Interpreting Laser Doppler Recordings from Free Flaps

Abstract

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)

Results of monitoring fasciocutaneous, myocutaneous, osteocutaneous and perforator flaps: 4-year experience with 166 cases

“…This enables a depth-selective measuring of flow and velocity. Earlier studies criticized the lack of absolute values and difficulty in interpreting measured values because of high variability 5,29 . This difficulty can be limited through intra-individual values measured when the flap is raised.…”

Free flap monitoring using simultaneous non-invasive laser Doppler flowmetry and tissue spectrophotometry

“…Many authors have found this to be an objective, reproducible and non-invasive method which is accurate and reliable (Kind et al, 1998;Yuen and Feng, 2000). However, the recordings of laser Doppler flowmetry require careful interpretation (Svensson et al, 1993). Furthermore, there are some inherent limitations when it is used for monitoring free flaps.…”

Evaluation der Perfusion von Lappenplastiken mittels Laserfluoreszenz von Indocyaningrün

“…Klinische Parameter wie die Rekapillarisierungszeit, die Temperatur des Transplantats, die Farbe der Haut und eine Blutung nach Punktion sind einfach zu erhebende und aussagekräftige Hilfen im postoperativen Lappen-Monitoring, erlauben jedoch keine detaillierte topographische Darstellung der Durchblutungssituation. Objektive und kontinuierliche Techniken wie die Pulsoxymetrie [28], Laser-Doppler-Flowmetrie [10,29], die Messung der Partialdrücke von O 2 und CO 2 [11,16,17], Temperaturmessung [3, 15,18] und andere Verfahren sind experimentell untersucht worden und haben nur an wenigen Abteilungen den Weg in die Klinik gefunden. Einige der Methoden erlauben bis zu einem gewissen Grad auch eine topographische Darstellung der Durchblutung, sind jedoch nur eingeschränkt zur Vorhersage der Nekroseentwicklung fähig.…”