Initial reperfusion with magnesium after cardioplegic arrest attenuates myocardial reperfusion injury.
BACKGROUND
Magnesium's effect on calcium ion concentrations may attenuate myocardial reperfusion injury. The aim of this study was therefore to investigate the effects on the recovery of myocardial function of initial reperfusion with varying Mg(2+) concentrations following cardioplegic arrest.


METHODS
Isolated guinea pig hearts underwent 3.5 hours of cardioplegic arrest in St. Thomas Hospital II solution (STH) or Bretschneider HTK solution (HTK) at 24 degrees C. Control hearts were reperfused with normal Krebs-Henseleit solution (KHS). In the therapy groups, hearts were initially reperfused with 5, 10, or 20 mM Mg(2+) for 15 minutes, followed by 30 minutes of perfusion with KHS.


RESULTS
During initial reperfusion, elevated Mg(2+) concentrations markedly reduced rate-pressure product, dP/dt and O 2 demand. Release of LDH and CK was reduced in the therapy groups pretreated with Bretschneider HTK. After Mg(2+) washout, left ventricular function recovery and compliance was improved after HTK but not after STH cardioplegia. Following both STH and HTK cardioplegia, Mg(2+) reperfusion reduced reperfusion arrhythmias.


CONCLUSIONS
The combination of HTK cardioplegia with 15 min initial Mg(2+) (5 and 10 mM, but not 20 mM) reperfusion was clearly superior to HTK followed by immediate Krebs-Henseleit reperfusion as well as STH cardioplegia with or without initial Mg(2+) reperfusion. The high Mg(2+) concentrations in the STH solution might mask beneficial effects of Mg(2+) reperfusion.
Fuchs
F
F
Institute for Surgical Research, Ludwig-Maximilians-Universität München, Germany.
Messmer
K
K
Kuppe
H
H
Habazettl
H
H
D000818:Animals; D001639:Bicarbonates; D002122:Calcium Chloride; D002314:Cardioplegic Solutions; D003402:Creatine Kinase / Q000097:blood; D005947:Glucose; D006168:Guinea Pigs; D006324:Heart Arrest, Induced; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000097:blood; D008274:Magnesium / Q000008:administration & dosage*; D008353:Mannitol; D015428:Myocardial Reperfusion Injury / Q000628:therapy*; D011189:Potassium Chloride; D011343:Procaine; D012965:Sodium Chloride
D001639:Bicarbonates; C039984:Bretschneider cardioplegic solution; D002314:Cardioplegic Solutions; C041711:St. Thomas' Hospital cardioplegic solution; D008353:Mannitol; D012965:Sodium Chloride; D011343:Procaine; D011189:Potassium Chloride; D007770:L-Lactate Dehydrogenase; D003402:Creatine Kinase; D008274:Magnesium; D005947:Glucose; D002122:Calcium Chloride