Renal function estimations and dose recommendations for Gabapentin, Ibuprofen and Morphine in acute hip fracture patients

Abstract

Abstract Aims Optimization of pain management is essential for fasttrack surgery and safety in acute hip fracture (AHF) patients. Kidney function determines the doses of several postoperative painkillers, but previous studies have shown the standard Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation overestimate glomerular filtration rate (GFR) in elderly and underweight patients. The optimized Cockcroft Gault (CGop) equation might be more accurate in this patient group. The study aims to (1) investigate the differences in estimated GFR (eGFR) based on CKD-EPI and CGop and (2) to simulate this impact on recommended dosing of standard painkillers in AHF patients. Methods Patients admitted with AHF from January to April 2015 were included. eGFR was calculated for each patient by CKD-EPI and CGop based on the lowest measured serum creatinine between 1 and 4 days postoperatively. CKD-classification (1–5) was performed based on both eGFR values. If patients were classified differently based on the two eGFR values, then drug dosages were simulated for Morphine, Ibuprofen and Gabapentin according to prescribing recommendations in Renbase®.Two-sided Mann–Whitney test was used to compare median values between groups. Results 176 patients (62% women) with a median age of 76 years were included. CKD-EPI (78.0mL/min/m2) estimated eGFR significantly higher compared with GGop (58.9, P < 0.001). Depending on the equation used to estimate GFR, CKD ≥ 3 (eGFR < 60 mL/min/m2) occurred in 23–53% all patients. Using CGop to estimate GFR resulted in CKD re-classification for 63% of all patients. Using CKD-EPI to estimate GFR resulted in significantly higher doses of Morphine, Ibuprofen and Gabapentin (P < 0.0001) in re-classified patients. Conclusions GFR estimates are significantly higher when calculated by CKD-EPI compared to CGop, and this difference results in significantly higher recommended doses of painkillers in AHF patients. Future studies should include a gold standard for measuring GFR and maybe alternative biomarkers for the renal function.