Spinal anaesthesia represents the technique of choice for elective caesarean section. The purpose of this study was to compare the puncture failure rates with 25, 26 or 27gauge (G) pencil-point, Whitacre type (with introducer) needles during spinal anaesthesia for caesarean section.

Prospective, randomised, experimental study in healthy subjects.

We recruited 330 adults, consecutively scheduled parturients, randomised into three groups. The subarachnoid puncture procedure was standardised. The flexibility of the three needle types was assessed in vitro, and a force was applied using a dynamometer. The occurrence of postdural puncture headache was also evaluated.

The number of spinal puncture failures was significantly higher in the 27G group, than in the 25G (P=0.006) group and the 26G (P<0.001) group, but did not differ between the 25G and 26G groups (P=0.606). Ten postdural puncture headaches were observed without significant differences among the groups.

This prospective study showed that puncture failures occur less frequently with the use of 25G or 26G pencil-point needles as compared to 27G needles, probably due to the higher flexibility of the latter. This characteristic was demonstrated in vitro, in a reproducible model. This experiment suggests that a 26G pencil-point needle is the optimal gauge for performing spinal anaesthesia for scheduled caesarean sections.