Banic A, Krejci V, Erni D, Petersen-Felix S, Sigurdsson G H
Department of Plastic and Reconstructive Surgery, University of Berne, Switzerland.
Plast Reconstr Surg. 1997 Sep;100(4):945-55; discussion 956. doi: 10.1097/00006534-199709001-00017.
Free musculocutaneous flaps are used frequently in plastic surgery to reconstruct soft-tissue defects after radical cancer surgery and trauma. Despite improved surgical techniques, some of these flaps fail due to insufficient blood supply. Extradural anesthesia causes both sensory (pain relief) and sympathetic (vasodilatation) block that may be advantageous in free-flap surgery. This hypothesis, however, has not yet been studied. An experimental model in pigs was developed in which clinical conditions for anesthesia and microvascular surgery on the lower extremity were simulated as closely as possible. The effects of extradural anesthesia as well as phenylephrine infusion, combined with general anesthesia, on central hemodynamics and on microcirculatory blood flow in skin and muscle of the latissimus dorsi free flap were studied. After surgery, seven animals received extradural anesthesia during stable normovolemic conditions and another seven during mild hypovolemia (10 percent blood loss). The extradural block was objectively evaluated using the temporal summation test. Thirty minutes after induction of extradural anesthesia, the animals received an intravenous infusion of phenylephrine 1 microgram/kg per minute over a period of 15 minutes. Multichannel laser-Doppler flowmetry was used to measure microcirculatory blood flow in skin and muscle of the free flap as well as in control skin and muscle on the same extremity simultaneously. In normovolemic animals, extradural block caused a 10 percent decrease in mean arterial pressure and cardiac output and an approximately 20 percent decrease in microcirculatory blood flow in both the skin and muscle of the flap (all changes were nonsignificant). In slightly hypovolemic animals, however, extradural anesthesia caused a significant decrease in cardiac output (31 percent, p < 0.01), mean arterial pressure (24 percent, p < 0.01), and in mean blood flow in the flap muscle (22 percent, p < 0.05) and skin (20 percent, p < 0.05). During phenylephrine infusion, mean arterial pressure increased significantly (p < 0.05) in both hypovolemic and normovolemic animals, while cardiac output and microcirculatory blood flow in the flap remained almost unchanged. Extradural anesthesia does not improve microcirculatory blood flow in free musculocutaneous flaps in pigs. It causes a significant decrease in cardiac output, mean arterial pressure, and microcirculatory blood flow in slightly hypovolemic animals. During phenylephrine infusion, the microcirculatory blood flow in free flaps slightly improves due to the increase in mean arterial pressure. We suggest that extradural anesthesia for microvascular surgery should be used with great caution until human data are available.
游离肌皮瓣在整形外科中常用于根治性癌症手术和创伤后软组织缺损的重建。尽管手术技术有所改进，但其中一些皮瓣仍因血供不足而失败。硬膜外麻醉会导致感觉（疼痛缓解）和交感神经（血管舒张）阻滞，这在游离皮瓣手术中可能具有优势。然而，这一假设尚未得到研究。我们建立了一个猪的实验模型，尽可能紧密地模拟下肢麻醉和微血管手术的临床情况。研究了硬膜外麻醉以及去氧肾上腺素输注联合全身麻醉对背阔肌游离皮瓣皮肤和肌肉的中心血流动力学及微循环血流的影响。手术后，七只动物在血容量稳定的情况下接受硬膜外麻醉，另外七只在轻度血容量不足（失血10%）的情况下接受硬膜外麻醉。使用时间总和试验对硬膜外阻滞进行客观评估。硬膜外麻醉诱导30分钟后，动物在15分钟内以每分钟1微克/千克的速度静脉输注去氧肾上腺素。使用多通道激光多普勒血流仪同时测量游离皮瓣皮肤和肌肉以及同一肢体对照皮肤和肌肉的微循环血流。在血容量正常的动物中，硬膜外阻滞导致平均动脉压和心输出量下降10%，皮瓣皮肤和肌肉的微循环血流下降约20%（所有变化均无统计学意义）。然而，在轻度血容量不足的动物中，硬膜外麻醉导致心输出量显著下降（31%，p<0.01）、平均动脉压下降（24%，p<0.01）以及皮瓣肌肉平均血流下降（22%，p<0.05）和皮肤平均血流下降（20%，p<0.05）。在输注去氧肾上腺素期间，血容量不足和血容量正常的动物平均动脉压均显著升高（p<0.05），而皮瓣的心输出量和微循环血流几乎保持不变。硬膜外麻醉并不能改善猪游离肌皮瓣的微循环血流。在轻度血容量不足的动物中，它会导致心输出量、平均动脉压和微循环血流显著下降。在输注去氧肾上腺素期间，由于平均动脉压升高，游离皮瓣的微循环血流略有改善。我们建议，在获得人体数据之前，微血管手术使用硬膜外麻醉应格外谨慎。
