Beta‐blockers and Thoracic Epidural Analgesia. Cardioprotective and Synergistic Effects

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Abstract
Seven groups of patients with and without hypertension or with ischaemic heart disease, treated with different beta blockers were investigated to study the circulatory effects of neurolept anaesthesia alone or combined with thoracic epidural analgesia from T4 to T12/L2 during abdominal surgery. The combination of thoracic epidural analgesia and neurolept anaesthesia in hypertensive subjects treated with non‐cardiosclective beta blockers induced slightly lower blood pressure than measured in similar patients on cardioselective beta blockers with neurolept anaesthesia only. Patients on non‐selective beta blockers with intrinsic stimulatory activity (ISA) had higher blood pressure and heart rate after neurolept anaesthesia induction than patients on cardioselective blockers. During surgery, heart rate remained at a higher level in the patients treated with ISA blockers, whereas blood pressure increased to the same level as in patients with cardioselective blockers. Cardiovascular stability was, however, best maintained in the epidural group, where myocardial energy expenditure during maximal surgical stress was comparable to that in a group of healthy subjects with the same format of anaesthesia and significantly lower than in healthy subjects with neurolept anaesthesia alone. No circulatory side effects of the combination of thoracic epidural analgesia and beta blockade were seen. In patients with ischaemic heart disease, with or without non‐selective beta blockade, similar haemodynamic changes were recorded following neurolept anaesthesia. During maximal surgical stress, unmasking of alpha adrenergic activity with marked rise in blood pressure was seen in the beta‐blocked patients. Despite the more accelerated haemodynamic changes in the blocked patients, a lower increase in myocardial oxygen consumption was recorded compared with the non‐blocked patients. Simultaneously, a lower myocardial uptake of catecholamines, especially noradrenaline was measured in the beta‐blocked group. It is suggested that beta blockade may inhibit the uptake of catecholamines in the myocardium, thereby reducing metabolic rate. Addition of thoracic epidural analgesia during surgery restored cardiovascular stability and did not induce circulatory side effects. Myocardial uptake of catecholamines was completely abolished after the epidural block.