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
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.
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
< 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
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.