Finger injuries are common presentations to a paediatric emergency department. Anaesthesia and pain control are critical elements in managing finger injuries in the paediatric emergency department. A digital anaesthesia technique which is easy to administer, requires a single injection and is effective would give emergency physicians confidence to treat finger injuries in children and possibly avoid procedural sedation. Traditional digital blocks can be difficult, requiring two injections which may be poorly tolerated by the child. The single injection volar subcutaneous technique is preferred to the traditional digital block in adults.1 Extrapolating from adult studies, we investigated the use of the subcutaneous single injection A1 pulley digital block technique for children presenting with finger injuries in our paediatric emergency department.

METHODS

Twelve children aged 3–14 years were seen over a period of 2 months with finger injuries including nail bed injuries (n = 2), finger lacerations (n = 3), foreign body removals (n = 2), paronychia following minor trauma (n = 2), dislocation (n = 1) and displaced fractures (n = 2).

Tetracaine gel (1.5 g) was applied to the injection site for 30 min before the procedure in those aged <10 years. The infiltration site was thoroughly cleaned prior to infiltration. The infiltration site was at the proximal origin of the A1 pulley in the palm about 1–2 cm from the proximal finger crease, depending on the age of the child. The A1 pulley is easily identified by a horizontal line drawn across the palm joining the two transverse creases (fig 1).

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Figure 1 Line diagram depicting the A1 pulleys in relation to the metacarpal heads. The horizontal dashed line shows the landmark for subcutaneous injection. Reproduced with permission from Green’s Operative Hand Surgery published by Elsevier.

The digit was examined for anaesthesia before the procedure and 3 ml of 1% lignocaine was injected subcutaneously in the midline to the finger (fig 2). The injection site was gently massaged for 1 min to ensure spread to the dorsal aspect. Failure of anaesthesia was defined as no loss of pain sensation at the operation site 10 min after the injection. This was assessed by pinching the operation site with a tooth forceps and asking the children whether they felt any pain sensation and observing them for facial grimacing and limb withdrawal.

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Figure 2 Anaesthetising the middle finger of the right hand using the subcutaneous single injection technique.

RESULTS

Complete anaesthesia was reported in all 12 patients, allowing the planned procedure to be successfully completed.

DISCUSSION

The A1 pulley is a condensation of the synovial sheath which arises from the volar plate of the metacarpophalangeal joint (fig 1). The average length of the A1 pulley is 1 cm. The proximal edge of the A1 pulley lies about 2 cm and the distal edge about 1 cm from the proximal finger crease, respectively.

A double blind randomised study comparing the single injection transthecal (flexor tendon sheath) digital block2 and a subcutaneous single injection A1 pulley digital block3 in adults showed success rates for equivalent anaesthesia of the entire digit. The subcutaneous technique was also found to be easy to administer and to produce less pain during and 24 h after the injection.

One of the limitations of the volar single injection digital anaesthesia administered at the palmophalangeal crease was failure to achieve dorsal anaesthesia over the proximal phalanx.4 We chose the proximal origin of the A1 pulley site for the single injection technique as micro-dissections of the hand have shown that the dorsal branch of the proper digital nerve arises at or proximal to the A1 pulley zone in 62% of the long digits, more proximally than previously reported.5 We were able to achieve dorsal anaesthesia with the subcutaneous single injection technique, although only one patient in the study group had a laceration over the dorsum of the proximal phalanx of his index finger. We did not buffer the lignocaine as a best evidence topic published in 2001 showed little evidence for buffered lignocaine in the acute setting and did not support its mandatory use.6 The single subcutaneous injection technique will facilitate performing painful procedures in children in both the acute and elective situation.

The advantage of the subcutaneous injection technique is that it requires a single injection. The midline subcutaneous injection is likely to reduce the risk of damaging the neurovascular bundle, flexor tendon or the joint, although they were not formally assessed.

This pilot study is limited by the low numbers of patients studied and the absence of a control group; however, it does support proceeding to a larger randomised and controlled investigation.