Rhabdomyolysis-Associated Acute Kidney Injury With Normal Creatine Phosphokinase.

Rhabdomyolysis is a syndrome characterized by the breakdown of skeletal muscle and leakage of intracellular myocyte contents, such as creatine phosphokinase (CPK) and myoglobin, into the interstitial space and plasma resulting in acute kidney injury (AKI). Elevated CPK of at least 5 times the upper limit of normal is an important diagnostic marker of Rhabdomyolysis. We present a case of rhabdomyolysis with severe AKI with a normal CPK at presentation. A 32-year-old man presented with acute respiratory failure and AKI after an overdose of recreational drugs. Urinalysis at presentation showed trace amounts of blood, identified as rare red blood cells under microscopy. CPK was 156 U/L at presentation. Workup for glomerulonephritis and vasculitis was negative. He was initiated on renal replacement therapy, and a kidney biopsy showed severe acute tubular injury with positive myoglobin casts. Supportive management and renal replacement therapy was provided, and renal function spontaneously improved after a few weeks. This is an uncommon clinical presentation of severe rhabdomyolysis complicated by AKI. This suggests that CPK alone may not be a sensitive marker for rhabdomyolysis-induced AKI in some cases.

Angiotensin II stimulates superoxide production by nitric oxide synthase in thick ascending limbs.

Angiotensin II (Ang II) causes nitric oxide synthase (NOS) to become a source of superoxide (O2 (-)) via a protein kinase C (PKC)-dependent process in endothelial cells. Ang II stimulates both NO and O2 (-) production in thick ascending limbs. We hypothesized that Ang II causes O2 (-) production by NOS in thick ascending limbs via a PKC-dependent mechanism. NO production was measured in isolated rat thick ascending limbs using DAF-FM, whereas O2 (-) was measured in thick ascending limb suspensions using the lucigenin assay. Consistent stimulation of NO was observed with 1 nmol/L Ang II (P < 0.001; n = 9). This concentration of Ang II-stimulated O2 (-) production by 50% (1.77 ± 0.26 vs. 2.62 ± 0.36 relative lights units (RLU)/s/µg protein; P < 0.04; n = 5). In the presence of the NOS inhibitor L-NAME, Ang II-stimulated O2 (-) decreased from 2.02 ± 0.29 to 1.10 ± 0.11 RLU/s/µg protein (P < 0.01; n = 8). L-arginine alone did not change Ang II-stimulated O2 (-) (2.34 ± 0.22 vs. 2.29 ± 0.29 RLU/s/µg protein; n = 5). In the presence of Ang II plus the PKC α/ß1 inhibitor Gö 6976, L-NAME had no effect on O2 (-) production (0.78 ± 0.23 vs. 0.62 ± 0.11 RLU/s/µg protein; n = 7). In the presence of Ang II plus apocynin, a NADPH oxidase inhibitor, L-NAME did not change O2 (-) (0.59 ± 0.04 vs. 0.61 ± ×0.08 RLU/s/µg protein; n = 5). We conclude that: (1) Ang II causes NOS to produce O2 (-) in thick ascending limbs via a PKC- and NADPH oxidase-dependent process; and (2) the effect of Ang II is not due to limited substrate.

Bicarbonate Therapy in End-Stage Renal Disease: Current Practice Trends and Implications.

Management of metabolic acidosis covers the entire spectrum from oral bicarbonate therapy and dietary modifications in chronic kidney disease to delivery of high doses of bicarbonate-based dialysate during maintenance haemodialysis (MHD). Due to the gradual depletion of the body's buffers and rapid repletion during MHD, many potential problems arise as a result of our current treatment paradigms. Several studies have given rise to conflicting data about the adverse effects of our current practice patterns in MHD. In this review, we will describe the pathophysiology and consequences of metabolic acidosis and its therapy in CKD and ESRD, and discuss current evidence supporting a more individualized approach for bicarbonate therapy in MHD.