Cannulation of the epidural space: a comparison of 18- and 16-gauge needles

A group of 685 obstetric patients were randomly allocated to have their epidural block performed using either a 16-gauge or an 18-gauge Tuohy needle. Bleeding was noted from needle or catheter trauma in 18% of patients and it proved impossible to insert the catheter in 3%. The majority of mothers experienced little discomfort during the procedure but 2% found insertion to be very uncomfortable. There was no significant difference in the complication rate, ease of use, or patient discomfort between the 18- or 16-gauge needles. Epidural analgesia, although safe, is not without hazard. It may be difficult to perform and may, rarely, cause considerable discomfort.