Plasma concentration of ketorolac after local infiltration analgesia in hip arthroplasty

Background Local infiltration analgesia (LIA) with local anaesthetic (ropivacaine), a nonsteroidal anti-inflammatory drug (ketorolac) and epinephrine after lower extremity arthroplasty has gained increasing popularity during the last decade. This method has certain advantages, which include minimal systemic side effects, faster post-operative mobilization, earlier post-operative discharge from hospital and less opioid consumption. However, information regarding plasma concentrations of ketorolac after LIA mixture is insufficient to predict the risk of renal impairment in patients subjected to arthroplasty. Aim To determine the maximal plasma concentration and the exposure of ketorolac during the first 30 h following LIA in hip arthroplasty. Methods Thirteen patients scheduled for primary total hip arthroplasty with LIA (ropivacaine 200 mg, ketorolac 30 mg and epinephrine 0.5 mg in a volume of 106 ml) were included. Plasma concentration of ketorolac was quantified by liquid chromatography-mass spectrometry. In addition, we assessed the effect of increasing age and decreasing glomerular filtration rate on the maximal plasma concentration and the total exposure to ketorolac during 30 h. Results The range of the maximal plasma concentration, 0.3–2.2 mg/l, was detected 30 min–4 h after completing the infiltration. Similar plasma levels have been reported after intramuscular injection of the same dose of ketorolac to healthy elderly volunteers. Conclusion Exposure to ketorolac after LIA may be comparable to an intramuscular injection of the same dose. Decision of dose reduction should be based on clinical assessment of risk factors.