Kinins and intracranial hemorrhages

Activation of the coagulation system in the subarachnoid space after subarachnoid haemorrhage: serial measurement of fibrinopeptide A and bradykinin of cerebrospinal fluid and plasma in patients with subarachnoid haemorrhage

Fibrinopeptide A (FPA) levels as an indicator of thrombin activity in the cerebrospinal fluid (CSF) and plasma of 25 patients with subarachnoid haemorrhage (SAH) were measured serially by radioimmunoassay (RIA). FPA levels in CSF were extremely high on days 0-1 (1253 +/- 269 ng/ml, mean +/- standard error) but decreased rapidly (11.3 +/- 3.9 ng/ml on days 2-4, 10.7 +/- 5.9 ng/ml on days 5-7, and 6.3 +/- 1.5 ng/ml on days 8-14). In the controls the FPA concentration in CSF was 1.2 +/- 0.9 ng/ml (mean +/- standard deviation). Plasma FPA levels in patients with SAH showed no statistically significant changes with time. The bradykinin (BK) concentration in CSF and plasma in 27 patients with SAH was measured serially by RIA. The concentrations in CSF were 122.7 +/- 22.7 pg/ml (mean +/- standard error) on day 0, 38.6 +/- 6.1 pg/ml on day 1, 22.7 +/- 6.3 pg/ml on day 2, and 17.1 +/- 3.0 pg/ml or less thereafter. Plasma BK levels in patients with SAH were higher than those in the control group, but there was no statistically significant change over time. From the measurement of FPA it was apparent that the coagulation system in the subarachnoid space is strongly activated in the early stage of SAH. The formation of BK in CSF after SAH is thought to be due to the contact activation of Hageman factor (intrinsic factor) in the subarachnoid space. Trabeculae as collagen bundles in the subarachnoid space were considered to have a possible role in activating the Hageman factor of the coagulation system in SAH.

The pathogenetic and prognostic significance of blood-brain barrier damage at the acute stage of aneurysmal subarachnoid haemorrhage. Clinical and experimental studies

In a retrospective study, pathological tissue enhancement was found in nearly two fifths of patients with acute SAH on contrast-enhanced cranial computed tomography. By means of absorption measurements with the region of interest technique over the basal ganglia, it was proved indirectly that pathological tissue enhancement should be brought about not only by hyperaemia, i.e., a blood volume increase, but also by extravasation of the contrast material, i.e., blood-brain barrier (BBB) disruption. A similar conclusion was drawn from the retrospective isotope brain scintigraphy study. It was further established that, although the pathological contrast enhancement was most obvious in the cortex, and particularly in the neighbourhood of the subarachnoid spaces, the phenomenon is probably widespread throughout the brain. Patients with abnormal enhancement are likely to be in less favourable clinical grades, have a high incidence of marked or diffuse spasm, have a poorer outcome independent of surgical or conservative treatment, and develop cerebral infarction more frequently. Systemic arterial hypertension was associated with an increased incidence of abnormal enhancement. Pathological tissue contrast enhancement or isotope accumulation in the first few days of SAH may serve as prognostic signs indicative of the late development of vasospasm and ischaemia. As ischaemic disruption of the capillary system is not prominent in the initial days following any stroke, vasoactive substances arising from the breakdown of the blood clot should play important part in the BBB damage in the acute stage of SAH. The "cortical SAH" model developed in the animal experiments ensured a constant subarachnoid blood volume with minimal local brain damage. The intracranial pressure and mean arterial blood pressure did not change significantly, and perfusion defects did not arise. Thus, this model proved suitable for studying the influence on the BBB of vasoactive blood breakdown products (responsible for arterial spasm) without the accompanying effects of pathological conditions such as raised intracranial pressure, systemic hypertension, non-reflow phenomena, which also disrupt the BBB. Measurements on the water, electrolyte, albumin contents of brain tissue, as well as the immunohistochemical localization of albumin, clearly indicated that the brain oedema developing at the acute stage of experimental SAH could be classified as having a primary vasogenic component in addition to the cytotoxic component. This increased capillary permeability was found to be brought about by opening of tight junctions and pinocytosis in the endothelial cells. The pathological capillary permeabilit

The kallikrein-kinin system as mediator in vasogenic brain edema

✓ Vasogenic edema was induced in mongrel cats by cold injury to study uptake and activation of the plasma-kallikrein-kinin system in central nervous system (CNS) tissue. A method was developed for quantitative assessment of kinin formation in affected brain tissue areas. Gross disruption of the blood-brain barrier by focal trauma causes marked penetration of plasma kininogens into necrotic and edematous brain tissue. Moreover, the kallikrein-kinin (KK) system was activated in both necrotic and perifocal edematous areas, and was markedly enhanced by additional cerebral ischemia. Formation of kinins in necrotic brain tissue led to consumption of approximately 60% to 80% of the amount of kininogens being taken up. In perifocal edematous tissue, formation of kinins was less pronounced, or even absent. However, if cerebral ischemia evolved after severe intracranial hypertension, kinins were also formed in the perifocal edematous brain. The intravascular origin of kininogens found in pathological tissue areas secondary to injury was deduced from the observation that cerebral tissue of the contralateral hemisphere with an intact blood-brain barrier had no measurable quantities of kininogens. Consumption of plasma kininogens or formation of kinins were assessed as the difference of the total amount of plasma kininogens taken up into the tissue minus the amount of kininogens found in the brain at postmortem examination.

The data indicate that uptake and activation of the plasma-KK system might occur under all pathological conditions in which blood-brain barrier damage permits cerebral penetration of plasma proteins, such as with cerebral contusion, focal ischemia, and tumors. The potent pathophysiological mechanisms induced by kinins in CNS tissue, such as formation of brain edema, microcirculatory dysfunction, and enhancement of blood-brain barrier permeability, together with their formation in focal and perifocal pathological brain tissue, provide further support for a mediator function of the KK system. Methods that specifically interfere with the formation of kinins in damaged brain should therefore be expected to attenuate vasogenic edema.

The kallikrein-kinin system as mediator in vasogenic brain edema

✓ Plasma and bradykinin were perfused into the ventricular system of mongrel dogs to investigate whether either or both induce brain edema. Formation of cerebral edema was determined by measurement of cerebral water and electrolytes in periventricular white matter, cerebral cortex, and caudate nucleus. The response of cerebral tissue to exposure to bradykinin or to plasma, as a carrier of kininogens, was analyzed by assessment of the perfusate composition after ventricle passage. The authors report that cerebral administration of bradykinin induces cerebral edema. Ventricular perfusion with plasma also led to an increase of cerebral water content which was restricted to the white matter, but involved all brain tissue areas, if bradykinin was used. Ventricular perfusion with plasma was associated with consumption of the kinin precursor (kininogens) indicative of formation of kinins. Significant consumption of the precursor was found in five out of nine animals subjected to plasma perfusion of the ventricular system. In these animals a close correlation between the increase of white matter water content and kininogen-consumption as a measure of kinin-formation was obtained. Marked kinin-degrading activity was observed during ventricular perfusion with bradykinin as concluded from a considerable decrease of bradykinin concentration in the cisternal effluent compared to the inflowing perfusate concentration. Ventricular perfusion with plasma was associated with a decrease of K+ clearance capacity with continued duration, and in two animals with a release of glutamate into the plasma perfusate, suggesting an involvement of cytotoxic mechanisms.

These findings provide support for the hypothesis of a mediator function of the kallikrein-kinin (KK) system in vasogenic brain edema. The next question that needs to be answered to complete the picture — does spontaneous activation of the KK system occur in conditions leading to vasogenic edema? — is studied in a subsequent report.

Significance of contrast enhancement in cranial computerized tomography after subarachnoid hemorrhage

Eighty patients with subarachnoid hemorrhage underwent computerized tomography (CT) scanning before and after administration of Conray contrast medium. Abnormal enhancement was seen in visual evaluation of the CT scans in 26 cases, in the regions bordering the subarachnoid spaces. Abnormal enhancement was associated with a poor clinical condition, angiographic spasm, and a poor outcome. Measurements of absorption values in the thalamus revealed significant increases in density after contrast enhancement in those patients whose scans showed abnormal enhancement in the regions bordering the subarachnoid spaces on visual evaluation. The authors suggest that the abnormal enhancement is parenchymal, in the gyri, and is not "subarachnoid." They suggest that it is due to gyral hyperemia or extravasation of contrast material into the cortex resulting from breakdown of the blood-brain barrier, or a combination of both factors.

Blood-brain barrier changes after experimental subarachnoid haemorrhage

Cerebral vascular permeability and blood-brain barrier in the acute stage of subarachnoid haemorrhage were studied in experiments on cats. The bleeding was induced by a special method, imitating the natural course os subarachnoid haemorrhage. Fluorescence of the Evans blue injected intravitally was used as an indicator. It was found that one hour after the subarachnoid haemorrhage there are discrete diffuse spots of translucency related to the individual vessels, appearing bilaterally in the cerebral cortex and to a lesser extent in the white substance. Four hours after the bleeding, the extravasations and tissue staining become more widespread and confluent. There are more areas with disturbed blood-brain barrier, and they are better differentiated from the normal tissue. They are distributed bilaterally throughout the brain with predominance on the side of the bleeding vessel. The possible mechanisms of the blood-brain barrier disturbance afer subarachnoid haemorrhage are discussed.

Brain energetics and circulatory control after subarachnoid hemorrhage

Ischemia-provoking factors such as vasospasm, decreased cerebral perfusion pressure, and intravascular thrombosis may be present after subarchnoid hemorrhage (SAH). When these factors were not present during controlled SAH, a primary depression of cerebral glycolysis associated with normal stores of energy-rich phosphates was found. Although cerebral blood flow usually changes in response to changes in cerebral metabolic needs, this influence on the circulation was not evident in the early hours after SAH. After 3 to 4 hours an erratic decrease in blood flow occurred, probably related to vasospasm, and there were measurable decreases in energy-rich phosphates similar to those occurring after more severe and prolonged ischemias. These findings are indicative of abnormally erratic vascular responses to metabolic cues and may play a role in producing the encephalopathy of SAH.

The effect of a simulated subarachnoid hemorrhage on cerebral blood flow in the monkey

The hydrogen clearance method was used to measure local and total cerebral blood flow (CBF) in the rhesus monkey before and for five hours after a simulated subarachnoid hemorrhage (SAH). CBF remained stable after SAH unless SAH was associated with a fall in cerebral perfusion pressure. In addition, cerebrovascular resistance did not increase after SAH. These results suggest that vasoactive agents in fresh whole blood, and the arterial spasm they produce when added to cerebrospinal fluid (CSF), play only a limited role in the pathogenesis of ischemic encephalopathy that follows an SAH.