Pediatric lower limb peripheral nerve blocks: Indications, effectiveness, and the incidence of adverse events.

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What?

A review of 1438 lower limb nerve blocks in 1038 children.

Where?

Royal Children’s Hospital, Melbourne

How?

Retrospective review of prospective data from 2016-2021 in children who had had lower limb surgery. Data obtained from the electronic record included demographics, type of block, technique, catheter use, adjuvant drugs used.

Findings

There were a wide range of surgical indications.
The majority of blocks were adductor canal, popliteal, femoral or fascia iliaca blocks. There were no recorded lumbar plexus blocks.
Ultrasound was used in 76.4% of blocks, ultrasound and nerve stimulation in 16.1% and a landmark technique in 7.6%.
Ropivacaine was most commonly used with concentration ranging from 0.2-0.75%. Median dose was < 2mg/kg.
The majority (88.9%) of blocks had no adjuvants. Clonidine was used in 7.9%, dexamethasone in 0.8% and clonidine/dexamethasone in 1.3%.
An effective block occurred in 97% on wakening based on age-adapted pain scores and the need for rescue analgesia.
Persistent postoperative nerve injury occurred in 4 patients (3/1000 95% CI 1.1-8:1000).

Comments

A thorough review of data from a single institution.

Of note was the general effectiveness of the various lower limb blocks.
The vast majority of blocks were completed with ultrasound. It is interesting to note that a small portion were completed without ultrasound. Furthermore, no comment was made on the use of pressure monitoring during injection which has been proposed as an additional safety tool for peripheral nerve blocks.
The most notable feature was the apparently high incidence of significant nerve injury of 3/1000. This differs significantly from other published paediatric and adult series. The Pediatric Regional Anesthesia Network (PRAN) has a complication rate of 2.4/10000, although, as the authors state, this includes all blocks, not just lower limb blocks. This series is also more in detail.
All nerve injuries occurred in tibial lengthening or derotational procedures. These may represent a specific high-risk subgroup for nerve injury.
Investigation post injury revealed no identifiable cause of nerve injury.
It would appear prudent to be aware of potential increased risk of nerve injury associated with these tibial procedures. If utilising nerve blocks, then the use of low concentration local anaesthetic for a single-shot block may have some benefit in allowing assessment of evolving nerve injury. If catheters are being used, then intermittent bolus dosing of a low concentration local anaesthetic may offer a safer alternative to continuous infusion with regards to being able to assess evolving nerve injury.

Reviewed by Dr James Houghton