In this thesis we will use the current state of knowledge that PI can provide a reliable information about the state of peripheral microcirculation during the state of sepsis and septic shock in ICU patients and that can interfere with the timing of starting vasopressor treatment in sepsis and septic shock

Septic shock is the leading cause of death worldwide, with in-hospital and intensive care mortality rates of 11.9% to 47.2%, depending on the setting and severity of the disease .

Endothelial dysfunction is a key element in sepsis pathophysiology. It is responsible for the sepsis-induced hypotension. So the essential step in the management of sepsis is to increase systemic and regional/microcirculatory flow. Increasing arterial blood pressure (ABP) with vasopressors when patients are hypotensive is used to improve the input pressure driving organ perfusion .

Experts' recommendations currently position norepinephrine (NE) as the first-line vasopressor in septic shock. Its early administration may allow achieving the initial mean arterial pressure (MAP) target faster and reducing the risk of fluid overload. However , controversies still exist on some issues such as, whether very early use of norepinephrine (NE) could improve outcome, whether individualized target of mean arterial pressure (MAP) should be applied . Perfusion index (PI) is a reliable noninvasive indicator of peripheral perfusion derived from the photoelectric plethysmographic (PPG) signal of a pulse oximetry . The perfusion index (PI) represents the ratio of pulsatile on non-pulsatile light absorbance or reflectance of the PPG signal. PI determinants are complex and interlinked, involving and reflecting the interaction between peripheral and central hemodynamic characteristics, such as vascular tone and stroke volume. Recently, several studies have shed light on the interesting performances of this variable, especially assessing hemodynamic monitoring in anesthesia, perioperative and intensive care.

Peripheral perfusion index is an early predictor of central hypovolemia. In a prospective observational study in an emergency department, PPI was not significantly different between patients admitted to the hospital and patients discharged from the emergency department suggesting that it could not be used as a triage tool . However, Lime A with his colleagues found that PPI is significantly lower in critically ill patients with a peripheral perfusion alteration(0.7 vs 2.3, p < 0.01) Another study showed that the PPI is altered in septic shock patients, as compared to control subjects in postoperative scheduled surgery. Moreover, in the same study, the PPI was significantly lower in non-survivors. With a 0.20 cutoff value, PPI was predictive of ICU mortality with an AUC of 84% (69-96), a sensitivity of 65% and a specificity of 92%.

Inclusion Criteria:

- All ICU patients with clinically suspected sepsis and septic shock ( signs include fever hypotension oliguria and confusion combined with culture results showing infection .Septic shock is a subset of sepsis involves persistent hypotension (mean arterial pressure ≥ 65 mm Hg, and a serum lactate level > 18 mg/dL [2 mmol/L)not responding to fluid resuscitation ) .

Exclusion Criteria:

• Pregnant females
• Patients on vasopressor or positive inotropic drugs
• Patients with hypothermia (defined as central temperature <35°C).
• Patient with impairment of upper extremity circulation,(such as those who underwent radial artery harvesting for coronary artery bypass grafting or had suspected occlusion of the radial artery prior to surgery,)
• Patients had undergone an operation that involved the large arteries of the aortic arch.
• Patients with atherosclerosis .](streamdown:incomplete-link)

ICU patients with sepsis