Internal Carotid Artery Flow Research Articles

1343 SEIZURES-A NEGLECTED PATHOGENESIS IN NEONATAL INTRAVENTRICULAR HEMORRHAGE

We investigated the cerebrovascular responses of immature piglets to Pentylenetetrazol (PTZ)-induced seizures. Our objective was to demonstrate that seizures induce hemodynamic changes known to cause intraventricular hemorrhage (IVH), and should be considered an important triggering mechanism.14 piglets were artificially ventilated with 0.25% Halothane in 50% N2O-50% O2 after tracheotomy and neuromuscular blockade. Flow in external and internal carotid and femoral arteries was continuously recorded, along with aortic blood pressure (BP),EEG and EKG. Animals were subjected to hypercapnia (HC) by breathing 7% CO2 to produce respiratory acidosis (Pco2=53.9± 1.0; pH=7.263 ± 0.008.) Following return of blood gases to baseline values, PTZ was administered in a threshold (I-V) epileptogenic dose (75 mg/Kg.). HC produced a significant (30-50%) increase in internal carotid blood flow (ICBF), accompanied by a 10% drop in BP. PTZ produced a much greater (80-198%) and more rapid increase in ICBF, with a parallel large (60-70%) increase in BP. Auto-regulation was lost during PTZ-induced seizures.We conclude that the increase in cerebral blood flow and BP, plus loss of autoregulation, occurring during a seizure duplicate the hemodynamic conditions which trigger IVH. The changes are of much greater abruptness and magnitude than those seen with respiratory acidosis. Hence, seizures are likely to have a significant role in germinal matrix hemorrhages in premature newborns.

Changes in internal carotid artery flow velocities with cerebral vasodilation and constriction.

Non-invasive Doppler-shift ultrasound, together with spectral analysis, have been used to study the changes in internal carotid artery flow velocity patterns that occur with cerebral vasoconstriction and vasodilation provoked by over-breathing and breath-holding. Significantly different waveform shapes, characteristic for each vessel, were demonstrated from the internal and external carotid arteries, making identification of the internal carotid certain. In 5 healthy subjects over-breathing for 3 minutes significantly lowered the mean height of the internal carotid waveform by an average of 32% (p less than 0.001). Breath-holding for 40-60 seconds raised the mean height by an average of 31% (p less than 0.001). The pulsatility index of the waveforms varied inversely to mean height. These results show that the effects of cerebral dilation or constriction are easily detected by flow-velocity changes in the internal carotid artery.

Cerebral arterial blood flow and aneurysm surgery. Part 1: local arterial flow dynamics.

Cerebral arterial blood flow was monitored in 22 patients undergoing surgery for intracranial saccular aneurysms. An electromagnetic flow probe was used to record the internal carotid artery (ICA) flow in the neck or intracranially in seven patients. The ICA flow ranged between 100 and 175 ml/min (average 144 ml/min). Intracranial flow measurements with specially designed probes were made in 17 patients. The middle cerebral artery (MCA) showed flow values between 75 and 120 ml/min (average 97 ml/min). Flow figures recorded from the proximal anterior cerebral artery (ACA) were lower (average 65 ml/min), and had a wider range from 30 to 110 ml/min. Test occlusion of the terminal ICA showed a retrograde flow in the proximal ACA to the MCA ranging from 15 to 125 ml/min (average 78 ml/min). This test was used to investigate the collateral potential of the anterior portion of the circle of Willis, which is essential to the decision of whether to undertake trap ligation procedures in this location. Flow monitoring in the parent vessel was also of use in some patients to assess flow conditions after the clipping of the aneurysm neck.

Trachea–Innominate Artery Fistula: Successful Management or 3 Consecutive Patients

Trachea-innominate artery fistula is an uncommon but frequently fatal complication of tracheostomy. Three successive patients who developed this complication while receiving ventilatory assistance through a tracheostomy tube were successfully managed, with long-term survival. Bleeding was controlled by direct digital pressure on the innominate artery or by hyperinflation of the balloon cuff of the tracheostomy tube. In 2 patients, replacement of the tracheostomy tube with an orotracheal tube improved direct access to the innominate artery for digital compression. Late follow-up examination of the right carotid circulation revealed complete reversal of flow in the right internal and common carotid arteries in the 2 patients studied.

Precerebral arterial blood flow pattern in intracranial hypertension with cerebral blood flow arrest.

A pulsed echo Doppler flowmeter was used to confirm cerebral flow arrest in patients with intracranial hypertension resulting in a cerebral perfusion pressure of zero or close to zero. The cerebral angiograms showed non-filling. The term brain tamponade is used for this condition. The patient had a mean arterial blood pressure at the time or recording ranging from 70 to 160 mmHg. Under these conditions the transcutaneous recording of internal carotid artery flow velocity immediately distal to the carotid bifurcation showed a reverberating flow pattern with marked pulsations. The forward flow in systole was counterbalanced by the retrograde flow during diastole resulting in a net flow of zero. This flow pattern is basically caused by a combination of intracranial vascular obstruction, the arterial blood pressure at the site of measurement, and finally the compliance of the distal arterial segment as well as the intracranial compliance. This non-invasive method is of potential value in the determination of intracranial flow arrest.

Influence of Xantinoli nicotans (Complamin) and papaverine upon internal carotid artery blood flow after arterial reconstruction.

The effect of intravenous administration of 0.3 g of Xantinoli nicotans (Complamin) and 40 mg of papaverine on internal carotid artery (ICA) blood flow in 17 conscious, newly operated patients was studied with the aid of electromagnetic flowmetry. A flow probe was attached to the ICA after carotid reconstruction. Administration of Complamin resulted in a significant decrease in arterial mean pressure and a corresponding decrease in ICA flow. The arterial mean pressure also diminished after administration of papaverine, but the decrease was moderate and did not influence ICA flow. The results indicate that the cerebral vascular autoregulation may be impaired in the early postoperative period. Vasoactive substances, which cause decreased arterial pressure, also influence ICA flow and should be avoided in patients newly operated upon for occlusive disease of the carotid artery.

Effect of physical exercise on internal carotid artery blood flow after arterial reconstruction.

The effect of physical exercise on internal carotid artery (ICA) blood flow in conscious man was studied with the aid of electromagnetic flowmetry. A flow probe was implanted on the ICA in 25 patients after reconstruction of the artery. ICA mean blood flow and brachial artery mean blood pressure were continuously monitored in supine (25 patients) and sitting (24 patients) position at rest, during 5-6 minutes exercise on a bicycle ergometer and at rest after exercise. Arterial carbon dioxide tension (PaCO2) was studied in 6/25 work tests in supine and 7/24 in sitting position. Cardiac output was measured at rest and during exercise in 10/25 patients in supine and 8/24 patients in sitting position. In the supine group, ICA flow increased significantly within 1 minute and reached a maximal flow 15% above control flow within 2 minutes after the onset of exercise. The ICA flow then gradually declined, but remained almost significantly elevated, 7.5% above control, on termination of exercise. At rest, after exercise, the ICA flow decreased almost significantly to a level of 5% below the control flow within 5 minutes. There was a significant PaCO2 increase of 2.6 mmHg during exercise and a highly significant increase (72%) in cardiac output during exercise. The ICA flow at rest, before exercise, was about 15% lower in the sitting group than in the supine group. It increased in average 11.5% with 2 minutes of exercise and then gradually diminished. At rest, after exercise, ICA flow decreased further to a level of 8% below control flow within 5 minutes. PaCO2 increased significantly in average 1.6 mmHg during exercise. Cardiac output increased highly significantly (85%) during exercise. The ICA flow changes obtained during exercise in the present study indicate the presence of a regulatory mechanism counteracting the increasing perfusion pressure, but it is unable to compensate the decreased perfusion pressure when the body position was altered from supine to sitting. The cerebral vascular bed in the present patient material seems to operate above and below the lower limit of its pressure range for an adequate autoregulation.

Effect of Posture on Internal Carotid Artery Blood Flow J After Arterial Reconstruction

The effect of changes in posture, i.e. from supin e to upright position, on internal carotid artery (ICA) blood flow in conscious man was studied with the aid of electromagnetic flowmetry. A flow probe was implanted on the ICA in 23 patients after carotid reconstruction. ICA mean blood flow and brachial artery mean blood pressure were continuously monitored in 25 tilting tests and arterial carbon dioxide tension (PaCO2) was studied in 11/25. Cardiac output was measured in supine and upright position in 9/25 tilting tests. the patients (24/25) reacted to orthostatic blood shifts with a markedly hypokinetic circulation and a high incidence of fainting (6/25) in upright position.In 19 studies on non-fainting patients, ICA flow decreased in upright position in average by 25 % below supine control flow within one minute. ICA flow then gradually declined to a level 30% below control flow in supine position within five minutes. PaCO, decreased at the same time in average by 4 mmHg and the brachial artery pressur...

The Effect of Glucagon on the Internal Carotid Artery Blood Flow after Carotid Artery Surgery in Man

The effect of intravenously administrated glucagon on the internal carotid artery flow, brachial artery pressure and vascular resistance was studied in 13 patients operated on for arteriosclerotic disease. An implantable electromagnetic flow probe was left on the artery postoperatively and the studies were performed on the first or second postoperative day in the awake patient. There were no significant changes in the internal carotid artery flow after glucagon. The mean brachial artery pressure was almost unchanged with a slight but insignificant decrease after 5 minutes. No significant change of the vascular resistance was found. A slight but not significant increase of the PaCO2 with 3.4 mmHg was found after 25 minutes in 5 patients followed with repeated PaCO2 checks.According to the present study, administration of 1 mg glucagon intravenously does not influence the internal carotid artery flow and indirectly indicates that the cerebral blood flow is unchanged.

Continuous per- and postoperative blood flow measurements on the internal carotid artery after arterial reconstruction.

A method is presented for continuous per- and postoperative blood flow measurements, with the aid of an implantable electromagnetic flow probe, on the internal carotid artery after arterial reconstruction. A flow probe was implanted on 39 arteries. The internal carotid artery flow increased significantly, by 67 % above the peroperative flow on the first postoperative day and then gradually declined. Postoperative hyperaemia may indicate a temporarily impaired autoregulation of the cerebral blood flow after brief internal carotid artery occlusions during the reconstruction. Some different flow patterns, due to different cardiac rhythms and respiration, are described and briefly discussed. The method proved safe and valuable for studying flow changes in the internal carotid artery, particularly for repeated flow measurements and during non-steady-state situations.

Influence of hypo- and hypercapnia on internal carotid artery blood flow after arterial reconstruction.

The influence of arterial PaCO2 on internal carotid artery (ICA) blood flow was studied with the aid of an electromagnetic flow probe implanted on the ICA after arterial reconstruction in 13 patients.ICA flow (QICA) varied as a single exponential function of PaCO2 according to the least squares equation adjusted to the observations:log QICA=1.784 + 0.013 PaCO2, S.D. ± 0.104, n = 46, r = 0.85.This relationship is similar to that reported in the literature for that between cerebral blood flow (CBF) and PaCO2, a fact which is considered to indicate that changes in ICA flow reflects changes in CBF through the tissue supplied by the ICA studied. The cerebral vasoreactivity to CO2 seems to be well preserved in arteriosclerotic, conscious patients, operated upon a few days earlier with internal carotid artery reconstruction.

Competition between cutaneous vasodilator and vasoconstrictor reflexes in man.

A two-part experiment was carried out on seven men to determine whether skin will respond to increased neurogenic vasoconstrictor activity during heating. The latter was induced by lower body negative pressure of -50 mm Hg applied for 5 of each 15 min in 12 studies with constant, neutral skin temperature (32.2-34.4 C) in a 40-min control period and with skin temperature held at 38 C for 40-70 min. We conclude that during heating, skin retains the ability to vasoconstrict but that this vasoconstriction cannot completely override heat-induced vasodilatation.

Cerebrovascular response to intracarotid injection of serotonin before and after middle cerebral artery occlusion.

The effect of intracarotid injection of serotonin (5-HT) on internal carotid artery flow and oxygen availability (O(2)a) of the cerebral cortex was studied in 10 baboons. Vasoconstriction occurred in the vascular bed of the territory supplied by the injected artery. After one middle cerebral artery was occluded the vasoconstrictor effect of 5-HT was more pronounced, particularly in the non-ischaemic hemisphere. The capacity of the cerebral vessels to provide collateral blood flow was reduced in both ischaemic and non-ischaemic areas of brain. As a result of focal cerebral ischaemia, 5-HT may accumulate in the brain and contribute to the progression of infarction.

The role of the circle of Willis in graded occlusion of the internal carotid artery in man.

Protracted studies on bilateral internal carotid artery (ICA) flow using implantable electromagnetic flow probes were performed in ten patients undergoing graded occlusion for infraclinoid saccular aneurysm. The ICA flow was generally lower on the side of the aneurysm in the eight patients with previous subarachnoid haemorrhage, and the difference was statistically significant at the 5% level. This was attributed to the increased vascular resistance in the affected hemisphere. A contralateral ICA flow increase, varying between 14 and 73%, was found in all patients at test occlusion of the ipselateral ICA. Three patients showed electro-encephalographic evidence of intolerance to clamping of the artery. They also showed the lowest contralateral compensatory increase (14–17%) at test occlusion. Furthermore, a delay in contralateral flow response to stepwise trial occlusion was observed in these patients. Two of these patients suffered ischaemic attacks in spite of special precautions taken during the subsequent graded clamping procedure. Complications also occurred in two patients who showed a satisfactory response to test oclusion. These complications, however, were found to be caused by thrombo-embolic processes in the ipselateral ICA during the period of graded occlusion and were not related to insufficient collaterals.

Hemodynamic aspects in the management of carotid-cavernous fistula.

✓ A method for intraoperative evaluation of the hemodynamic state in patients with carotid-cavernous fistula is described. Electromagnetic flow probes were applied on the internal carotid artery (ICA) in the neck and on the intracranial part of the artery distal to the fistula in five patients. Fistula “steal5 ranged from 90 to 975 ml/min. Forward flow rate in the intracranial portion of the ICA, distal to the fistula, was from 40 to 170 ml/min. The reverse flow rate during test occlusion of the ICA in the neck was between 35 and 60 ml/min. The ratio reverse flow/forward flow is assumed to give an indication of the collateral capacity of the cerebral vasculature and of the tolerance to trap ligation of the ICA. The pulsatile pattern of the intracranial ICA flow in this series varied considerably, and this parameter is also found to be of importance in the evaluation of the capacity of the collateral arterial system. The monitoring of cervical ICA flow proved to be a reliable way to supervise the procedure of plugging the fistula with flow-carried muscle emboli in conjunction with trap ligation.

Cerebral blood flow and internal carotid artery flow during carotid surgery.

In a series of 17 patients operated on for stenosis of the internal carotid artery, measurement of the blood flow in the internal carotid artery by a squarewave electromagnetic flowmeter was performed simultaneously with measurement of the regional cerebral blood flow (rCBF) by the 133 Xenon injection technique. The measurements were made before and after endarterectomy. On completion of endarterectomy there was significant increase in mean internal carotid artery flow (ICAF), from 133 ml/min to 212 ml/min (P<0.05), whereas mean rCBF remained unaltered. The ratio ICAF/rCBF gives brain substance in grams supplied by the internal carotid artery. The mean value of this ratio increased significantly from 231 gm to 452 gm after endarterectomy (P<0.01). Thus cerebral hemodynamics tended to the normal postoperatively.

EFFECTS OF THE SITTING POSITION ON BLOOD FLOW IN THE INTERNAL CAROTID ARTERY OF MAN DURING GENERAL ANESTHESIA

p LACING a pa t ien t in a sitting position during an operat ion on the cervical spine or the posterior fossa offers a t least two technical advan tages to the neurosurgeon: it is easier to main ta in a given position, and there is less bleeding. However , two well-recognized potent ia l hazards are associated with this surgical position, namely, air embolism and inadequate cerebral blood flOW. When a pa t ien t is in the sit t ing position, venous pressure a t the cervical level can fall below a tmospher ic pressure during inspiration; thus, an opening in a vein could allow a fatal amoun t of air to enter the hear t2 -5 Although clinical experience with pat ients who have undergone surgery in the sit t ing position has shown tha t cerebral perfusion is usually sufficient to preserve normal cerebral function, the degree to which cerebral flow is depressed during these procedures has ne t been previously measured. Since anesthesia accompanied b y hypocarb ia is known to cause a marked reduction in cerebral blood flow, ~4 any fur ther decrease resulting f rom the sit t ing position could lower cerebral blood flow to a dangerous level. The following experiments were designed to determine the effects of the sitting position on blood flow and pressure in an internal carotid a r te ry in anesthet ized patients. In addit ion, the effects of general anesthesia combined with hypervent i la t ion on internal carotid arterial flow and pressure were evaluated.

Internal carotid artery flow rate during craniotomy and muscle embolization for carotid cavernous fistula. Report of four cases.

Case Reports Case 1. A 24-year-old man came to the hospital on July 7, 1965, complaining of pain in the left eye and double vision which had begun after a fall 3 weeks earlier. Two years previously the patient had sustained fractures of the left facial bones and was operated upon for depression of the floor of the left orbit; afterwards diplopia was present intermittently. When he fell he struck his head on the ground, but remained conscious. After this he noticed a bruit, and the diplopia became constant. Examination. Conjunctival edema, exophthalmos, and a bruit were present on the left. The left retinal veins were distended, but vision was normal. A left carotid arteriogram demonstrated a left carotid cavernous fistula (Fig. 1). The contrast medium left the cavernous sinus via the superior petrosal sinus, the superior ophthalmic vein, the Sylvian vein, and the basal vein of Rosenthal. A right carotid arteriogram with compression of the left carotid artery demonstrated the anterior and middle cerebral arteries bilaterally and the fistula. Operation. A left frontal craniotomy was performed, and the common, internal, and external carotid arteries were exposed in the neck. An electromagnetic flow meter was

Effects of the Sitting Position on Blood Flow in the Internal Carotid Artery of Man During General Anesthesia

p LACING a pa t ien t in a sitting position during an operat ion on the cervical spine or the posterior fossa offers a t least two technical advan tages to the neurosurgeon: it is easier to main ta in a given position, and there is less bleeding. However , two well-recognized potent ia l hazards are associated with this surgical position, namely, air embolism and inadequate cerebral blood flOW. When a pa t ien t is in the sit t ing position, venous pressure a t the cervical level can fall below a tmospher ic pressure during inspiration; thus, an opening in a vein could allow a fatal amoun t of air to enter the hear t2 -5 Although clinical experience with pat ients who have undergone surgery in the sit t ing position has shown tha t cerebral perfusion is usually sufficient to preserve normal cerebral function, the degree to which cerebral flow is depressed during these procedures has ne t been previously measured. Since anesthesia accompanied b y hypocarb ia is known to cause a marked reduction in cerebral blood flow, ~4 any fur ther decrease resulting f rom the sit t ing position could lower cerebral blood flow to a dangerous level. The following experiments were designed to determine the effects of the sitting position on blood flow and pressure in an internal carotid a r te ry in anesthet ized patients. In addit ion, the effects of general anesthesia combined with hypervent i la t ion on internal carotid arterial flow and pressure were evaluated.

Studies of carotid-artery blood flow in man.

DESPITE general interest in the physiology of the carotid circulation of man, there is little precise information about blood flow through these vessels. Neurosurgeons have long been accustomed to ligating the common carotid artery in the neck for intracranial vascular abnormalities, but controversy still exists regarding direction and volume of external and internal carotid-artery flow thereafter. More recently internists, neurologists and vascular surgeons have exhibited increasing interest in diseases of the internal carotid artery and in collateral circulation through the external carotid artery that may compensate for it. Therefore, it seemed appropriate to undertake an investigation of the hemodynamics of . . .