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 >2,000 mL exhibited a reduction in the peak pressure (p=0.027). No changes in the partial pressure of oxygen in arterial blood (PaO2) or in the PaO2/the fraction of inspired oxygen (PaO2/FiO2) 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.