Patients with hemodialysis-induced hypoxemia had a poor prognosis of COVID-19.

Background: We experienced that some hemodialysis (HD) patients with coronavirus disease 2019 (COVID-19) exacerbated hypoxemia during HD. Though HD-induced hypoxemia has been reported, there have been no reports of HD-induced hypoxemia in patients with COVID-19 and its effect on prognosis of COVID-19.

Methods: Eleven HD patients admitted with COVID-19 from August 2020 to April 2021 were classified into the patients whose oxygen demand increased by more than 3 L/min with mask during HD (worsened group,  = 5) and others (not-worsened group,  = 6). The background, laboratory findings, severity of COVID-19 and prognosis were compared between the two groups. In addition, blood gases were measured before and after dialysis among HD patients admitted with COVID-19 on April 2021 ( = 3).

Results: There were no significant differences in backgrounds, except for a higher proportion of diabetes mellitus in worsened group ( = 0.04). Although laboratory findings were not significantly different on admission day, albumin and LDH levels 7 days after admission were significantly lower and higher in worsened group, respectively ( = 0.03 and < 0.01). The severity of COVID-19 and survival rate were significantly worse in worsened group ( = 0.01 and 0.03). The alveolar-arterial oxygen pressure difference (Aa-DO) opened during HD in a patient with HD-induced hypoxemia, but did not open in patients without HD-induced hypoxemia.

Conclusions: There is a close relationship among HD-induced hypoxemia and poor prognosis of COVID-19. The HD-induced hypoxemia of patients with COVID-19 may be caused by ventilation/perfusion mismatching.

Supplementary Information: The online version contains supplementary material available at 10.1186/s41100-022-00408-5.