A Prospective Study Evaluating the Use of Intraoperative Stroke Volume Variation Via the FloTrac Device to Guide Fluid and Vasopressor Management in Head and Neck Free Flaps

Few animal models have shown that intravenous vasopressor administration (including use of pure alpha agonists such as phenylephrine) can decrease blood flow to free musculocutaneous flaps (1-3). This has led to a dogmatic belief that all vasopressors should be avoided intraoperatively during a microvascular free flap reconstruction regardless of patient hemodynamics, even though there is little published evidence that pressors negatively affect free flap outcome (4). As a result, these patients often receive generous amounts of fluids during their intraoperative course to combat periods of hypotension. However, patients receiving head and neck free tissue transfers tend to be older with serious comorbidities related to long term tobacco use such as significant cardiovascular and pulmonary disease. Thus, they often exhibit intraoperative hemodynamic lability with periods of hypotension that may not necessarily be related to hypovolemia. Consistently treating periods of hypotension with more intravenous fluids can lead to serious postoperative complications such as graft failure (4), pulmonary edema, and congestive heart failure. In fact, we have just completed a retrospective review of 248 patients over a 34 month period that received a head and neck free tissue transfer; we discovered that a 1ml/kg/hr increase in intraoperative fluid administration significantly increased 30 day flap complication rate while intraoperative administration of vasopressors did not affect 30 day flap complication or 30 day failure rate.

The FloTrac device is an approved and validated medical device that analyzes the arterial pressure waveform to calculate a stroke volume variation. This stroke volume variation can be used to better guide intraoperative patient therapy with regard to need for fluid vs. pressor management during periods of intraoperative hypotension (5). The use of the FloTrac device for goal directed therapy has been investigated in major abdominal surgery and found to decrease length of hospital stay and complication rate in this surgical population (5-6). Thus, it is possible that the intraoperative use of the FloTrac device can better guide anesthesia providers to provide the necessary therapy for intraoperative hypotension in patients undergoing head and neck freet tissue transfer, thus improving postoperative outcome.

Inclusion criteria

• adults requiring "free flap" tissue reassignment surgery for head and neck cancer at either MUSC or Vanderbilt Medical Center

Exclusion criteria

• Patients < 55kg or > 140 kg based on literature regarding accuracy of flotrac.
• Patients with sustained intraoperative dysrrhythmias based on literature regarding accuracy of flotrac (ie, atrial flutter, atrial fibrillation).
• Patients with diagnosed NYHA class III-IV failure or documented EF < 30%
• Patients with pulmonary disease preventing administration of goal tidal volumes without excessive inspiratory pressures.