Labor epidural anesthetics comparing loss of resistance with air versus saline: does the choice matter?

This study examined whether air or saline, used for the loss-of-resistance (LOR) technique, resulted in a difference in pain relief or adverse events for laboring parturients. Previous studies had mixed findings regarding the onset of analgesia and subsequent pain relief. Research questions were as follows: Is there difference in analgesic onset for patients receiving air vs saline during the LOR technique? Do women receiving the air method for LOR experience any difference in the quality of pain relief from that of women receiving saline? Is there any difference in the incidence of analgesic distribution or segmental pain relief in women receiving the air vs the saline method? Is there any difference in the incidence of adverse effects in women receiving air vs saline during the LOR technique? This was an experimental, prospective study with 50 women. Subjects were randomized to receive air or saline. The visual analogue scale was used to measure pain. A dermatome level recorded the spread of analgesia. No significant differences were found between groups for onset or quality of analgesia. There was a significant increase in the number of subjects who experienced segmental blocks after receiving air during the LOR technique.