CARDIOVASCULAR CHANGES DURING FAT EMBOLISM CAUSED BY MULTIPLE VERTEBROPLASTY IN SHEEP

Abstract

Introduction: Vertebroplasty (VP) is a new prophylactic treatment for preventing osteoporotic compression fractures of vertebral bodies. During this procedure polymethylmethacrylate (PMMA) is injected into several vertebral bodies. It has been shown that fat embolism (FE) with acute cardiopulmonary deterioration occurs during VP as in a variety of other orthopaedic procedures (e.g. knee and hip replacements). The aim of the study is to investigate cardiovascular changes during FE caused by multiple VP using an animal model.

Method: In six sheep, PMMA was injected unilaterally, into L1 – L6, with ten minutes in-between injections. Arterial, venous and pulmonary artery pressure, cardiac output and blood gas values were recorded pre injection and 1, 3, 5 and 10 minutes post injection. Post mortem lungs were harvested and the histopathologic score (percentage of lung fields occupied by intravascular fat globules as seen in the microscope) was calculated.

Results: The sequential injection of bone cement into six vertebral bodies from values pre injection of L1 to 10 minutes post injection of L6 resulted in: significant falls in arterial blood pressure (P< 0.0001), cardiac output (P< 0.0001) (P=0.0049), pO₂ and pH (P< 0.0001) and significant rises in pulmonary arterial pressure (P=0.0005) and pCO₂ (P< 0.0001),but no significant change in central venous pressure. The histopathological score was 19.1±1.94%.

Conclusion: This study clearly shows that multiple VP in sheep leads to FE with major cardiovascular reactions. Arterial blood pressure showed a stepwise, cumulative fall and was clearly the best parameter to demonstrate these reactions. This suggests, in human patients, particular attention should be paid to falls in arterial blood pressure during multiple VP.