Beta-blockade as an alternative to cardioplegic arrest during cardiopulmonary bypass.
BACKGROUND
As an alternative to cardioplegic arrest, cardiac surgical conditions have been produced using beta-blocker-induced minimal myocardial contraction (MMC) during cardiopulmonary bypass. The technique of MMC involves the use of high-dose intravenous esmolol to suppress myocardial chronotropy and inotropy sufficiently to produce cardiac surgical conditions. The purpose of this study was to compare conventional crystalloid cardioplegic arrest with MMC in terms of ischemia avoidance, myocardial edema formation, and cardiac function.


METHODS
Twelve dogs were placed on cardiopulmonary bypass. Six dogs were subjected to crystalloid cardioplegic arrest for 2 hours. Surgical conditions were produced in the other 6 dogs for 2 hours using intravenous esmolol without aortic clamping or cardioplegia. Arterial and coronary sinus lactate concentrations were determined as a gauge of myocardial ischemia. Myocardial water content was determined using microgravimetry and preload recruitable stroke work was determined using sonomicrometry and micromanometry.


RESULTS
Significant lactate washout was demonstrated after cardioplegic arrest but not after MMC. Myocardial water content was significantly less during and after MMC compared with cardioplegic arrest (p < 0.05). Preload recruitable stroke work was decreased compared with baseline values in both groups (p < 0.05).


CONCLUSIONS
In contrast to a previous study that involved 1 hour of MMC, in this study, ventricular function was decreased to the same extent as with cardioplegic arrest after 2 hours of MMC. This was attributed to the accumulation of ASL-8123, the primary metabolite of esmolol, which possesses beta-antagonist properties. Although postbypass ventricular function is similar in both groups, MMC appears to be superior in terms of ischemia avoidance and myocardial edema formation.
Warters
R D
RD
Center for Microvascular and Lymphatic Studies, Department of Anesthesiology, University of Texas-Houston Medical School, 77030, USA. dwarters@anes1.med.uth.tmc.edu
Allen
S J
SJ
Davis
K L
KL
Geissler
H J
HJ
Bischoff
I
I
Mutschler
E
E
Mehlhorn
U
U
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D000818:Animals; D001834:Body Water / Q000737:chemistry; D002314:Cardioplegic Solutions / Q000627:therapeutic use; D002315:Cardiopulmonary Bypass; D003331:Coronary Vessels; D000077324:Crystalloid Solutions; D004285:Dogs; D004489:Edema, Cardiac / Q000378:metabolism / Q000517:prevention & control; D005260:Female; D006321:Heart / Q000187:drug effects; D006324:Heart Arrest, Induced; D006339:Heart Rate / Q000187:drug effects; D007262:Infusions, Intravenous; D007275:Injections, Intravenous; D007552:Isotonic Solutions; D007773:Lactates / Q000097:blood; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D017202:Myocardial Ischemia / Q000097:blood / Q000517:prevention & control; D009206:Myocardium / Q000737:chemistry; D010952:Plasma Substitutes / Q000627:therapeutic use; D011412:Propanolamines / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D013318:Stroke Volume / Q000187:drug effects; D016277:Ventricular Function, Left / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D002314:Cardioplegic Solutions; D000077324:Crystalloid Solutions; D007552:Isotonic Solutions; D007773:Lactates; D010952:Plasma Substitutes; D011412:Propanolamines; C055582:ALS 8123; C036604:esmolol