography had higher combined values for
sensitivity, specificity, and positive and negative predictive values than both cold and
pinprick at all time intervals, with statistically significant differences at 15 min (thermography
versus cold, P = 0.006; thermography versus pinprick, P = 0.026) and 30 min (thermography
versus cold, P = 0.038; thermography versus pinprick, P = 0.040). For thermography as a method
of block assessment, an optimal time of 15 min after mepivacaine local anesthetic injection gives
the highest combined values for predicting a successful block (P = 0.004). We conclude that
thermography provides an early and objective assessment of the success and failure of axillary
regional blockades.