Continuous addition of adenosine with a micropump system improves warm whole blood cardioplegia.
BACKGROUND
Micropump additive systems allow for continuous modification of cardioplegia composition during heart surgery. Although the use of such systems in warm heart surgery is theoretically desirable, the role of the systems has been clinically limited by coronary vasoreactivity with higher potassium concentration and unreliable mechanical arrest at lower potassium concentration. Adenosine, a potent coronary vasodilator and arresting agent, has the potential to reduce the potassium concentration required for arrest and to improve distribution of cardioplegia. However, clinical use of adenosine has been limited by a short half-life in blood and difficulty in titrating the dose. This study tested the hypothesis that continuous addition of adenosine with an in-line linear micropump system would facilitate whole blood hyperkalemic perfusion for cardiac surgery.


METHODS
Canine hearts (n = 9) were randomized to 20 minutes of arrest with whole blood cardioplegia or cardioplegia with adenosine at either low (0.5 M) or high (8 M) concentration. Potassium was supplemented at an arresting dose (24 mEq/L) for 5 minutes and then at a maintenance dose (6 mEq/L) for an additional 15 minutes. Coronary flow was held constant (4 mL/kg per minute), and aortic root pressure was measured. Myocardial performance was assessed by measurement of the end-diastolic pressure to stroke volume relationship at constant afterload. Myocardial tissue perfusion was evaluated with colored microspheres.


RESULTS
During the initial period of high-concentration potassium arrest, coronary resistance rose progressively regardless of adenosine addition. Coronary resistance remained elevated during the period of low potassium perfusion, except when high-concentration adenosine was added. With addition of 8 M adenosine, coronary resistance returned to baseline, and left ventricular endocardial perfusion was augmented. Electromechanical quiescence improved with adenosine perfusion and was complete with high-dose adenosine addition. Function was preserved in all hearts.


CONCLUSIONS
Use of a modern micropump system allowed for continuous addition of adenosine and potassium to whole blood cardioplegia. Adenosine minimized potassium-induced coronary vasoconstriction and improved endocardial perfusion and mechanical quiescence. These findings supported addition of adenosine to the perfusate during warm whole blood cardioplegia.
Agnihotri
Arvind K
AK
Cardiac Surgical Unit, Department of Surgery, Massachusetts General Hospital, Boston, Massachusetts, USA. Aagnihotri@partners.org
Recanati
Maurice-Andre
MA
White
Jennifer K
JK
Titus
James
J
Fischer
Jonathan I
JI
Schon
Jennifer
J
Torchiana
David F
DF
D000241:Adenosine / Q000008:administration & dosage*; D000818:Animals; D002314:Cardioplegic Solutions / Q000008:administration & dosage*; D002315:Cardiopulmonary Bypass; D003326:Coronary Circulation; D004285:Dogs; D005260:Female; D006324:Heart Arrest, Induced / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D007260:Infusion Pumps; D008297:Male; D009200:Myocardial Contraction; D011188:Potassium / Q000008:administration & dosage* / Q000097:blood; D013997:Time Factors; D014655:Vascular Resistance; D014665:Vasodilator Agents / Q000008:administration & dosage*; D016277:Ventricular Function, Left / Q000502:physiology
D002314:Cardioplegic Solutions; D014665:Vasodilator Agents; D000241:Adenosine; D011188:Potassium