Influence of beta 1-blockade on myocardial substrates early after a coronary operation

[Perioperative beta-blockers. Part two: therapeutic indications]

PURPOSE

To review the pharmacologic and pathophysiologic information necessary to prescribe beta-blockers (BB) in perioperative medicine.

DATA SOURCE

Manual retrieval and electronic research of the literature using MEDLINE (key-words: anesthesia and beta- blocker; surgery and beta-blocker).

DATA SYNTHESIS

In non cardiac surgery, the beneficial effects of BB have been demonstrated in hypertensive patients since 1979. In 1996, the beneficial effects of atenolol in patients with coronary artery disease (reduction of postoperative myocardial ischemia and overall reduction in two-year mortality) were demonstrated. In coronary surgery, the interest of preoperative BB treatment has been shown since 1983. Administration of BB has been shown to be beneficial in acute myocardial infarction or chronic cardiac failure (except in NYHA class IV patients).

CONCLUSION

BB have been shown to exert a beneficial effect on postoperative outcomes in patients with cardiovascular disease or risk factors, and their more widespread use in perioperative medicine is encouraged.

Myocardial protection by pressure- and volume-controlled continuous hypothermic coronary perfusion in combination with Esmolol and nitroglycerine for correction of congenital heart defects in pediatric risk patients

OBJECTIVE

This study assesses the technical applicability and the clinical value of the continuous coronary perfusion with oxygenated blood as a method for myocardial protection used for congenital heart surgery in pediatric risk patients.

METHODS

Thirty non-consecutive pediatric risk patients aged from 1 month to 16 years (mean 3.9 years; 11/30 patients aged <6 months) underwent open heart procedures on the beating heart for simple and complex cardiac malformations using a self designed perfusion system with pressure- and volume-controlled continuous hypothermic coronary perfusion (PVC-CONTHY-CAP) in combination with ultra-short beta1-receptor blockade (Esmolol) and nitroglycerine for myocardial protection. The following procedures were done: VSD patch closure (n = 6), repair of total a-v canal with 'double patch' (n = 4), total repair of tetralogy of Fallot (n = 7), correction of truncus arteriosus communis type IV (n = 1), mitral valve reconstruction (n = 4), total cavo-pulmonary connection (n = 4), and Rastelli procedure (n = 4).

RESULTS

The mean cardio-pulmonary bypass time was 131.5 min (range: 44-245 min), the mean coronary perfusion time: 90.1 min (range: 13-202 min). The weaning off extracorporeal circulation was uneventful in all patients, in 21 patients with low-dose and in nine patients with moderate catecholamine support: the mean weaning time was 25 min (range: 7 58 min). The post-operative mean peak creatine kinase (CK-MB) value was 58 U/l, (range: 14-202 U/l). The mean ICU stay in the cardiac surgery unit was 2.9 days, (range: 1-10 days). The mean post-operative mechanical ventilatory support was 2 days (range: 6 h-9 days). Six patients developed thrombocytopenia with values <40 tsd/microl, four patients renal dysfunction, two patients ascites, five patients heart rhythm disturbances, one patient neurological deficits. In three patients (VSD closure: n = 2; age: 1 and 2 months; total a-v-canal: n = 1; age: 3 months) re-do procedures for significant intraventricular shunt had to be done, in one patient implantation of a permanent pacemaker system was necessary. One patient died due to multiple organ failure after uneventful surgery (total cavo-pulmonary connection for single ventricle).

CONCLUSIONS

PVC-CONTHY-CAP can be successfully used for repair of simple and complex congenital cardiac malformations. However, in children less than 3 months of age, the transatrial repair of intraventricular defects is technically much more demanding and challenging than under conventional cardioplegic arrest and is possibly accompanied by an increased incidence of residual or recurring intraventricular shunts.

Esmolol and percutaneous cardiopulmonary bypass enhance myocardial salvage during ischemia in a dog model

Despite recent advances in techniques of reperfusion for acute myocardial ischemia, myocardial salvage remains suboptimal. Beta-blockers have been shown to limit infarct size during acute ischemia, but their negative inotropic properties have limited their use. Cardiopulmonary bypass is an attractive technique for cardiac resuscitation because it can stabilize a hemodynamically compromised patient and potentially reduce myocardial oxygen consumption. In an attempt to maximize myocardial salvage in the setting of acute ischemia, the combination of esmolol, an ultrashort-acting beta-blocker, with percutaneous cardiopulmonary bypass was evaluated. Four groups of instrumented dogs underwent 2 hours of myocardial ischemia induced by occlusion of the proximal left anterior descending coronary artery, followed by 1 hour of reperfusion. Throughout the period of ischemia and reperfusion, esmolol plus percutaneous cardiopulmonary bypass was compared with esmolol alone, percutaneous cardiopulmonary bypass alone, and control conditions. After the reperfusion period, the extent of infarction of the left ventricle at risk was determined. Four animals had intractable arrhythmias: one in the esmolol plus bypass group, one in the esmolol group, and two in the control group. The extent of infarction of the left ventricle at risk was significantly reduced in the esmolol plus bypass group (30%) compared with bypass alone (52%), with esmolol alone (54%), and with the control groups (59%; p < 0.05). We conclude that in this experimental model the combination of esmolol with bypass improves myocardial salvage after ischemia and reperfusion.

Myocardial metabolism 8 hours after coronary surgery: effects of dopamine

Myocardial substrate metabolism is abnormal in the early period after cardiac surgery. Myocardial uptake of substrates remains restricted 6 hours postoperatively and cannot match the demand during periods of increased energy requirements. We investigated the relationship between myocardial oxidative rate and substrate uptake in 22 men c. 8 hours after coronary surgery. Myocardial energy demand was raised experimentally by infusing dopamine. The influence of selective beta 1-blockade was analyzed. The uptake of free fatty acids dominated (34.74 +/- 8.83 mmol/min*10(-3) and sufficed to explain the oxygen consumption in basal postoperative conditions (0.468 +/- 0.051 mumol/min) and during amplified energy requirements (0.881 +/- 0.117, r = 0.71). Although the capacity to adjust substrate uptake to energy requirements thus was regained, the uptake of glucose and of lactate (6.14 +/- 13.13 and 2.29 +/- 20.31 mmol/min*10(3) respectively) was marginal, which may be important for ischaemic tolerance. Metoprolol influenced oxygen consumption during amplified adrenergic activity, but did not markedly affect substrates.