Skin temperature measured by infrared thermography
after ultrasound-guided blockade of the sciatic nerve.
Abstract
BACKGROUND:
In the present study, we assessed
the relationship between subgluteal sciatic nerve blocking and skin temperature
by infrared thermography in the lower extremity. We hypothesized that blocking
the sciatic nerve will lead to an increase in temperature, and that this will
correlate with existing sensory block tests.
METHODS:
We studied 18 healthy individuals
undergoing orthopaedic surgery of the foot under ultrasound-guided subgluteal
blockade of the sciatic nerve with 30 ml ropivacaine 7.5 mg/ml. Skin
temperature was measured on the toes, the dorsal and plantar side of the foot,
the malleoli, and the lateral side of the lower leg, just before sciatic nerve
blockade and at 10-min intervals thereafter.
RESULTS:
Baseline skin temperatures showed a
significant distal-to-proximal gradient. After sciatic block, temperatures on
the blocked side increased significantly in the toes and foot. When comparing
pinprick to skin temperature in a receiver operating curve, there was an AUC of
85.9% (95% confidence interval = 83.7-88.2%, P < 0.001). The medial
malleolus (not being innervated by the sciatic nerve) showed no significant
difference to the lateral.
CONCLUSIONS:
After sciatic nerve block,
temperatures of the foot increased significantly. There was a good correlation
between pinprick testing and infrared temperature measurement. This makes
infrared skin temperature measuring a good test in determining block success
when sensory testing is impossible.
© 2013 The Acta Anaesthesiologica
Scandinavica Foundation. Published by John Wiley & Sons Ltd.
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