The use of adenosine as a trigger for pharmacological preconditioning to protect human myocardium during coronary bypass surgery

Introduction

In former studies on ischaemic preconditioning, adenosine was found to trigger this cardioprotective process. After promising experiments in rabbit hearts and the first clinical use during emergency percutaneous transluminal coronary angioplasty in patients, we started to investigate the ability of adenosine to protect the myocardium during standard cross-clamping bypass surgery. Because adenosine is metabolized within a few seconds, no systemic effects occur.

Method

Two groups of patients (placebo: n = 4, age 69.5 ± 5.2 years; adenosine: n = 4, 59.2 ± 10.3 years) were studied. All patients of both groups were male, had an ejection fraction greater than 50%, and underwent three-vessel bypass during elective cardiac surgery. On first aortic cross-clamping, 5 mg/min adenosine was infused simultaneously with a sufficient blood perfusion via the aortic root over 10 min. The patients in the placebo group received the same dose of physiological saline solution. Blood samples were collected before onset of anaesthesia, before the onset of extracorporeal circulation (ECC), 1 h after the end of surgery, and on the first and second days after surgery in order to assess the following parameters: CK, CK-MB, LDH, GOT, GPT, troponin I, potassium, sodium, Hb, Hct and leukocytes. The following haemodynamic parameters were assessed: heart rate, central venous pressure, left ventricular pressure (LVP), and the maximal and minimal pressure rises (dP/dt_max and dP/dt_min). For electrophysiological analyses, various ECG leads were assessed.

Results

The blood parameters and haemodynamic data are presented in Table 1. One placebo patient and two adenosine patients needed mild intraoperative epinephrine treatment. Whereas in the placebo group one patient developed first-degree atrioventricular block, one patient receiving adenosine showed absolute arrhythmia after surgery.

Table 1 Blood parameters and haemodynamic data

Conclusion

According to these preliminary results, there was no significant difference between the two groups. This is probably explained by the small number of patients studied, or the low temperature used during the ECC, which might have obscured the expected beneficial effect of pharmacological preconditioning.