Abstract 100: Intravenous Calcium as a Pressor After Hypoxic Cardiac Arrest

Background: Resuscitation from hypoxic cardiac arrest presenting with pseudo-electromechanical dissociation (P-EMD) may be associated with hypotension after ROSC. This hypotension may be refractory to catecholamine pressors. Reversing hypotension is critical for stabilizing patients successfully resuscitated from P-EMD, so other therapeutic avenues should be explored. Hypothesis: The post-resuscitation phase after hypoxic pseudo-EMD cardiac arrest may be associated with hypocalcemia. The refractory hypotension may be responsive to intravenous calcium. Methods: Using our hypoxic pseudo-EMD swine model, we measured blood pressure, hemodynamics, and electrolytes after ROSC. In 12 animals with refractory hypotension we administered 37 boluses of intravenous calcium in the dosage range of 5 -20 mg. Physiological data were analyzed on a heartbeat by heartbeat basis. The midpoint of the calcium response was defined using change of curvature feature detection. Hemodynamic parameters were shifted such that the value at the midpoint was equal to zero. Comparisons were made between the average values in the time period 40-35 seconds before the bolus and 35-40 seconds after the bolus. Results: Of the 37 administered boluses, 34 manifested a reaction in the aortic blood pressure. Mean aortic pressure, systolic and diastolic pressures all increased due to the calcium bolus. Aggregating the timepoints in the range -40 s to -36 s and comparing with the timepoints in the range 36 s to 40 s shows that the mean aortic pressure increased 11.2 ± 0.6 mmHg, the systolic pressure increased 16.2 ± 0.8 mmHg, and the diastolic pressure increased 8.0 ± 0.5 mmHg. Conclusions: Resuscitation from hypoxic pseudo-EMD is often associated with hypotension and hypocalcemia. Administration of intravenous calcium is associated with an abrupt pressor-like response. Calcium as a therapeutic in this setting should be further studied.