Spinal trauma: pharmacological evidence for vasoconstrictor activity in cerebrospinal fluid

Cerebrospinal fluid from six cases of acute spinal trauma collected 0--6 days after injury was examined for vasoconstrictor activity using both human isolated cerebral arteries and animal tissues. The cerebrospinal fluid of four out of six patients was vasoactive. The identities of the vasoconstrictor substances were not established, but experiments with pharmacological antagonists showed that arterial contractions were not due to serotonin, histamine, noradrenaline, acetylcholine or angiotensin II, substances which are known potent spastic agents on cerebral arteries. Our findings would explain by the mechanism of arterial spasm, principally in the anterior spinal artery, the neuropathological appearance of central haemorrhagic necrosis in spinal cord injury. The infarction of the core of the spinal cord could be caused by vasoconstrictor substances, reported here, in the cerebrospinal fluid after spinal injury. If the identities of the substances could be established, drug therapy to prevent or relieve the spasm would be possible.

[Plastic properties of the arterial bed of the cervical area in the dog]

In 12 dogs sources of blood supply for certain cervical organs have been studied in norma. Anastomoses between them are grouped according to their origin as intersystemic and intrasystemic. The main intersystemic anastomoses are situated in the superficial ventral muscles, and the intrasystemic ones--in the superficial dorsal muscles, trachea and esophagus. In 24 dogs both the common carotid and vertebral arteries have been ligated simultaneously. The main compensatory-adaptive mechanisms contribute for the collaterals to develop, dilate and acquire their winding character, for the angle of the collateral branches alteration to change. Main and additional by-pass ways of the blood stream have been revealed.

Changes in cerebral blood flow during hyperventilation and CO2-breathing measured transcutaneously in humans by a bidirectional, pulsed, ultrasound Doppler blood velocitymeter

We have used a bidirectional pulsed ultrasound doppler system which measures the instantaneous mean velocity across the lumen of a blood vessel in order to determine the relationship between alveolar PCO2 (PACO2) and blood flow in the four arteries supplying the brain in humans. Both high and low PACO2-values were explored. Six subjects, 3 males and 3 females (22-40 years) were studied by use of this non-invasive technique. To increase the PACO2 the subjects were breathing 4, 6 and 8% CO2 in air. PACO2 was reduced by voluntary hyperventilation down to a chosen end-expiratory PCO2 value of about 2.2 kPa. We found a linear relationship between arterial blood flow expressed as a percentage of control level and PACO2 in the range from 3.3 to 7.3 kPa. At the very lowest PACO2 values a levelling off of the response, with flow values of 40 to 45%, was observed. The CO2-reactivities in the 6 persons varied between 28.1 and 30.0%/kPa. The time course and the magnitude of the flow response were similar in all four arteries.

Subclavian steal syndrome. Part 2: Intraoperative vertebral artery blood flow measurement

Intraoperative vertebral artery blood flow was measured in two patients with symptomatic subclavian steal syndrome, before and after proximal end-to-side vertebral to common carotid artery transposition. This confirmed retrograde flow in the vertebral artery before transposition, and antegrade flow after transposition. The measured flow rates were compared to values in other series involving different operative procedures for correction of symptomatic subclavian steal. The greatest mean antegrade flow rates in the vertebral artery were restored by proximal end-to-side vertebral to common carotid artery transposition.

Circulatory effect of jet noise, with special reference to cerebral circulation

The circulatory effect of jet noise on heart rate, systolic blood pressure and cerebral blood flow was investigated by means of the on-line Doppler ultrasonic technique devised by the author in 20 normal young males, normal elderly males and elderly patients with cerebral vascular disease. The jet noise ranged from 60 dBA to 110 dBA. Heart rate and systolic blood pressure showed slight and transient increase at the level of over 90 dBA. Although the cerebral blood flow was increased at the level of 90--110 dBA, conspicuous dissociation was observed between the vertebral artery and internal carotid artery. The vertebral artery dominant type was more frequent than the internal carotid artery dominant type. Headache and discomfort due to the noise were observed in all the subjects. The above facts suggest that the jet noise induces dysfunction of the autonomic nervous system and various kinds of psychosomatic diseases.

[Damping of oscillations in arterial pressure in the internal carotid arteries]

In dogs, recording of fluctuations of the inlet and outlet pressure in the internal carotid artery showed a decrease of the amplitude of fluctuations along the artery, the damping index (Id) being about 60-90%. The Id was almost unchanged when the skull was either intact or largely opened. The amplitude of blood pressure fluctuations in the circle of Willis was always decreased after occlusion of the vertebral arteries, being evidently unrelated to superposition of the pulse waves that reach the circle of Willis through the internal carotid and the vertebral arteries. Therefore the decrease of the amplitude of pulsation was dependent on the damping of the pulsatile waves along the internal carotid arteries. The rise of the tone of the latter increased the Id, and vice cersa. The Id was almost independent of the size of amplitude and of the frequency of the fluctuations of the systemic arterial pressure, but decreased when the latter rised.

[Studies on the role of high pressure baroreceptors in vasopressin (ADH) secretion. Effect of occlusion of common carotid and vertebral arteries on blood ADH level (author's transl)]

The role of baroreceptors in common carotid and vertebral arteries and arteries in the thoracic cavity in vasopressin secretion was investigated in this study. Effects of bilateral occlusion of common carotid and vertebral arteries on blood ADH level as well as mean arterial pressure were studied in common carotid arterial plexus-denervated dogs, cervically vagotomized dogs and intact dogs. Blood ADH titers were determined by bioassay technic before and 5 minutes after the occlusion of the arteries and were compared with the changes of mean arterial pressure (MAP). The following results were obtained. (1) Blood ADH titers and MAP were elevated by the occlusion of the common carotid arteries in both intact and vagotomized dogs, while they were not significantly affected in denervated dogs. Elevation of blood ADH titers was more pronounced in vagotomized dogs than in intact dogs. (2) Blood ADH titers and MAP were elevated by the occlusion of vertebral arteries in all groups of dogs. However, the elevation of blood ADH titers in denervated dogs was more pronounced than in intact dogs, but less than in vagotomized dogs. (3) The effects of the occlusion of common carotid arteries on blood ADH titers and MPA were more pronounced than those of the occlusion of vertebral arteries. These results may suggest that: a. baroreceptors involved in vasopressin secretion are present in vertebral arteries as well, and that b. the intrathoracic baroreceptors are dominant in controlling vasopressin secretion, while those in common carotid arteries are secondly and those in vertebral arteries thirdly dominant.

Carotid-vertebral artery blood transit time in health and in neurological patients: a preliminary study by a non-invasive impedance method

Thirty-one healthy subjects and nineteen neurological patients covering a range of chronic neurological and neurovascular syndromes were examined by an electrical impedance method. Two estimates of carotid-vertebral artery transit times were measured: one time taken between the Q wave of the EKG to the commencement of the next succeeding impedance pulse-volume wave (CT1), and the other, this estimate together with the time to maximum point of the impedance wave (CT2). Results indicated prolonged circulation times for the patients as compared with the controls without relevance to age in the case of CT1, although transit times did increase with age for CT2. It is suggested that this impedance technique may be valuable in the initial screening of transient cerebral ischaemia.

Carotid-vertebral artery blood transit time: results in healthy subjects and patients with schizophrenia and brain disease

Estimation of blood transit time in the neck and the extension of this into the head was made by a method of electrical impedance, over a wide age range, in 159 healthy subjects, 160 schizophrenic patients, and 199 patients with organic brain disease. In each case, the distance between the electrocardiogram and the next succeeding pulse-volume impedance wave was measured and averaged over 30 serial wave forms. Chronological age proved a significant variable, transit times lengthening progressively with the age, but only for measurements extending into the head. Sex and hemispheric laterality played no significant role. With age held constant, mean transit times into the head were significantly prolonged in both groups of patients as compared with controls. No significant differences were found however between means of psychiatric andneurological patients. It is suggested that these results reinforce the organic etiology of schizophrenia.

Distribution of the blood flow supplied by the vertebral artery in rats: anatomical, functional and pharmacological aspects

In rats, the vertebral artery make only a minor contribution to the blood perfusion of the ponto-medullary area. This was measured with radioactive microspheres and was confirmed by methylmetacrylate casts and local injection of a centrally acting hypotensive drug.

[Transoral Doppler ultrasound echography under local anaesthesia for the assessment of vertebral artery blood flow (author's transl)]

Uncalibrated flow in the vertebral arteries was registered with a bidirectional CW Doppler ultrsound apparatus. It was applied to 20 patients, results being compared with aortic arch angiograms in which the extracranial part of all four cerebral vessels was seen. In 14 the vertebral arteries had a symmetrical flow and lumen, a similar symmetrical result being obtained with the Doppler. Hypoplasia of one vertebral artery was present in two patients the distinct asymmetry being recorded by the ultrasound. Three patients with central stenosis in one subclavian artery and subclavian "steal" were found to have reverse flow by the Doppler method in the vertebral artery on the side of the stenosis. Endarterectomy was performed on the affected subclavian artery in two of these patients: post-operative vertebral ultrasound recordings demonstrated a return to physiological flow direction in both vertebral arteries.

Localized neurogenic vasoconstriction of the basilar artery

Ring segments from the caudal end of the basilar artery of the rabbit contract to electrical stimulation of their intramural nerve supply more than those from adjacent parts of the vertebral and the rostral three-fourths of the basilar arteries. The magnitude of developed neurogenic tension is approximately one-fourth that of the ear artery, a highly reactive muscular artery. The position of this reactive arterial segment suggests its role in the regulation of cerebral blood flow.

A comparative study of middle cerebral pressure in dogs and macaques

1. A comparison has been made of the pressures recorded from pial branches of the middle cerebral artery in dogs and macaques. This pressure has been shown to be between 88 and 95% of femoral arterial pressure in dogs under chloralose anaesthesia, and between 80 and 90% of femoral arterial pressure in macaques similarly anaesthetized.2. The effect of occlusion of the main vessels in the neck is shown to differ considerably in the two species. Blood pressure within the forebrain of the dog is shown to be largely dependent upon the integrity of the external carotid artery, whereas in the monkey the external carotid artery is without effect in the maintenance of forebrain blood pressure. Occlusion of the four major arteries in the neck is shown to produce a greater effect in the macaque and to be accompanied by signs of medullary ischaemia in this species.3. After occlusion of the main middle cerebral artery, arterial pressure measured distal to the occlusion depends upon the integrity of collateral vessels from the other cerebral arteries. When only a branch of the middle cerebral artery is occluded, the greater part of the residual blood pressure depends upon anastomoses from other branches of the middle cerebral artery itself.

Autoregulation of cerebral blood flow. Electromagnetic flow measurements during acute hypertension in the monkey

Changes in blood flow through the internal carotid, vertebral and external carotid arteries were measured by electromagnetic flowmeters during and after acute hypertension induced by closing a clamp around the thoracic aorta in anesthetized monkeys.

The internal carotid and vertebral arterial system showed both rapid and delayed autoregulatory responses to rapid increases in blood pressure; the rapid (primary) responses occurred within seconds, the progressive (delayed) within 3 to 4 minutes. In contrast, the flow response within the external carotid system appeared to be passive. Cervical sympathetic innervation and myogenic reflexes (Bayliss reflex) both appear to play a part in the rapidly occurring (primary) regulation of cerebral blood flow. The mechanism responsible for delayed and progressive (secondary) autoregulation in the cerebral vasculature appeared to be metabolic, since it was predominantly influenced by changes in blood Pco 2 . Changes in intracranial pressure did not seem to be involved in autoregulation.