Thermal Imaging to Predict Failed Supraclavicular Brachial Plexus Block: A Prospective Observational Study

Abstract

Background

Successful brachial plexus blockade produces sympathetic blockade, resulting in increased skin temperature in the blocked segments. This study aimed to evaluate the accuracy of infrared thermography in predicting failed segmental supraclavicular brachial plexus block.

Methods

This prospective observational study included adult patients undergoing upper-limb surgery under supraclavicular brachial plexus block. Sensation was evaluated at the dermatomal distribution of the ulnar, median, and radial nerves. Block failure was defined as absence of complete sensory loss 30 min after block completion. Skin temperature was evaluated by infrared thermography at the dermatomal supply of the ulnar, median, and radial nerves at baseline, 5, 10, 15, and 20 min after block completion. The temperature change from the baseline measurement was calculated for each time point. Outcomes were the ability of temperature change at each site to predict failed block of the corresponding nerve using area under receiver-operating characteristic curve (AUC) analysis.

Results

Eighty patients were available for the final analysis. The AUC (95% confidence interval [CI]) for the ability of temperature change at 5 min to predict failed ulnar, median, and radial nerve block was 0.79 (0.68–0.87), 0.77 (0.67–0.86), and 0.79 (0.69–0.88). The AUC (95% CI) increased progressively and reached its maximum values at 15 min (ulnar nerve 0.98 [0.92–1.00], median nerve 0.97 [0.90–0.99], radial nerve 0.96 [0.89–0.99]) with negative predictive value of 100%.

Conclusion

Infrared thermography of different skin segments provides an accurate tool for predicting failed supraclavicular brachial plexus block. Increased skin temperature at each segment can exclude block failure in the corresponding nerve with 100% accuracy.

Keywords:

• supraclavicular brachial plexus block
• infrared thermography
• skin temperature
• block failure
• analgesia
• upper-limb surgery

Data Sharing

The data that support the findings of this study are available from the authors upon reasonable request after gaining permission from Cairo University.

Ethics Approval and Informed Consent

We conducted this study after obtaining Research Ethics Committee of Cairo University approval (MD-376-2020). Written informed consent was obtained from all patients before enrollment. Our study complies with the Declaration of Helsinki.

Disclosure

This paper or the abstract of this paper has not been presented at a conference or published.

Additional information

Funding

There is no funding to report.