How does hypophosphatemia present?
Since phosphorus is a key ingredient to the cellular energy molecule, adenosine triphosphate (ATP), hypophosphatemia causes symptoms related to the lack of ATP. Symptoms are rare until the phosphorus falls below 1 mg/dL (0.32 mmol/L). The most severe hypophosphatemia can cause hemolysis from decreased red blood cell deformability due to ATP depletion. Hypophosphatemia can also cause rhabdomyolysis. Hemolysis and rhabdomyolysis both release intracellular phosphorus covering the tracks of the inciting hypophosphatemia.
A number of studies have associated hypophosphatemia with increased hospital mortality; however, the lack of randomized, interventional trials keeps the question open of whether the hypophosphatemia causes or is associated with the increased mortality.
Hypophosphatemia has been associated with decreased respiratory muscle strength resulting in increased duration of mechanical ventilation. Others have reported decreased myocardial contractility, and improved left ventricular performance was documented with the correction of severe (<1 mg/dL or 0.3 mmol/L) but not moderate hypophosphatemia. Decreased phosphorus can result in central nervous system (CNS) symptoms ranging from paresthesias (perioral numbness) to irritability, delirium, seizures, and coma.