Monitoring of Free Tram Flaps with Microdialysis

Abstract

The aim of this investigation was to follow the metabolism of free TRAM flaps using microdialysis. Microdialysis is a new sampling technique that provide opportunities to follow the biochemistry in specific organs or tissues. A double-lumen microdialysis catheter or probe, with a dialysis membrane at the end, is introduced into the specific tissue. Perfusion fluid is slowly pumped through the catheter and equilibrates across the membrane with surrounding extracellular concentrations of low molecular weight substances. The dialysate is collected in microvials and analyzed by an instrument using very small volumes. Glucose, glycerol, and lactate concentrations were measured in the flaps and compared with those in a reference catheter that was placed subcutaneously in the femur. The investigation continued 72 hr postoperatively. The study group consisted of 14 women who underwent reconstruction with a free TRAM flap, and one woman with a double TRAM flap. During flap ischemia, the concentration of glucose was reduced, while the lactate and glycerol levels increased. The differences between the flaps and controls were statistically highly significant. After reperfusion of the flaps, the concentrations of glucose, lactate, and glycerol approached normal. One flap failed because of an arterial anastomosis thrombosis. This was clearly demonstrated by the samples from the microdialysis: the concentration of glucose fell to an unmeasurable level; the concentration of lactate increased for a period before it stopped due to lack of glucose; and the concentration of glycerol increased to a very high level, probably because ischemia caused damage to the cell membranes of which glycerol is an important part. The authors concluded that microdialysis can detect ischemia in free flaps at an early stage, making early surgical intervention possible.

Current Evidence for Postoperative Monitoring of Microvascular Free Flaps

“…Typical metabolites used for this technique are lactate, glucose, glycerol, and pyruvate. [84][85][86] Several other molecules, such as complement 3a and thromboxane A2, have been mooted as candidates for further study. 87,88 Udesen et al used a similar catheter placed elsewhere in the body for a reference comparison, whereas some later studies have simply compared results to reference values or used increasing lactate/pyruvate ratios as a measure of ischemia.…”

“…It should be used to replace the clinical examinations in buried and poorly accessible flaps and, when in doubt, needs to be complemented by clinical monitoring and handheld Doppler. 78,81 Microdialysis First described in the setting of free flap monitoring by Udesen et al, 84 microdialysis consists of a double-lumen catheter with a semipermeable membrane at the end, which is placed within the flap to be monitored, and a small amount of fluid is pumped through the catheter. As this fluid passes through the semipermeable membrane, small molecules may pass into the dialysate, which can then be analyzed.…”

The metabolism of the diabetic footIn vivo investigation with microdialysis

“…Our study showed higher concentrations of glycerol and similar levels of glucose and lactate in the ulcers. The sympathetic tone increases during surgical stress and lipolysis is promoted (Udesen et al 2000). However, this universal response cause higher concentrations of glycerol in both the ulcer and reference tissue.…”

Clinical biochemical tissue monitoring during ischaemia and reperfusion in major vascular surgery

“…6 Udesen et al underlined the clinical value of microdialysis monitoring in the detection of metabolic disorders in skin and muscle £aps during reconstructive surgery. 7 Lundberg et al used microdialysis for grading the severity of peripheral vessel diseases before and after elevation of the symptomatic limb. Interstitial concentrations of lactate and the lactate/pyruvate ratio responded rather heterogeneously to blood £ow reduction, whereas glucose concentration subsequently fell.…”