Terminal magnesium cardioplegia: protective effect in the isolated rat heart model using calcium accentuated ischemic damage

Magnesium substitution in elective coronary artery surgery: a double-blind clinical study

Magnesium may be beneficial in the control of ventricular ectopy and supraventricular tachyarrhythmias after coronary artery bypass graft (CABG) surgery, but it is not known whether a high-dose magnesium regimen is superior to a regimen keeping the patient normomagnesemic. A prospective randomized and double-blind clinical comparison was performed in 81 elective CABG patients in order to assess the effects of two different magnesium infusion regimens on electrolyte balance and postoperative arrhythmias. Forty-one patients (high-dose group, H) received 4.2 +/- 0.7 g (mean +/- SD), of magnesium sulfate before cardiopulmonary bypass, followed by an infusion of 11.9 +/- 2.8 g of magnesium chloride until the first postoperative (PO) morning, and a further 5.5 +/- 1.0 g until the second PO morning. Forty patients (low-dose group, L) received magnesium sulfate only after bypass to a total of 2.9 +/- 0.5 g at the first, and 1.4 +/- 0.1 g at the second PO morning. A blood cardioplegia technique was used in both groups, including bolus doses of magnesium chloride to a total of 2.4 +/- 0.6 g and 2.3 +/- 0.6 g to H and L patients, respectively. Continuous Holter tape-recording was used for 12 to 15 hours preoperatively, and for 48 hours postoperatively. Serum magnesium peaked in H patients on the first PO morning at 1.60 +/- 0.25 mmol/L, whereafter it declined to the normal level on the third PO morning. Patients in the L group were normomagnesemic, except after the start of bypass.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term outcome after intravenous magnesium sulphate in suspected acute myocardial infarction: the second Leicester Intravenous Magnesium Intervention Trial (LIMIT-2)

The second Leicester Intravenous Magnesium Intervention Trial (LIMIT-2) examined the effect of an intravenous regimen of magnesium sulphate in 2316 patients with suspected acute myocardial infarction. Treatment, according to a double-blind randomised protocol, was started with a loading injection, before any thrombolytic therapy, and continued with a maintenance infusion for a further 24 h. Cause-specific mortality of randomised patients has now been examined over 1.0-5.5 (mean 2.7) years of follow-up. Mortality rate from ischaemic heart disease was reduced by 21% (95% CI 5-35%, p = 0.01) and all-cause mortality rate reduced by 16% (2-29%, p = 0.03) in magnesium-treated patients. Magnesium protects the contractile function of the myocardium from reperfusion injury ("stunning") in experimental models; this observation accords with the 25% (7-39%, p = 0.009) reduction in early left ventricular failure in the magnesium group of LIMIT-2. For such protection to occur, magnesium must be raised by the time of reperfusion since the injury is immediate. In the clinical context the timing of magnesium treatment in relation to thrombolytic therapy or spontaneous reperfusion is likely to be critical. The early benefits of this simple and safe intervention are reflected in improved long-term survival.

Prevention of postischemic reperfusion injury: the improvement of myocardial tissue blood flow after ischemia by terminal nicorandil-Mg cardioplegia

We evaluated the preventive effect of postischemic reperfusion injury by Nicorandil-Mg cardioplegia given just prior to reperfusion as "terminal cardioplegia." Twenty seven dogs were placed on cardiopulmonary bypass and the aorta was cross-clamped for 90 min under hypothermic (17-19 degrees C) cardioplegic arrest. The canine hearts were divided into three groups: in group A (n = 10) the hearts reperfused without any treatment; in group B (n = 9) the hearts received coronary perfusion with Nicorandil-Mg solution (Nic, 8 mg/l; Mg, 20 mEq/l; glucose, 50 g/l) for 2 min just prior to reperfusion; and in group C (n = 8) the hearts received coronary perfusion with Nicorandil-Mg free solution (glucose, 50 g/l). During and after ischemia, the myocardial tissue PCO2 (t-PCO2) was continuously monitored by an ion-sensitive field effective transistor (ISFET) sensor. In addition, the myocardial tissue blood flow (TBF), oxygen consumption, and lactate flux were then calculated at 5, 10, 20, and 40 min of reperfusion. In the initial reperfusion period, Group B showed an improved TBF compared to group A and C (at 5 min, group B was 42.7 +/- 11.9; group A was 29.4 +/- 11.2, P < 0.025; and group C was 33.9 +/- 9.2% of the preischemic control level, P < 0.05). T-PCO2 in group B was significantly decreased at 5 min of reperfusion (group B, 127.5 +/- 22.5-->42.5 +/- 9.7; group A, 117.5 +/- 23.0-->85.2 +/- 17.4, P < 0.001; group C, 122.3 mmHg-->68.2 +/- 18.7 mmHg, P < 0.01), and group B had a better metabolic recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Accelerated myocardial metabolic and functional recovery with terminal nicorandil-Mg cardioplegia in heart transplantation

Cardiac reperfusion injury after heart transplantation or cardiopulmonary bypass has been difficult to control due to the variable degree of myocardial damage with respect to the length of ischemia and the complexity of the surgical procedure. Here, we evaluated the myocardial metabolic and functional recovery of hearts infused with a nicorandil vasodilator-magnesium (Mg) solution just prior to reperfusion (terminal cardioplegia). Donor hearts (20 dogs) were removed and immersed in a 4 degrees C water bath containing 20 mEq/l KCL-5% glucose for 6 hours, and then were transplanted to recipient dogs. Orthotopically transplanted dog hearts were either reperfused without any further treatment or received a terminal cardioplegic solution containing 8 mg/l nicorandil, 30 mEq/l Mg, and 50 g/l glucose, which was infused at a pressure of 75 cm H2O for 2 minutes. During the reperfusion period, myocardial tissue PCO2 (t-PCO2) and calcium ion (t-Ca) were continuously monitored by an ISFET (ion-sensitive field effect transistor) sensor. Myocardial oxygen consumption and lactate flux were calculated/monitored at 5, 10, 20 and 40 minutes of reperfusion. Thereafter, myocardial function was evaluated at 45 minutes of reperfusion using LVSWI. Just after reperfusion, the treatment group (group B, n = 10) had a significantly greater coronary flow than the control group (Group A, n = 10, 35.0 +/- 10.1; group B, 47.4 +/- 8.5 ml/100 g/min, p less than 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)