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Calcium and cardioplegia. The optimal calcium content for the St. Thomas' Hospital cardioplegic solution
Insights
Optimizing St. Thomas
Area of Science:
- Cardiology
- Biochemistry
- Physiology
Background:
- Cardioplegic solutions are crucial for myocardial protection during cardiac surgery.
- The St. Thomas' Hospital cardioplegic solution is widely used, but its optimal calcium concentration requires precise definition.
- Understanding calcium's role is vital to prevent ischemia-reperfusion injury and the calcium paradox.
Purpose of the Study:
- To determine the optimal calcium chloride concentration in the St. Thomas' Hospital cardioplegic solution for maximal tissue protection.
- To characterize the relationship between calcium concentration and myocardial protection during normothermic ischemic arrest.
- To investigate the consequences of calcium absence and supra-optimal concentrations.
Main Methods:
- Isolated working rat heart preparation subjected to normothermic ischemic arrest.
- Infusion of St. Thomas' Hospital cardioplegic solutions with varying calcium chloride concentrations (0-2.4 mmol/L).
- Measurement of postischemic creatine kinase leakage and aortic flow recovery as indicators of tissue protection.
Main Results:
- Optimal myocardial protection was achieved with a calcium concentration of 1.2 mmol/L.
- Creatine kinase leakage was significantly reduced, and aortic flow recovery was maximized at 1.2 mmol/L calcium.
- A rapid decline in protective efficacy was observed with calcium concentrations deviating from the optimum, including the induction of the calcium paradox with zero calcium.
Conclusions:
- A calcium concentration of 1.2 mmol/L is optimal for the St. Thomas' Hospital cardioplegic solution under normothermic conditions.
- Precise calcium concentration is critical for effective myocardial protection, highlighting the need for dose-response studies.
- This study underscores the importance of optimizing all components of cardioplegic solutions.
Abstract:
The relationship between the calcium content of the St. Thomas' Hospital cardioplegic solution and the degree of tissue protection it affords has been characterized by means of an isolated working rat heart preparation subjected to normothermic ischemic arrest. With a 3 minute period of preischemic infusion of solutions containing calcium chloride concentrations of 0, 0.6, 1.0, 1.1, 1.2, 1.3, 1.4, and 2.4 mmol/L and 35 minutes of normothermic ischemic arrest, postischemic creatine kinase leakage was 562.3 +/- 26.7, 64.8 +/- 12.1, 63.3 +/- 9.9, 37.5 +/- 5.4, 33.4 +/- 3.1, 41.2 +/- 4.1, 58.6 +/- 7.4, and 65.7 +/- 9.1 IU/15 min/gm dry weight, respectively. The postischemic recovery of aortic flow was 0%, 29.2% +/- 6.8%, 29.0% +/- 3.3%, 45.8% +/- 4.9%, 55.5% +/- 1.4%, 38.5% +/- 2.7%, 27.8% +/- 8.6%, and 19.5 +/- 7.1%, respectively. The results indicate optimal protection with a calcium concentration of 1.2 mmol/L and a rapid decline in protection with even small changes in concentration either side of the optimum. The hazard of total absence of calcium was confirmed by the induction of the calcium paradox. This study shows that under normothermic conditions a calcium concentration of 1.2 mmol/L is optimal for the St. Thomas' Hospital solution. This study reinforces the importance of undertaking dose-response studies for all components of all cardioplegic solutions.
