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Sustained ventilation: perfusion imbalance during hemodialysis
Insights
Hemodialysis in children may cause hypoxemia due to ventilation-perfusion mismatch. This study in pediatric patients found sustained gas exchange abnormalities during hemodialysis (HD) at altitude.
Area of Science:
- Pediatric Nephrology
- Pulmonary Physiology
- Dialysis Medicine
Background:
- Chronic renal failure necessitates renal replacement therapy in children.
- Hemodialysis (HD) is a common treatment for pediatric end-stage renal disease.
- Understanding the pulmonary effects of HD is crucial for patient management.
Purpose of the Study:
- To investigate the central and pulmonary effects of hemodialysis on gas exchange in pediatric patients.
- To evaluate changes in ventilation and perfusion during HD in children.
- To identify potential mechanisms for dialysis-related hypoxemia.
Main Methods:
- Studied five children (6-15 years) on chronic HD.
- Measured dialysate and arterial blood gases, end-tidal CO2, and minute ventilation pre- and post-HD initiation.
- Calculated arterial-alveolar CO2 gradient (aADCO2) to assess ventilation-perfusion (V/Q) status.
Main Results:
- Minute ventilation remained unchanged during HD.
- The aADCO2 significantly increased post-HD, indicating a V/Q mismatch.
- A significant inverse relationship was observed between aADCO2 and arterial pO2.
Conclusions:
- Dialysis-related hypoxemia in these pediatric patients appears linked to sustained V/Q mismatch.
- A decrease in pulmonary perfusion may contribute to the observed gas exchange abnormalities.
- Findings suggest potential implications for HD protocols in children, especially at altitude.
Abstract:
Five children between the ages of 6 and 15 years, who required chronic hemodialysis (HD) for renal failure, were studied to evaluate the central and pulmonary effects of HD on gas exchange. Acetate dialysate was used, and dialysate pO2 and pCO2, arterial pO2 and pCO2, endtidal CO2 and minute ventilation were measured pre-HD and 15, 30, 60, 120 and 240 minutes after commencement of HD. Arterial-alveolar CO2 gradient (aADCO2) was calculated to determine the ventilation: perfusion (V/Q) status. Minute ventilation did not change significantly from the pre-HD value of 8.9 +/- 1.1 l/min (mean +/- SD). The aADCO2 increased significantly from 3.2 +/- 3.7 mmHg to 8.4 +/- 2.4 mmHg at 15 mins (p less than .01) and was still elevated at 120 mins. (9.1 +/- 3.4 mmHg, p less than .02). There was a weak but significant inverse relationship between aADCO2 and arterial pO2 (r -0.42, p less than 0.05). The results suggest that, in these children, dialysed at altitude, dialysis-related hypoxemia appears to be the result of a sustained V/Q mismatch, possibly related to a decrease in pulmonary perfusion.