Continuous perioperative monitoring of microcirculatory blood flow in pectoralis musculocutaneous flaps

Hypovolemia and hypotension in traumatized patients as well as those undergoing long‐lasting surgical procedures lead to hypoperfusion of tissues. Combined with the trauma of flap elevation and the warm ischemia during performance of the anastomoses, hypoperfusion of flap tissues may lead to flap failure. The influence of hypovolemia, ischemia and reperfusion on flap macro‐ and microcirculation was studied in an acute experiment on a new musculocutaneous pectoralis flap developed in minipigs. Using a multichannel laser Doppler system we studied, simultaneously and continuously, microcirculatory flow (MBF) in both the skin and muscle of the flap as well as in the contralateral control skin and muscle in anesthetized minipigs (n = 7). Measurements were done before and after raising the flap, after 90 min of flap ischemia, during mild to moderate hypovolemia (5%, 10%, 15%, and 20% blood loss) and during and after restoration of blood volume. Electromagnetic flowmetry was used to measure total blood flow (TBF) to the flap. All animals remained hemodynamically stable during the experiment. The flap MBF decreased by 20% in the skin and 25% in the muscle after flap elevation with no changes in the control skin and muscle. After flap ischemia and reperfusion, MBF returned to post‐elevation values while TBF showed a significant increase as compared to MBF (P<0.05). Hypovolemia caused a gradual drop in cardiac output (25%) and mean arterial pressure (40%), but both recovered above the baseline after reinfusion of shed blood. Hypovolemia also caused a 60% reduction in MBF in both flap skin and muscle, and only 20–23% in control skin and muscle (P<0.01). After reinfusion of shed blood the MBF in the flap remained 30–40% below and the TBF increased 20% over the baseline. The MBF in control skin and muscle increased more than 20% over baseline (P<0.01). It was concluded that MBF in flap skin and muscle decreased by approximately 20–25% as a consequence of flap elevation, while central parameters remained normal. It was shown that even during moderate hypovolemia, MBF in the flap might decrease to critical levels. We suggest that intensive monitoring of central hemodynamics and continuous LDF monitoring of the flap during and after surgery should be performed in order to restore the blood volume expeditiously and prevent irreversible damage to flap tissues. © 1995 Wiley‐Liss, Inc.