Ambulatory continuous posterior lumbar plexus nerve blocks after hip arthroplasty: a dual-center, randomized, triple-masked, placebo-controlled trial

Abstract

Background: The authors tested the hypotheses that after hip arthroplasty, ambulation distance is increased and the time required to reach three specific readiness-for-discharge criteria is shorter with a 4-day ambulatory continuous lumbar plexus block (cLPB) than with an overnight cLPB.

Methods: A cLPB consisting of 0.2% ropivacaine was provided from surgery until the following morning. Patients were then randomly assigned either to continue ropivacaine or to be switched to normal saline. Primary endpoints included (1) time to attain three discharge criteria (adequate analgesia, independence from intravenous analgesics, and ambulation > or = 30 m) and (2) ambulatory distance in 6 min the afternoon after surgery. Patients were discharged with their cLPB and a portable infusion pump, and catheters were removed on the fourth postoperative day.

Results: Patients given 4 days of perineural ropivacaine (n = 24) attained all three discharge criteria in a median (25th-75th percentiles) of 29 (24-45) h, compared with 51 (42-73) h for those of the control group (n = 23; estimated ratio = 0.62; 95% confidence interval, 0.45-0.92; P = 0.011). Patients assigned to receive ropivacaine ambulated a median of 34 (9-55) m the afternoon after surgery, compared with 20 (6-46) m for those receiving normal saline (estimated ratio = 1.3; 95% confidence interval, 0.6-3.0; P = 0.42). Three falls occurred in subjects receiving ropivacaine (13%), versus none in subjects receiving normal saline.

Conclusions: Compared with an overnight cLPB, a 4-day ambulatory cLPB decreases the time to reach three predefined discharge criteria by an estimated 38% after hip arthroplasty. However, the extended infusion did not increase ambulation distance to a statistically significant degree.

Fig. 1

Study design overview. POD = postoperative day.

Fig. 2

Effect of posterior lumbar plexus perineural ropivacaine infusion on the time to reach three predefined discharge criteria (adequate analgesia, independence from intravenous opioids, and the ability to ambulate at least 30 m) after hip arthroplasty. Data presented are Kaplan-Meier estimates of the cumulative percentages of patients meeting all three discharge criteria at each time point and subsequent time points. Data are for patients randomly assigned to the ropivacaine group (perineural ropivacaine from surgery through postoperative day 4) or the placebo group (perineural ropivacaine from surgery through 06:00 postoperative day 1 followed by perineural normal saline through postoperative day 4).

Fig. 3

Effects of posterior lumbar plexus perineural ropivacaine infusion on ambulation and passive hip flexion after hip arthroplasty. Kaplan-Meier estimates include the cumulative percentages of patients ambulating at least 30 m at each time point and subsequent time points. Other data are expressed as median (horizontal bar) with 25th-75th (box) and 10th-90th (whiskers) percentiles for patients randomly assigned to the ropivacaine group (perineural ropivacaine from surgery through postoperative day postoperative day 4) or the placebo group (perineural ropivacaine from surgery through 06:00 postoperative day 1 followed by perineural normal saline through postoperative day 4). Because each comparison dilutes all other P values, we restricted our analysis to 11 comparisons among secondary endpoints. P values are provided where statistical comparisons were applied.

Fig. 4

Effects of posterior lumbar plexus perineural ropivacaine infusion on postoperative pain after hip arthroplasty. Pain severity indicated using a numeric rating scale of 0-10, with 0 equal to no pain and 10 being the worst imaginable pain. Data are expressed as median (horizontal bar) with 25th-75th (box) and 10th-90th (whiskers) percentiles for patients randomly assigned to the ropivacaine group (perineural ropivacaine from surgery through postoperative day 4) or the placebo group (perineural ropivacaine from surgery through 06:00 postoperative day 1 followed by perineural normal saline through postoperative day 4). Because each comparison dilutes all other P values, we restricted our analysis to 11 comparisons among secondary endpoints. For this reason, no statistical comparisons were applied to the data of this figure. PACU = postanesthesia care unit.

Fig. 5

Effects of posterior lumbar plexus perineural ropivacaine infusion on intravenous morphine consumption after hip arthroplasty. Kaplan-Meier estimates include the cumulative percentages of morphine-free patients at each time point and subsequent time points. Other data are expressed as median (horizontal bar) with 25th-75th (box) and 10th-90th (whiskers) percentiles for patients randomly assigned to the ropivacaine group (perineural ropivacaine from surgery through postoperative day 4) or the placebo group (perineural ropivacaine from surgery through 06:00 postoperative day 1 followed by perineural normal saline through postoperative day 4). Because each comparison dilutes all other P values, we restricted our analysis to 11 comparisons among secondary endpoints. P values are presented where statistical comparisons were applied. PACU = postanesthesia care unit.