Effect of hypophosphatemia on the prognosis of critically ill patients

Abstract

To explore the impact of hypophosphatemia on the occurrence and prognosis of critically ill patient. The clinical data of critically ill patients admitted to the intensive care unit (ICU) of Tianjin First Central Hospital from October 2021 to April 2022 were retrospectively analyzed. Patients were divided into hypophosphatemia group (serum phosphorus level < 0.80 mmol/L) and non-hypophosphatemia group (serum phosphorus level ≥ 0.80 mmol/L) when they were admitted to the ICU. The following variables were also collected, including gender, age, acute physiology and chronic health evaluation II (APACHE II), sequential organ failure assessment (SOFA), serum phosphorus level, serum calcium level, serum magnesium level, white blood cell count (WBC), neutrophil count (NEU), lymphocyte count (LYM), neutrophil/lymphocyte ratio (NLR), C-reactive protein (CRP), presence of infection and infection site, length of hospital stay, ICU stay, 28-day mortality, and mechanical ventilation time. Multivariate Logistic regression analysis was used to evaluate the relationship between each variable and the 28-day mortality. The receiver operator characteristic curve (ROC curve) was drawn, and the area under the ROC curve (AUC) and 95% confidence interval (95%CI) were calculated to evaluate the predictive value of serum phosphorus levels for the prognosis of ICU patients. A total of 263 patients were enrolled, including 54 patients with hypophosphatemia and 209 patients without. The SOFA score, LYM level and the infection rate of patients in the hypophosphatemia group were significantly higher than those in the non-hypophosphatemia group [SOFA score: 6.70±3.17 vs. 5.64±3.59, LYM (×109/L): 0.99±0.54 vs. 0.77±0.54, infection rate: 77.78% (42/54) vs. 59.33% (124/209), all P < 0.05], the NLR was significantly lower than that of the non-hypophosphatemia group [10.67 (7.08, 18.02) vs. 12.25 (7.25, 21.68), P < 0.05]. The length of hospital stay, ICU stay, and mechanical ventilation duration in the hypophosphatemia group were significantly longer than those in the non-hypophosphatemia group [length of hospital stay (days): 15 (11, 28) vs. 12 (6, 21), length of ICU stay (days): 10.35±7.80 vs. 7.15±6.61, mechanical ventilation duration (days): 3 (0, 12) vs. 2 (0, 5), all P < 0.05]. There was no significant difference in the 28-day mortality between the hypophosphatemia group and the non-hypophosphatemia group [9.26% (5/54) vs. 11.00% (23/209), P > 0.05]. Multivariate Logistic regression analysis showed that APACHE II score [odds ratio (OR) = 1.188, 95%CI was 1.110-1.271], CRP (OR = 1.016, 95%CI was 1.007-1.026), and NLR (OR = 1.002, 95%CI was 0.996-1.008) were independent risk factors affecting the 28-day mortality of critically ill patients in ICU (all P < 0.05). ROC curve analysis showed that the AUC of serum phosphorus levels for predicting the length of hospital stay of critically ill patients in ICU > 10 days, ICU stay > 5 days, and mechanical ventilation duration > 5 days were 0.701 (95%CI was 0.632-0.770), 0.771 (95%CI was 0.691-0.852), 0.617 (95%CI was 0.541-0.692), respectively, all P < 0.01. Hypophosphatemia has some predictive value for the length of hospital and ICU stay and mechanical ventilation time in critically ill patients, but it cannot predict the 28-day mortality.