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.
Prospective observational study.
Single-center, mixed medical-surgical ICU in Europe.
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.
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.
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 < 0.001). There was no diurnal variation of renin or significant interaction of renin-angiotensin-aldosterone system drugs with renin in this population. Continuous renal replacement therapy renin removal was negligible (mass clearance ± sd 4% ± 4.3%). There was a significant difference in the rate of change of renin over time between survivors and nonsurvivors (–32 ± 26 μU/timepoint vs +92 ± 57 μU/timepoint p = 0.03; mean ± sem), but not for lactate (–0.14 ± 0.04 mM/timepoint vs +0.15 ± 0.21 mM/timepoint; p = 0.07). Maximum renin achieved significant prognostic value for ICU mortality (receiver operator curve area under the curve 0.80; p = 0.04), whereas maximum lactate did not (receiver operator curve area under the curve, 0.70; p = 0.17).
In an heterogeneous ICU population, renin measurement was not significantly affected by diurnal variation, continuous renal replacement therapy, or drugs. Renin served as a marker of tissue-perfusion and outperformed lactate as a predictor of ICU mortality.
1Department of Intensive Care, Cliniques Universitaires de Bruxelles-Hôpital Erasme, Brussels, Belgium.
2Immunoreceptors and Renal Immunopathology Laboratory, INSERM U1149, Université Diderot, Paris, France.
3Division of Nephrology, Royal College of Physicians of Ireland, Dublin, Republic of Ireland.
4Faculté de Médecine, Université Libre de Bruxelles, Brussels, Belgium.
*See also p. 288.
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Supported, in part, by the Irish Nephrology Society “Amgen Bursary”, Dublin, Republic of Ireland.
Dr. Gleeson received funding from Irish Nephrology Society (INS), who in turn, received the money from Amgen via the INS Amgen Research Bursary grant; he had no direct dealings with Amgen, and Amgen has no involvement in the study. The remaining authors have disclosed that they do not have any potential conflicts of interest.
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