Acute effects of local tissue trauma on skin perfusion evaluated with laser-Doppler flowmetry

Single fiber laser-Doppler flowmetry (SF-LDF) is a new technique for continuous monitoring of microvascular perfusion within tissues. The insertion of the SF-LDF probe generates a tissue trauma. The object of this study was to evaluate short-term effects on local skin perfusion caused by the probe insertion. A standard laser-Doppler flowmeter probe (Std-LDF) was used for continuous recordings of human skin perfusion. A flexible SF-LDF probe (phi = 0.5 mm) was inserted intradermally in the same measuring region, and recordings were performed for 70 min with both probes simultaneously. Intracutaneous placement of the SF-LDF probe caused a considerable hyperemic response with a slow normalization. Maximal values were obtained after 5 to 10 min. After 70 min values were still twice the perfusion level at startup. A 3-min tourniquet occlusion test was performed two times during the study. Thirty minutes after the insertion a postocclusive hyperemic response was not observed, indicating a maximal vasodilatation before the test. At 60 min a significant hyperemic response was recorded with both probes. Vasomotion observed prior to the insertion was transiently abolished. The flow motion waves reappeared in both probes, in the Std-probe after 20 min (range 11-35) and in the SF-LDF probe after 12.5 min (range 7-20). The SF-LDF technique can be used in evaluating microvascular perfusion within tissues, but in skin the SF-LDF values are influenced by the insertional trauma. The effects of the trauma are probably different in other tissues, but should be examined for each tissue before conclusions based on SF-LDF measurements are drawn.