Epidural analgesia using loss of resistance with air versus saline: does it make a difference? Should we reevaluate our practice?

The choice of using air or saline in epidural syringes during the loss-of-resistance technique, for identifying the epidural space, has been based largely on personal preference of the anesthesia provider. A survey of practice in the United Kingdom, thought to be similar to practice in the United States, revealed that the majority of anesthesia providers use air. Case reports have appeared in the literature suggesting that air may be harmful to patients or, at the very least, impede the onset and quality of epidural analgesia. Two studies have evaluated air vs saline to determine whether one may lead to more rapid or better quality epidural analgesia in laboring parturients. Results are mixed. However, they seem to indicate that the use of saline for the loss-of-resistance may result in more rapid and satisfactory quality of pain relief in laboring parturients. Current anesthesia literature suggests using saline with an air bubble in the loss-of-resistance syringe. Many anesthesia training programs continue to teach the use of air, saline, and saline with an air bubble. Further studies may help to determine whether there is a scientific or safety basis for using air vs saline.