Continuous versus intermittent cardioplegia in the presence of a coronary occlusion

Cardioplegia in Open Heart Surgery: Age Matters

INTRODUCTION

Cardioplegia is a pharmacological approach essential for the protection of the heart from ischemia-reperfusion (I-R) injury. Over the years, numerous cardioplegic solutions have been developed, with each cardioplegic approach having its advantages and disadvantages. Cardioplegic solutions can be divided into crystalloid and blood cardioplegic solutions, and an experienced surgeon chooses the type of solution based on the individual needs of patients in order to provide optimal heart protection. Importantly, the pediatric immature myocardium is structurally, physiologically, and metabolically different from the adult heart, and consequently its needs to achieve cardioplegic arrest strongly differ. Therefore, the present review aimed to provide a summary of the cardioplegic solutions available to pediatric patients with a special focus on emphasizing differences in heart injury after various cardioplegic solutions, the dosing strategies, and regimens.

MATERIAL AND METHODS

The PubMed database was searched using the terms cardioplegia, I-R, and pediatric population, and studies that investigated the influence of cardioplegic strategies on markers of cardiac muscle damage were further analyzed in this review.

CONCLUSIONS

A large body of evidence suggested more prominent benefits achieved with blood compared to those with crystalloid cardioplegia in pediatric myocardium preservation. However, standardized and uniform protocols have not been established so far, and an experienced surgeon chooses the type of cardioplegia solution based on the individual needs of patients, while the severity of myocardial damage strongly depends on the type and duration of the surgical procedure, overall patient condition, and presence of comorbidities, etc.

The effect of bupivacaine on myocardial tissue hypoxia and acidosis during ventricular fibrillation

Previously we observed that during bupivacaine-induced circulatory collapse, myocardial tissue pH declined more slowly than expected. Here we evaluated the effect of bupivacaine on myocardial acidosis induced by ventricular fibrillation. Sixteen dogs were anesthetized with 1.5% end-tidal isoflurane, the chest was opened, and a probe that measured oxygen pressure (PmO(2)), carbon dioxide pressure, pH, and temperature was inserted into myocardial tissue. After baseline measures, each dog received either 10 mg/kg bupivacaine (n = 8) or a sham saline treatment (n = 8). Three minutes later ventricular fibrillation was initiated electrically, and the rate of change in PmO(2) and pH during ventricular fibrillation was measured. Baseline physiological measures were similar in the two groups of dogs. During ventricular fibrillation there was a rapid decrease in PmO(2), and the rate of decrease was not different between sham- and bupivacaine-treated dogs. Tissue pH decreased during ventricular fibrillation, and the rate of decrease was 4 times faster in sham- compared with bupivacaine-treated dogs (P < 0.05). These results show that bupivacaine attenuated myocardial tissue acidosis during ventricular fibrillation. This potentially beneficial effect may be a result of bupivacaine's ability to inhibit myocardial lactate and carbon dioxide production. This suggests a potential clinical application of bupivacaine for myocardial preservation.

IMPLICATIONS

In this animal study pretreatment with bupivacaine attenuated the progression of myocardial acidosis during ventricular fibrillation. The dogs regained normal hemodynamic variables after lipid infusion. The findings suggest such that bupivacaine may protect the heart against ischemic acidosis.

Zinc-bis-histidinate preserves cardiac function in a porcine model of cardioplegic arrest

BACKGROUND

We examined the ability of zinc-bis-histidinate to preserve postarrest myocardial function when added to a standard crystalloid cardioplegic solution.

METHODS

Domestic pigs (35 to 50 kg) on left-sided cardiopulmonary bypass were subjected to 90 minutes of regional ischemia followed by 60 minutes of hypothermic cardioplegic arrest induced by antegrade infusion of 20 mL/kg cold St. Thomas' #2 cardioplegic solution with or without 100 mumol/L of zinc-bis-histidinate and maintained by infusion of 10 mL/kg of the same every 20 minutes. During reperfusion function was assessed at 1 and 3 hours over increasing preloads using the right-sided bypass method.

RESULTS

At roller pump flows up to 2,000 mL/min, stroke work index-end-diastolic pressure curves were significantly (p < 0.05) higher and shifted to the left in treated hearts. In a series of pigs, echocardiography was used to determine end-diastolic and end-systolic volumes. At roller pump flows up to 3,500 mL/min, end-systolic pressure-end-systolic volume curves were significantly higher and shifted to the left in treated hearts. Left ventricular ejection fraction, fractional shortening, stroke volume, and cardiac output were significantly (p < 0.05) higher in treated hearts. Electron microscopy revealed that mitochondria in tissue not at risk appeared more swollen in control hearts.

CONCLUSIONS

The results of this study support the conclusion that zinc-bis-histidinate is effective as a myocardial preservative when added to a crystalloid cardioplegic solution.