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NCT Number: NCT06779331

Phosphate Urine Excretion in Critically Ill Patients

Hypophosphatemia is a common disorder in critically ill patients, appearing in 15-35% of Intensive Care Unit (ICU) admissions. Its reasons are multifactorial, including sepsis, refeeding syndrome, and continuous renal replacement therapy. Hypophosphatemia is generally accepted as a predictor of poor outcomes, such as prolonged ventilation and higher mortality. However, conflicting evidence exists and several works demonstrated no effect on length of ventilation, nor mortality. We have recently demonstrated no effect of hypophosphatemia on mortality and length of ventilation. However, both parameters were affected by energy delivery to the patient, with higher energy delivery associated with lower mortality and longer length of ventilation, suggesting a complex interaction between energy delivery to the patient, hypophosphatemia appearance, and patient outcomes. This raised hypothesis that hypophosphatemia is a marker of recovery, as in fulminant hepatic failure, or recovery after hepatectomy.

Phosphate is mainly an intracellular anion, with only 1% of its total body amount is extracellular. It is absorbed from the small intestine, mainly at the jejunum, both through passive para-cellular and active trans-cellular process. Phosphate is excreted in the urine, after being filtered in the glomeruli, and reabsorbed mainly in the proximal tubule (less than 10% of the reabsorption occurs in the distal nephron), by sodium-phosphate co-transporters. Phosphate regulation in the body is complex. It is regulated by vitamin D, parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF-23). Therefore, phosphate regulation is affected both from intestine dysfunction and kidney injury. Although hyperphosphatemia in various kidney injury is well described, the effect of kidney function regarding phosphate excretion in critically ill patients with hypophosphatemia has been scarcely described. French and Bellomo described 7 patients who had decreased phosphate kidney reabsorption during hypophosphatemia. Charrone et. al demonstrated increased phosphate excretion after IV phosphate infusion to 47 critically ill patients with hypophosphatemia. Dickerson et. al demonstrated higher rates of hypophosphatemia in 20 thermally injured patients (compared to 20 multiple trauma patients) despite greater phosphate delivery through nutrition, along with increased (although insignificant) phosphate urinary excretion in this group. This might suggest that increased renal phosphate loss has a role in hypophosphatemia development. Better understanding these processes is important, with regard to the effect of nutritional support and hypophosphatemia effects on patients' outcomes. This study aims to describe urinary phosphate excretion in critically ill patients with regard to kidney function, phosphate serum level, and phosphate intake.

Active, Not Recruiting

This study is active but is not currently recruiting participants.

Key information

Conditions

Critically Ill Intensive Care Unit Patients Hyperphosphatemia Hypophosphatemia Metabolic Diseases Nutritional and Metabolic Diseases Phosphorus Metabolism Disorders

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

Rabin Medcial Center

Petah Tikva, 4941492, Israel

About this study

Data collection

We will document the following data for each patient, for maximum of five days from admission:

  • Demographic data, including age; sex, height, weight, admission reason to ICU.
  • Acute Physiology And Chronic Health Evaluation II (APACHE II) Score (24 hours after ICU admission)
  • Daily Sequential Organ Failure Assessment (SOFA) Score and SOFA components.
  • Daily Ventilation status
  • Daily vasopressor requirement
  • Daily Renal replacement therapy (if any)
  • Daily urine volume
  • Daily fluid balance - including daily fluid input and output
  • Daily 6 hours urine collection, with documentation of collection volume, urine creatinine, and urine electrolytes. Specimens from the first two days of admission will be sent to laboratory analysis only after the patient is admitted for more than 48 hours.
  • Calculation of glomerular filtration rate (GFR) based on urine collection findings.
  • Calculation of phosphate excretion amount based on urine collection findings - both maximal phosphate tubular reabsorption rate (TmP) and Fractional Excretion of phosphate (FePi).
  • Daily serum phosphate and calcium levels
  • Daily phosphate intake - from enteral nutrition, parenteral nutrition, and supplemental (enteral and parenteral).
  • For the last 60 patients - a single measurement of PTH and vitamin D.
  • Patient outcomes: ICU length of stay; Hospital length of stay; Length of ventilation; Ventilator free days at 28 days; Mortality - at ICU, during hospital admission, and at 28 & 90 days.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Adult (>18) Critically ill patients who are admitted for at least 48 hours in the ICU, who are being ventilated in the first time it's 00:00 during their admission, with a urinary foley catheter.

Exclusion criteria

  • Age < 18 years
  • Pregnancy.
  • Recent admission to an ICU (within 30 days)
  • Chronic kidney disease treated with hemodialysis.
  • Oral nutrition by the patient at admission time
  • Existence of another urinary catheter (e.g nephrostomy), or ileal conduit.
  • Hematuria
  • RRT treatment within 48 hours of admission

Treatment and study plan

Primary outcomes

  1. 90 day mortality

    Time frame: 90 days from ICU admission

    Mortality within 90 days of ICU admission.

Secondary outcomes

  1. 28-Ventilation free days

    Time frame: 28 days of ICU admission

    Number of ventilator free days within 28 days of ICU admission

  2. ICU Length of stay

    Time frame: 90 days from ICU admissino

    ICU admission duration

  3. hospital length of stay

    Time frame: up to 90 days after ICU admission

    hospital admission duration

  4. ICU and hospital mortality

    Time frame: 90 days from ICU admissino

    whether mortality happened during ICU/hospital admissino

  5. Differences in Glomerular Filtration Rate

    Time frame: Daily during first five days of ICU admission

    Differences in glomerular filtration rate (GFR) (ml/min)

  6. Maximal tubular reabsorption of phosphate (TmP)

    Time frame: Daily during first five days of ICU admission

    Differences in Maximal tubular reabsorption of phosphate (TmP) (mg/min) will be examined in each group and between groups.

  7. Phosphate Balance

    Time frame: Daily during first five days of ICU admission

    Differences in phosphate balance (mg) will be examined between the groups

  8. Ratio of Maximal Tubular Reabsorption rate to Glomerular Filtartaion Rate (Tmp/GFR)

    Time frame: Daily during first five days of ICU admission

    Differences in the ratio Tmp/GFR (mg/ml), and daily phosphate balance will be examined in each group and between groups.

  9. PTH level and Vitamin D level

    Time frame: One measurement, during first five days of ICU admission

    Differences in PTH (ng/ml) and Vitamin D (IU/ml) between groups

  10. caloric intake

    Time frame: daily measurement during first five days of ICU admission

    Differences in the caloric intake provided (Kcal/day) will be examined between the groups

  11. timing of nutritional support initiation

    Time frame: within first five days of ICU admission

    timing of nutritional support initiation will be compared between groups.

Sponsors and collaborators

Lead sponsor

Rabin Medical Center

Other

Registry information

Official study title

Phosphate Urine Excretion in Critically Ill Patients - a Prospective Observational Study

Important dates

Study start
2023
Primary completion
2025
Study completion
2026
First posted
Jan 16, 2025
Registry last updated
May 28, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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