Continuous Femoral Nerve Block for Knee Arthroplasty: A Comparison of Three Evolving Regimens
Nantthasorn Zinboonyahgoon MD*,**, Kristin Schreiber MD, PhD*, Jose Zeballos MD*, Rejean Gareau MD***, Michael Zaccagnino MD*, Carolyn Beagan PT, DPT****, David Janfaza MD*, Xiaoxia Liu MS*, Kamen Vlassakov MD*
Affiliation : * Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital/Harvard Medical School, Boston, MA, USA ** Department of Anesthesiology, Siriraj Hospital, Mahidol University, Bangkok, Thailand *** Department of Anesthesiology, University of Ottawa, Ottawa, ON, Canada **** Department of Physical Therapy, Brigham and Women’s Hospital, Boston, MA, USA
Objective : Continuous femoral nerve block (CFNB) for knee arthroplasty can provide adequate postoperative pain relief,
however it also can cause muscle weakness and delay ambulation. The present study attempted to determine the optimal
CFNB regimen for pain control, without compromising postoperative physical therapy (PT).
Material and Method: The medical records of 214 patients who had undergone knee replacement with three different
CFNB regimens were reviewed. Group 1: bolus with 0.5% ropivacaine or bupivacaine, followed by 0.2% or 0.25% bupivacaine
infusion; Group 2: bolus with 0.5% ropivacaine or bupivacaine, followed by 0.125% bupivacaine infusion; Group 3: bolus
with 1.5% mepivacaine, followed by 0.125% bupivacaine infusion. The primary outcome assessed was the ability to participate
in PT on postoperative day (POD) 2, and was compared between groups. Additionally, the association of demographic
variables, pain score, opioid consumption, and anesthetic data with impairment of PT participation was investigated.
Results : The incidence of impaired PT was 8% in group 1, 0% in group 2, and 7.8% in group 3. There were no differences
in pain scores between the three groups, but group 3 had higher opioid consumption and shorter time to first analgesic, as
well as higher average pain score on POD1. Impaired PT performance on POD2 was associated with regimens 1 and 3,
older age, higher ASA class and general anesthesia, and associated with longer hospital stay.
Conclusion : A more aggressive femoral nerve block regimen may result in motor weakness, but a less aggressive regimen
may lead to inadequate pain control. A mid-level regimen improved PT performance without compromising pain control.
Keywords : Femoral nerve block, Local anesthetics, Knee arthroplasty, Posteroperative pain, Motor weakness, Physical therapy
