Cardiovascular and pulmonary effects of epidural anaesthesia.

Abstract

Epidural anaesthesia has been used since the early 1900s. Consequently the general characteristics of these procedures have been well defined. More studies have provided a better understanding of the cardiopulmonary changes produced by epidural anaesthesia. The cardiovascular effects observed with epidural anaesthesia are complex and variable, depending on a multitude of factors. The extent of sympathetic denervation, balance of sympathetic and parasympathetic activity, the pharmacological effect of systemically absorbed local anaesthetic agents, inclusion of adrenaline in the anaesthetic solution, the distribution of blood in relation to cardiac filling and cardiovascular function of the patient must be taken into account when considering the circulatory effects of epidural anaesthesia. Individual cardiovascular response to different levels of sympathetic blockade varies widely, depending on the degree of sympathetic tone before the block. Epidural anaesthesia that is restricted to the level of the low thoracic and lumbar region (T5-L4) results in a "peripheral" sympathetic blockade with vascular dilatation in the pelvis and lower limbs. High thoracic epidural anaesthesia, from the first to fifth thoracic, blocks the cardiac afferent and efferent sympathetic fibres with loss of chronotropic and inotropic drive to the myocardium. Thoracic epidural anaesthesia appears to at least partly reverse the diaphragmatic dysfunction that is a major determinant of the decrease in lung volumes observed after upper abdominal surgery. This article summarizes cardiovascular and pulmonary responses to epidural anaesthesia. Details of clinical management are not included in the review.