Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection.

Septic shock is a subset of sepsis in which underlying circulatory and cellular/metabolic abnormalities are profound enough to substantially increase mortality.

Septic shock represents the most severe form of sepsis and remains a leading cause of admission to intensive care units (ICUs) worldwide. It is characterized by profound circulatory, cellular, and metabolic abnormalities resulting from a dysregulated host response to infection .

Despite significant advances in antimicrobial therapy, haemodynamic monitoring, organ support, and critical care management, septic shock continues to be associated with high morbidity and mortality. Patients frequently develop multiple organ dysfunction requiring prolonged ICU stay, mechanical ventilation, vasopressors support, and renal replacement therapy .

Identification of modifiable risk factors that influence clinical outcomes remains a major priority in the management of septic shock. Electrolyte disturbances are common among critically ill patients, with hypophosphatemia being one of the most frequently encountered abnormalities .

Serum phosphate plays a vital role in numerous physiological processes, including cellular energy production, adenosine triphosphate (ATP) synthesis, oxygen delivery through regulation of 2,3-diphosphoglycerate, membrane integrity, intracellular signaling, acid-base balance, and neuromuscular function .

In septic shock, hypophosphatemia may develop because of intracellular phosphate redistribution induced by catecholamine release, respiratory alkalosis, insulin administration, aggressive fluid resuscitation, renal phosphate wasting, malnutrition, and continuous renal replacement therapy. Consequently, phosphate depletion may occur early during the course of critical illness and may persist despite standard supportive treatment .

Hypophosphatemia has important clinical implications in critically ill patients. Severe phosphate deficiency impairs diaphragmatic contractility, respiratory muscle strength, myocardial performance, leukocyte function, and skeletal muscle metabolism. These abnormalities may delay liberation from mechanical ventilation, impair oxygen delivery, increase susceptibility to infection, prolong ICU stay, and adversely affect patient outcomes .

Several studies have suggested that hypophosphatemia is associated with increased disease severity, prolonged mechanical ventilation, and higher mortality in critically ill patients, although the available evidence remains inconsistent, particularly among patients with septic shock.

Mechanical ventilation is frequently required in septic shock because of respiratory failure, acute respiratory distress syndrome, impaired consciousness, or hemodynamic instability. Successful weaning from mechanical ventilation depends largely on adequate respiratory muscle function and sufficient cellular energy production, both of which require normal phosphate homeostasis .

Hypophosphatemia may reduce diaphragmatic strength and impair respiratory muscle endurance, resulting in prolonged ventilator dependence and delayed weaning. Therefore, early recognition and correction of phosphate deficiency may represent a potentially modifiable factor capable of improving respiratory outcomes in critically ill patients .

Although phosphate disturbances are well recognized in the ICU, data regarding the incidence of hypophosphatemia upon ICU admission and its relationship with the duration of mechanical ventilation in patients with septic shock remain limited, particularly in developing countries. Understanding this relationship may facilitate early identification of high-risk patients, optimize electrolyte management, improve ventilator weaning strategies, and ultimately reduce ICU morbidity and healthcare costs .