Cerebral blood flow variations in CNS lupus

We studied the patterns of cerebral blood flow (CBF), over time, in patients with systemic lupus erythematosus and varying neurologic manifestations including headache, stroke, psychosis, and encephalopathy. For 20 paired xenon-133 CBF measurements, CBF was normal during CNS remissions, regardless of the symptoms. CBF was significantly depressed during CNS exacerbations. The magnitude of change in CBF varied with the neurologic syndrome. CBF was least affected in patients with nonspecific symptoms such as headache or malaise, whereas patients with encephalopathy or psychosis exhibited the greatest reductions in CBF. In 1 patient with affective psychosis, without clinical or CT evidence of cerebral ischemia, serial SPECT studies showed resolution of multifocal cerebral perfusion defects which paralleled clinical recovery.     

Cerebral blood flow and CO2 reactivity in patients with transient ischemic attack]

To elucidate the changes in cerebral blood flow (CBF) and CO2 reactivity in patients with transient ischemic attack (TIA), 10 patients with TIA and 5 healthy adults (controls) underwent two consecutive CBF measurements (i.e. the first measurement during room air inhalation and the second measurement during 5%CO2 inhalation). Hemispheric mean CBF was determined by each CBF measurement using 133Xenon inhalation method. CO2 reactivity was evaluated by analysing delta CBF (= mean CBF during hypercapnea-mean CBF at rest) and delta CBF/delta PaCO2. The resting mean CBF values in the bilateral hemispheres (i.e. both of the affected and unaffected hemispheres) were significantly lower in TIA patients than controls (p less than 0.05). Inhalation of 5%CO2 significantly increased mean CBF in TIA patients bilaterally, however the mean CBF value during hypercapnea was again significantly lower in TIA patients than controls (p less than 0.05). CO2 reactivity in TIA patients was not significantly different from controls (p greater than 0.05). The result demonstrated that TIA patients have a chronic and global cerebral oligemia with normal CO2 reactivity. The chronic and global cerebral oligemia may develop a transient ischemic neurological symptom by being superimposed with local decrease of CBF.     

Quantification of regional cerebral blood flow with IMP-SPECT. Reproducibility and clinical relevance of flow values

Single-photon emission computed tomography with N-isopropyl[123I]-p-iodoamphetamine (IMP-SPECT) was performed in 14 normal volunteers (seven men and seven women aged 25.1 +/- 5.3 years) and 29 patients with cerebrovascular disease (18 men and 11 women aged 54.1 +/- 13.7 years). The fluid microsphere model was used to estimate cerebral blood flow (CBF). Normal subjects were scanned twice, 1 week apart, to determine the reproducibility of the CBF estimates. Hemispheric blood flow (hCBF) was calculated as the mean of regional cerebral blood flow (rCBF) values in 16 gray matter regions per hemisphere. In normal subjects mean hCBF was 68 ml/100 g/min. The highest rCBF was found in the occipital cortex, followed by the frontal, temporal, and parietal cortexes. CBF values were reproducible (p less than 0.001 except the right thalamic region, where p less than 0.01). Intraindividual variation ranged between 0.3% and 15%. Women exhibited significantly higher (16%, p less than 0.02) CBF than men. Patients were subdivided into groups with reversible (n = 19) and persistent (n = 10) symptoms. Significant hCBF differences between the affected and the contralateral hemispheres were recorded only in the group with reversible symptoms (p less than 0.005), whereas the group with persistent symptoms showed a significant bilateral decrease of hCBF compared with normal subjects and patients with reversible symptoms. Focal CBF was significantly lower in patients with completed stroke than in patients with transient symptoms (p less than 0.001). Our results indicate that IMP-SPECT can be used for the routine estimation of CBF in normal and pathologic states.     

Improvement of cerebral blood flow by olprinone, a phosphodiesterase-3 inhibitor, in mild heart failure

Cerebral blood flow (CBF) is reduced in heart failure (HF). For the treatment of acute HF, a phosphodiesterase-3 inhibitor, olprinone (OL), yields an increase in myocardial contractility and a decrease in arterial afterload. During a 15-min intravenous infusion of OL (0.2 microg/kg/min), regional CBF at 6 sites of each cerebral cortex was examined using technetium-99m-ethylcysteinate dimer brain SPECT in 18 HF patients and 7 age-matched normal subjects. The baseline CBF was significantly reduced in HF (43.0 +/- 3.9 ml/min/100 g) compared to that in normal subjects (48.0 +/- 4.6 ml/min/100 g, p < 0.01). The baseline CBF showed a significant negative correlation with the increase in CBF during the OL infusion in HF (r = -0.38, p < 0.01) and normal subjects (r = -0.65, p < 0.01). The percent increase in CBF was significantly greater in HF (13.7%) than in normal subjects (9.8%, p < 0.046). In patients with HF, the CBF of the cerebral cortex was decreased, but was increased by OL infusion.     

Vascular responses in cerebrovascular "Moyamoya" disease--evaluated by positron emission tomography

We investigated cerebral blood flow and metabolism, and cerebral vascular response in 9 patients with cerebrovascular Moyamoya disease or unilateral Moyamoya phenomenon using positron emission tomography (PET). The subjects consisted of 5 men and 4 women, and were from 9 to 60 years old. Five patients had bilateral occlusion in the carotid fork with Moyamoya vessels (fulfilled the criteria of cerebrovascular Moyamoya disease), and four patients had unilateral Moyamoya phenomenon. The PET scanner used was the HEADTOME III, of which spatial resolution in clinical use was 10 mm full width at half-maximum (FWHM) in the image plane. Cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), cerebral oxygen extraction fraction (OEF), and cerebral blood volume (CBV) were measured in resting state by the 15O-labelled gases steady state method in every patient and 22 normal controls (17 men and 5 women, and from 26 to 64 years old). Consecutively cerebral vascular responses were measured by H215O autoradiographic method in resting state, hypercapnia, hypocapnia, and hypertension. Forced hypercapnia, hypocapnia, and hypertension were achieved by 7% CO2 inhalation, hyperventilation, and venous infusion of angiotensin II, respectively. CMRO2 of the whole brain was significantly lower in patients than in normal controls (p less than 0.05), and CBV of the lentiform nucleus significantly increased in patients (p less than 0.01). This reflected Moyamoya vessels in the basal ganglionic regions. In 3 of 5 patients with bilateral Moyamoya vessels, CBF and CMRO2 in the symptomatic cerebral hemisphere were lower than that in the nonsymptomatic hemisphere.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hemodynamic and metabolic effects of extracranial carotid disease

Cerebral blood flow (CBF), cerebral blood volume (CBV), the CBF/CBV ratio - an index of the hemodynamic reserve capacity - the rate of oxygen metabolism (CMRO2), and the fractional extraction of oxygen by the brain (OEF) were studied by positron emission tomography (PET) in the cortical territory of both internal carotid arteries in 15 cases of transiently symptomatic or progressive extracranial atherosclerotic carotid disease. None of the patients had a major stroke or had a significant neurological deficit except 1 whose damaged hemisphere is excluded from study. All were asymptomatic at the time of PET scanning. Values were obtained in the middle cerebral artery (MCA) distribution, and in the anterior and posterior borderzone regions. Eight cases had unilateral carotid stenosis of 80% or greater and 7 had unilateral or bilateral occlusion of the origin of the internal carotid artery. Results obtained in patients were compared using Student's t-test, to those obtained in neurologically normal, elderly volunteers. Patients with carotid stenosis had a significantly decreased CBF (p less than .025) and CBF/CBV ratio (p less than .025) selectively in the anterior borderzone regions. This was accompanied by a trend toward elevated OEF and declining CMRO2 values. Patients with carotid occlusion had significantly decreased CBF (p less than .005), decreased CBF/CBV ratio (p less than .005) and decreased CMRO2 (p less than .025) in the ipsilateral anterior borderzone and MCA territories. Similar changes were present in the opposite hemisphere of patients with bilateral carotid disease. These results indicate that carotid stenosis is associated with hypoperfusion and diminished hemodynamic reserve capacity in the anterior borderzone, and that carotid occlusion produces more widespread hypoperfusion and metabolic depression.     

Effect of hypocapnia on cerebral oxygen metabolism and blood flow in ischemic cerebrovascular disorders

Effects of hypocapnia on cerebral oxygen consumption (CMRO2) and blood flow (CBF) in cerebral ischemia were studied in 19 patients. The CMRO2 did not change significantly during hypocapnia within the whole group of patients, because 10 out of 19 cases showed a decrease (p less than 0.001) and other 9 showed an increase (p less than 0.01) of CMRO2 during hypocapnia. The first 10 showed higher resting CMRO2 (p less than 0.001) and arteriovenous differences of oxygen content (AVDO2; p less than 0.02) than the other 9. However, the resting CBF and CO2 reactivity to hypocapnia were not different between them, and clinical situations were also similar. A dissociation between flow and metabolism was suggested in the first 10 with rather preserved CMRO2, while reduced metabolic demands were suggested in the other 9. Different responses of CMRO2 to hypocapnia are expected in cerebral ischemia, i.e. in cases with rather preserved CMRO2 it decreases despite an AVDO2 increase, suggesting a capability of CMRO2 to respond to CBF reduction, while it increases in cases with more decreased CMRO2, as the AVDO2 increase exceeds the CBF reduction to maintain the decreased CMRO2 for a further CBF reduction. The vascular CO2 reactivity, therefore, might be maintained to be constant between these patients.     

CBF and transcranial Doppler sonography during vasodilatory stress tests in patients with common carotid artery occlusion.

Cerebral blood flow (CBF) and the cerebral vasoreactivity was measured in patients with cerebrovascular disease and longstanding occlusion of the common carotid artery (CCA). In addition, regional CBF was correlated with transcranial doppler (TCD) measurements at baseline and during 6% CO2 inhalation and after intravenous administration of 1 g of acetazolamide. Twelve patients with a mean age of 62 years (range 45 to 71 years) were included, and the data compared to age-matched healthy controls. CBF was measured by intravenous injection of xenon-133 and SPECT (Tomomatic 564). TCD of the middle cerebral artery (MCA) was done by EME TC-64B. A very low global CBF value of 28 +/- 5 (SD) ml 100 g-1 min-1 was found at baseline as compared to 55 +/- 5 ml 100 g-1 min-1 in the normal controls. During 6% CO2-inhalation and after acetazolamide administration, CBF increased by 58 +/- 24% and 51 +/- 21%, respectively, indicating substantial collateral supply. Correlative analysis of CBF in the MCA territory and TCD in the MCA showed statistical significance only for the pooled data, i.e. compiling the data obtained during baseline and the two vasodilatory tests, and then only for the mean and peak TCD velocity (e.g. r = 0.59, p less than 0.002, n = 35, mean velocity, right side). We conclude that TCD measurements do not predict regional CBF in patients with CCA occlusion. The study emphasizes that these two methods yield supplementary information, with TCD measurements providing information of the circle of Willis and CBF studies of the flow distribution.     

Analysis of cerebellar functions in spinocerebellar degeneration using positron emission tomography (PET)

We quantitatively evaluated the cerebellar functions of 23 patients with spinocerebellar degeneration (SCD) and 10 normal controls using positron emission tomography (PET). Statistical analysis was performed using the Student's test. Regional cerebral blood flow (CBF) and regional cerebral metabolic rate (CMR) of the cerebellar hemisphere and cerebellar vermis were significantly lower in patients with SCD than in normal subjects (p less than 0.001). However, no significant difference between the both groups was seen in the CBFs and the CMRs of the occipital cortex and frontal cortex. Even in the patients with SCD who had not apparent cerebellar atrophy on CT, their CBFs and CMRs of the cerebellum were significantly low, and with advance of cerebellar atrophy, they tended to fall. In the patients with SCD, the fall of CMR was more prominent than that of CBF. Neither CBF, nor CMR of the cerebellum showed correlation to the duration of the illness. The present investigation suggested that PETs were valuable for the early diagnosis and the research on the pathogenesis of SCD.     

Cognition and cerebral blood flow fluctuate together in multi-infarct dementia

Longitudinal measurements of cognitive ability measured by serial testing using the Cognitive Capacity Screening Examination (CCSE) were correlated with cerebral blood flow (CBF) throughout (mean +/- SD) 19.9 +/- 12.6 months among 57 patients with multi-infarct dementia, 17 with dementia of the Alzheimer's type, 10 with both, and among 32 age-matched elderly normal controls. Longitudinal CCSE and CBF measurements among controls yielded stable normative values. Reduced mean CCSE scores correlated directly with CBF reductions in patients with multi-infarct dementia (p less than 0.0005) and dementia of the Alzheimer's type (p less than 0.028). Patients with multi-infarct dementia had CCSE scores with retest variability exceeding those of controls (p less than 0.001) and of patients with dementia of the Alzheimer's type (p less than 0.003). CCSE scores and CBF changed together 78.6% (p less than 0.001) of the time in patients with multi-infarct dementia compared with 66.2% of the time (p less than 0.01) in those with both, 62.9% of the time (p less than 0.05) in those with dementia of the Alzheimer's type, and 47.7% of the time (NS) in controls. Further analyses indicated that changes in CCSE scores and CBF were predominantly progressive declines in patients with dementia of the Alzheimer's type, whereas the changes were more bidirectional (both increases and decreases) in patients with multi-infarct dementia; these differences were also significant. Results support the diagnostic usefulness of the Hachinski ischemic scale and confirm that both cognition and CBF fluctuate together among patients with multi-infarct dementia, whereas patients with dementia of the Alzheimer's type exhibit a more stable course, with progressive declines in cognition and CBF.     

Haemodynamic evaluation of the cerebral circulation by periorbital Doppler examination and cerebral blood flow (CBF) measurement in carotid artery disease

To assess the haemodynamic significance of an internal carotid artery (ICA) stenosis, angiography or direct ultrasound examination should be supplemented by indirect physiologic testing of the collateral circulation. Among the tests proposed, we used the periorbital flow direction, assessed by Doppler technique, and cerebral blood flow reactivity to vasodilation, by i.v. xenon-133 technique, in 35 patients before carotid endarterectomy. The results were related to the actual perfusion pressures, measured during surgery in the distal ICA. All 15 patients with normal orthograde periorbital flow had normal cerebral blood flow (CBF) vasoreactivity and no, or only minor, reduction in ICA perfusion pressure. Of the 20 patients with inverted flow, 12 had normal and 8 had abnormal CBF reactivity. These 8 patients proved to have significantly lower cerebral perfusion pressures, as compared with the remaining 12 patients with inverted periorbital flow (p less than 0.001), who in turn had lower perfusion pressures than the 15 patients with orthograde flow (p less than 0.005). Based on these results, we suggest periorbital Doppler examination as a haemodynamic adjunct to direct ICA visualization. A normal orthograde flow will most certainly rule out any severe pressure reduction. By measuring CBF at rest and following vasodilation in cases with inverted flow, most patients with severe reduction in cerebral perfusion pressure may be identified.     

Periventricular lucencies on computed tomography in multiple cerebral infarcts: correlation with cerebral blood flow measurements

Forty-nine patients with multiple cerebral infarcts with a mean age of 70.2 years were studied to elucidate the effect of periventricular lucencies (PVLs) on cerebral blood flow (CBF). Patients with multiple cerebral infarcts showed significantly lower mean cortical blood flow (F1) values compared to 15 age-matched normal subjects (p less than .01). The mean F1 values were most significantly decreased in severe group of PVLs and moderately decreased in moderate and mild groups (p less than .05 between severe and mild groups); however, no significant differences in mean F1 values were found between severe and moderate groups. Demented patients showed significantly lower F1 values compared to nondemented patients (p less than .001) and normal subjects (p less than .001). There was no significant difference in the degree of PVL between demented and nondemented groups. As well, the mean F1 values were not significantly correlated with either the number of infarcts or ventricular dilatation. These results suggest that PVLs on CT (especially in severe cases of PVLs) may have some role in the reduction of cortical blood flow in patients with multiple cerebral infarcts.     

Mechanism of morphine-induced suppression of central nervous system blood flow

Narcotic agonists such as morphine are well known to decrease cerebral blood flow and metabolism. To investigate a possible mechanism for this action of narcotics, cerebral blood flow (CBF) and spinal cord blood flow (SCBF) were simultaneously measured by the hydrogen clearance technique following intravenous or subarachnoid administration of morphine and subsequent naloxone in lightly anesthetized dogs. The effects of new opiate agonist + antagonists, cyclazocine and buprenorphine, alone or in a combination with naloxone on those CNS blood flow were also investigated. Morphine, 1 mg/kg iv, produced significant decreases in both CBF and SCBF (p less than 0.01), which were reversed by naloxone, 40 micrograms/kg. Naloxone per se did not produce any change in both. Cyclazocine, 50 micrograms/kg iv, also produced significant decreases in both CBF and SCBF (p less than 0.05), but the decreased CBF was not reversed by naloxone. Buprenorphine, 30 micrograms/kg, showed variable changes in both CBF and SCBF, resulted insignificant reduction. However, spinal subarachnoid administration of morphine, 0.2 mg, with which profound analgesia can be obtained in human adults, did not cause any changes in SCBF as well as CBF. These results suggest that narcotic analgesics affect SCBF similar to CBF and morphine decreases CNS blood flow via the activation of supraspinal opiate receptors.     

Single photon emission computed tomography in systemic lupus erythematosus with psychiatric symptoms.

Single photon emission computed tomography (SPECT) with n-isopropyl-p-[123I]iodoamphetamine (IMP) was performed on 20 patients with systemic lupus erythematosus (SLE). Fifteen of the patients showed areas of hypoperfusion. All nine patients who had florid psychiatric manifestations at the time the SPECT was performed had hypoperfusion areas. Four patients who had abnormal SPECT findings during psychiatric remission had psychiatric exacerbation one to six months after the SPECT. Four patients who had no hypoperfusion during psychiatric remission had good psychiatric prognoses. Two patients who had no history of psychiatric abnormality but showed hypoperfusion had psychiatric manifestations one month after the SPECT. The IMP-SPECT may be useful as a biological marker that represents the activity of cerebral involvement underlying psychiatric manifestations and the presence of subclinical CNS involvement.     

Intra-aortic balloon counterpulsation: a treatment for ischaemic stroke?

Intra-aortic balloon counterpulsation (IABC) augments cardiac output (CO) and pulse pressure (PP) allowing patients with low output heart failure to be supported for a period of time. Augmentation of CO and PP may also be beneficial to the patient with acute cerebral ischaemia. In this paper we investigated the possibility of using IABC to increase local cerebral blood flow (CBF) in ischaemic brain. In 12 anaesthetized mongrel dogs, a canine stroke model was produced by occluding the left internal carotid and middle cerebral arteries with aneurysm clips. Six dogs were then treated with IABC for 2 h, and 6 other dogs acted as controls (no IABC). Haemodynamic data were measured continuously and CBF (microsphere technique) and CO measurements were performed pre- and post-occlusion, and then twice during the treatment period. In the IABC-treated animals, PP increased from 32 +/- 5.9 to 39 +/- 7.8 mmHg (p less than 0.01) but CO and local CBF in the ischaemic brain did not change significantly during IABC. However, in 4 dogs with significant increases in CO due to IABC [1.7 +/- 0.3 to 2.8 +/- 0.7 l/min (p less than 0.05)], local CBF in ischaemic brain also increased significantly from 22 +/- 12 to 26 +/- 11 cc/100 g/min (p less than 0.05). In the control animals, CO and local CBF did not change significantly during the observation period. These data suggest that augmentation of CO and PP by IABC results in an increase in local CBF in ischaemic brain. IABC may be an effective treatment for ischaemic stroke in those patients with compromised cardiac performance whose cardiac output and pulse pressure can be augmented by IABC.     

Cerebral blood flow is regulated by changes in blood pressure and in blood viscosity alike

There is still considerable controversy regarding the influence of blood viscosity upon CBF. We have measured CBF with microspheres in 23 cats. Autoregulation was disturbed in the left caudate nucleus by microsurgical occlusion of the left middle cerebral artery. Induced hypertension or hypotension was used and i.v. mannitol (1 g/kg) administered. In all cats blood viscosity decreased an average of 16% at 15 minutes and, in 16 cats, increased 10% at 75 minutes post-mannitol. CBF in the right caudate was 79 +/- 6 ml/100g/min, in the left 38 +/- 6 (p less than 0.001). Only minor changes of CBF occurred in areas with presumed normal autoregulation, including the right caudate, in conjunction with pressure or viscosity changes. In the left caudate CBF decreased 21% with hypotension and 18% with higher viscosity, more than on the right (p less than 0.01 and p less than 0.2, respectively). CBF increased in the left caudate 56% with hypertension and 47% with lower viscosity, again much more than on the right (p less than 0.001 and p less than 0.01, respectively). In the other area which is (nearly) exclusively supplied by the middle cerebral artery of the cat, i.e., the ectosylvian cortex, results were similar to those in the caudate nucleus. These results show that viscosity changes must result in compensatory readjustments of vessel diameter, but that these adjustments do not occur where autoregulation to pressure changes is known to be defective. The adjustments to viscosity changes might be called blood viscosity autoregulation of CBF. We hypothesize that pressure autoregulation and blood viscosity autoregulation share the same mechanism.     

Effect of bromocriptine on cerebral blood flow in Parkinson's disease

We measured regional cerebral blood flow (CBF) with single photon emission computed tomography and Xenon 133 in 8 patients with Parkinson's disease (stages I or II) before and after acute oral administration of 10 mg bromocriptine. Moreover, Columbia University Rating scale and neuropsychological tests were assessed before and after drug administration. Bromocriptine induced a significant (p less than 0.01) increase in CBF (+ 12 p. 100) in all the regions studied unrelated to pCO2 variations. The Columbia motor scale score decreased (by 16 p. 100) whereas those on the neuropsychological tests did not vary. There was no relationship between the improvement in motor performance and the increase in CBF. The results suggest that the effect of bromocriptine on CBF is not mediated by an action on the major dopaminergic pathways in the brain but rather by a direct effect on dopaminergic receptors located on cerebral vessels.     

Regional cerebral blood flow in partial complex epilepsy with and without the presence of lesions

Regional cerebral blood flow (r CBF) was measured by the I.V. 133 Xenon method and use of 27 detectors in 91 patients with complex partial epilepsy in interictal periods (at least 48 h over a complex partial seizure). Some were also examined less than 48 h before or after seizures. All were studied with ictal and interictal electroencephalography (EEG), polysomnography, computed tomography (CT), some had nuclear magnetic resonance scans (MR). The blood flow values were compared with a group of a 20 normal subjects matching for age. A significant decrease of r CBF ranged from 15% to 25% was found in the temporal region in three groups of epileptic patients: with repeated normal CT scans and lateralized EEG abnormalities (N = 46); with cortical atrophy in CT scan (N = 12); with neurosurgical focal lesions on CT and or MR scans glioma, arteriovenous malformation) (N = 10). r CBF was normal or decreased by less than 15% in the other regions of the brain. Patients with repeated normal CT scans and bilateral EEG abnormalities either asynchronous or alternatively observed in the right side or left side on waking EEG or during NREM sleep and REM sleep, did not show reduction in r CBF. In a previous study, r CBF distribution was also found normal during interictal phase in patients with primary generalized epilepsy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of endothelium-derived nitric oxide on cerebral circulation during normoxia and hypoxia in the rat.

The aim of this study was to determine the effects of endogenous nitric oxide (NO) on cerebral blood flow (CBF) and cerebrovascular resistance (CVR) under conditions of normoxia and hypoxia. Experiments were performed on anesthetized, mechanically ventilated Wistar rats. CBF was measured using the intracarotid 133Xe injection technique. NO formation was inhibited by NG-monomethyl-L-arginine (L-NMMA). Administration of L-NMMA (100 mg kg-1 i.v.) during normoxia resulted in an increase in mean arterial blood pressure from 113 +/- 4 to 145 +/- 4 mm Hg (p less than 0.001), a decrease in CBF of 21% (from 91 +/- 4 to 75 +/- 5 ml 100 g-1 min-1, p less than 0.001), and an increase in CVR of 53% (from 1.3 +/- 0.1 to 2.0 +/- 0.2 mm Hg ml-1 100 g min, p less than 0.001). These effects were reversed by i.v. administration of 300 mg kg-1 of L-arginine but not D-arginine. Moreover, the administration of L-NMMA abolished the enhancement of CBF and the diminution in CVR observed during intracarotid infusion of acetylcholine (ACh). The increase in CBF and decrease in CVR during hypoxia in the group of rats that received L-NMMA were similar to that in the control group, although CBF and CVR levels attained during hypoxia in both groups were different. The results show that NO is involved in the maintenance of basal CBF and CVR, and is responsible for the ACh-elicited increase in CBF and the decrease in CVR in rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of cerebral autoregulation following diffuse brain injury in rats

Abstract

The normal cerebral circulation has the ability to maintain a stable cerebral blood flow over a wide range of cerebral perfusion p(essures and this is known as cerebral autoregulation. This autoregulation may be impaired in the injured brain. Closed head injury was induced in 28 Sprague-Dawley rats weighing 400-450 g. Four groups were studied: control group, head injured rat from meter height using 350 g, 400 g and 450 g respectively. CBF, volume velocity was monitored using laser-Doppler flowmetry together with monitoring of ICP and arterial blood pressure. Correlation to assess the relationship between CBF and CPP was done in each animal every hour. If correlation coefficient was> 0.85 and CPP was within normal range, loss of autoregulation was hypothesized. Chi square test, ANOVA test and unpaired Studen(s t-test were done and significant level of p < 0.05 was established. Mean CBF in injured rats was significantly lower than controls (p = 0.028) at the fifth hour. CBV was lower in the group of 450 g 1 m impact than in controls at 3 h (p = 0.04). Velocity in the group ofall injured rats, was significantly lower than in controls at 3 h (p = 0.032) and at 4 h (p = 0.027). Loss ofautoregulation was seen during first four hours after trauma in all groups of rats who sustained injury. Statistical significant difference (p = 0.041) in loss of autoregulation between injured and control animals was seen. No loss of autoregulation was observed in the control group. In conclusion CBF and CPP provide information about loss of autoregulation in diffuse brain injury. Decrease in CBF and increase of ICP is observed as a result ofloss of cerebral autoregulation. Knowledge of loss of autoregulation could give important information and help in the management of head injured patients. [Neural Res 1997; 19: 393-402]