Second infant spinal anesthetic
Incidence, dose modification, and adverse events after initial failure
Pediatric Anesthesia
Submitted June 2024 by Dr H Hack
Read by 305 Journal Watch subscribers
Study Aim & background
To determine the overall spinal failure rate, incidence of second spinal attempt and success rate and any associated adverse events in infants. The Royal Children's Hospital, Melbourne has a long established practice of providing (and teaching) awake spinal anaesthesia for infants undergoing lower abdominal surgery such as inguinal hernia repair (this reviewer learnt the technique whilst working at RCH many years ago!). Additionally it has a more recently established protocol for the management of a “failed” spinal anaesthetic involving the provision of a second “rescue” spinal anaesthetic by a more experienced anaesthetist.
Design
Retrospective review of infant spinal anaesthetics between May 2016 and June 2023.
Results
There were 551 cases (mean gestational age 33.9 weeks, mean PMA 42.9 weeks, mean Wt.3.8kg).
Overall success rate 90.6%
First attempt success rate 85.5%.
Common causes of failure were “dry tap” (23, 44.2%), poor motor block (16, 30.2%), repeat bloody taps (12, 23.5%).
First attempt failure was most commonly associated with operator inexperience. A repeat spinal anaesthetic by a more experienced operator was very likely to be successful (26/28) but associated with an increased incidence of adverse events: High block (2/28, 7.1% v 3/551, 0.5%) and apnoeas ( 4/28, 14.3% v 37/551, 6.7%). Both cases of high block were occurred in infants that had inadequate motor block following first spinal (suggesting an inadequate LA dose or only partial correct anatomical delivery of the initial LA dose?) and where the second spinal was performed at a higher level (L3,4). Both cases required intubation, IPPV and a brief period of CPR but they were not associated with any long term sequele.
Comments
The author reports valuable data from a centre with a huge amount of departmental experience of providing awake spinal anaesthesia for infant surgery. The vast majority of cases were done by a consultant or fellow. This experience is reflected in the high overall first time success rate of the technique and of a second rescue spinal.
The use of non styletted needles may be considered controversial by some but the rationale (including a lower dry tap rate) and evidence base behind it are cogently discussed.
Potentially concerning is the relatively rare but serious occurrence of a high block following a second spinal. Both cases occurred in the situation of an inadequate motor block following the first spinal anaesthetic, rather than a dry tap or repeated bloody tap and were characterised by the gradual creep upwards of a block causing respiratory depression and bradycardia necessitating intubation and CPR. The reviewer wonders whether one or both cases involved the delivery of an inadequate first LA dose, either an incorrect actual dose or only a partial delivery to the subarachnoid space of a “correct” dose due to technical reasons at injection time. Repeat, identical spinal doses of LA were given (as per protocol), albeit at a higher injection site (L3,4); although the total dose of LA given is below recommended safe limits associated with LA toxicity an excessive subarchnoid dose is likely.
Perhaps in such future, similar cases consideration should be given to a lower access level, use of techniques such as head up position and/or a reduced second dose? The author does not discuss the rationale and/or evidence behind the choice of second spinal anaesthesia rather than the alternative technique of a combined spinal followed by caudal anaesthesia.
