Renin as a Marker of Tissue-Perfusion and Prognosis in Critically Ill Patients*

Objectives: To characterize renin in critically ill patients. Renin is fundamental to circulatory homeostasis and could be a useful marker of tissue-perfusion. However, diurnal variation, continuous renal replacement therapy and drug-interference could confound its use in critical care practice. Design: Prospective observational study. Setting: Single-center, mixed medical-surgical ICU in Europe. Patients: Patients over 18 years old with a baseline estimated glomerular filtration rate greater than 30 mL/min/1.73 m2 and anticipated ICU stay greater than 24 hours. Informed consent was obtained from the patient or next-of-kin. Interventions: Direct plasma renin was measured in samples drawn 6-hourly from arterial catheters in recumbent patients and from extracorporeal continuous renal replacement therapy circuits. Physiologic variables and use of drugs that act on the renin-angiotensin-aldosterone system were recorded prospectively. Routine lactate measurements were used for comparison. Measurements and Main Results: One-hundred twelve arterial samples (n = 112) were drawn from 20 patients (65% male; mean ± SD, 60 ± 14 yr old) with septic shock (30%), hemorrhagic shock (15%), cardiogenic shock (20%), or no circulatory shock (35%). The ICU mortality rate was 30%. Renin correlated significantly with urine output (repeated-measures correlation coefficient = –0.29; p = 0.015) and mean arterial blood pressure (repeated-measures correlation coefficient = –0.35; p

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