Anesth Analg 2007;104:740-741
© 2007 International Anesthesia Research Society
doi: 10.1213/01.ane.0000253920.68356.f8
LETTER TO THE EDITOR
Section Editor:
Lawrence Saidman
Further Evidence that Temperature Measurement Is a Useful Indicator of Regional Anesthesia Outcomes
Eilish Galvin, MB, FCARCSI, and
Sjoerd Niehof, BSc
Department of Anesthesia; Erasmus University Medical Center; Rotterdam, The Netherlands; eilishgalvin{at}hotmail.com
To the Editor:
Stevens et al. (1) documented the utility of temperature change as a monitor of regional anesthesia onset in the lower extremity, similar to our results (2), evaluating temperature change in the upper extremity after regional anesthesia. Specifically, the authors recorded a temperature increase of up to 6°C on the plantar aspect of the foot after successful blockade of the sciatic nerve, similar to our findings of an increase of 4.5°C after a successful axillary block. We are surprised at the authors’ lack of a plausible explanation for the apparent absence of a temperature increase after successful femoral nerve blocks. Perhaps temperature change could have been more successfully measured at the site of planned incision, the site of greatest clinical utility. In our study, we used an infrared thermographic camera, which clearly demarcated the temperature difference between blocked and unblocked dermatomes after local anesthetic injection.
We are also puzzled by the negative conclusion that the authors drew from their findings. Their results state that "sensitivity, specificity, and accuracy of a skin temperature increase for a successful sciatic nerve block were 100%." The sensitivity and specificity of pinprick, cold sensation, or motor function are not given. They also report that a temperature increase preceded or was reached at the same time as sensory block in 63.2% of sciatic block patients and 100% of epidural block patients. Paradoxically, the authors conclude that "skin temperature measurement is a reliable, but late sign of successful sciatic nerve block" which is "of limited clinical value." In our study (2), thermographic temperature measurement had higher combined values for sensitivity, specificity, and positive and negative predictive values than both cold and pinprick at all time intervals, with the earliest statistically significant difference occurring at 15 min (P = 0.006).
In our view, the findings of Stevens et al. represent further evidence that temperature measurement is a reliable, early, objective, and noninvasive technique for assessing the success or failure of regional blocks. The use of temperature and other objective techniques, such as peripheral flow index (3), for predicting regional block outcome may advance the acceptability of regional techniques among both doctors and patients.
REFERENCES
- Stevens MF, Werdehausen R, Hermanns H, Lipfert P. Skin temperature during regional anesthesia of the lower extremity. Anesth Analg 2006;102:1247–51.[Abstract/Free Full Text]
- Galvin EM, Niehof S, Medina HJ, et al. Thermographic temperature measurement compared with pinprick and cold sensation in predicting the effectiveness of regional blocks. Anesth Analg 2006;102:598–604.[Abstract/Free Full Text]
- Galvin EM, Niehof S, Verbrugge SJ, et al. Peripheral flow index is a reliable and early indicator of regional block success. Anesth Analg 2006;103:239–43.[Abstract/Free Full Text]
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