Authors: Aghajani E.¹; Korvald C.²; Nordhaug D.²; Revhaug A.¹; Myrmel T.²

Source: Scandinavian Cardiovascular Journal, Volume 38, Number 3, June 2004 , pp. 187-192(6)

Publisher: Informa Healthcare

Abstract:

Objective--Myocardial oxygen consumption (MVO ₂ ) in the septic myocardium is comparatively high in relation to the sepsis-induced reduction in ventricular work. Our previous studies indicate that this energetic inefficiency is due to increased energy consumption in excitation-contraction (EC) coupling, i.e. myocardial calcium handling.

Design--To further confirm this observation, we assessed the oxygen cost of contractility in anesthetized pigs before and 2 h after induction of endotoxemia (1 g/kg endotoxin infusion over 1 h, Escherichia coli toxin, n=6). Baroreceptor reflexes were blocked by hexamethonium. Contractility was increased by stepwise dopamine infusions at baseline and 2 h after induction of endotoxemia. Oxygen cost of contractility was assessed as the relationship between myocardial contractility (E _es or elastance) and non-mechanical oxygen consumption (unloaded MVO ₂ ), a measure of energy consumption in EC coupling or calcium handling.

Results--Non-mechanical oxygen consumption (unloaded MVO ₂ ) was higher after endotoxin infusions than at baseline (0.641±0.05 vs 0.383±0.07 J/beat/100 g, p < 0.05). The relationship between unloaded MVO ₂ and E _es , constructed by the dopamine response, was highly linear both at baseline and endotoxemia (r ² =0.76-0.99). However, endotoxin increased oxygen cost of contractility by 45% (baseline 0.06±0.03 vs endotoxin 0.09±0.04 J ml/mmHg/beat/100 g).

Conclusion--Acute endotoxemia increases oxygen cost of contractility, a measure of energy consumed in EC coupling or myocardial calcium handling.

Keywords: sepsis; cardiac energetic; myocardium; pigs; oxygen; cost of contractility

Document Type: Research article

DOI: http://dx.doi.org/10.1080/14017430410031164

Affiliations: 1: Department of Digestive Surgery University Hospital North Norway Tromsø Norway 2: Department of Cardiothoracic and Vascular Surgery University Hospital North Norway Tromsø Norway

Publication date: 2004-06-01

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