Assessment of iatrogenic fat embolism with Nile red

Abstract

Fat embolism frequently occurs as a consequence of trauma, long bone injury and orthopedic procedures and is known to cause lung, brain and cutaneous lesions. There are currently no standardized laboratory tests for quantifying fat intravasation. This study investigates the use of a lipophilic fluorescent stain (9‐ diethylamino‐5‐benzo[α] phenoxazinone, Nile red) for assessing the fat embolic burden associated with intraosseous infusion of saline into the proximal tibia (N = 14) of swine (Sus scrofa ). After intraosseous cannulation, blood samples were obtained from the common iliac vein at baseline and following saline (0.9% NaCl) infusions (10 ml bolus, infusion at 300 mmHg, and at 0.3–4.0 ml per second). The effluents were centrifuged at 2000 × g for 10 minutes and supernatant aspirated and stained with 200 μl Nile Red (500 μg/ml in acetone). The buffy coat was separated with 8.0μ cellulose filters and lipids quantified by fluorescent imaging (excitation: 480 nm, emission: 535 nm). A >12 fold increase in relative fluorescence was noted with initial saline flush compared with baseline (P<0.05). The relative fluorescence was >20% baseline in 93% of effluent samples during saline infusion at 300 mmHg and at infusion rates ≥1.0 ml per sec. Significant (P<0.05) increases in relative fluorescence were observed with infusion rates of 1.0, 2.0, 3.0 and 4.0 ml per sec. These data suggest that Nile red may prove useful for quantifying iatrogenic fat embolism.