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Published on: September 6, 2013
Effects of high plasma epinephrine and Ca2+ concentrations on neonatal myocardial function after ischemia
J Caspi1, J G Coles, L N Benson
1Division of Cardiovascular Surgery, Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
Low calcium concentrations in cardioplegic solutions protect neonatal hearts from reperfusion injury. This study found that reduced calcium levels better preserve left ventricular function in young piglets after cardiac arrest, even with epinephrine exposure.
Area of Science:
- Cardiology
- Neonatal Physiology
- Cardiovascular Surgery
Background:
- Neonatal hearts are susceptible to reperfusion injury due to immature sarcoplasmic reticulum and potential catecholamine potentiation.
- Catecholamine administration may exacerbate injury by increasing transsarcolemmal calcium influx in immature hearts.
Purpose of the Study:
- To investigate the impact of modified serum ionized calcium (Ca2+) concentrations in cardioplegic solutions and perfusate on postischemic left ventricular function in neonatal piglets.
- To assess the combined effects of epinephrine administration and varying calcium concentrations on neonatal heart recovery after ischemia.
Main Methods:
- 25 piglets (5-7 days old) underwent 90 minutes of cold blood cardioplegic arrest.
- Piglets were divided into four groups based on perfusate calcium concentration (1.2 mmol/L or 0.25 mmol/L) and epinephrine administration.
- Left ventricular function was evaluated using a conductance catheter to measure pressure-volume relationships during vena caval occlusion.
Main Results:
- Lower perfusate calcium concentrations (0.25 mmol/L) significantly preserved left ventricular systolic and diastolic function post-ischemia compared to normal concentrations (1.2 mmol/L).
- Epinephrine administration before ischemia increased chamber stiffness, an effect mitigated by low calcium perfusate.
- Adenosine triphosphate stores were better preserved in low calcium groups (18%) versus normal calcium groups (48%) after ischemia.
Conclusions:
- Low calcium concentrations in perfusate and cardioplegic solutions are crucial for preserving left ventricular function in neonatal hearts subjected to ischemia and reperfusion.
- This strategy is effective in both normal and epinephrine-stressed neonatal hearts, offering a protective approach against cardiac injury.
Abstract:
Administration of catecholamines to newborn infants may potentiate reperfusion injury because of increased transsarcolemmal Ca2+ influx and the presence of less developed sarcoplasmic reticulum in the immature hearts. We investigated the effect of administration of epinephrine (1.5 micrograms/kg per minute for 120 minutes) before ischemia and modified serum ionized Ca2+ concentrations in the cardioplegic solution and perfusate on postischemic left ventricular systolic and diastolic function in 25 piglets (5 to 7 days old) undergoing 90 minutes of cold blood cardioplegic arrest. The piglets were divided into four groups; Ca2+ 1.2 mmol/L, group A (n = 6), Ca2+ 0.25 mmol/L, group B (n = 6), Ca2+ 1.2 mmol/L and epinephrine, group C (n = 6), Ca2+ 0.25 mmol/L and epinephrine, group D (n = 7). Left ventricular function was assessed by a conductance catheter in the left ventricle measuring end-systolic and end-diastolic pressure-volume relationships during transient vena caval occlusion. By analysis of covariance, only Ca2+ concentration was important in predicting ventricular function recovery after ischemia (p < 0.01). End-systolic elastance decreased in all groups after ischemia; the magnitude was significantly greater in the normal groups (51% versus 35%, p < 0.01). There was a significant increase in the chamber stiffness index after administration of epinephrine before ischemia (p < 0.05). Groups with low Ca2+ perfusate (B and D) had no change in chamber stiffness index after ischemia. In contrast, there was a significant increase in chamber stiffness in the normal Ca2+ groups with (C) or without (A) epinephrine after ischemia (p < 0.05). Adenosine triphosphate stores declined significantly in the normal Ca2+ groups--48% versus 18% in the low Ca2+ groups (p < 0.01). We conclude that low Ca2+ concentrations in the perfusate and cardioplegic solutions better preserve left ventricular function in the normal and in epinephrine-stressed neonatal heart after ischemia.
