BACKGROUND: During epidural catheterization, aspiration of the content of the catheter is helpful to check for blood or CSF (cerebrospinal fluid), but the incidence of false-negative aspiration is too high to rely on this technique alone. A test dose of local anesthetics, with epinephrine, to identify intravascular or subarachnoid injection may not be as evident in the old, women in labor and patients taking β-adrenergic blockers. The aim of this study was to determine the safety and efficacy of an air test to conform the appropriate placement of an epidural catheter.

METHODS: The authors performed a clinical trial on 160 patients, who underwent an operation under epidural anesthesia. The patients were divided into 4 groups according to the puncture site. After placement of the epidural catheter, 3 ml of air was injected through the catheter, and amounts of air aspirated via the epidural catheter were measured.

RESULTS: Eight patients were excluded due to blood or CSF was aspirates. Amoung the remaining 152 patients, 139 patients underwent successful operations under epidural anesthesia, but 13 patients needed general anesthesia. The amounts of air aspirated via the epidural catheter were about 2 ml. No patients, who had undergone the air test showed signs or symptoms of local anesthetic toxicity, PDPH (postdural puncture headache), air embolism or pneumoencephalus.

CONCLUSIONS: The authors conclude that the air test is a useful alternative method for identifying the appropriate placement of epidural catheters.