Reduction of blood loss during spinal surgery by epidural blockade under normotensive general anesthesia

Abstract

Study design: This study consisted of a comparison of intraoperative blood loss during posterior spins surgery under normotensive general anesthesia with and without epidural blockade, and a hemodynamic study after epidural injection.

Objectives: To determine the effect of epidural blockade in reducing blood loss and intraosseous pressure in the vertebral body.

Summary of background data: Epidural anesthesia is effective in reducing surgical bleeding. This effect has been thought to be due to systemic arterial hypotension. There was no report on its effect on venous pressure or intraosseous pressure.

Methods: In comparison of blood loss epidural blockade was achieved by preincisional caudal epidural injection of 20 ml of 0.25% bupivacaine during cervical laminoplasty or posterior lumbar interbody fusion. For each surgical procedure, there were 20 patients who received epidural blockade and 20 who did not. In a hemodynamic study, intraosseous pressure in the second thoracic or the second or third lumbar vertebral body, intraosseous pressure in the calcaneus, and systemic arterial blood pressure were measured continuously before and after the caudal epidural injection of 20 ml of 1% lidocaine during posterior cervical or lumbar spine surgery in 42 patients.

Results: Total and hourly intraoperative blood loss during posterior lumbar interbody fusion was significantly less in the group with blockade than in the group without blockade, but the values during cervical laminoplasty showed no significant difference between the two groups. The lumbar vertebral intraosseous pressure decreased significantly after epidural injection, whereas the second thoracic vertebral and the calcaneal in traosseous pressure did not decrease significantly. The ratio of lumbar vertebral intraosseous pressure to arterial pressure decreased continuously after epidural injection, whereas the ratio of the calcaneal intraosseous pressure to arterial pressure transiently increased.

Conclusions: The epidural blockade reduces intraoperative bleeding, even under normotensive conditions, and it takes effect in the lumbar spine, but not in the upper thoracic or cervical spine. This effect appears to be due chiefly to venous hypotension in the lumbar spine, which may be created by sympathetic blockade, with arteriolar dilatation and venous pooling in the lower limbs and reactive vasoconstriction in the lumbar vertebrae.