Comparison of extended-release epidural morphine with femoral nerve block to patient-controlled epidural analgesia for postoperative pain control of total knee arthroplasty: a case-controlled study

Abstract

Background: Because newer anticoagulation strategies for total knee replacement present potentially increased risk of neuraxial analgesia, there is movement away from using patient-controlled epidural analgesia (PCEA) for pain control. This concern opens the door for other regional modalities in postoperative analgesia, including the use of extended-release epidural morphine (EREM) combined with a femoral nerve block (FNB).

Methods: This study was a prospective observational chart review with the use of recent historical controls in patients undergoing unilateral total knee replacement. Outcomes of interest were 0-, 24-, and 48-hour postoperative pain scores using the visual analog scale (VAS); incidence of side effects; and time spent in the postanesthesia care unit (PACU).

Results: Postoperative pain scores at 24 and 48 hours in the EREM and FNB group (n = 14; 2.6 ± 0.6 and 5.0 ± 0.9, respectively) were comparable to the PCEA group (n = 14; 3.8 ± 0.6 and 4.2 ± 0.9). The PACU time was shorter in the EREM and FNB group (2.4 ± 0.3 hours) compared with PCEA (3.6 ± 0.3 hours, P = .02). No statistically significant difference was found in the incidence of side effects between the 2 groups.

Conclusions: The VAS scores at 24 and 48 hours indicate that EREM and FNB provide comparable analgesia to PCEA. The trend toward shorter PACU times represents an opportunity for cost-identification analysis. The study data are limited by their observational nature and the small number of patients involved; nevertheless, this study demonstrates a therapeutic equivalence to PCEA that may be more cost effective.

Keywords: Analgesia; extended-release epidural morphine; femoral nerve block; patient-controlled epidural analgesia; total knee arthroplasty.

Figure 1

Quantile box plots of 24-hour visual analog scale scores of control group (patient-controlled epidural analgesia [PCEA]) versus study group (extended-release epidural morphine [EREM] and femoral nerve block [FNB]).

Figure 2

Quantile box plots of 48-hour visual analog scale scores of control group (patient-controlled epidural analgesia [PCEA]) versus study group (extended-release epidural morphine [EREM] and femoral nerve block [FNB]).

Figure 3

Quantile box plots of hours spent in the postanesthesia care unit of control group (patient-controlled epidural analgesia [PCEA]) versus study group (extended-release epidural morphine [EREM] and femoral nerve block [FNB]). n, number of patients in each group.

Figure 4

Bar graph comparing aggregate hospital postanesthesia care unit (PACU) cost based on time spent in PACU of control group (patient-controlled epidural analgesia [PCEA]) versus study group (extended-release epidural morphine [EREM] and femoral nerve block [FNB]).