Protection of the ischemic myocardium: dose-response relationships with glucocorticoids in filtered cardioplegic solutions.
A concentration-responsive study of supplementation with methyl prednisolone sodium succinate (MPSS: 0-10-100-500-1000 mg/l) to a potassium-based crystalloid cardioplegic solution, administered under hypothermic conditions, has been undertaken in the isolated working rat heart. The solution was filtered through a very fine filter (0.22 micron), thereby excluding particles able to increase vascular resistance and reduce postischemic performance. The solution was administered intermittently at a constant flow rate during 180 min of ischemia at 20 degrees C. The per cent postischemic recovery of aortic flow rate for the following concentrations of MPSS was: 0 mg/l 57%; 10 mg/l 49%; 100 mg/l 52%; 500 mg/l 38%; and 1000 mg/l 28%. MPSS supplementation did not improve upon any of the physiological, enzymatic or metabolic (total tissue high-energy phosphates, lactate, glycogen, Ca++) variables. The highest concentrations (500 and 1000 mg/l) of MPSS decreased postischemic performance. The hearts perfused with sodium succinate in a concentration equimolar to MPSS 1000 mg/l recovered less than the hearts subjected to unmodified cardioplegia. It is concluded that MPSS does not confer any additional protection to a potassium-based, calcium-containing crystalloid cardioplegic solution when it is effectively filtered. High concentrations of MPSS may prove toxic to the ischemic myocardium.
D000818:Animals; D001834:Body Water / Q000378:metabolism; D003327:Coronary Disease / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism / Q000503:physiopathology; D003402:Creatine Kinase / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005938:Glucocorticoids / Q000627:therapeutic use*; D006324:Heart Arrest, Induced / Q000295:instrumentation; D008297:Male; D009206:Myocardium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012996:Solutions
D005938:Glucocorticoids; D012996:Solutions; D003402:Creatine Kinase