Risk of low calcium and high magnesium in continuous warm hyperkalemic cardioplegia.
BACKGROUND
The recent introduction of operations on a warm heart has prompted clinical reports on the usefulness of continuous blood cardioplegia, but no in-depth basic evaluation of continuous cardioplegia has been done. The cardioprotective effects of magnesium (Mg) and calcium (Ca) in continuous warm hyperkalemic crystalloid cardioplegic solutions were investigated in an isolated rat heart model.


METHODS
Isolated rat hearts were arrested for 180 minutes at 37 degrees C with a continuous warm hyperkalemic (20 mmol/L) modified Krebs-Henseleit bicarbonate buffer solution containing 1.2, 8.0, or 16.0 mmol/L of Mg and 0.1 to 2.5 mmol/L of Ca in different concentrations. Recovery of cardiac function and tissue damage were estimated.


RESULTS
For each Mg concentration, the percentage recovery of aortic flow generated dose-response curves depending on Ca concentration. However, as Mg concentration increased, the recovery of aortic flow decreased in the groups with 0.5 mmol/L of Ca or less.


CONCLUSIONS
In continuous warm cardioplegia the combination of low Ca and high Mg concentration caused severe cardiac injury, and normal Ca concentration avoids cardiac injury regardless of Mg concentrations.
Nakamura
Y
Y
Second Department of Surgery, Tottori University Faculty of Medicine, Japan.
Kuroda
H
H
Takemoto
N
N
Ohgi
S
S
Mori
T
T
D000818:Animals; D002118:Calcium / Q000097:blood; D002314:Cardioplegic Solutions / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000494:pharmacology; D006324:Heart Arrest, Induced / Q000379:methods*; D006996:Hypocalcemia / Q000097:blood* / Q000473:pathology; D008274:Magnesium / Q000008:administration & dosage / Q000097:blood*; D008297:Male; D008854:Microscopy, Electron; D015428:Myocardial Reperfusion Injury / Q000097:blood / Q000473:pathology; D009206:Myocardium / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D012307:Risk Factors; D013696:Temperature; D014325:Tromethamine / Q000494:pharmacology
D002314:Cardioplegic Solutions; C074097:Krebs-Henseleit solution; D014325:Tromethamine; D008274:Magnesium; D005947:Glucose; D002118:Calcium