The effect of local anaesthetic cream (EMLA) applied with an occlusive dressing on skin thickness. Does it matter?

EMLA cream is used in plastic surgery as a topical anaesthetic to harvest split skin grafts. It has been observed that the skin appears pale and oedematous after the application of EMLA. The aim our study was to determine the effect of EMLA with an occlusive dressing on skin thickness using a high frequency ultrasound. Twenty volunteers took part in this study after approval from the ethics committee. An area of skin was marked on both thighs and the skin thickness of each, measured using ultrasound. EMLA with an occlusive dressing was applied to one thigh. This was removed after at least 2 h of application time but at different time points and skin thickness of each thigh measured again. Data was analysed using t-test and Pearson's correlation. Mean age in years +/- SD (range) was 36.1 +/- 12.1 (23 - 61). Male:female ratio was 8:12. Mean skin thickness +/- SEM increased from 1.86 +/- 0.055 mm prior to EMLA application to 1.96 +/- 0.051 mm post-EMLA application p= 0.02. There was a significant correlation between the increase in skin thickness and duration of application of EMLA cream (p = <0.001, R2 = 0.59). The results conclude that EMLA applied under an occlusive dressing has an effect on skin tissue thickness and any surgeon who harvests split skin grafts under EMLA should be aware of this. Further research is needed to compare laser treatments performed under local anaesthetic creams against general anaesthesia as an increase in skin thickness may affect the depth of laser penetration.