Investigation of Fluid- and Electrolyte Balance in Post Cardiac-surgery Patients
Condition: Electrolyte Imbalances; Acute Kidney Injury
MeSH terms: Acute Kidney Injury
Study type: Observational [Patient Registry]

Summary: 
      Critically ill patients need intravenous fluid therapy in order to correct or prevent
      problems with their fluid and/or electrolyte status and for renal protection. The decision
      for the optimal composition and amount of IV-fluids can be difficult and complex. It is well
      known that errors in fluid- and electrolyte management contribute to overall morbidity and
      mortality. For decades, urinary sodium was used to diagnose renal disease. Nevertheless,
      renal excretion of sodium is largely impaired in critically ill patients, particularly in
      patients with acute kidney injury. Due to the high frequent measurement of renal output, it
      would be possible to measure the urinary electrolytes and its relative changes. Urinary
      electrolyte measurement may alert for the presence of the development of an akute kidney
      injury before occurring increases in creatinine or oliguria. The rationale of this
      investigation is therefore to collect data related to fluid- and electrolyte management from
      critically ill patients in order to find patterns of fluid- and electrolyte imbalances which
      may lead to disturbances and further, may allow an early detection of acute kidney injury.
    

Detailed description: 
      Critically ill patients need intravenous fluid therapy in order to correct or prevent
      problems with their fluid and/or electrolyte status and for renal protection. The decision
      for the optimal composition and amount of IV-fluids can be difficult and complex. It is well
      known that errors in fluid- and electrolyte management contribute to overall morbidity and
      mortality.

      Due to the administration of large volumes of normal saline and/or a decreased urinary output
      of sodium or chloride iatrogen electrolyte disorders, such as hyperchloremic acidosis or
      dysnatremia are common abnormalities in the clinical practice. The common fact that normal
      saline has non-physiological levels of chloride and sodium, intensifies this problem with
      high volume administration. (Burdett et al. 2003; Adrogué & Madias 1997).

      Hypernatremia is an independent risk factor for mortality in critically ill patients and
      increases the length of ICU stay (Lindner et al. 2010; Stieglmair et al. 2013) Hypernatremia
      is associated with impaired renal fluid regulation, as well as a lack of thirst mechanisms.
      In the ICU this fact requires exact measurement of all fluid- and electrolyte intake and
      (non-)renal losses. (Lindner et al. 2009). Therefore, in critical care settings measuring
      fluid balance (the difference between infusion input and renal / non-renal losses) is daily
      routine. The renal output is measured frequently by the nursing staff. An automated
      acquisition of the urinary output combined with the data of the infusion site would reduce
      the workload of the staff and would allow visualization of the fluid status.

      Furthermore, beyond volume, the concentration and composition of the fluid is an important
      parameter. The comparison of urinary electrolytes with the electrolyte input from infusions
      allows an early detection of electrolyte disorders (Besen et al. 2015). Sodium and chloride
      are the main ions of solutions infused into critically ill patients. The excessive infusion
      of fluids lead to sodium and chloride overloads and is associated with higher mortality
      (Noritomi et al. 2009). For decades, urinary sodium was used to diagnose renal disease.
      Nevertheless, renal excretion of sodium is largely impaired in critically ill patients,
      particularly in patients with acute kidney injury. Due to the high frequent measurement of
      renal output, it would be possible also to measure the urinary electrolytes and its relative
      changes which are likely to be more relevant than the absolute electrolyte concentrations.
      Urinary electrolyte measurement may alert for the presence of AKI development before
      occurring increases in creatinine or oliguria (Maciel 2013; Maciel et al. 2015; Molitoris
      2013).

      The rationale of this investigation is therefore to collect data related to fluid- and
      electrolyte management from critically ill patients in order to find patterns of fluid- and
      electrolyte imbalances which may lead to disturbances and further, may allow an early
      detection of acute kidney injury (AKI).

      Patients undergoing scheduled cardiac surgery will be included in this trial. The rationale
      behind this is on the one hand, that the patient cohort is homogenous and on the other hand,
      that the risk for developing an AKI is 30-40% among cardiac surgery patients (Rosner et al.
      2006). The aim is to detect characteristic patterns in electrolyte metabolism between
      patients who develop an AKI and those who do not.
    

Intervention name(s): Observational Study
Intervention type(s): Other
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        50 adult patients (<18 years, m&f) will be included in this study. All patients will be
        assigned with randomized numbers to stay anonymous. Patients scheduled for cardiac-surgery
        with normal renal function will be included to assure a homogenous clinical picture. These
        patients will be transferred to the intensive care unit post-surgery where electrolyte and
        fluid data will be collected along with serum and urine samples. The will remain in the
        study only during their stay at the ICU.
      
Biospecimen description: 
      In the course of the stay at the ICU we will collect serum and urine samples during routine
      patient care to analyze for electrolytes, oxygen and kidney biomarkers.