Effect of autonomic neuropathy on ventilatory response to progressive hypercapnia in dialysis patients

The impact of autonomic neuropathy (common in patients on haemodialysis) on ventilatory response to hypercapnia has been studied. We investigated cardiac reflex tests in 20 patients on chronic haemodialysis (8 patients were found with and 12 without neuropathy of the autonomic nervous system). Using the hyperoxic CO2-rebreathing method (according to Read), we tested the above-mentioned two groups of patients and compared them with 14 healthy control subjects. Accumulation of CO2 in blood with hyperoxic CO2 rebreathing stimulates central chemoreceptors, and therefore causes a progressive rise in minute ventilation. In patients with autonomic neuropathy (n = 8), ventilatory response to increasing pCO2 was significantly lower than that in the controls (1.7 +/- 0.3 versus 3.2 +/- 0.5 l/min/mmHg, P < 0.001). On the other hand ventilatory response in patients without autonomic damage (n = 12) showed no significant difference when compared to controls (3.1 +/- 0.8 l/min/mmHg). There were no differences in lung function, arterial blood gas analysis, blood chemistry, duration on dialysis, and demographic data when comparing the patients with and those without autonomic damage. Our analysis shows different patterns of ventilatory response to increasing pCO2 in patients on haemodialysis. Autonomic neuropathy has to be considered when rebreathing tests are interpreted. The clinical relevance of these findings needs further investigation.