Neuraxial blockade and patient risk

Abstract

Reply EDITOR: We appreciate the interest of Dr Hunter and of Drs Egan and Brown in our study [1] and thank them for their comments. This area of regional anaesthesia, and especially those aspects relating to safety, remains controversial. As far as we are aware, there are no studies published that establish that an ‘awake’ approach confers additional safety over an ‘asleep’ one. In the absence of Class 1 evidence, we agree with the opinion of Fisher [2]. In addition, we would like to quote an extract from a lecture by Professor Boezaart [3], an acknowledged expert on the subject of regional anaesthesia and interscalene block in particular: Intraneural injection of a local anaesthetic is not painful and we should probably not be fooled by the false security that doing blocks in non-anaesthetized patients would protect us from intraneural injection. The real ‘horror stories’ of pain associated with intraneural injection come from the radiology literature where contrast medium and not local anaesthetic agent is injected. Secondly, injection of local anaesthetic agent next to a nerve in a confined space, e.g. the intervertebral foramen, can cause the excruciating pain referred to by some. Another example would be the ulnar nerve at the elbow. In 2000, Benumof [4] reported 4 cases of permanent loss of cervical cord function associated with interscalene block performed under general anaesthesia. From these cases, but also from numerous other case reports, it was concluded that doing blocks on patients who are not under general anaesthesia or heavily sedated protects from intraneural injection and subsequently against nerve damage. Nobody looked at the technique used and the direction of the needles. And people do not seem to realize that the injection of local anaesthetic agent near (or even inside) a nerve immediately ends all motor function of that nerve. So why would the motor function be blocked immediately but the sensory function be spared? And can we rely on pain to protect us from doing intraneural injections? I think not! Horlocker and colleagues [5] looked at more than 4000 lumbar epidurals inserted after induction of general anaesthesia and concluded that ‘… although the risk of neurological complications associated with lumbar epidural catheter placement in anaesthetised patients is small, the relative risk compared with epidural catheterisation in awake patients is unknown’. Therefore, the subject is controversial and opinions are divided. In our article we presented the data showing that in our series, interscalene block performed in anaesthetized patients is safe. To prove whether it is safer than an ‘awake’ technique was not the aim of our study and as far as we aware there are no studies on that subject. We of course agree with the good practice implicit in informing patients fully of all pertinent choices and their attendant risks. However, we would strongly disagree with the statement that ‘it does not require a double-blind trial to recognise that the likelihood of, especially neural, damage is greater whilst needles are being inserted into an anaesthetised patient rather than one from whom immediate feedback is available’. This statement would seem to be based upon opinion alone. A. Bogdanov R. Loveland 1Royal Berkshire Hospital, Reading, UK 2Wexham Park Hospital, Slough, UK