Refeeding hypophosphatemia is a common cause of delirium in critically ill patients: a retrospective study

Background The purpose was to explore the correlation between refeeding hypophosphatemia and delirium and analyze the related factors in critically ill patients. Methods We conducted a retrospective review of critically ill patients admitted to Nanjing Drum Tower Hospital between September 2019 and March 2021. The patients were divided into delirium and nondelirium groups. Demographic data, underlying diseases, laboratory findings, comorbidities, nutritional intake and overall prognosis were collected and analyzed. Results In total, 162 patients were included and divided into delirium (n=54) and nondelirium (n=108) groups. Serum phosphorus levels in the two groups decreased significantly in the first three days (P1, P2, P3) after nutrient intake compared with baseline before nutrient intake (Ppre). P1 and P2 were significantly lower in the delirium group compared to the nondelirium group. The maximum blood phosphorus reduction (Pmax) in the first three days after nutrient intake was significantly higher in the delirium group than in the nondelirium group. The time of Pmax in the delirium group was on the first day after nutrient intake. Multivariable logistic regression analysis identified starting route of nutrition and P1< 0.845 mmol/L as the independent predictors of delirium development in critically ill patients. Conclusion The incidence of delirium in critically ill patients is high and associated with refeeding hypophosphatemia. Delirium may occur with serum phosphorus levels less than 0.845 mmol/L on the first day.