A new technique of identifying the epidural space "dripping infusion method"

We developed a new visual technique o identifying the epidural space, using the hydrostatic pressure produced by a suspended micro-drip intravenous apparatus. When the needle pierces the ligamentum flavum, the resistance to positive pressure disappears and the saline in the apparatus flows freely into the epidural space. Thus, the entry of the needle point into the epidural space is visually confirmed by the appearance of dripping flow in the drip bulb (dripping infusion sign). This procedure was clinically evaluated at the thoraco-cervical area in 114 patients; the thoracic area in 116; and the lumbar area in 272, respectively. In 491 (97.8%) of the patients, the epidural space was identified with facility. In the remaining 11 patients (2.2%), a false dripping infusion sign appeared at the more superficial site than expected. If the pressure waveform in the epidural space is analyzed, the correct positioning of the needle can be easily confirmed. We believe that this method is one of the most accurate visual methods of identifying the epidural space and useful for teaching the epidural blockade to students and residents.