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Single-injection femoral nerve block lacks preemptive effect on postoperative pain and morphine consumption in total knee arthroplasty Full Text
Acta Anaesthesiologica Taiwanica, 07/11/2012
Chan MH et al. – Patients who received femoral nerve block (FNB) used for total knee arthroplasty consumed significantly less postoperative morphine and had significant relief of post–total knee arthroplasty (TKA) pain on postoperative day 1 than those who did not have FNB. However, at follow–up the authors found no significant differences in these values between those receiving FNB before surgery and those receiving it after surgery.
Methods- In this double–blind, randomized, controlled trial, the authors divided 82 patients (ASA physical status I–III) undergoing unilateral TKA into four groups:
- A pre–treatment group, in which FNB was performed with 0.4mL/kg 0.375% bupivacaine plus 1:200,000 epinephrine after spinal anesthesia but before the operation
- A post–treatment group, in which FNB was performed with the same drugs at similar dosages immediately after the operation
- A pre–control group, in which FNB was performed with normal saline in the same volume as the tested drugs before the operation
- A a post–control group, in which FNB was performed with normal saline in the same volume as the tested drug after the operation
- At 2, 4, 6, 24, 48 and 72 postoperative hours, they recorded cumulative morphine consumption, visual analog pain scales (VAS), the time of first request for morphine and its side effects.
- They also measured knee maximum flexion range of motion once a day for 3days.
- The primary aim was to obtain cumulative morphine consumption in 24hours.
- Within the postoperative 24hours, the authors found significant differences in cumulative morphine consumption between patients who received true FNB and those who did not (at 24hours, treatment groups=45.6±31.7 and 33.5±20.6mg vs. controls=70.8±31.2 and 78.8±37.7mg, p<0.001).
- They also found significant differences in VAS (at 24hours, p<0.001) and time to first request of morphine (p=0.005) between the treatment group and the sham group.
- However, there were no significant differences in these values between the pre–surgical treatment group and the post–surgical treatment group.
- Beyond 24hours, there were no significant differences in morphine consumption or maximum flexion range on day 2 and day 3 among the four groups.
