Analysis on effective concentrations and adverse reactions of Ropivacaine in the modified fascial iliac compartment block for pain relief after total knee arthroplasty in elderly patients / 中华老年医学杂志

ABSTRACT

Objective:To identify the effective concentrations of Ropivacaine in the modified fascial iliac compartment block(FICB)that would not affect the movement of the affected limb but would offer effective pain relief after total knee arthroplasty(TKA)in elderly patients.In addition, adverse reactions within 24 hours of FICB were examined.Methods:This study was a prospective, single-arm sequential trial.Forty-five elderly patients treated with TKA at the First Affiliated Hospital of Soochow University between September 2021 and March 2022 were selected, with an American Society of Anesthesiologists(ASA)score of Ⅰ or Ⅱ.All patients were given ultrasound-guided FICB on the surgical side under general anesthesia and 10 minutes before the operation, and the injection volume was 30 ml.According to preliminary experiments and relevant literature, the initial concentration of Ropivacaine was 0.1%, and the concentration for the next patient was determined using a modified Dixon sequential method.If the quadriceps femoris muscle strength score of the first patient was ≥4, there was no resting pain[visual analogue scale(VAS)score ≤1], and the VAS score during activity was ≤3, the concentration for the next patient would be reduced.Conversely, the concentration would be increased.The Ropivacaine concentration was increased or decreased by 0.01% each time and the trial would be stopped after 12 reentries.The median effective concentration(ED50), 95% effective concentration(ED95)and corresponding 95% confidence interval(CI)of ropivacaine were calculated using the probit model.Meanwhile, adverse reactions within 24 hours of FICB were monitored.Results:Of 43 elderly patients who completed the trial, the intervention was effective in 23 and ineffective in 20.While ensuring that postoperative limb movement in elderly patients was not affected, a single injection of 30 ml ropivacaine through FICB was able to effectively inhibit postoperative pain, and the ED50 and ED95 of ropivacaine were 0.072%(95% CI: 0.065%-0.078%)and 0.093%(95% CI: 0.084%-0.124%), respectively.Within 24 hours of FICB, 2 patients had lower limb weakness and could not get out of bed and walk, and 5 patients had severe pain and needed additional analgesics.No other adverse reactions were found. Conclusions:The effective ED50 and ED95 of Ropivacaine for postoperative pain relief in elderly patients after TKA are 0.072% and 0.093%, respectively.And the incidence of adverse reactions is low.