Infrared thermographic assessment of spinal anaesthesia-related cutaneous temperature changes during caesarean section.

INTRODUCTION

Assessment of adequacy of spinal anaesthesia, prior to obstetric surgery is extremely important but can be problematic because currently available clinical assessment methods are indirect and subjective. As the sympathectomy associated with spinal anaesthesia is known to cause vasodilation and heat redistribution, we sought to assess whether spinal anaesthesia led to significant and consistent cutaneous temperature changes as measured by infrared thermography.

METHODS

Following ethics committee approval, this observational study was conducted in a tertiary level obstetric centre. Participants included women undergoing elective caesarean section under spinal anaesthesia. Following consent, a Flir T540 infrared camera captured thermographic images over the feet, patella, buttock, iliac crests, xiphisternum and axilla. Temperature was measured prior to spinal needle insertion (T0) and following clinical assessment when the block was deemed adequate.

RESULTS

Thirty patients were included. Baseline temperature varied considerable by site. Spinal anaesthesia altered skin temperature in all areas of interest: right and left hallux (mean of differences (MD) +4.0°C and 5.2°C respectively, P <0.0001), right and left plantar (MD +6.1°C and 6.8°C respectively, P <0.0001), patella (MD -0.33°C, P=0.0445), buttock (MD -0.5°C, P=0.009), iliac crest (MD -0.7°C, P=0.0004), xiphisternum (MD -0.95°C, P <0.0001) and axilla (MD -0.71°C, P=0.0002).

CONCLUSIONS

Following spinal anaesthesia thermographic imaging identified different patterns of skin temperature changes, with pronounced temperature increases measured in the feet and cooling of a lesser amplitude in the thoracic and lumbar dermatomes. Infrared thermography has the potential to provide objective measurement of sympathectomy.