Effect of pre-emptive analgesia by continuous femoral nerve block on early postoperative cognitive function following total knee arthroplasty in elderly patients

Abstract

To the best of our knowledge, the effect of pre-emptively blocking pain transmission on acute postoperative cognitive dysfunction (POCD) has not yet been assessed. Therefore, the present study aimed to investigate the effect of pre-emptive analgesia via a continuous femoral nerve block (CFNB) on postoperative pain and early cognitive function following total knee arthroplasty (TKA) surgery in elderly patients. CFNB was performed prior to TKA surgery in the pre-emptive analgesia group (n=30) and following TKA surgery in the control group (n=30). POCD was defined as a two-point reduction in the postoperative score compared with the preoperative score in the mini-mental state examination. The visual analog scale (VAS) was used to evaluate the intensity of pain at rest and during exercise. The intraoperative dose of remifentanil in the pre-emptive analgesia group was significantly lower than in the control group (P<0.01). In the preemptive analgesia group, VAS scores at three days post-surgery were lower than those in the control group (P<0.01). The incidence of POCD on the third postoperative day was slightly lower in the pre-emptive analgesia group compared with the control group. In conclusion, the results demonstrate that pre-emptive analgesia by CFNB may promote the recovery of early cognitive function following TKA in elderly patients.

Keywords: femoral nerve block; postoperative cognitive dysfunction; pre-emptive analgesia; total knee arthroplasty.

Figures

Figure 1.

Diagram of patient grouping. MMSE, mini mental state examination.

Figure 2.

Changes in VAS score between days 1–5. (A) Changes in VAS at rest and (B) during activity. (C) The mini mental state examination of all patients over time. Data are expressed as mean ± standard deviation and tested by generalized estimation equation. The post hoc test of time effect was examined using the Bonferoni correction. The data from the pre-anesthesia group are presented as solid lines and the results from the control group are presented as dotted lines. P#day 3 and ##day 5. VAS, visual analog scale.