Impact of renal replacement therapy on the respiratory function of patients under mechanical ventilation

OBJECTIVE: To assess the oxygenation behavior and ventilatory mechanics after hemodialysis in patients under ventilatory support. METHODS: The present study was performed in the general intensive care unit of a tertiary public hospital. Patients over 18 years of age under mechanical ventilation and in need of dialysis support were included. Each patient was submitted to 2 evaluations (pre- and post-dialysis) regarding the cardiovascular and ventilatory parameters, the ventilatory mechanics and a laboratory evaluation. RESULTS: Eighty patients with acute or chronic renal failure were included. The analysis of the ventilatory mechanics revealed a reduction in the plateau pressure and an increased static compliance after dialysis that was independent of a reduction in blood volume. The patients with acute renal failure also exhibited a reduction in peak pressure (p=0.024) and an increase in the dynamic compliance (p=0.026), whereas the patients with chronic renal failure exhibited an increase in the resistive pressure (p=0.046) and in the resistance of the respiratory system (p=0.044). The group of patients with no loss of blood volume after dialysis exhibited an increase in the resistive pressure (p=0.010) and in the resistance of the respiratory system (p=0.020), whereas the group with a loss of blood volume >2,000mL exhibited a reduction in the peak pressure (p=0.027). No changes in the partial pressure of oxygen in arterial blood (PaO(2)) or in the PaO(2)/the fraction of inspired oxygen (PaO(2)/FiO(2)) ratio were observed. CONCLUSION: Hemodialysis was able to alter the mechanics of the respiratory system and specifically reduced the plateau pressure and increased the static compliance independent of a reduction in blood volume.