Increase in myocardial interstitial adenosine and net lactate production in brain-dead pigs : An in vivo microdialysis study

Brain death-related cardiovascular dysfunction has been documented; however, its mechanisms remain poorly understood. We investigated changes in myocardial function and metabolism in brain-dead and control pigs. Heart rate, systolic (SAP) and mean (MAP) arterial pressure, left ventricular (LV) dP/dtmax, rate-pressure product, cardiac output (CO), left anterior descending coronary artery blood flow, lactate metabolism, and interstitial myocardial purine metabolite concentrations, monitored by cardiac microdialysis, were studied. A volume expansion protocol was performed at the end of the study. After brain death, a transient increase in heart rate (from 90 [67-120] to 158 [120-200] beats/min) (median, with range in brackets), MAP (82 [74-103] to 117 [85-142] mmHg), LV dP/dtmax (1750 [1100-2100] to 5150 [4000-62,000] mmHg x sec(-1), rate-pressure product (9100 [7700-9700] beats mmHg/min to 22,750 [20,000-26,000] beats mmHg/min), CO (2.2 [2.0-4.0] to 3.3 [3.0-6.0] L/min), and a limited increase in left anterior descending coronary artery blood flow (40 [30-60] to 72 [50-85] ml/min) were observed. Net myocardial lactate production occurred (27 [4-40] to -22 [-28, -11] mg/L, P