Myocardial Metabolism 8 Hours After Coronary Surgery: Effects of Dopamine

Abstract

Myocardial substrate metabolism is abnormal in the early period after cardiac surgery. Myocardial uptake of substrates remains restricted 6 hours postoperatively and cannot match the demand during periods of increased energy requirements. We investigated the relationship between myocardial oxidative rate and substrate uptake in 22 men c. 8 hours after coronary surgery. Myocardial energy demand was raised experimentally by infusing dopamine. The influence of selective beta 1-blockade was analyzed. The uptake of free fatty acids dominated (34.74 +/- 8.83 mmol/min*10(-3) and sufficed to explain the oxygen consumption in basal postoperative conditions (0.468 +/- 0.051 mumol/min) and during amplified energy requirements (0.881 +/- 0.117, r = 0.71). Although the capacity to adjust substrate uptake to energy requirements thus was regained, the uptake of glucose and of lactate (6.14 +/- 13.13 and 2.29 +/- 20.31 mmol/min*10(3) respectively) was marginal, which may be important for ischaemic tolerance. Metoprolol influenced oxygen consumption during amplified adrenergic activity, but did not markedly affect substrates.

Myocardial interstitial glucose and lactate before, during, and after cardioplegic heart arrest

“…Research in this area has focused mainly on the pre-and immediately postoperative situations, and various studies on plasma sampling techniques have been published (1,5,17), including single-and multiple-isotope balance studies (24,38,44). Some (5,36,37,39), but not all (31), investigators have demonstrated decreased cardiac uptake and oxidation of glucose and lactate in the initial postoperative period.…”