DOI: 10.1097/01.aoa.0000288306.52188.2d
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Issn Print: 0275-665X
Publication Date: 2007/09/01
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Excerpt
Injection of fluid for identification of the epidural space by the loss-of-resistance (LOR) technique is common, and it has been shown that different volumes of saline may affect subsequent epidural analgesia. In this prospective, randomized, doubled-blinded study, the authors sought to determine whether 2 mL versus 10 mL of saline injected into the epidural space affects the ease of epidural catheter insertion, frequency of blood vessel trauma and paresthesia, spread of block, and subsequent pain relief.
A total of 105 healthy, ASA I-II, term parturients with singleton vertex presentation in active labor (cervical dilation of <5 cm) and requesting neuraxial analgesia were enrolled. Women were randomized to receive either 2 mL (2 mL Group, n=53) or 10 mL (10 mL group, n=52) of saline after identification of the epidural space. Immediately after saline injection, a 20-G, closed-tip, nylon, multiport epidural catheter was placed, with ease of passing it on the first attempt recorded. Analgesia was initiated 5 min later with a bolus of 10 mL of diluted concentration of bupivacaine 0.1% with fentanyl 2 μg/mL. Women were then moved from the sitting position to semi-sitting with left uterine displacement, and any occurrence of paresthesia was noted. After 25 min, the spread of block to cold and pain on both sides of the body was assessed using a dermatome chart. Also recorded were degree of pain relief by 10-point visual analog scale (VAS), motor block, and the incidence of blood vessel trauma. Student's t, chi-square, Wilcoxon, and Fisher's exact tests were used as appropriate.
One woman in the 2-mL group was excluded for failure of catheter insertion, as were three in the 2-mL group and two in the 10-mL group who had the catheter threaded into the intravascular space or a vasovagal attack during insertion, leaving 49 women in the 2-mL group and 50 in the 10-mL group. The two groups had similar demographics and obstetric characteristics. The median number of dermatomes (range in parenthesis) blocked for cold and pinprick sensation was significantly higher in the 10 mL group; 19 (6-29) versus 15 (4-27) for cold, P=0.000; 15 (3-29) versus 11.5 (3-26) for pinprick, P=0.002. A higher median level of block to cold was also seen in the 10-mL group; T9 (T4-L1) versus T10 (T6-L1), P=0.049. However, the height of block to pinprick was comparable between the two groups (P=NS). Motor block was minimal in all women. VAS pain relief at 25 min was the same in both groups (P=NS), and there was no difference in the percentage of women who experienced unilateral block or incomplete pain relief requiring additional medication. The epidural catheter was inserted easily in almost all women and the incidence of blood vessel trauma was low, without any significant difference between groups. The frequency of paresthesia, however, was high in both groups (57.6% in the 2-mL group, vs. 63.4%; P=NS).
The authors concluded that use of 10 mL versus 2 mL of saline after identification of the epidural space in women during first-stage labor increases the total number of dermatomes blocked for both cold and pinprick sensation. Ease of catheter insertion, prevention of intravascular cannulation, and adequate pain relief, however, were similar throughout.
