Adjuvant drugs in neuraxial anaesthesia

Abstract

The addition of adjuvants to local anaesthetics for use in labour epidurals or for intrathecal administration is common practice in obstetric anaesthesia. This chapter provides an overview of the pharmacology of receptors within the epidural and intrathecal spaces and discusses the options available. Adjuncts are classified as opioid and non-opioid and each agent is explored in detail. The mechanism of action, clinical uses, effective dose ranges, speeds of onset and duration, side effects, disadvantages, and special circumstances associated with each agent are explored. Where formal guidelines exist, these are discussed in detail. Although large randomized controlled trial data is lacking, information regarding current knowledge of the behaviour of these agents in obstetric and non-obstetric practice is presented to assist clinicians when deciding about the appropriateness of each agent for their individual practice.

Maternal hemodynamics during labor epidural analgesia with and without adrenaline: a secondary analysis of a randomized trial

“…[5] Epidural analgesia, an effective treatment of labor pain, is shown to decrease plasma levels of adrenaline in the mother. [6,7] Adrenaline is used as an additive in the epidural mixture, with the intent of producing local vasoconstriction in the epidural space [8], thus reducing the systemic uptake of the epidural solution and thereby enhance the effect of the epidural analgesia. Opponents of this use, claim that the addition of adrenaline may have systemic sympathomimetic effects, raising blood pressure and cardiac output, which may be unfortunate in selected patients with pre-eclampsia and certain heart conditions.…”

“…Opponents of this use, claim that the addition of adrenaline may have systemic sympathomimetic effects, raising blood pressure and cardiac output, which may be unfortunate in selected patients with pre-eclampsia and certain heart conditions. [8] In fact, early works of JJ Bonica and colleagues on healthy male volunteers showed an initial rise in systolic blood pressure and cardiac output when adrenaline was added to a dense epidural block. [9] However, little is known about the possible effects of epidural labor analgesia with respect to attenuated hemodynamic changes during labor.…”