Venous outflow obstruction in myocutaneous flaps: changes in microcirculation detected by the perfusion fluorometer and laser Doppler

Comparison of laser Doppler flowmeter and radioactive microspheres in measuring blood flow in pig skin flaps

Laser Doppler flowmetry is a noninvasive technique commonly used to monitor skin perfusion after free-tissue transfer or replantation in reconstructive surgery. Several investigators have expressed concern about the reliability of the quantitative value provided by laser Doppler flowmeters (LDF) and the extent to which they reflect nutrient blood flow. This experiment was designed to compare quantitatively the skin blood flow in the pig measured by LDF and by 15-micron radioactive microspheres (RMs). It was observed that the skin blood flow rates measured by LDF and RMs in the normal skin and in acute random-pattern and arterialized skin flaps were highly correlated (r = 0.93, P < .01). However, the skin blood flow rates measured by LDF were consistently higher (P < or = .05) than the corresponding flow rates measured by RMs, and this discrepancy increased considerably at low skin blood flow rates (< 2 mL/min/100 g). We speculated that the LDF most likely measured both nutrient and arteriovenous shunt flow in the skin and that this arteriovenous shunt flow at least in part caused the discrepancy in skin blood flow rates measured by the LDF and RMs because the 15-micron RMs are known to measure nutrient blood flow only. The inherent variations and errors in LDF technique were also discussed.

Laser Doppler imaging of axial and random pattern flaps in the maxillo-facial area. A preliminary report

Objective, non-invasive examination, techniques in addition to clinical parameters, are required to follow-up the wound healing of flaps. With the new laser Doppler Scanner (LDI DIM 1.0 Lisca Development AB, Sweden) it is possible, for the first time, to measure and image the microcirculation continuously, non-invasively and without contact with the wound, in an area of 12 cm square maximum. We performed measurements and simultaneous two-dimensional imaging of the microcirculation 24, 48, 72 h and 5 and 14 days postoperatively in 20 patients, who had had reconstruction procedures performed using random or axial pattern flaps. The perfusion diagrams were correlated to the clinical appearance. Necrotic areas, venous stasis and normal course of wound healing can be clearly visualized and differentiated from one another. The new laser Doppler imaging system seems to be an excellent aid for following up and planning of flaps in plastic and reconstructive surgery.

Interpreting laser Doppler recordings from free flaps

Although the transfer of free flaps is nowadays accomplished with an increasing degree of safety, thrombosis of the microvascular anastomoses is still a problem. In order to avoid delay in re-operating, various methods for objective blood flow monitoring have been tried, among them Laser Doppler Flowmetry (LDF). When one reviews the literature, it is apparent that opinions differ about whether or not LDF is a reliable technique for this purpose. To focus on the need to interpret continuous recordings, this paper reports our findings in six latissimus dorsi free flaps chosen from our series of LDF monitoring procedures. One uneventful flap, no. 1, had an immediate postoperative LDF value of 4.5 perfusion units (PU). LDF values improved during the recovery period and the graphic recording showed fluctuations due to normal physiological variations of the blood flow in the flap. Another uneventful flap, no. 4, showed the same pattern, though at an appreciably lower level, 2 PU, on average. Flap no. 2 had an acceptably high value of 3.5 PU despite suffering a venous thrombosis. However, the LDF recording showed no fluctuations and the value declined gradually. Another flap, no. 3, showed fluctuations and blood flow was normal although the value decreased to 2.5 PU. In flap no. 5, any value between 2 and 3.5 PU could be obtained merely by adjusting the position of the probe in the holder. In no. 6, the LDF value suddenly dropped, accompanied by a decrease in the total amount of backscattered light, indicating venous obstruction which was confirmed at re-operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Laser Doppler monitoring of free microvascular flaps in maxillofacial surgery

In free microvascular flap transplantation, reliable postoperative monitoring is necessary to indicate the necessity for early re-exploration in the event of decreased blood supply. In this study the positive evidence of laser Doppler monitoring of free flaps was investigated in 28 cases. Myocutaneous, osteomyocutaneous and small intestine flaps were measured. The laser Doppler flowmetry values ranged within a wide band and were relative to the different tissues measured, and the patients. It was not possible to define a reliable inferior limit for the various tissues. Only the assessment of the development of the values was interesting. Flaps with high measured laser Doppler flowmetry values were successful, flaps with decreasing values showed problems. The most important tool for the surgeon is his clinical experience, but laser Doppler monitoring in flap transplantation can be helpful to the surgeon.

Real time multivariable laser Doppler analysis of arterial and venous compromise

Laser Doppler perfusion monitoring was used to assess microcirculatory blood flow, volume, and velocity before and after total arterial or total venous occlusion in 18 buttock island flaps. Critical analysis of these three laser Doppler perfusion values was found to be useful in differentiating adequately perfused skin from inadequately perfused skin, as well as in distinguishing arterial from venous compromise. Multivariable laser Doppler analysis demonstrated that arterial occlusion produced a more rapid and greater percentage decrease in flow and volume values than did venous occlusion. Arterial occlusion produced an insignificant percentage change in velocity values, whereas venous occlusion produced a substantial percentage decrease in velocity values. The substantial intrasubject and intersubject variability in absolute laser Doppler perfusion values suggests that normalized or percentage change values are more revealing than absolute values, although they require the acquisition of reliable baseline data.