Postoperative Monitoring of Microvascular Free Flaps

Monitoring vascular patency and flap perfusion is an essential component of the d postoperative care of patients undergoing free tissue transfer. Postoperative compromise of arterial inflow or venous outflow results in the lack of nutrient blood flow to flap tissue and inevitable flap loss without therapeutic intervention. Approximately 10% of flaps will have a detectable perfusion abnormality in the ยง

immediate postoperative period. Most of these flaps are salvageable; however, an effective postoperative monitoring method is essential if salvage interventions are to be initiated in a timely fashion. There are no currently available monitoring techniques that can provide flawless objective and continuous flap evaluations in the postoperative period. An international review of practices in microvascular surgery (1991) reported that postoperative monitoring of tissue viability was performed, at least in part, by clinical methods in 75% of respondents (34). In addition to direct observation of tissue, clinical observation involves the use of exteriorized monitoring segments when the useful portion of the flap is buried. Exteriorized segments brought to the skin surface allow for monitoring and should ideally reflect perfusion abnormalities in the main flap (Fig. 3). The cutaneous portion of the free flap is monitored by observing the capillary refill: a pale flap with no capillary refill indicates a problem with inflow or arterial thrombosis; skin with a blue hue and very rapid refill indicates a problem with outflow, usually venous kinking or thrombosis. The presence of bright red blood on pinprick is a sign of a healthy flap; no blood may indicate an inflow problem and dark blood may indicate an outflow problem. Timing of these evaluations varies; however, a commonly used protocol is every hour for the first 24 h postoperatively; every 2 h for the next 24-48 h; and every 3h thereafter until postoperative day 5.

Figure 3 An example of an exteriorized monitor segment. Depicted on the left is a partially tubed lateral thigh free flap. Once the tubing is complete and the neck flaps replaced, the flap will be buried and unavailable for monitoring effectively. A subcutaneous-based skin paddle was created at the time of flap harvest and brought out to be incorporated into the neck incision (right). This allows effective monitoring of the main flap, since the health of this exteriorized monitoring segment reflects the health of the buried flap. The four-pointed star marks the nasogastric tube, five-pointed star marks the interior of the neopharynx and main flap, and the arrow indicates the exteriorized marking segment. (Photos courtesy of John Gooey, M.D.)

Figure 3 An example of an exteriorized monitor segment. Depicted on the left is a partially tubed lateral thigh free flap. Once the tubing is complete and the neck flaps replaced, the flap will be buried and unavailable for monitoring effectively. A subcutaneous-based skin paddle was created at the time of flap harvest and brought out to be incorporated into the neck incision (right). This allows effective monitoring of the main flap, since the health of this exteriorized monitoring segment reflects the health of the buried flap. The four-pointed star marks the nasogastric tube, five-pointed star marks the interior of the neopharynx and main flap, and the arrow indicates the exteriorized marking segment. (Photos courtesy of John Gooey, M.D.)

The most reliable method of monitoring skin circulation is through the use of radioactive microspheres; obviously, this method is limited to the laboratory. Although clinical observation is the most common method of monitoring the health of free flaps postoperatively, several other methods are available and relied upon in some institutions.

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