Uric acid: a novel risk factor for acute kidney injury in high-risk cardiac surgery patients?

BACKGROUND: Uric acid has been reported to be a risk factor for the development of chronic kidney disease; however, no study has examined whether uric acid may confer a risk for acute kidney injury. METHODS: We investigated the relation between serum uric acid and the incidence of postoperative acute kidney injury in patients undergoing high-risk cardiovascular surgery (cardiac valve and aneurysm surgery). RESULTS: Following cardiovascular surgery, 18 of 58 patients (31%) developed acute kidney injury, with 11 of 24 (45.8%) in the elevated uric acid group (defined as >6 mg/dl) and 7 of 34 (20.5%) in the normal uric acid group (p = 0.05). After controlling for baseline renal function, left ventricular ejection fraction, use of nesiritide, type of surgery, and history of previous surgery, an elevated preoperative uric acid conferred a 4-fold risk for acute kidney injury (OR: 3.98, CI: 1.10-14.33, p = 0.035) and longer hospital stay (36.35 vs. 24.66 days, p = 0.009). CONCLUSION: This preliminary study suggests that uric acid may be a novel risk factor for acute kidney injury in patients undergoing high-risk cardiovascular surgery.

Effect of uric acid lowering therapy on the prevention of acute kidney injury in cardiovascular surgery.

PURPOSE: Serum uric acid (SUA) is a novel risk factor for acute kidney injury (AKI), which adversely affects renal blood flow autoregulation, glomerular filtration rate (GFR), and promotes inflammation and angiogenesis. This pilot study investigated the effect of lowering SUA therapy on AKI, by using traditional and non-traditional markers. MATERIALS AND METHODS: In this prospective, double-blind, placebo-controlled, randomized pilot trial, 26 hyperuricemic patients undergoing cardiac surgery were randomized to receive rasburicase or placebo in the preoperative period. RESULTS: Subjects receiving rasburicase showed no difference in serum creatinine compared with the control group receiving placebo. Despite no difference in primary endpoint, the rasburicase group had less evidence of renal structural injury as reflected by urine neutrophil-associated lipocalin (uNGAL) concentrations, especially in subjects with higher SUA levels, more severe renal dysfunction (baseline GFR ≤ 45 mL/min/1.73 m(2)) or heart failure (left ventricular ejection fraction ≤45 %). CONCLUSIONS: In this study, rasburicase showed no benefit on postoperative serum creatinine in hyperuricemic subjects undergoing cardiac surgery. However, the observation that markers of structural renal injury such as uNGAL tended to be lower in rasburicase-treated subjects suggests potential different effects of uricase treatment on hemodynamic alterations in renal function versus structural mechanisms of kidney injury.

Long-term outcome of patients treated with prophylactic nesiritide for the prevention of acute kidney injury following cardiovascular surgery.

BACKGROUND: Previously, we reported that the prophylactic use of nesiritide did not reduce the incidence of dialysis or death following cardiovascular (CV) surgery despite reducing the incidence of acute kidney injury (AKI) in the immediate postoperative period. Therefore, we investigated whether the observed renal benefits of nesiritide had any long-term impact on cumulative patient survival and renal outcomes. METHODS: Participants of the Nesiritide Study, a previously reported prospective, double-blind, placebo-controlled, randomized clinical trial investigating the effect of nesiritide on the incidence of dialysis or death at 21 days in adult patients undergoing high-risk CV surgery, were included in the study. Data of the participants' most recent health and renal function status were obtained using institutional review board-approved patient questionnaires, medical records, and the database of the Social Security Administration. RESULTS: Data on all 94 patients from the Nesiritide Study were obtained. The mean follow-up period was 20.8 +/- 10.4 months. No differences in cumulative survival between the groups were noted at follow-up (nesiritide 77.7% vs placebo 81.6%, P = 0.798). Patients with in-hospital incidence of AKI had a higher rate of mortality than those with no AKI (AKI 41.4% vs no AKI 10.7%, P = 0.002). However, differences in survival time were not significant between the groups when the analysis was restricted to patients with AKI (nesiritide 16.8 +/- 4 months vs placebo 18.5 +/- 2.3 months, P = 0.729). CONCLUSIONS: Renoprotection provided by nesiritide in the immediate postoperative period was not associated with improved long-term survival in patients undergoing high-risk CV surgery.

Normotensive ischemic acute kidney injury as a manifestation of intra-abdominal hypertension.

Intra-abdominal hypertension (IAH), leading to abdominal compartment syndrome (ACS), is a frequent cause of acute kidney injury (AKI) in surgical and trauma intensive care units not commonly recognized by nephrologists. Multiple organ systems are often affected and frequently culminate in disastrous outcomes. The diagnosis of AKI as a manifestation of IAH requires a high index of clinical suspicion, especially, because laboratory and imaging studies are unreliable. Early recognition and treatment of the condition is associated with good clinical outcome. We report a typical case of normotensive ischemic AKI as a manifestation of IAH following abdominal surgery.