Beta-adrenergic receptor antagonism preserves myocardial function after brain death in a porcine model.
BACKGROUND
Cardiac dysfunction after brain death decreases the already limited number of potential donors for cardiac transplantation. Acute beta-adrenergic receptor (betaAR) desensitization after the brain death-associated catecholamine surge is an important mechanism. We hypothesized that acute betaAR antagonism could improve myocardial function after brain death by preserving betaAR signaling.


METHODS
Pigs were randomly assigned to three study groups (n = 5): sham; brain death; and brain death with betaAR antagonist (200 microg/kg/min esmolol), 30 minutes before brain death until 45 minutes after brain death. Functional data were collected for 6 hours after brain death and tissues procured.


RESULTS
Compared with baseline, pre-load recruitable stroke work (PRSW), a pre-load-independent measure of systolic function (21.4 +/- 7.5 vs 43.3 +/- 6.8, slope of regression line during vena caval occlusion, p < 0.001), diastolic function (Tau, 101 +/- 54.7 vs 36.4 +/- 5.4 ms, p = 0.03) and systemic oxygen delivery (151 +/- 79.7 vs 298 +/- 78.7 ml/min, p < 0.001) deteriorated in untreated animals at 6 hours after brain death. In contrast, betaAR antagonist maintained baseline systolic function (PRSW, 37.8 +/- 5.6 vs 38.2 +/- 4.7, slope of regression line during vena caval occlusion, p = 0.92), diastolic function (Tau, 32.6 +/- 5.1 vs 48.5 +/- 28.3 ms, p = 0.57) and oxygen delivery (427 +/- 116 vs 397 +/- 98.8 ml/min, p = 0.36) at 6 hours after brain death. betaAR antagonist preserved betaAR signaling, as demonstrated by similar left ventricular (LV) basal (55.4 +/- 32.8 vs 58.8 +/- 10.9 pmol/mg/min, p = 0.40) and isoproterenol-stimulated (125 +/- 70.5 vs 124 +/- 52.0 pmol/mg/min, p = 0.49) adenylate cyclase activity at 6 hours after brain death, upon comparing betaAR antagonist and sham treatment groups. Both LV basal and isoproterenol-stimulated adenyl cyclase activity were higher with betaAR antagonist (25.9 +/- 4.8 pmol/mg/min, p = 0.03) than with untreated brain death (55.6 +/- 17.3 pmol/mg/min, p = 0.02).


CONCLUSIONS
Beta-adrenergic receptor antagonism before brain death preserves cardiac function by preventing betaAR desensitization. This therapy in potential donors might increase the number of organs available for transplantation.
McLean
Kelly M
KM
Division of Cardiothoracic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.
Pandalai
Prakash K
PK
Pearl
Jeffrey M
JM
Bulcao
Christian F
CF
Lyons
Jefferson M
JM
Wagner
Connie J
CJ
Akhter
Shahab A
SA
Duffy
Jodie Y
JY
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001926:Brain Death / Q000503:physiopathology*; D004195:Disease Models, Animal; D006339:Heart Rate / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D009926:Organ Preservation; D011336:Probability; D011412:Propanolamines / Q000494:pharmacology*; D011897:Random Allocation; D011943:Receptors, Adrenergic, beta / Q000187:drug effects; D012680:Sensitivity and Specificity; D013552:Swine; D013997:Time Factors; D016277:Ventricular Function, Left / Q000187:drug effects* / Q000502:physiology
D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C036604:esmolol