PULMONARY MICROVASCULAR FAT - THE SIGNIFICANCE

Objective: To determine the effects of fat emboli on cardiopulmonary f unction in critically ill patients. Design: A prospective study. Setti ng: Tertiary referral medical/surgical shock/trauma intensive care uni t (ICU). Patients: A total of 51 critically ill medical and surgical ( including acute trauma) patients who required supplemental oxygen (FIO 2 of greater-than-or-equal-to 0.35) to maintain arterial blood oxyhemo globin saturation of greater-than-or-equal-to 90% and who had 62 pulmo nary artery catheters placed for patient care reasons. Interventions: Pulmonary capillary blood samples were obtained via the pulmonary arte ry catheters in the ''wedged position'' at insertion and postinsertion at 8, 24, 48, and 72 hrs. Cytospun smears of the buffy coat aspirates of these samples were made and were stained with Oil Red-O for fat. M easurements and Main Results. One investigator, without knowledge of t he patients' cardiopulmonary function, examined all smears and graded them 0 to 4+ for amount of fat. Fat scores were correlated with chest radiograph appearance, hemodynamic and respiratory parameters, complet e blood cell counts with differential white blood cell counts, whether the patient was receiving lipid-containing parenteral nutrition, prin cipal organ system failure, and reason for ICU admission. Samples from 27 pulmonary artery catheter insertions had no fat, 13 samples had lo w-grade (1+) episodic fat, and 22 samples had repeated episodes of gre ater-than-or-equal-to 2+ fat or isolated episodes of 4+ fat. There was a significant association between the amount of pulmonary microvascul ar fat and trauma as the reason for ICU admission. Of the other parame ters, only chest compliance and body temperature showed unequivocal si gnificant associations. These associations were opposite to the expect ed findings, but would support a conclusion that fat emboli did not ca use the observed cardiopulmonary dysfunction. The inconsistent associa tions for the FIO2, PCO2, and mixed venous blood oxyhemoglobin saturat ion may be random events. Conclusion: Cardiopulmonary dysfunction comm only attributed to fat emboli is likely due to other causes.