Session VIII - Basic Science

The Physiologic Effects of the Reamer-Irrigator-Aspirator on Fat Embolism Outcome Using a Porcine Model

Robert Y. Wang, MD¹ (*); Michael Blankstein, MSc¹ (*);

Ru Li, MD² (*); Emil H. Schemitsch, MD² (*);

¹University of Toronto, Toronto, Ontario, Canada

²St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada

Purpose: The objective of this study is to investigate the effects of the Reamer-Irrigator-Aspirator (RIA) on fat embolism outcome, as compared to the standard AO reamer, utilizing physiologic parameters as outcome measures.

Methods: All animal procedures were approved by the Animal Care Committee. 15 animal experiments were completed. Following anesthesia, each pig was intubated and ventilated. Initial blood samples were analyzed for proper ventilation and acceptable baseline conditions (PaCO₂ between 35 and 40 mm Hg). One third of the pig's blood volume was withdrawn to simulate hemorrhagic shock. Each animal was kept in a state of hypovolemia for an hour before transfusion and resuscitation. Each pig underwent alternate assignment into either the RIA or AO group. The distal femur was exposed and reamed in a retrograde fashion, followed by cement pressurization with methylmethacrylate. Physiologic measurements included mean arterial pressure (MAP), pulmonary arterial pressure (PAP), partial pressure of arterial oxygen (PaO₂), and cardiac output. Upon completion, the animals were euthanized. The data were analyzed using the SPSS statistical program.

Results: One animal in the AO group expired after cement pressurization associated with profound hypotension, pulmonary hypertension, and eventual cardiac arrest. There was a statistically significant difference for PaO₂ (P = 0.004), cardiac output (P = 0.002), and PAP (P = 0.005) between the AO and RIA groups. That is, by the completion of the experiment, the RIA group had higher PaO₂, lower PAP, and higher cardiac output measurements as compared to the AO group. There was no statistical significance between the two groups with respect to MAP (P = 0.468).

Conclusion: Using established physiologic parameters, there appears to be a difference between the standard AO reamer and the RIA in terms of fat embolism outcome. The RIA showed a more favorable outcome with respect to PAP, PaO₂, and cardiac output. With its simultaneous irrigation and aspiration, the RIA may result in less intramedullary fat being displaced into the systemic circulation.