Septic shock is a life-threatening condition with mortality rate of up to -40%. Septic shock is catheterized by altered microcirculation that leads to tissue hypoperfusion and ultimately multi-organ dysfunction. Hence, maintenance of adequate tissue perfusion is the mainstay of resuscitation of patients with septic shock.

Serum lactate is still considered the gold standard for evaluation of tissue perfusion. Thus, according to the latest definition, elevated serum lactate, as an indicator of tissue hypo-perfusion, is required for diagnosis of septic shock. However, lactate level change in response to resuscitation is slow even in survivors.

Capillary refill time (CRT) is a simple method for assessing peripheral perfusion. Monitoring CRT was found to be a good tool for guiding resuscitation and delayed CRT showed good ability in predicting mortality in patients with septic shock.

To the best of our knowledge, there is no previous report assessing the reliability of an index that include both serum lactate and CRT (lactate/CRT index) in predicting mortality in patients with septic shock.

We hypothesize that the lactate/CRT index would have good accuracy in predicting mortality in patient with septic shock.

All patients will be monitored with; non-invasive and invasive arterial blood pressure, five-lead electrocardiography (ECG), hourly urinary output, and central venous pressure (CVP). Management of the patients will be done according to the latest surviving sepsis campaign guidelines in 2016. APACHE II score will be calculated on the time of admission using MDCalc ©.

Arterial blood gases, including serum lactate (blood gas analysis device GEM premier 300, Instrumentation Laboratory, Bedford, MA, USA), will be obtained at the time of intensive care unit admission, 6 and 12 hours after admission. Capillary refill time will be measured by applying enough pressure to cause skin blanching to the ventral surface of the distal phalanx of right index finger and the pressure will be then maintained for 10 seconds. The time for return of the normal skin color will be registered with a stopwatch. CRT will be recoded at the same time point as the blood sample.

The change in serum lactate (∆ Lactate), and CRT (∆ CRT) will be calculated as the difference between each two-consecutive measurement. Lactate/CRT index will be calculated as the product of multiplying the CRT and serum lactate.

Inclusion Criteria:

• Patients with clinically suspected septic shock, older than 18 years old

Exclusion Criteria:

• Patients less than 18 years.
• patients with evident blood loss.
• patients with metastatic cancer.
• Patients with Child B or C liver cirrhosis
• patients with estimated glomerulo filtartion rate less than 30 ml/min/m2

All consecutive patients with clinically suspected septic shock according to the latest definition of septic shock (sepsis-3) "hypotension in a patient with sepsis requiring vasopressor therapy to maintain mean arterial pressure above 65 mmHg despite adequate fluid resuscitation in addition to elevated serum lactate level (above 2 mmol/L)"

the protocol and data supporting this study will be available from the PI upon reasonable request