Introduction: Oral anticoagulants (OACs) are often initiated in hospital after cardioembolic stroke. The agent and dose are both dependent on renal function. The optimal assessment of renal function in the early post-stroke period is unknown. We tested the hypotheses that 1) renal function is impaired early after stroke and 2) weight-based estimates of glomerular filtration rate (eGFR) are more sensitive to this acute change.
Methods: We retrospectively recorded all serum creatinine measurements within 1 week of stroke in patients with atrial fibrillation (AF). Measurements were also taken in the year post-stroke. The Cockroft-Gault (CG), Modification of Diet in Renal Disease Study (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations were used to calculated eGFR. Renal function was classified as normal (eGFR>50 ml/min), moderately (eGFR<50 ml/min), or severely impaired (eGFR<30 ml/min).
Results: Measurements were recorded from 300 acute stroke patients over a 1 year period. Median time from symptom onset to first creatinine measurement was 5.2±14.2 h. Within 24 h of symptom onset, 66/300 (22%) and 72/300 (24%) patients had renal impairment (eGFR<50 ml/min/1.73m2) using the MDRD and CKD-EPI equations. The proportion of renal impairment increased to 37.4% (102/273, p<0.0001), when a weight-based calculation (CG) was used. Mean eGFR (CG) within 24 h of symptom onset (65.1±33.5 ml/min) was lower than that by day 7 (68.7±33.3 ml/min, p=0.001). The acute baseline renal impairment improved into normal range in 14/68 (20.6%, p<0.0001) patients within 7 days. Mean eGFR (64.7± 30.7 ml/min, p=0.383) remained stable following discharge (mean time from symptom onset to final assessment 47.4± 5.8 wks). Of the 20 patients with severe renal impairment, eGFR increased to >30 ml/min in 8 (40%, p<0.0001) within 7 days. A total of 231 patients (77%) were treated with an OAC within 7 days of onset. In 145 patients treated with a new OAC, the incorrect dose was initially prescribed in 60 patients.
Conclusion: Acute renal impairment after stroke is common, and is most evident when weight-based eGFR is calculated. The transient nature of this renal impairment suggests OAC agent and dose selection may need to be adjusted following the acute stroke period