Continuous versus intermittent warm blood cardioplegia: functional and energetics changes.
BACKGROUND
The aim of this study was to compare the protective effects of continuous warm blood cardioplegia (CWBC) and intermittent warm blood cardioplegia (IWBC) in an experimental model of blood-perfused, isolated rabbit heart.


METHODS
In the CWBC group, cardiac arrest was induced by continuous infusion of blood cardioplegia (10 mEq/L KCl) followed by 30 minutes of reperfusion with blood. In the IWBC group, after 5 minutes of perfusion with blood cardioplegia (10 mEq/L KCl), coronary flow was abolished for 10 minutes, followed by reperfusion with blood cardioplegia for 5 minutes. This sequence was repeated three times for a total period of 45 minutes. Finally the hearts were reperfused for 30 minutes with blood.


RESULTS
Infusion of potassium induced a marked increase in coronary perfusion pressure (from 50 +/- 3 to 98 +/- 1 mm Hg; p < 0.01), which remained elevated throughout in the CWBC group, whereas in the IWBC group, it dropped to 0 during each no-flow period. In both groups, cardioplegia resulted in a significant reduction in oxygen consumption (from 5.5 +/- 0.2 to 0.6 +/- 0.03 mL O2.min-1.100 g-1 wet wt; p < 0.01). During CWBC, glucose extraction was significantly reduced (from 152 +/- 10 to 64 +/- 18 micrograms.min-1.g-1 wet wt; p < 0.01). Free fatty acid uptake and creatine kinase and lactate release were not affected. During IWBC, in contrast, a transient but significant release of creatine kinase (from 643 +/- 254 to 2,234 +/- 296 mU.min-1.g-1 wet wt; p < 0.01) and lactate (from 63 +/- 22 to 374 +/- 32 micrograms.min-1.g-1 wet wt; p < 0.01) occurred after each period of ischemia. Despite these metabolic differences, both cardioplegic procedures allowed a prompt and complete recovery of mechanical function and tissue content of high-energy phosphates.


CONCLUSIONS
Both CWBC and IWBC exert optimal protection in the isolated blood perfused rabbit heart. Thus, IWBC can be safely used to improve visualization of the surgical field.
Torracca
L
L
Divisione di Cardiochirurgia, Spedali Civili, Brescia, Italy.
Pasini
E
E
Curello
S
S
Ceconi
C
C
Coletti
G
G
Alfieri
O
O
Solfrini
R
R
Ferrari
R
R
D000227:Adenine Nucleotides / Q000378:metabolism; D000818:Animals; D001769:Blood; D001794:Blood Pressure; D003326:Coronary Circulation; D003402:Creatine Kinase / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006324:Heart Arrest, Induced / Q000379:methods*; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D011817:Rabbits; D013696:Temperature; D016277:Ventricular Function, Left
D000227:Adenine Nucleotides; D005230:Fatty Acids, Nonesterified; D019344:Lactic Acid; D003402:Creatine Kinase; D005947:Glucose