Acta neurochirurgica
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Acta neurochirurgica · Jan 1999
Experimental study of intracisternal administration of tissue-type plasminogen activator followed by cerebrospinal fluid drainage in the ultra-early stage of subarachnoid haemorrhage.
This experimental study evaluated the effect of intrathecal injection of tissue-type plasminogen activator followed by cisternal drainage in the ultra-early stage of aneurysmal subarachnoid haemorrhage to prevent vasospasm. Twenty Japanese white rabbits were divided into five groups. Either tPA (groups A, B, and E) or saline (groups C and D) was injected intrathecally 1 hour (groups A, B, C, and D) or 21 hours (group E) after the intrathecal injection of blood. ⋯ Examination of the series of CSF samples (groups A and C) showed that fibrinolysis with tPA effectively cleared clots early. In the two groups treated with tPA and CSF drainage (groups A and E), early removal of subarachnoid clots reduced the degree of vasospasm. Early fibrinolysis with tPA and early removal of subarachnoid clots by drainage is effective for preventing vasospasm.
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Acta neurochirurgica · Jan 1999
Monitoring of intracranial compliance: correction for a change in body position.
The objectives of our study were 1. to investigate whether the intracranial compliance changes with body position; 2. to test if the pressure-volume index (PVI) calculation is affected by different body positions; 3. to define the optimal parameter to correct PVI for changes in body position and 4. to investigate the physiological meaning of the constant term (P0) in the model of the intracranial volume-pressure relationship. Thirteen patients were included in this study. All patients were subjected to 2 to 3 different body positions. ⋯ Using the constant term P0 to correct the PVI we found no changes between the different body positions. Our results suggest that during the variation in body position there is no change in intracranial compliance but a change in hydrostatic offset pressure which causes a shifting of the volume-pressure curve along the pressure axis without its shape being affected. PVI measurements should either be performed only with the patient in the 0 degree recumbent position or that the PVI calculation should be corrected for the hydrostatic difference between the level of the ICP transducer and the hydrostatic indifference point of the craniospinal system close to the third thoracic vertebra.
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Acta neurochirurgica · Jan 1999
Assessment of critical closing pressure in the cerebral circulation as a measure of cerebrovascular tone.
Critical closing pressure (CCP) calculated from the blood flow velocity (FV) and arterial blood pressure (ABP) waveforms has been previously reported to be useful in the assessment of the dynamics of cerebral circulation. We investigated the relationship between CCP and intracranial pressure (ICP) and cerebrovascular tone in a model of intracranial hypertension in 22 anaesthetised New Zealand White rabbits during manipulations of arterial CO2, ABP and vasodilatation caused by hypoxia. Recordings were made of FV in the basilar artery, ABP and ICP during subarachnoid infusion of saline. ⋯ Generally, CCP decreased significantly (p<0.05) with hypercarbia, arterial hypotension and after and post-hypoxia and the difference: CCP-ICP decreased consistently after each vasodilatatory manoeuvre studied. Our data confirmed the linear relationship between CCP and ICP, and between the difference: CCP-ICP and cerebrovascular tone. However, because the magnitude of increase in ICP was not correlated to magnitude of change in CCP, CCP cannot be use for detection of increasing ICP quantitatively.
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This study tested the hypothesis that colloidal blood volume expansion could improve the cerebral circulation during high intracranial pressure. We studied cerebrovascular haemodynamic variables during high intracranial pressure with and without colloidal blood volume expansion in 12 pigs, whereas five pigs served as controls with intracranial pressure increase twice without colloidal blood volume expansion. Cerebral blood flow was measured with ultrasonic flowmetry on the internal carotid artery, and cerebral microcirculation with laser Doppler flowmetry. ⋯ Cerebral micro-circulation tended to increase, but this was not statistically significant (P = 0.07). Augmentation of the intravascular blood volume during high intracranial pressure increased the arterial inflow to the brain and possibly the cerebral microcirculation by increasing the cerebral perfusion pressure. Our results tend to support that the effect of colloidal blood volume expansion is beneficial for the cerebral circulation during high intracranial pressure.
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Acta neurochirurgica · Jan 1999
Disturbance of cerebral blood flow autoregulation in hypertension is attributable to ischaemia following subarachnoid haemorrhage in rats: A PET study.
The effects of subarachnoid haemorrhage (SAH) on cerebral blood flow (CBF) autoregulation during induced hypertension were studied by positron emission tomography (PET) during chronic vasospasm in anaesthetized Sprague-Dawley rats. SAH was induced by intracisternal injection of autologous blood. In the control animals saline was injected instead. ⋯ AI (%/10-mmHg) was 13.5+/-2.4 in the control group (n=24). In the SAH group, AI decreased (p<0.05) to 4.5+/-2.5 in non-ischaemic areas (n=15), while in the ischaemic areas (n=5) AI increased (p<0.05) to 25.2+/-4.1. Since the spastic artery is intrinsically resistant to hypertension, the marked increase in CBF during hypertension can be attributable to ischaemia following SAH.