Pain control after total knee arthroplasty: a randomized trial comparing local infiltration anesthesia and continuous femoral block

Local infiltration analgesia (LIA) is a new multimodal wound infiltration method. It has attracted growing interest in recent years and is widely used all over the world for treating postoperative pain after knee and hip arthroplasty. This method is based on systematic infiltration of a mixture of ropivacaine, a long acting local anesthetic, ketorolac, a cyclooxygenase inhibitor (NSAID), and adrenalin around all structures subject to surgical trauma inknee and hip arthroplasty. Two patient cohorts of 40 patients scheduled for elective total knee arthroplasty (TKA) and 15 patients scheduled for total hip arthroplasty (THA) contributed to the work presented in this thesis. In a randomized trial the efficacy of LIA in TKA with regard to pain at rest and upon movement was compared to femoral block. Both methods result in a high quality pain relief and similar morphine consumption, but fewer patients in the LIA group reported pain of 7/10 on any occasion during the 24 h monitoring period (paper I). In the same patient cohort the maximal total plasma concentration of ropivacaine was below the established toxic threshold for most patients although a few reached potentially toxic concentrations of 1.4-1.7 mg/L. The time to maximal detected plasma concentration was around 4-6 h after release of tourniquet in TKA (paper II). All patients in the THA cohort were subjected to the routine LIA protocol. In these patients both the total and unbound plasma concentration of ropivacaine was determined. The concentration was below the established toxic threshold. As ropivacaine binds to a-1 acid glycoprotein(AAG) we assessed the possibility that increased AAG may decrease the unbound concentration of ropivacaine. A40 % increase in AAG was detected during the first 24 h after surgery, however the fraction of unbound ropivacaine remained the same. There was a trend towards increased C max of ropivacaine with increasing age and decreasing creatinine clearance but the statistical power was too low to draw any conclusion (paper III). Administration of 30mg ketorolac according to the LIA protocol both in TKA and THA resulted in a similar Cmax as previously reported after 10 mg intramuscular ketorolac (paper II, paper IV). Neither age, nor body weight or BMI, nor creatinine clearance, correlates to maximal ketorolac plasma concentration or total exposure to ketorolac (AUC) (paper IV). In conclusion, LIA provides good postoperative analgesia which is similar to femoral block after total knee arthroplasty. The plasma concentration of ropivacaine seems to be below toxic levels in most TKA patients. The unbound plasma concentration of ropivcaine in THA seems to be below the toxic level. The use of ketorolac in LIA may not be safer than other routes of administration, and similar restrictions should be applied in patients at risk of developing side effects

Local infiltration analgesia adds no clinical benefit in pain control to peripheral nerve blocks after total knee arthroplasty.

PURPOSE: To evaluate the effect of the local infiltration of analgesics for pain after total knee arthroplasty in patients treated with femoral and sciatic peripheral nerve blocks. The secondary objective was to detect differences in analgesic consumption as well as blood loss after local infiltration of analgesics. METHODS: Prospective randomized double-blinded study in patients who underwent a TKA for knee osteoarthritis under spinal anesthesia and treated with femoral and sciatic nerve blocks. This study compared 50 patients treated with local infiltration with ropivacaine, epinephrine, ketorolac and clonidine and 50 patients treated with a placebo with the same technique. The visual analogic score was registered postoperatively at 2, 6, 12, 24, 36, 48 and 72 h after surgery. Analgesic consumption was also registered. Both groups of patients were treated with the same surgical and rehabilitation protocols. RESULTS: A significant difference of one point was found in the visual analogic pain scores 12 h after surgery (0.6 ± 1.5 vs. 1.7 ± 2.3). There were no significant differences in the visual analogic pain scores evaluated at any other time between 2 and 72 h after surgery. No significant differences were found in the required doses of tramadol or morphine in the postoperative period. Postoperative hemoglobin and blood loss were also similar in both groups. CONCLUSION: Adding local infiltration of analgesics to peripheral nerve blocks after TKA surgery only provides minimal benefit for pain control. This benefit may be considered as non-clinically relevant. Moreover, the need for additional analgesics was the same in both groups. Therefore, the use of local infiltration of analgesics treatment in TKA surgery cannot be recommended if peripheral nerve blocks are used