The St. Thomas' hospital cardioplegic solution: a characterization in two species

Following detailed investigation and definition of some of the critical factors relating to the composition and use of cardioplegic protective solutions, we have formulated the St. Thomas' Hospital cardioplegic solution number 2. This cardioplegic solution (NaCl 110.0 mM, NaHCO3 10.0 mM, KCl 16.0 mM, MgCl2 16.0 mM, CaCl2 1.2 mM, pH 7.8) is designed for routine clinical use combining optimal protection with simplicity of formulation and administration/infusion. In order to characterize the efficacy of this modified solution, experiments have been carried out in two species: the isolated rat heart and the in-situ dog heart. In parallel protocols, hearts were subjected to ischemic arrest of up to 4 hours. Multidose (every 40 minutes) cardioplegic infusion of the St. Thomas' solution combined with topical hypothermia extended the tolerable period of ischemia from less than 30 minutes to about 120 minutes in the rat and from less than 60 minutes to more than 180 minutes in the dog. These conclusions were based on the measurement of functional indices together with biochemical, cellular chemical and ultrastructural assessments. The studies confirmed the additive protective properties of hypothermia and chemical cardioplegia and the utility of the rat heart model in the assessment of protective interventions.