Respiratory Alterations of Acid-base Equilibrium: Acute and Chronic Renal Response

Study Overview
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Brief Summary
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Alterations of acid-base equilibrium are very common in critically ill patients. Thus, understanding their pathophysiology and the possible compensatory mechanisms acting in different organs may play an important role in better set the consequent clinical treatment. The lung and the kidney are the two principal actors of such regulations. Although the respiratory response to acid-base alterations is well understood, less information are available for what the renal system is concerned. Such lack of information is partially due to: 1) the historical consideration of the kidney as a slow organ, in response to variations in acid-base equilibrium; 2) the lack of a monitoring system to closely assess renal response. Our group has recently developed a monitoring system aimed at analyzing, in a quasi-continuous and non-invasive manner (every 10 min) the urinary profile in terms of urinary pH and electrolyte concentrations (sodium, potassium, chloride, ammonium). The investigators hypothesize that the renal system reacts to large as well as to minimal variations of the acid-base equilibrium (especially induced by a variation in the respiratory function) in a very fast way, modifying the urinary concentration (and therefore the urinary excretion) of ammonium and some electrolytes (especially chloride).

Detailed Description
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Primary aim: To investigate the acute renal response to respiratory alterations of acid-base equilibrium in order to better understand the underlying physiological mechanisms and to evaluate the validity of a renal monitoring system to indirectly assess the effectiveness of the respiratory function. Secondary aim: To collect data on the chronic response of the renal system in patients affected by chronic obstructive pulmonary disease (COPD), as well as on the acute response to acute variation of the chronic respiratory acidosis characterizing patients affected by COPD exacerbation. Study protol: Mechanically ventilated patients will undergo controlled variation of the ventilatory setting (hyperventilation vs. hypoventilation) in order to induce a controlled reduction or increase in arterial partial pressure of carbon dioxide (and an increase or reduction of arterial pH), within normal range of pH (7.35 - 7.45) During the variations, urinary concentrations of electrolytes and pH will be monitored.

Official Title
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Respiratory Alterations of Acid-base Equilibrium: Acute and Chronic Renal Response

Conditions
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Acute Respiratory Variations of Acid-base Equilibrium

Intervention / Treatment
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* Other: Increase minute ventilation
* Other: Decrease minute ventilation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Presence of mechanical ventilation Presence of arterial and central venous line Presence of urinary catheter Exclusion Criteria: acute or chronic renal failure with anuria presence of continuous renal replacement therapy hemodynamic instability less than 16 years of age

Ages Eligible for Study
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Minimum Age: 16 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Hyperventilation<br>Minute ventilation will be increased of about 30% of baseline value, through an increase in respiratory rate | Other: Increase minute ventilation<br>* Respiratory rate will be increase in order to have a 30% increase of minute ventilation<br>|
| Experimental: Hypoventilation<br>Minute ventilation will be decreased of about 30% of baseline value, through a decrease in respiratory rate | Other: Decrease minute ventilation<br>* Respiratory rate will be decrease in order to have a 30% decrease of minute ventilation<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Variations in urinary electrolyte concentrations and pH |  | From 0 to 4 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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acid-base equilibrium, renal system, urinary electrolytes