Comparison of two methods of continuous femoral nerve block with elastomeric pump after total knee arthroplasty

Background
The best method of continuous femoral nerve block (CFNB) after total knee arthroplasty (TKA) has not been determined. The study aimed to assess the effectiveness of CFNB based on patient-controlled regional analgesia (PCRA) with basal infusion of local anesthetic in decreasing pain and providing functional restoration after TKA and to compare it with the method of basal infusion only.

Methods
The prospective randomized controlled trial included 90 patients who were divided into three groups. Group I: control group with basal morphine infusion, without CFNB. Group II: CFNB with continuous infusion of ropivacaine. Group III: CFNB with basal infusion of ropivacaine plus boluses. Intensity of pain, morphine consumption, patient satisfaction, adverse effects, the effect on range of motion (ROM) in the knee joint, as well as using the measure of a distance were analyzed.

Results
A lower level of pain was observed (P < 0.005), as was reduced opioid consumption (P < 0.005), a greater ROM (P < 0.005), a longer distance covered (P < 0.005), and a smaller incidence of nausea in group III when compared with group II. No statistically significant difference was noted between the groups in terms of other side effects. There was higher satisfaction between group II and group III on days 1 and 2 (P < 0.08).

Conclusions
It was demonstrated that CFNB with continuous infusion of 5 mL h-1 of 0.2% ropivacaine plus 5 mL as a bolus causes a greater reduction in pain intensity and opioid consumption; it also shortens the time of functional restoration in comparison to perineural infusion of 5mL h-1 only during the first 4 days after TKA and constitutes an effective and safe alternative to using an electronic pump.