Sharon Trevino

Urinary cystatin C as an early biomarker of acute kidney injury following adult cardiothoracic surgery

There is a need to develop early biomarkers of acute kidney injury following cardiac surgery, where morbidity and mortality are increased by its presence. Plasma cystatin C (CyC) and plasma and urine Neutrophil Gelatinase Associated Lipocalin (NGAL) have been shown to detect kidney injury earlier than changes in plasma creatinine in critically ill patients. In order to determine the utility of urinary CyC levels as a measure of kidney injury, we prospectively collected plasma and urine from 72 adults undergoing elective cardiac surgery for analysis. Acute kidney injury was defined as a 25% or greater increase in plasma creatinine or renal replacement therapy within the first 72 hours following surgery. Plasma CyC and NGAL were not useful predictors of acute kidney injury within the first 6 hours following surgery. In contrast, both urinary CyC and NGAL were elevated in the 34 patients who later developed acute kidney injury, compared to those with no injury. The urinary NGAL at the time of ICU arrival and the urinary CyC level 6 hours after ICU admission were most useful for predicting acute kidney injury. A composite time point consisting of the maximum urinary CyC achieved in the first 6 hours following surgery outperformed all individual time points. Our study suggests that urinary CyC and NGAL are superior to conventional and novel plasma markers in the early diagnosis of acute kidney injury following adult cardiac surgery.

Development and Standardization of a Furosemide Stress Test to Predict the Severity of Acute Kidney Injury

IntroductionIn the setting of early acute kidney injury (AKI), no test has been shown to definitively predict the progression to more severe stages.MethodsWe investigated the ability of a furosemide stress test (FST) (one-time dose of 1.0 or 1.5 mg/kg depending on prior furosemide-exposure) to predict the development of AKIN Stage-III in 2 cohorts of critically ill subjects with early AKI. Cohort 1 was a retrospective cohort who received a FST in the setting of AKI in critically ill patients as part of Southern AKI Network. Cohort 2 was a prospective multicenter group of critically ill patients who received their FST in the setting of early AKI.ResultsWe studied 77 subjects; 23 from cohort 1 and 54 from cohort 2; 25 (32.4%) met the primary endpoint of progression to AKIN-III. Subjects with progressive AKI had significantly lower urine output following FST in each of the first 6 hours (p<0.001). The area under the receiver operator characteristic curves for the total urine output over the first 2 hours following FST to predict progression to AKIN-III was 0.87 (p = 0.001). The ideal-cutoff for predicting AKI progression during the first 2 hours following FST was a urine volume of less than 200mls(100ml/hr) with a sensitivity of 87.1% and specificity 84.1%.ConclusionsThe FST in subjects with early AKI serves as a novel assessment of tubular function with robust predictive capacity to identify those patients with severe and progressive AKI. Future studies to validate these findings are warranted.

Furosemide Stress Test and Biomarkers for the Prediction of AKI Severity

Clinicians have access to limited tools that predict which patients with early AKI will progress to more severe stages. In early AKI, urine output after a furosemide stress test (FST), which involves intravenous administration of furosemide (1.0 or 1.5 mg/kg), can predict the development of stage 3 AKI. We measured several AKI biomarkers in our previously published cohort of 77 patients with early AKI who received an FST and evaluated the ability of FST urine output and biomarkers to predict the development of stage 3 AKI (n=25 [32.5%]), receipt of RRT (n=11 [14.2%]), or inpatient mortality (n=16 [20.7%]). With an area under the curve (AUC)±SEM of 0.87±0.09 (P<0.0001), 2-hour urine output after FST was significantly better than each urinary biomarker tested in predicting progression to stage 3 (P<0.05). FST urine output was the only biomarker to significantly predict RRT (0.86±0.08; P=0.001). Regardless of the end point, combining FST urine output with individual biomarkers using logistic regression did not significantly improve risk stratification (ΔAUC, P>0.10 for all). When FST urine output was assessed in patients with increased biomarker levels, the AUC for progression to stage 3 improved to 0.90±0.06 and the AUC for receipt of RRT improved to 0.91±0.08. Overall, in the setting of early AKI, FST urine output outperformed biochemical biomarkers for prediction of progressive AKI, need for RRT, and inpatient mortality. Using a FST in patients with increased biomarker levels improves risk stratification, although further research is needed.

Argatroban and Renal Replacement Therapy in Patients with Heparin-Induced Thrombocytopenia

BACKGROUND: Argatroban, a direct thrombin inhibitor, is an effective anticoagulant for patients who have heparin-induced thrombocytopenia (HIT). Anticoagulation is usually required for renal replacement therapy (RRT). OBJECTIVE: To prospectively evaluate the pharmacokinetics, pharmacodynamics, and safety of argatroban during RRT in hospitalized patients with or at risk for HIT. METHODS: Five patients with known or suspected HIT underwent hemodialysis (n = 4) or continuous venovenous hemofiltration (CVVH, n = 1), while receiving a continuous infusion of argatroban 0.5–2 μg/kg/min. Activated partial thromboplastin times (aPTTs), activated clotting times (ACTs), argatroban concentrations (plasma, dialysate, CVVH effluent), and safety were assessed before, during, and after a 4-hour session of RRT. Systemic and dialytic argatroban clearances were calculated. RESULTS: Among the 4 hemodialysis patients, aPTT, ACT, and plasma argatroban concentrations remained stable during RRT, with respective mean ± SD values of 74.3 ± 34.2 seconds, 198 ± 23 seconds, and 499 ± 353 ng/mL before RRT, and 70.6 ± 21.4 seconds, 181 ± 12 seconds, and 453 ± 295 ng/mL 2 hours after starting RRT (p values NS). Systemic clearance was 17.7 ± 12.8 L/h before hemodialysis and 17.0 ± 9.5 L/h during hemodialysis (n = 2). The dialyzer clearance (dialysate recovery method) was 1.5 ± 0.4 L/h (n = 4). Generally similar responses occurred in the CVVH patient: systemic argatroban clearance was 4.8 L/h before CVVH and 4 L/h during CVVH. The hemofilter argatroban clearance was 0.9 L/h. No bleeding or thrombosis occurred. CONCLUSIONS: Argatroban provides effective alternative anticoagulation in patients with or at risk for HIT during RRT. Argatroban clearance by high-flux membranes during hemodialysis and CVVH is clinically insignificant, necessitating no dose adjustment.

Argatroban Anticoagulation in Patients with Heparin-Induced Thrombocytopenia Requiring Renal Replacement Therapy

BACKGROUND: Argatroban, a direct thrombin inhibitor, is used for prophylaxis or treatment of thrombosis in heparin-induced thrombocytopenia (HIT). The recommended initial dose is 2 μg/kg/min (0.5 μg/kg/min in hepatic impairment), adjusted to achieve activated partial thromboplastin time (aPTT) values 1.5–3.0 times baseline. However, few argatroban-treated patients with HIT and renal failure requiring renal replacement therapy (RRT) have been described. OBJECTIVE: To evaluate the safety and efficacy of argatroban anticoagulation during RRT in patients with HIT. METHODS: We retrospectively reviewed records from 47 patients with HIT and renal failure requiring RRT who underwent 50 treatment courses with argatroban. Patients with HIT had received argatroban during prospective, multicenter studies. Outcomes, safety, and dosing information were summarized. RESULTS: In the multicenter experience, no patient died due to thrombosis and 2 (4%) patients developed new thrombosis while on argatroban. No adverse outcomes occurred during argatroban reexposure. Starting doses were typically 2 μg/kg/min in patients without hepatic impairment and <1.5 μg/kg/min in those with hepatic impairment. Median (range) infusion doses were 1.7 (0.2–2.8) and 0.7 (0.1–1.7) μg/kg/min, respectively, with associated median (range) aPTT ratios, relative to baseline, of 2.2 (1.6–3.6) and 2.0 (1.4–4.1), respectively. Major bleeding occurred in 3 (6%) of 50 treatment courses. CONCLUSIONS: Argatroban provides effective anticoagulation upon initial and repeated administration in patients with HIT and renal impairment requiring RRT, with an acceptably low bleeding risk. Current dosing recommendations are adequate for these patients.

Cytokine Clearances in Critically Ill Patients on Continuous Renal Replacement Therapy

Background/Aims: We sought to quantify any differences in cytokine clearance between continuous venovenous hemofiltration (CVVH-convective) compared to continuous venovenous hemodialysis (CVVHD-diffusive). Methods: We conducted a 20 patient, multicenter, prospective, open-label randomized trial (CVVH or CVVHD) at continuous renal replacement therapy (CRRT) initiation. Blood, urine, and effluent were collected at 0, 4, 24, and 48 h after initiation of CRRT. Serum electrolytes, cytokines levels, and clearances were measured. Cytokines studies included IL-1β, IL-1RA, IL-6, IL-10, and TNFα. Results: We randomized 20 patients to receive CRRT. After 4 h of CRRT there was no difference in total cytokine levels or change in cytokine concentrations across the 2 groups. With the exception of IL-1 RA, all cytokines levels decreased across patient groups regardless of modality. There was no significant difference in cytokine concentration across CRRT modality for any time point. Conclusion: Within the first 4 h of CRRT initiation, there is no significant difference between cytokine or solute clearance between CVVH and CVVHD.

9 URINARY CYSTATIN C IN PATIENTS WITH ACUTE KIDNEY INJURY FOLLOWING CARDIAC SURGERY.

Patients developing acute kidney injury (AKI) after cardiac surgery have increased mortality compared with those with stable postoperative renal function. A reliable marker of early AKI in serum or urine has not been found. To test the hypothesis that urinary cystatin C (CyC) increases with greater severity of AKI, we prospectively studied 45 patients undergoing cardiac surgery. Perioperatively, blood and urine were sampled for standard chemistries and CyC (measured by ELISA). AKI was defined as > 25% increase in serum creatinine or the initiation of renal replacement therapy (RRT) within the first 3 postoperative days. AKI developed in 24 patients (53.33%), 5 of whom received RRT (11.1% of the total). The 3-day postoperative maximum increase of urinary CyC from the preoperative baseline was significantly different via ANOVA in those receiving RRT (n = 5) from those with AKI without RRT (n = 16) and those with no AKI (n = 12) (p = .033). This effect is present for the first four postoperative samples, which encompass the first 48 postoperative hours. There was no statistical difference in the preoperative (baseline) urine CyC values. Furthermore, the maximum 3-day increase in perioperative urinary fractional excretion of CyC (FECC) was significantly different across all three groups (no AKI, AKI without RRT, and RRT), p = .01. Similar to urinary CyC, this difference was seen for the first 48 postoperative hours. There was no statistical significance to the preoperative values across all three groups. Increased urinary cystatin C excretion in the early postoperative period precedes the development of severe AKI (requiring RRT) and correlates with AKI severity. Urinary CyC and FECC are promising biomarkers of AKI following adult cardiac surgery. Table 1 Clinical Characteristics of University of Chicago Cardiac Surgery Study Subjects (N= 45)