Optimum Length of Catheter in the Epidural Space for Labor Analgesia in Non-obese Women: a Randomised Controlled Trial of 4 cm Versus 5 cm

Optimum Length of Catheter in the Epidural Space for Labor Analgesia in Non-obese Women: a Randomised Controlled Trial of 4 cm Versus 5 cm

Optimum Length of Catheter in the Epidural Space for Labor Analgesia in Non-obese Women: a Randomised Controlled Trial of 4 cm Versus 5 cm

Epidural analgesia was introduced to the world of obstetrics in 1909 by Walter Stoeckel. Over the following 100 years it has developed to become the gold-standard for delivery of intra-partum analgesia, with between 60 and 75% of North American parturients receiving an epidural during their labor. Effective labor analgesia has been shown to improve maternal and fetal outcomes. One aspect of catheter insertion that has not been fully evaluated, and with very little recent work undertaken, is the optimal length of epidural catheter to be left in the epidural space. Dislodgement or displacement of epidural catheter remains a significant cause for failure with analgesia. Novel methods of fixation may further reduce the risk of catheter migration. Another factor is the direction of travel within the epidural space, only 13% of lumbar catheters remain uncoiled after insertion of more than 4 cm into the epidural space. Hypothesis: The investigators hypothesize that catheters inserted to 4 cm will have a lower rate of failure when compared to those inserted to 5 cm. Objective: This study aims to evaluate the difference in quality of labor analgesia delivered by epidural catheters inserted to either 4 or 5 cm into the epidural space. This study will be conducted as an interventional double-blinded randomised control trial to establish best practice.

Effective labor analgesia has been shown to improve maternal and fetal outcomes. It is of paramount importance to the obstetric anesthesiologist to optimize the quality of labor analgesia and identify any factors leading to ineffective epidural analgesia. One aspect of catheter insertion that has not been fully evaluated, and with very little recent work undertaken, is the optimal length of epidural catheter to be left in the epidural space. Previous studies have advocated, for varying reasons, different lengths of catheter to be left in the space; these range from 2cm to 8cm. Longer epidural lengths in the space can be associated with foraminal escape, leading to unilateral block, and intravascular insertion, prompting additional manipulation. Shorter lengths have previously been associated with more frequent dislodgement. The directionality of the epidural catheter once in the space has been demonstrated to correlate with misdirection. The aim of the study would be to standardize practice in how much epidural catheter is threaded into the epidural space.

Sensory block level to ice will be measured 1 hour after the loading dose is administered. Yes: inadequate block No: adequate block

Unilateral block or block height discrepancy of >3 dermatomal levels at any time prior to delivery. Yes: inadequate block No: adequate block

Re-siting of the epidural at any time during labour will indicate an inadequate block, for any of the following reasons: Inadequate analgesia Persistent unilateral block Persistent intravascular placement Extensive motor block Hypotension High block

Abandonment of epidural or substitute for alternative method of analgesia after initial failure: questionnaire

The epidural analgesia will also be considered inadequate if the procedure is abandoned or another method of analgesia is used. This will be recorded by the anesthesiologist.

A verbal numerical rating score (VNRS), where 0=no pain and 10=worst pain ever. A verbal numerical rating score (VNRS) greater than 3, where 0=no pain and 10=worst pain ever.

Hourly sensory block height assessment, using sensation to ice. This is recorded hourly as standard practice.

Bromage scale will be recorded hourly as standard practice. 3: Unable to move feet or knees 2: Able to move feet only 1: Able to just move knees 0: Full flexion of knees and feet

Adequacy of conversion to surgical block in cases requiring cesarean deliveries for failed labor or fetal issues. This will be recorded by the anesthesiologist.

Inclusion Criteria: All women aged 18 years and above. In established second stage of labor. 3-7 cm dilation at time of insertion. Women with BMI < 40 kg/m2 Exclusion Criteria: Known contraindication to epidural insertion. Inability or unwillingness to provide written consent. Previous difficult epidural insertion. Previous failed epidural. Imminent instrumental or operative delivery. Dural puncture. Combined spinal epidural analgesia. High BMI > 40 kg/m2