Does epidural injection of physiological saline facilitate the advancement of catheters?

Seventy patients (ASA I, ASA II), scheduled for a surgical intervention under epidural or combined spinal-epidural anaesthesia, were randomly allocated to one of two groups. The epidural space was identified by loss of resistance using air, followed by injection in Group A (35 patients) of 10 ml of physiological saline directed cephallad and in Group B (35 patients) by no injection. Thereafter an anaesthetist, different to the one who placed the Tuohy in the epidural space, advanced a catheter up to 10 cm into the epidural space. At each cm of advance the resistance was judged. No significant difference in resistance was found between the groups. The authors conclude that the injection of 10 ml of physiological saline into the epidural space does not facilitate the advancement of an epidural catheter.