Identification of the epidural space: is loss of resistance to air a safe technique? A review of the complications related to the use of air.

BACKGROUND AND OBJECTIVES The major determinant of successful epidural anesthesia is the localization of the epidural space. The manual loss of resistance technique is widely used by anesthesiologists in identifying the epidural space. Should air or saline be used in detecting the point of loss of resistance? No consensus exists as to which technique is superior, and individual providers currently use the technique with which they are most comfortable. The incidence of adverse effects associated with the use of epidural air is unknown and may be underreported as the effects may be unrecognized or considered trivial. The authors comprehensively review the complications of epidural air from published reports. METHODS Using the appropriate key words, the authors searched the Medline (National Library of Congress) scientific data bank from 1966 to 1995, for case reports of epidural complications. RESULTS There are few prospective, controlled, double-blinded studies comparing the relative merits of using air versus saline for the loss of resistance technique of epidural placement. There are, however, numerous case reports. Complications associated with the use of air for the loss of resistance technique included pneumocephalus, spinal cord and nerve root compression, retroperitoneal air, subcutaneous emphysema, and venous air embolism. Additionally, inadequate analgesia and paresthesia have been associated with the loss of resistance technique using air. Transient and permanent neurologic sequelae have been attributed to some of the complications. The simultaneous administration of nitrous oxide and positive. Pressure ventilation has also been reported to expand localized collections of air, resulting in heightened symptoms. CONCLUSIONS The potential complications associated with the use of air for identifying the epidural space with the loss of resistance technique may outweigh the benefits. The use of saline to identify the epidural space may help to reduce the incidence of these complications.