Postoperative Evaluation of Free Flap Reconstructions

In addition to the basic postoperative approach to any surgical patient, the patient with a free flap reconstruction requires specific attention to detect and prevent a potentially compromised flap. An important rule of thumb is to physically inspect a flap when there is any question of a change in status. Unless you are very experienced, any examination of a flap with a suspected change in status should be reported to the attending surgeon responsible for the flap.

Assessment

Vital Signs

Heart rate monitoring is important for assessing pain control, intravascular volume status, and possible arrhythmias. Inadequate pain control is a frequent cause of tachycardia. Be sure to ask how comfortable the patient is and assess whether additional pain medication is needed. Watch for bradycardia, which can result from heart blocks or overuse of antihypertensive medications such as β-blockers and analgesics. Most free flap patients will spend the first night in the intensive care unit on telemetry, therefore attention should be paid to the tracing to rule out atrial fibrillation, flutter, or other arrhythmias. It is important to control these arrhythmias, not only for the safety of the patient, but to maintain the viability of the flap. Sudden fluctuations in blood pressure can lead to turbulent flow across the microvascular anastomosis or within the flap, which could lead to compromised perfusion of the flap.

Blood pressure should be monitored very closely in the postoperative period. Most free flap patients should have a MAP >90 and SBP >120. Of paramount importance is keeping the patient from becoming hypotensive. Hypotension can result in recipient artery spasms and venous stasis that can lead to thrombosis. Due to the prolonged surgery, insensible losses, and postoperative third spacing, free flap patients are usually intravascularly depleted and often require fluid supplementation in the acute postoperative period. Intravascular fluid status is most accurately represented by the patient’s urine output. Free flap patients should produce at least 0.5 cc/kg/hour of urine (35 cc/hour for a 70-kg patient), but preferably 50 to 100 cc/hour. Patients suspected to be intravascularly depleted should receive LR or normal saline boluses. After the first 24 hours, D5 1/2NS at maintenance rate is used for the stable patient.

Patients should never receive diuretics to induce urine output unless there are clear signs of renal compromise in a well-hydrated patient. Likewise, pressors should not be used to treat hypotension. Pressors should be a last resort and only used when absolutely necessary (profound hypotension).

Hypertension (> 180/100) can lead to bleeding in a fresh postoperative patient. Elevated blood pressure is most commonly a sign of inadequate pain control. Extremes in hypertension unresponsive to analgesics should be managed with low-dose antihypertensives (hydralazine 10 mg IV, or labetalol 10 to 20 mg IV PRN) to prevent rapid decreases in the MAP that can ultimately be detrimental to a flap.

Oxygenation should also be assessed with a pulse oximeter to keep the blood oxygen saturation >93%. In replants, the oximeter is a useful tool to monitor the replanted digit. When placed on the part, loss of the signal indicates arterial compromise, whereas progressively declining saturations are suggestive of venous congestion.

Hypothermia is avoided to prevent vasospasm. The patient’s room should be kept above 70°F (21 °C), with heating units used liberally if the room temperature cannot be adequately controlled.

Drain output should be closely monitored. Although drainage may be high in the immediate postoperative period due to expected oozing, a drop in output followed by a sustained increase may be indicative of venous thrombosis. Extensive drainge should prompt immediate evaluation of the flap.

Clinical Observation

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