Cutaneous microdialysis in man: effects of needle insertion trauma and anaesthesia on skin perfusion, erythema and skin thickness.

Cutaneous microdialysis is a method of measuring endogenous and exogenous compounds in the dermal interstitial fluid. The microdialysis probe is inserted in the dermis using a guide cannula. The insertion trauma was studied in dorsal forearm skin in a total of 28 human healthy volunteers. Twenty-four volunteers received local anaesthesia (Xylocain 10 mg/ml) in both forearms and a microdialysis probe was inserted in one of the arms. In 12 volunteers the insertion trauma and the effect of anaesthesia on skin blood flow and erythema were studied by laser Doppler perfusion imaging, Minolta Chromameter CR 200 and Dermaspectrometer. In the other 12 subjects trauma-induced oedema and effects on skin thickness were studied by ultrasound imaging. In addition, a microdialysis probe was inserted without prior anaesthesia in 4 volunteers, and the effects on skin blood flow and erythema were investigated. Significant increases in skin blood flow, erythema and skin thickness were found after insertion of the microdialysis probe. Local anaesthesia prior to the insertion reduced the effects of trauma. Probe depth in dermis did not influence the effects of trauma. At least 90-120 min is required after insertion in order to allow the vascular reaction to needle trauma to return to the baseline range.