Changes in tissue oxygenation in response to sudden intradialytic hypotension

A 76-year-old woman on hemodialysis (HD) for diabetic nephropathy was admitted to our hospital with occasional intradialytic hypotension (IDH). We continuously monitored the regional oxygen saturation (rSO₂) in the brain, liver, and lower limb muscle during HD. The time course of changes in rSO₂ ratios in each region was evaluated throughout HD. The rSO₂ ratio was defined as the ratio of rSO₂ value at t (min) during HD to the rSO₂ value before HD. During the early phase of HD, blood pressure (BP) gradually decreased and both hepatic and lower limb muscle rSO₂ ratios decreased with changes in BP, whereas the cerebral rSO₂ ratio was relatively maintained. At around 90 min after HD initiation, the BP decreased to 71/46 mmHg (mean BP, 54 mmHg) and the previously maintained cerebral rSO₂ ratio also suddenly decreased. Soon after the onset of IDH, ultrafiltration was stopped, normal saline was infused, and intravenous noradrenaline infusion was started. After the BP recovered, cerebral and hepatic rSO₂ ratios improved, but the lower limb muscle rSO₂ ratio remained low. After restarting ultrafiltration, improvement in the lower limb muscle rSO₂ ratio was delayed, although cerebral and hepatic oxygenation were maintained. This observation aids in our understanding of the effect of IDH on regional tissue oxygenation.