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Eur J Cardiothorac Surg 2001;20:170-176
© 2001 Elsevier Science NL
Department of Cardiac Surgery, University of Heidelberg, Im Neuenheimer Feld 110, Heidelberg, 69120, Germany
Received 6 November 2000; received in revised form 21 February 2001; accepted 30 March 2001.
Corresponding author. Tel.: +49-6221-566111; fax: +49-6221-565585
e-mail: dzsi{at}hotmail.com
Objective: To test the hypothesis that altered loading conditions play a key role in hemodynamic instability and cardiac dysfunction in the brain dead (BD) organ donor. Methods: BD was induced by inflation of a subdural balloon catheter. In the first part of the study, left ventricular function was assessed in a canine in situ cross-circulated heart model (n=6). Pre- and afterload and coronary perfusion pressure were kept identical in all hearts throughout the experiment. In the second part of the study, hearts (n=6) were investigated in vivo allowing the interaction between left ventricular contractility and arterial load. Left ventricular pressurevolume loops were obtained by a combined conductance-pressure catheter and the slope of the endsystolic pressurevolume relationship (Ees), arterial elastance (Ea), stroke work (SW), pressurevolume area, ventriculo-arterial coupling ratio (VAC) and mechanical efficiency (Eff) were calculated. Results: Induction of BD led to a hyperdynamic response in both models with a significant increase of most hemodynamic parameters. In the in situ isolated heart model, left ventricular contractility returned to baseline without any further deterioration. In contrast, in the intact circulation the hemodynamic parameters declined significantly in comparison to baseline 4 h after BD (Ees: 4.07±0.51 vs. 8.06±1.09 mmHg/ml, P<0.05, Ea: 3.17±0.39 vs. 4.42±0.30 mmHg/ml, P<0.05). However, VAC (0.78±0.09 vs. 0.65±0.14 n.s.) and Eff (73.4±2.1 % vs. 76.8±3.7 %, n.s.) remained constant over the time. Conclusion: BD induction leads to an initial hyperdynamic reaction followed by hemodynamic instability. The facts that no cardiac dysfunction occurred if loading conditions were kept constant and the ventriculoarterial coupling ratio and mechanical efficiency remained constant in the intact animal model indicate that decreased contractility reflects to decreased arterial elastance after brain death. Therefore, reduced contractile function after brain death at a decreased afterload may contribute to stroke work optimization.
Key Words: Brain death Contractility Afterload Ventriculo-arterial coupling
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