Microangiopathic hemolysis and renal failure in malignant hypertension.

Renal dysfunction is an important cause of morbidity and mortality in patients with malignant hypertension. Microangiopathic hemolysis (MAHA) related to malignant hypertension may cause renal insufficiency by obstruction of interlobular arteries. We hypothesized that the presence of MAHA is an important indicator of renal dysfunction and recovery in malignant hypertension. We retrospectively analyzed 97 patients admitted between April 1994 and April 2004 with malignant hypertension. MAHA was defined as a low platelet count (<150x10(9)/L) with either an elevated lactic dehydrogenase (>220 U/L) or presence of schistocytes. MAHA was present in 26 of 97 patients (27%). Serum creatinine levels at admission were significantly higher in those with than in those without MAHA: median serum creatinine 690 micromol/L (interquartile range [IQR] 394 to 1105) and 120 micromol/L (IQR 82 to 211), respectively (P<0.01). Macroalbuminuria was present in 88% with versus 41% without MAHA (P<0.01). Patients with MAHA were more often black (73%; P<0.01) and had higher systolic blood pressure (mean 242 mm Hg versus 225 mm Hg; P<0.01). Dialysis was needed in 15 patients with MAHA (58%) versus 2 patients (3%) without MAHA. In 6 patients with MAHA, dialysis could be stopped. Cox regression analysis showed that MAHA and systolic blood pressure were the most important indicators of renal improvement during follow-up, with a hazard ratio of 0.24 (95% confidence interval [CI], 0.08 to 0.75; P=0.01) and 1.02 per mm Hg increase in systolic blood pressure (95% CI, 1.01 to 1.05; P=0.01). In conclusion, MAHA is an important indicator of renal insufficiency and recovery in patients with malignant hypertension.