Loss of resistance technique for locating the epidural space: evaluation of glass and plastic syringes.

Location of the epidural space in epidural anaesthesia usually involves the measurement of loss of resistance using glass or plastic syringes. In the present study two varieties of glass syringe and one plastic type were evaluated to determine the resistive forces associated with plunger movement. The mean static (fs) and dynamic (fd) forces for polished glass syringes having a ground plunger only were fs = 0.47 X 10(-3) +/- 0.22 X 10(-3) N and fd = 0.37 X 10(-3) +/- 0.19 X 10(-3) N and for polished glass syringes having a ground barrel and plunger were fs = 0.43 X 10(-3) +/- 0.16 X 10(-3) N and fd = 0.38 X 10(-3) +/- 0.15 X 10(-3) N. Each of these values was significantly lower (P less than 0.5) than those for plastic syringes fs = 2.22 X 10(-3) +/- 0.48 X 10(-3) N and fd = 1.46 X 10(-3) +/- 0.37 X 10(-3) N. It is concluded that glass syringes are favoured over plastic for locating the epidural space because frictional forces developed with glass syringes were significantly lower than with plastic.