The effect of total spinal anesthesia on cardiac function in a large animal model of brain death.

Brain death (BD) causes cardiac dysfunction in organ donors, attributable to the catecholamine storm that occurs with raised intracerebral pressure (ICP). However the direct contribution of the spinal sympathetics has not been well described. We examined the effect of total spinal anesthesia (TSA) on cardiac function in a large animal model of BD. Eighteen pigs were allocated to 3 experimental groups: Group 1, the saline-treated control group; Group 2, TSA administered prior to BD; and Group 3, TSA administered 30 min after BD. Inflation of an intracerebral balloon-tipped catheter was used to induce BD. Ventricular function was assessed using a pressure-volume loop catheter and magnetic resonance imaging. Serum catecholamine levels were assessed with high performance liquid chromatography. Inflation of the intracerebral balloon-tipped catheter was associated with a dramatic rise in heart rate and blood pressure, along with increased concentrations of serum epinephrine and norepinephrine. This phenomenon was not observed in Group 2. In Group 1, there was a significant decline in contractility, whereas groups 2 and 3 saw no change. Group 2 had greater contractile reserve than groups 1 and 3. Our data demonstrate the central role of spinal sympathetics in the hemodynamic response to raised ICP. Further work is required to determine the utility of TSA in reversing cardiac dysfunction in BD donors.

Quantitative assessment of cardiac output and left ventricular function by noninvasive phase-contrast and cine MRI: validation study with invasive pressure-volume loop analysis in a swine model.

PURPOSE: To validate noninvasive cardiac output measurements of phase-contrast magnetic resonance imaging (PC-MRI) and cine MRI using an invasive pressure-volume (PV) loop technique on a swine model. MATERIALS AND METHODS: We compared three methods for evaluating cardiac function at rest and under pharmaceutical low-dose inotropic infusion conditions: 1) phase-contrast MRI, 2) cine MRI, and 3) PV loop relationship. These measurements were made in 14 domestic pigs under rest conditions. Identical MRI acquisitions and PV loop analysis were performed on six pigs from the same group that received an infusion of dobutamine 2.5 µg/kg/min. Cardiac outputs from all measurements were analyzed and compared using linear regression and Bland-Altman analysis. RESULTS: Noninvasive PC-MRI and cine MRI did not show any significant differences compared to an invasive PV loop technique for measurement of cardiac output under both rest (PC-MRI, cine MRI, and PV loop, 3.17 ± 0.45, 3.18 ± 0.61, 3.45 ± 0.41 L/min, respectively) and pharmaceutical low-dose inotropic infusion conditions (PC-MRI, cine MRI, and PV loop, 4.78 ± 0.53, 4.7 ± 0.6, 4.96 ± 0.48 L/min, respectively). Statistical analysis showed good agreement of cardiac output measurements at rest (R(2) = 0.83) and under low-dose inotropic infusion conditions (R(2) = 0.74) using PC-MRI and PV loop techniques. Cardiac output measurement using cine MRI and PV loop techniques also showed good agreement at rest (R(2) = 0.85) and under low-dose inotropic infusion conditions (R(2) = 0.76). Furthermore, cardiac outputs determined with the three modalities showed good agreement over a wide range of heart rates (90-180 bpm). CONCLUSION: MRI can provide a reliable, noninvasive measurement of cardiac output that can be carried out without the complications that are inherent with current invasive procedures.