Abstract 329: High Volume Femoral Vein Infusion Significantly Increases EtCO2 During Prolonged CPR

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Introduction: Animal research has suggested that inducing therapeutic hypothermia during the arrest period (e.g. during chest compressions) may provide more benefit than inducing hypothermia after return of spontaneous circulation. Hypothermia induction technologies can be divided into two classes: technologies that require volume infusions, and technologies that do not. We hypothesize that a prolonged cold volume infusion during ongoing CPR will alter CPR hemodynamics, particularly venous return of blood to the heart. Methods: Eighteen temperatures were monitored in 24 domestic swine (~30 Kg) during intra-arrest hypothermia induction with ongoing CPR. Mechanical chest compressions and hypothermia induction were started after ten minutes of untreated VF. Chest compressions were performed at a rate of 100 per minute and a depth of 1.25 inches for 60 minutes. Hypothermia induction techniques included: control, femoral vein cold saline infusion, femoral vein ice slurry infusion, carotid cold saline infusion, carotid ice slurry infusion, nasopharyngeal cooling, heat exchange catheter cooling, and blanket cooling. The experiment was terminated after 60 minutes of chest compressions and cooling. Results: 3 Liter femoral vein (FV) infusions of cold saline and ice particulate slurry at a rate of ~ 75 ml/min significantly increased EtCO2 during CPR at times 20-30 min (ETCO2_FV = 29.63 mmHg vs. ETCO2 = 22.16 mmHg, p<0.05), 30-40 min (ETCO2_FV = 23.8 mmHg vs. ETCO = 13.94 mmHg, p<0.05), and 40-50 min (ETCO2_FV = 20.07 mmHg vs. ETCO2 = 10.69 mmHg, p<0.05), with a trend toward significance at 50-60 min (ETCO2_FV = 16.84 vs. ETCO2 = 8.26, p = 0.056). Carotid infusions of similar volumes at similar rates did not improve ETCO2 during prolonged CPR. Conclusions: High volume femoral infusions administered during CPR significantly increased measured values of ETCO2. While not definitive, this data supports the hypothesis that imposing a volume driven flow in the femoral vein during CPR improves venous return. Interestingly, imposing a similar flow through the carotid artery did not increase measured values of ETCO2. The interplay between volume infusions and chest compression generated blood flow requires further study.