[Identification of the epidural space by air-fluid reflux (author's transl)]

Detection of the epidural space by Dogliotti's method with a Tuohy needle (inner gauge 1.6mm) is followed by introduction of 3.0-5.0 ml of test solution and rapid injection of 3.0-5.0 ml air with a 5.0ml syringe. After the introduction of the air, the syringe is immediately removed from the needle. Location of the needle tip in the epidural space is marked by air bubbles coated by a thin fluid film, which hang over the hub of the needle and then burst. In some instances a slight wheezing can be heard as the air introduced into the epidural space comes out. The air-fluid reflux is determined by the elasticity of the dura and points always at the location of the tip of the needle in the epidural space. This sign is present in 95 per cent of the cases. The intensity of the air-fluid reflux depends upon the elasticity of the dura, the diameter of the needle and of the syringe and the force by which the plunger is pushed down.