Orthostatic hypoxaemia in dialysed adult polycystic kidney disease patients

Recently we observed a unique clinical phenomenon, namely, orthostatic or postural hypoxaemia in a 72-year-old female adult polycystic kidney disease (APKD) patient, maintained on CAPD. Extensive investigations failed to yield a satisfactory explanation for her ambulatory hypoxaemia.

To validate our observation, 15 dialysed patients underwent blood gases analyses in both the supine and ambulatory positions (SpO2 and ApO2 respectively). Patients were divided into two groups: group 1 (n-7) whose end-stage renal failure (ESRF) was due to APKD and group 2 (n-8) in whom ESRF was due to other causes. Both haemodialysed (HD) and CAPD patients were included. ApO2 was determined as the pO2 immediately upon standing up. Readings in HD patients were taken at the end of the dialysis session, that is, at the patients' dry weight.

Respective SpO2 and ApO2 of the two groups were 85 +/- 17.1 and 78 +/- 20.5 vs 85.8 +/- 19 and 91 +/- 21 mmHg. Delta change in pO2 defined as the mean decrease (negative value) or mean increase (positive value) of ApO2 in relation to SpO2 was -7.85 (group 1) vs + 5.2 mmHg (group 2), P < 0.005. In group 1, six of seven patients demonstrated a negative delta. In group 2, four of eight showed a positive delta whilst the remaining four had no change in the delta value.

Orthostatic hypoxaemia may occur in dialysed patients whose ESRF is due to APKD.