Dual guidance improves needle tip placement for peripheral nerve blocks in a porcine model.

BACKGROUND: The objective of the study was to evaluate whether the use of ultrasound (US) together with nerve stimulation (USNST) provides a better needle tip position for performing peripheral regional anaesthesia than the use of US or nerve stimulation (NST) alone.

METHODS: Needle placements were applied at the brachial plexus and sciatic nerves in 32 anaesthetised pigs. Following needle placement near the target nerve, using either the USNST or the US or NST, a volume of 0.3 ml synthetic resin was injected mimicking a 'test-dose' injection. The primary outcome was the incidence of close needle-to-nerve placement assessed by injectate localisation in direct contact with the nerve epineurium. Secondary endpoints were the incidences of intraneural injection and haematoma formation in direct contact with the target nerve.

RESULTS: A total of 611 punctures were performed. The evaluation for the criterion 'close needle placement' revealed significant differences in favour of the USNST group (98.5%) compared with the NST (90.1%) and the US group (81.6%) (P = 0.001). Significant differences were observed regarding 'intraneural needle placement' between the groups as well (USNST, 0.5%; US, 4%; NST, 2.5%; P = 0.034). The incidence of haematoma formation was significantly higher in the NST group (10.8%) than in the US group (2.5%) and in the USNST group (1.5%) (P = 0.001).

CONCLUSION: These findings suggest that the USNST approach combines the benefits of the US and the NST techniques in terms of a higher rate of close needle tip placements and a lower incidence of haematoma formation.