Effects of red blood cells with reduced deformability on cerebral blood flow and vascular water transport: measurements in rats using time-resolved pulsed arterial spin labelling at 9.4 T.

BACKGROUND: Our aim was to introduce damaged red blood cells (RBCs) as a tool for haemodynamic provocation in rats, hypothesised to cause decreased cerebral blood flow (CBF) and prolonged water capillary transfer time (CTT), and to investigate whether expected changes in CBF could be observed and if haemodynamic alterations were reflected by the CTT metric. METHODS: Damaged RBCs exhibiting a mildly reduced deformability were injected to cause aggregation of RBCs. Arterial spin labelling (ASL) magnetic resonance imaging experiments were performed at 9.4 T. Six datasets (baseline plus five datasets after injection) were acquired for each animal in a study group and a control group (13 and 10 female adult Wistar rats, respectively). For each dataset, ASL images at ten different inversion times were acquired. The CTT model was adapted to the use of a measured arterial input function, implying the use of a realistic labelling profile. Repeated measures ANOVA was used (alpha error = 0.05). RESULTS: After injection, significant differences between the study group and control group were observed for relative CBF in white matter (up to 20 percentage points) and putamen (up to 18-20 percentage points) and for relative CTT in putamen (up to 35-40 percentage points). CONCLUSIONS: Haemodynamic changes caused by injection of damaged RBCs were observed by ASL-based CBF and CTT measurements. Damaged RBCs can be used as a tool for test and validation of perfusion imaging modalities. CTT model fitting was challenging to stabilise at experimental signal-to-noise ratio levels, and the number of free parameters was minimised.

Hemorheological disorders in the microcirculation during septic shock in rats.

OBJECTIVES: The aim of the present study was the experimental analysis of blood rheological disorders in the microcirculation during endotoxic shock. METHODS: Experiments were carried out on 30 white laboratory rats of both sexes weighing about 200 g. The experimental animals were divided in two groups: the control group and the group undergoing experimental endotoxic shock. The following specific hemorheological properties were investigated in all animals during the experiments: red blood cells (RBC) aggregability, their deformability and the systemic hematocrit. RESULTS: We found that all the investigated hemorheological parameters appreciably changed underconditions of endotoxic shock. The RBC aggregability index was increased by a mean of 136%. As to the RBC deformability index was found to be decreased by 71%, and the systemic hematocrit lowered by 31%, as compared to the same parameters in the control group. CONCLUSION: The data obtained provide us with evidence that the hemorheological derangements associated with the development of the heavy microcirculatory disorders during endotoxic shock, are most significant factors.