Objective To determine whether a narrower gauge needle used in ABG sampling is associated with lower pain scores and complication rates without increasing the level of difficulty of the procedure.

Methods We performed a prospective single-blinded randomised control study of patients from a tertiary-level emergency department in Sydney who required an ABG analysis over the period of June 2010–July 2012. Patients were randomised to either a 23G or 25G needle and the primary outcome that included pain experienced by these patient were recorded as pain scores on a 10 cm hatched visual analogue scale. The difficulty scores and complications were also noted from the operator.

Results Data for 119 consenting eligible patients were included in the analysis. 63 patients were allocated to the 23G needle group and 56 to the 25G needle group. The mean pain score was 3.5 (SD=2.7) for the 23G group and 3.4 (SD=2.7) for the 25G group with a mean difference between the pain scores of 0.1 (95% CI −0.9 to 1.1, p=0.83). The 23G and 25G mean difficulty score was 3.4 (SD=2.6) and 4.3 (SD=2.4), respectively, with a mean difference of 0.9 (95% CI −0.03 to 1.7, p=0.06). 21.6% of patient in the 23G needle group experienced some complication with regard to the sampling in the form of haematoma, tenderness or paraesthesia in comparison to 5.4% of patients in the 25G needle group (p=0.03).

Conclusions There was no significant difference in pain scores experienced by patients undertaking ABG sampling with either a 23G or 25G needle.

Trial registration number ACTRN12609000957291.