“Initial, Continuous and Intermittent Bolus” Administration of Minimally-Diluted Blood Cardioplegia Supplemented with Potassium and Magnesium for Hypertrophied Hearts☆

Background

Hypertrophied hearts are subject to the deleterious effects of intraoperative ischemia–reperfusion, and stable maintenance of myocardial cardioplegic arrest is essential. Continuous cardioplegia infusion appears an ideal modification to overcome this issue, except for a large amount of crystalloid solution infused into the myocardium. We previously introduced “initial, continuous and intermittent bolus” administration of minimally-diluted blood cardioplegia (mini-BCP) supplemented with potassium and magnesium, and this study was designed to elucidate its efficacy in patients with hypertrophied hearts.

Methods

Thirty patients (M:F=17:13, 69.2±7.8 years) with left ventricular mass index greater than 150g/m² who underwent aortic valve replacement between 1996 and 2002 were enrolled, and were allocated to one of the two groups. The same infusion protocol was used for both groups as follows: initial and intermittent (every 20min) BCP was antegradely infused for 2min at the rate of 200mL/min, and continuous retrograde BCP flow rate was set at 60–100mL/min. Group C (n=15) received 4:1-diluted BCP modified with Buckberg solution, and Group M (n=15) were given mini-BCP supplemented with potassium (initial/others: 15.4/9.8mEq/L) and magnesium (initial/others: 6.5/4.0mEq/L).

Results

Stable cardioplegic arrest was maintained in all study patients, and total amount of crystalloid solution as cardioplegia was lesser in Group M (79.4±27.5mL) than in Group C (937.3±372.1mL, p<0.01). Group M showed a higher incidence of spontaneous heartbeat recovery after aortic unclamping (13 versus 6, p<0.05) and a lower incidence of postoperative atrial fibrillation (0 versus 5, p<0.05). Postoperatively, maximum dopamine dose (3.35±2.27μg/kg/min versus 5.49±2.30μg/kg/min, p<0.05) and peak plasma creatine kinase-myocardial band (CK-MB) (21.7±7.2IU/L versus 28.8±8.4IU/L, p<0.05) were lower in Group M. Early postoperative echocardiography revealed a lower incidence of paradoxical ventricular septal motion (M versus C; 3 versus 10, p<0.05) and greater left ventricular ejection fraction (M versus C; 70.7±4.0% versus 67.0±5.3%, p<0.05) in Group M.

Conclusions

These results suggest that “initial, continuous and intermittent bolus” administration of mini-BCP, supplemented with potassium and magnesium, is a novel modification for patients with hypertrophied hearts in terms of simplifying the maintenance of cardioplegic arrest with beneficial myocardial protective effects.

Keywords: Cardioplegia minimally diluted, Potassium, Magnesium, Continuous and intermittent administration, Hypertrophy