Influence of needle diameter on spinal anaesthesia puncture failures for caesarean section: A prospective, randomised, experimental study

ObjectivesSpinal 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 27 gauge (G) pencil-point, Whitacre type (with introducer) needles during spinal anaesthesia for caesarean section.Study designProspective, randomised, experimental study in healthy subjects.Patients and methodsWe 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.ResultsThe number of spinal puncture failures was significantly higher in the 27 G group, than in the 25 G (P = 0.006) group and the 26 G (P < 0.001) group, but did not differ between the 25 G and 26 G groups (P = 0.606). Ten postdural puncture headaches were observed without significant differences among the groups.ConclusionsThis prospective study showed that puncture failures occur less frequently with the use of 25 G or 26 G pencil-point needles as compared to 27 G 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 26 G pencil-point needle is the optimal gauge for performing spinal anaesthesia for scheduled caesarean sections.