Vasomotion, regional cerebral blood flow and intracranial pressure after induced subarachnoid haemorrhage in rats.

The objective of our study was to examine the relation of the intracranial pressure (ICP), cerebral perfusion pressure (CPP), regional cerebral blood flow (rCBF), and vasomotion in the acute phase in rats after having induced subarachnoid haemorrhage (SAH). The experiments were carried out on a total of 21 Wistar rats by means of neuroleptanalgesia and controlled mechanical ventilation. In 16 animals SAH was induced according to the method described by Solomon et al. with a fractionated application of 0.5 ml autologous blood into the cisterna magna. In a control group 0.5 ml of physiological saline solution was injected under identical conditions. The parameters were registered continuously before, during and at least 3 hours after the bolus application. The rCBF and vasomotion were recorded by laser-doppler fluxmetry. The ICP and the systemic arterial blood pressure were registered simultaneously. In the course of the experiment blood gas analyses were carried out regularly for documentary reasons of normoventilation. Our results show that the Cushing-response-after having induced SAH-led to a deterioration of the cerebral perfusion. In the control group however an increase in ICP and rCBF was recorded. The frequency and amplitude of the oscillations of Doppler signals, described as vasomotion, were significantly reduced in the SAH group as compared to the control group (p = 0.0004) during the course of the experiment. After having induced SAH an impairment of the cerebral autoregulation becomes apparent which seems to manifest itself on the level of microvascular structures as a suppressed behaviour pattern of vasomotion. Although basal vessels may constrict distal parenchymal vessels tend to dilate after SAH. The dilation-described as a reduction of vasomotion-could also be measured in clinical situations by means of laserdoppler fluxmetry.