Measurement of Whole Blood Lactate Concentrations Whole blood lactate concentrations will be measured at the time of study enrollment and at 24, 48, and 72 hours. Measurement of Plasma Renin Concentrations Serum renin concentration will be measured on blood samples drawn from arterial catheters on supine position right after inclusion. Discarded whole blood samples (waste blood samples) in EDTA tubes are prospectively collected from each patient at the time of study enrollment and at 24, 48, and 72 hours.

Elevated renin-levels in critically ill patients are associated with worse outcomes and outperform lactate as a prognostic indicator of survival. Using biomarkers to understand patient trajectory in the ICU has high utility.

Both whole blood lactate concentration and lactate clearance yield meaningful information, but lactate can be an insensitive prognostic marker. Renin has recently emerged as a prognostic marker for ICU mortality.

AIM OF THE WORK Evaluation of serum renin level to determine if it performs well as a marker of tissue-perfusion and prediction of mortality of critically ill patients in intensive care unit in comparison with serum lactate.

a prospective observational study will be conducted.. Patients can be enrolled at any point during their admission. The patients are followed once enrolled and the data are recorded till death or end of ICU stay by dedicated investigator. Primary and secondary outcomes will be analyzed after completing of the study.

Plasma renin concentrations and Whole blood lactate concentrations are measured at enrollment and at 24, 48, and 72 hours.

Measurements

1. Patient characteristics: including age, sex, chronic health conditions, weight.
2. Reasons of ICU admission.
3. length of stay in days (ICU and hospital).
4. Mortality (ICU and in-hospital).
5. Physiologic data: including heart rate, mean arterial blood pressure (MAP), temperature, respiratory rate, PaO2, FIO2, hematocrit, WBC count, serum creatinine, urine output, blood urea nitrogen, sodium, albumin, bilirubin, glucose, arterial carbon dioxide tension, pH, and the total Glasgow Coma Scale score.
6. The need for mechanical ventilation and renal replacement therapy.
7. Patient outcome either survivor or not survivor. Measurement of Whole Blood Lactate Concentrations Whole blood lactate concentrations will be measured at the time of study enrollment and at 24, 48, and 72 hours.

Measurement of Plasma Renin Concentrations Serum renin concentration will be measured on blood samples drawn from arterial catheters on supine position right after inclusion.

Discarded whole blood samples (waste blood samples) in EDTA tubes are prospectively collected from each patient at the time of study enrollment and at 24, 48, and 72 hours.

Samples will be centrifuged to yield 2mL of EDTA plasma and then stored at -20°C. After all samples for the study are collected, frozen samples are thawed for batch analysis.

Plasma active renin levels are measured using the active renin enzyme-linked immunosorbent assay kit.

Inclusion Criteria:

1. Patients aged 21-60 years old
2. Those receiving vasopressors for greater than or equal to 6 hours to maintain a mean arterial pressure (MAP) ≥65 mm Hg.
3. Anticipated stay >24 hours.

Exclusion Criteria:

1. Patients or families refusing to participate in the study.
2. Patients on renal replacement therapy.
3. Patients receiving betablockers

The study will be conducted at Al-Azhar university hospitals at intensive care unit (ICU). Patients can be enrolled at any point during their admission. The patients are followed once enrolled and the data are recorded till death or end of ICU stay by dedicated investigator