Cardiac surgical conditions induced by beta-blockade: effect on myocardial fluid balance.
BACKGROUND
Both crystalloid and blood cardioplegia result in cardiac dysfunction associated with myocardial edema. This edema is partially due to the lack of myocardial contraction during cardioplegia, which stops myocardial lymph flow. As an alternative, acceptable surgical conditions have been created in patients undergoing coronary artery bypass operations with esmolol-induced minimal myocardial contraction. We hypothesized that minimal myocardial contraction during circulatory support using either standard cardiopulmonary bypass (CPB) or a biventricular assist device would prevent myocardial edema by maintaining cardiac lymphatic function and thus prevent cardiac dysfunction.


METHODS
We placed 6 dogs on CPB and 6 dogs on a biventricular assist device and serially measured myocardial lymph flow rate and myocardial water content in both groups and preload recruitable stroke work only in the CPB dogs. In all dogs we minimized heart rate with esmolol for 1 hour during total circulatory support.


RESULTS
Although myocardial lymph flow remained at baseline level during CPB and increased during biventricular assistance, myocardial water accumulation still occurred during circulatory support. However, as edema resolved rapidly after separation from circulatory support, myocardial water content was only slightly increased after CPB and biventricular assistance, and preload recruitable stroke work was normal.


CONCLUSIONS
Our data suggest that minimal myocardial contraction during both CPB and biventricular assistance supports myocardial lymphatic function, resulting in minimal myocardial edema formation associated with normal left ventricular performance after circulatory support. The concept of minimal myocardial contraction may be a useful alternative for myocardial protection, especially in high-risk patients with compromised left ventricular function.
Mehlhorn
U
U
Department of Anesthesiology, University of Texas-Houston Medical School 77030, USA.
Allen
S J
SJ
Adams
D L
DL
Davis
K L
KL
Gogola
G R
GR
Warters
R D
RD
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001834:Body Water / Q000378:metabolism; D002315:Cardiopulmonary Bypass / Q000379:methods*; D004285:Dogs; D004487:Edema / Q000517:prevention & control; D005260:Female; D006324:Heart Arrest, Induced / Q000379:methods*; D006339:Heart Rate / Q000187:drug effects; D006353:Heart-Assist Devices; D008196:Lymph / Q000502:physiology; D008208:Lymphatic System / Q000502:physiology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism*; D011412:Propanolamines / Q000494:pharmacology*; D016277:Ventricular Function, Left / Q000502:physiology; D014882:Water-Electrolyte Balance
D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; C036604:esmolol