Correlation and Outcomes of Serum Phosphorous Levels among Critically Ill Patients – An Observational Study

INTRODUCTION: Phosphorous homeostasis is a complex process and critically ill patients undergo dynamic changes during their stay in ICU, which results in fluctuations of phosphorous levels. Recent literature has shown that Delta phosphorus is a predictive factor for adverse outcomes in critically ill patients. OBJECTIVES: To assess association and outcomes of Serum Phosphorous levels among critically ill patients: Impact of Phosphorous disturbances on mortality among critically ill patients. Whether Phosphorus disturbances associated with development of organ failure and alters outcomes in critically ill patients? MATERIALS AND METHODS: We enrolled 327 patients based on Inclusion and Exclusion criteria. It was a prospective, unblinded study. The study duration was 1year. Patients were categorized into 3groups (Normo, hypo and hyperphosphatemia groups) based on admission phosphorus levels. We measured Phosphorus at Admission (Day-1), on Day-3, Day-5, Day-7 and Discharge/death phosphorus levels. Delta phosphorus is the fluctuations/changes in phosphorus levels during first week of ICU stay. We calculated the Delta Phosphorus (ΔP1: Day3- baseline, ΔP2: Day5-baseline, ΔP3: Day 7-baseline, ΔP4: discharge/death-baseline). The primary outcome of our study was to assess the impact of phosphorous on ICU mortality and secondary outcomes were length of ICU stay, Duration of mechanical ventilation and Adverse events. Important high-risk sub-groups like Sepsis, AKI and Mechanical ventilation groups were also analyzed. Statistical Analysis was performed using SPSS (IBM SPSS statistics, version 25, IBM Corp, New York, USA) with statistical significance (P-value < 0.05) evaluated at 5% and 95% confidence interval. RESULTS: In our study, 14.98%(49/327) patients had ICU mortality. Moratlity in Normo-P group was 27(55.10%), hyper-P had 12 (24.49%) then hypo-P group had 10(20.41%). We observed that delta phosphorous (ΔP2 and ΔP3) were associated with ICU mortality (P = 0.05, P = 0.035). We found significant correlation of (ΔP4) with ICU length of stay (correlation coefficient: 0.11, P =0.047). There was no significant association of delta phosphorus with duration of mechanical ventilation. Patients with Hyperphosphatemia had higher ICU length of stay (non-survivors: 9.67± 10.03 days, survivors: 5.97 ± 2.67 days, P < 0.001) and duration of mechanical ventilation (Non-survivors; 7.82±10.92, Survivors: 4.83 ± 2.43, P = 0.436). 134(40.98%) patients out of 327 had adverse events. The most common adverse events in our study were Respiratory (24.2%) (Difficult weaning with Prolonged ventilation days) f/b Cardiovascular (11.6%) (Cardiogenic shock, dysarrythmias like Atrial fibrillation, SVT and Ventricular tachycardias). Around 11% of our study population had delirium and critical illness myopathy with prolonged length of ICU stay. In our study, 84 patients (25.68%) had sepsis and septic shock, among them 44 (52.38%) patients were survivors. We found statistically significant association of ΔP3 with ICU mortality (P = 0.017) in sepsis group. 117 (35.78%) patients out of 327 had AKI, out of which 29 (24.79%) patients required dialysis and 33 (28.2%) patients had ICU mortality. We demonstrated that Delta Phosphorous ΔP2 (Day 5-baseline) had significant correlation with ICU mortality in AKI group (P = 0.05). We did not find any significant association of delta phosphorous with patients requiring Mechanical ventilation. SUBGROUP ANALYSIS: CONCLUSION: This study emphasizes the importance of Delta phosphorous in determining the short term mortality in ICU. It is important to reduce fluctuations in phosphorous levels during ICU stay and to maintain Phosphorous concentrations within the normal range in order to improve patient outcomes.