Acute normovolemic hemodilution can aggravate neurological injury after spinal cord ischemia in rats.

BACKGROUND: Acute normovolemic hemodilution (ANH) is currently performed during thoracoabdominal aortic surgery. However, the effects of ANH on spinal cord ischemic injury are currently unknown. Because hemodilution below a certain level of hematocrit (Hct) aggravates the neurological damage after cerebral ischemia, we hypothesized that ANH may increase neurological damage after spinal cord ischemia. The aim of these experiments was to determine the effects of ANH on spinal cord ischemic injury. METHODS: Thirty male Sprague-Dawley rats were randomly assigned to 1 of the following 3 groups: no hemodilution (group C), target Hct level of 30% (group HD30), and target Hct level of 25% (group HD25). ANH was performed upon withdrawal of blood and simultaneous replacement with the same volume with hydroxyethyl starch. Spinal cord ischemia and reperfusion were induced by using a balloon-tipped catheter placed in the descending thoracic aorta, and changes in mean arterial blood pressure were recorded. Neurological function of the hindlimbs was evaluated for 7 days and recorded using a motor deficit score (MDS) (0 = normal; 5 = complete paraplegia). The number of motor neurons within the spinal cord was counted after final MDS evaluation. RESULTS: Group HD25 developed hypotension during the latter part of the ANH procedure. Group C and group HD30 experienced 3 minutes of reperfusion hypotension, whereas 6 minutes of hypotension was observed in group HD25. Two rats in group HD25 died during the experimental period. Seven days after reperfusion, the MDS of group C, group HD30, and group HD25 was 1.0 (0.5-2.0), 1.0 (0.5-2.0), and 4.0 (2.8-4.2) (median [95% confidence interval]), respectively. Group HD25 showed significantly higher MDS compared with group C (corrected P = 0.0018; 95% CI for median difference = 1.0-3.5). Motor neuron numbers in the anterior horns of group C, group HD30, and group HD25 were 26.5 (25.0-27.5), 23.5 (22.0-26.5), and 12.5 (8.4-16.6) (median [95% CI]), respectively. Motor neuron numbers of group HD25 were significantly lower than those of group C (corrected P < 0.0001; 95% CI for median difference = 9.0-18.0). CONCLUSION: The results of the present study indicate that intraoperative ANH to an Hct of 25%, combined with coincident hypotension, caused a delayed recovery of baseline mean arterial blood pressure during the reperfusion period and aggravated neurological outcome after spinal cord ischemia.

The effect of retrograde autologous priming of the cardiopulmonary bypass circuit on cerebral oxygenation.

OBJECTIVE: The aim of this study was to investigate the effect of retrograde autologous priming (RAP) of the cardiopulmonary bypass (CPB) circuit on cerebral oxygenation. DESIGN: A retrospective cohort study. SETTING: A university hospital. PARTICIPANTS: Ninety-four patients undergoing CPB. INTERVENTIONS: CPB was primed with a RAP technique in the RAP group (n = 46) or with a conventional technique in the control group (n = 48). MEASUREMENT AND MAIN RESULTS: Cerebral oxygenation was monitored by measuring the regional cerebral oxygen saturation (rSO(2)). The rSO(2) and Hct values were compared between the groups during surgery. During the CPB period, the RAP group showed significantly higher values for rSO(2) (%) (immediately after the onset of CPB: 51.3 ± 8.4 and 56.3 ± 8.3; 30 minutes after the onset of CPB: 56.3 ± 5.1 and 59.7 ± 7.0; control group and RAP groups, respectively; p < 0.01 for each) and Hct (%) (immediately after the onset of CPB: 21.1 ± 3.7 and 23.1 ± 3.3; 30 minutes after the onset of CPB: 21.9 ± 3.7 and 23.3 ± 2.3; control group and RAP group, respectively; p < 0.02 for each). However, the 2 groups did not differ in rSO(2) (%) (67.2 ± 6.3 and 67.8 ± 6.4) or Hct (%) (27.8 ± 4.1 and 28.9 ± 3.6, control group and RAP group, respectively) at the end of the surgery. CONCLUSIONS: The application of RAP to CPB limits the degree of hemodilution and improves cerebral oxygenation during CPB. The present findings suggest a potential benefit of RAP from a neurologic aspect.