Abstract
Release of fat and bone marrow during medullary pressurisation leads to fat embolism and pulmonary hypertension resulting in serious cardiorespiratory complications. This study aimed to determine whether pre-treatment with the phosphodiesterase type 5-inhibitor, Sildenafil, prevents pulmonary artery hypertension in an animal model. The animals either received Sildenafil (5 mg kg-1) or saline intra peritoneally 15 minutes prior to medullary pressurisation with bone cement. Cardiovascular parameters were recorded throughout the procedure. At the end radiopaque contrast was injected into the pulmonary circulation; the lungs were then harvested and imaged using micro CT. Medullary pressurisation in the control animals caused pulmonary hypertension and systemic hypotension. This was associated with a decrease in the area of perfusion of the lungs. These changes were attenuated by pretreatment with Sildenafil. We conclude that in this animal model fat embolism causes similar cardiovascular changes as observed in clinical practice and pretreat- ment with Sildenafil attenuates these effects.
Highlights
Fat is regularly displaced from the medullary cavity during orthopaedic surgery [1] and during fracture treatment or joint replacement. [1] The fat enters the circulation and has profound effects on the cardiorespiratory system, both acutely [2] and secondarily leading to respiratory failure as part of fat embolism syndrome
Previous studies from this research group have shown fat emboli released into the circulation during vertebroplasty, in a sheep model, leading to a rapid decrease in cardiac output and arterial blood pressure, and an increase in pulmonary artery pressure (PAP). [3,4,5] The increase in PAP is thought to be a result of the vasoactive properties of the emboli and the mechanical obstruction of the smaller blood vessels in the lungs. [6,7]
The main outcome of this study is that pre-treatment with the phosphodiesterase type 5 (PDE5) inhibitor, Sildenafil, significantly attenuated the increase in PAP resulting from fat emboli generated by bilateral femur cement augmentation in the rat
Summary
Fat is regularly displaced from the medullary cavity during orthopaedic surgery [1] and during fracture treatment or joint replacement. [1] The fat enters the circulation and has profound effects on the cardiorespiratory system, both acutely [2] and secondarily leading to respiratory failure as part of fat embolism syndrome. The major advantages of this model are that it is possible to have one person carry out the surgery and postoperative monitoring, and that it allows a more complete sampling of tissues, unlike in sheep, where only a small sample of tissue is taken, which may lead to selection bias. Using this rat model allows the entire lung to be imaged using micro CT, which wouldn’t be possible in a larger animal
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