Propranolol in thyrotoxicosis. Cardiovascular changes during thyroidectomy in patients pre-treated with propranolol

Perianaesthetic management of patients with endocrine disease

Hyper- or hypofunctioning endocrine organs present a number of perianaesthetic challenges. This review covers some of the issues of perianaesthetic management of patients with primary or coexisting pathology of the following endocrine organs: The pancreas with diabetes mellitus as the most common endocrine cause of primary and secondary organ dysfunctions affecting anaesthetic care. Adrenal cortical pathology with excess or deficiency of adrenocortical hormones. Pheochromocytoma of the adrenal medulla with infrequent but challenging perianaesthetic problems. Thyroid gland diseases with hyper- or hypothyroidism. Parathyroid gland pathology with hypercalcaemia or hypocalcaemia. Disorders of the anterior and posterior pituitary gland. The carcinoid syndrome and more uncommon endocrinopathies such as adenomas from the gastroenteropancreatic endocrine tissues and the ovarian hyperstimulation syndrome are also reviewed briefly.

Beta-adrenoceptor blockade and anaesthesia for thyroidectomy

The administration of beta-adrenoceptor blocking drugs in the pre-operative preparation and operative management of thyrotoxic patients undergoing subtotal thyroidectomy is reviewed. Particular reference is made to some of the recent advances and it is emphasised that there has been a considerable reduction in the incidence of problems following judicious use of these drugs. The choice of anaesthetic technique employed for thyroidectomy is less important than the degree of control of thyrotoxicosis by the beta-adrenoceptor blocking drug. Propranolol has proved safe and effective for the majority of patients. The longer acting agent nadolol is easier to administer, particularly in the peri-operative period. Patients are rendered less thyrotoxic and safety thereby enhanced by adding potassium iodide for 10 days preoperatively. The combination of nadolol and potassium iodide offers real advantages in the preparation of the thyrotoxic patient for surgery.

The interactions between beta-blockers and anaesthetics. Experimental observations

The possibility of interactions between beta-adrenoceptor antagonists and anaesthetic drugs is particularly relevant to the anaesthetic management of patients suffering from arterial hypertension and ischaemic heart disease. Maintenance of adrenergic beta-receptor blockade in patients with ischaemic heart disease and arterial hypertension is now widely accepted in order to avoid the cardiac risks of its sudden withdrawal and also to minimize the effects of sympathetic overactivity on the cardiovascular system. However, maintenance of adrenergic beta-receptor blockade may impose some constraints on the choice of the anaesthetic agent. While no adverse interaction has been found between beta blockade and anaesthesia with halothane, halothane supplementing nitrous oxide, or isoflurane, substantial reductions of cardiac performance have been observed in the case of the association of beta blockade and anaesthesia using methoxyflurane or trichloroethylene. An adverse interaction has also been observed between propranolol and enflurane anaesthesia but not between oxprenolol and enflurane anaesthesia. Recent studies of the effects of anaesthesia in the presence of critically narrowed coronary arteries have shown that both halothane and enflurane may cause regional myocardial dysfunction. This dysfunction is minimized by oxprenolol and it appears that adrenergic beta-receptor blockade, besides improving cardiovascular stability, protects the myocardium supplied by narrowed coronary arteries.