Cerebral haemodynamics in patients with chronic renal failure: effects of haemodialysis

Background. We measured middle cerebral artery (MCA) flow velocity(FV), dynamic pressure autoregulation, and carbon dioxide reactivity(CRCO₂) in patients with chronic renal failure before and afterhaemodialysis using transcranial Doppler ultrasonography. Methods. Twelve patients on long-term haemodialysis were recruited.MCA FV was measured continuously. The transient hyperaemic responsetest was used to assess cerebral autoregulation, and per centchange in FV per kPa change in end-tidal carbon dioxide wascalculated to assess CRCO₂. All measurements were recorded beforeand after haemodialysis. Results. MCA FV (mean SD]) decreased from 57 (10) cm s^–1before to 46 (13) cm s^–1 after haemodialysis (P<0.01).The transient hyperaemic response ratio (THRR) was (mean SD])1.29 (0.13) before haemodialysis and did not change significantlyfollowing haemodialysis (1.36 0.10]). CRCO₂ was 21.7 (8.3)%kPa^–1 before haemodialysis and remained unchanged afterwards(20.9 3.8]% kPa^–1). Values in normal subjects for MCAFV, THRR and CRCO₂ are 56 (12) cm s^–1, 1.26 (0.13) and22 (6)% kPa^–1, respectively. Conclusions. MCA FV decreases significantly after haemodialysis.Dynamic pressure autoregulation and CRCO₂ remain normal in patientswith chronic renal failure, and are not altered significantlyby haemodialysis. Presented at the European Society of Anaesthesiologists AnnualCongress Amsterdam, May 1999.