CoolStick vs. ethyl chloride spray for sensory block testing to light touch and cold for caesarean delivery under neuraxial anaesthesia: a paired method-comparison study with randomised test order.

BACKGROUND

Light touch sensation is recommended when testing neuraxial anaesthesia for caesarean delivery. This is commonly assessed using ethyl chloride spray. CoolStick is a more environmentally sustainable device that has not been compared to conventional methods.

METHODS

This was a multicentre prospective paired method-comparison study with randomised test order involving participants undergoing planned caesarean delivery with spinal or combined spinal-epidural anaesthesia. Participants were tested with both CoolStick and ethyl chloride 10 min post-spinal, with the initial method chosen at random. The primary endpoint was dermatomal level to light touch, and the secondary endpoint was dermatomal level to cold. We also assessed pain within 60 min of spinal injection. Agreement between testing methods was assessed using the intraclass correlation coefficient, with bias and limits of agreement assessed using Bland-Altman plots and the Wilcoxon signed rank test.

RESULTS

We recruited 64 women between April and November 2025. The median [interquartile range] age was 34 (30-37) years. The intraclass correlation coefficient for light touch was 0.87 (95% CI 0.78-0.92, P < 0.001), and for cold was 0.89 (95% CI 0.83-0.93, P < 0.001). Median bias for light touch was 0 dermatomes (95% limits of agreement -1 to 4, p = 0.002) and for cold was 0 dermatomes (-2 to 1, P = 0.06). No patient reported pain within 60 min.

DISCUSSION: We found high overall agreement between devices for both light touch and cold testing. However, CoolStick recorded light touch levels several dermatomes lower than ethyl chloride in a small proportion of patients.