Local anaesthetics belong in the caudal/epidural space, not in the veins!

Abstract

C AUDAL/EPIDURAL blocks have achieved world.wide acceptance as a start, dard for perioperauve pain management mappropnate infants and children. Ease of administration, effectiveness, reliability and, most importantly, a low complication rate explain their popularity. ~-3 However, the safe record of these blocks has been stained recently by reports of serious cardiac arrhythmias and cardiac arrests in anaesthetized healthy infants. 4,s In this issue, Fisher et al. report their one year experience (742 epidural anaesthetics) with these blocks focusing on the inddence of vascular puncture (5.6%) and the role of electrocardiography in the detection of intravascular injections of epinephrine-containing local anaesthetic solutions. 6 In view of their observations, it seems appropriate to comment on the circulatory effects of epinephrine-containing local anaesthetics and to consider strategies aimed at minimizing the risk of an intravascular injection in infants and children. In their study, Fisher et al. report several interesting observations. 6 First, they note that tachycardia is not a reliable sign of intravascular injection. Although heart rate increased 210 beats per minute in the majority of the children in whom intravascular injection was suspected, it remained unchanged or decreased in 25%. This is consistent with data from Desparmet et al. who suggested that intravenous administration of epinephrine-containing lidocaine solution does not consistently increase heart rate during halothane anaesthesia. 7 Second, of those in whom heart rate was unchanged or decreased after intravascular injection, 75% (three of four children) had received atropine. Although the number of children in this group is small, this observation merits further comment for two reasons because first, it is not consistent with the findings of Desparmet et al. that the reliability of the tachycardia after an intravenous injection is increased by previous administration of atropine 7 and second, atropine is administered roufinely to infants and children and clinicians should be aware of its potential to mask an early sign of an occult intravascular injection. Whether the difference in this apparent effect of atropine between these two studies is attributable to differences in the local anaesthetic used, the anaesthetic agent or the combination of the two, remains speculative. Nonetheless, recognizing the importance of this observation and that the results of the studies differed should prompt further investigation. Third, in contrast to the circulatory changes of tachycardia or hypertension which may be transient or absent after intravascular injection, Fisher et al. suggest that electrocardiographic ST segment and T wave changes may be clinically useful signs of an intravascular injection, 6 as reported previously. 4,s This suggestion also merits further study to determine its validity, specif