Precerebral haemodynamics in brain tamponade. Part 2: Experimental studies.
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Adolescent↗
Biomedical subjects
H Nornes
Publications and source records attributed to H Nornes.
Hemodynamic aspects of cerebral arteriovenous malformations.
Local hemodynamics were studied in 16 patients undergoing total extirpation of cerebral arteriovenous malformation (AVM). Directional Doppler technique was used for the registration of blood velocities in vessels feeding and draining the AVM. Calculated flow in single feeding arteries ranged from 3 to 550 ml/min (average, 180 ml/min). An estimation of total AVM flow was possible in nine patients, and ranged from 150 to more than 900 ml/min (average, 490 ml/min). Pressure recordings were made from feeding arteries at their entrance to the AVM. This pressure was well below the systemic arterial blood pressure in all cases, and ranged from 40 to 77 mm Hg (average, 56 mm Hg). On temporary occlusion, this stump pressure instantly rose to from 55 to 95 mm Hg (average, 76 mm Hg). Draining vein pressure before occlusion ranged from 8 to 23 mm Hg (average, 15 mm Hg), and fell to zero in all patients when the AVM was occluded. These data and other clinical observations are discussed with regard to adjacent brain-tissue perfusion, and with special emphasis on the circulatory breakthrough that can follow the occlusion of these high-capacity shunts.
Adult↗
[Carotid surgery in ischemic cerebrovascular disorders].
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Arteriosclerosis↗
Cerebral arteriovenous malformations; results of microsurgical management.
A series of 63 patients with cerebral arteriovenous malformation (AVM) operated on during an eight-year period is presented. Indications for surgery and the timing of operation are discussed. Monitoring of epidural pressure was of help in assessing the intracranial pressure state, which is important in patient management in the acute stage, in timing of surgery, and in postoperative supervision. The operative mortality was one patient (1.6%). Two patients died due to incomplete resection and late rebleeding two years after operation. Among the others the overall result of surgery was good with respect to neurological deficit and working capacity.
Adolescent↗
Surgical correction of subclavian steal syndrome.
Eleven patients with subclavian steal syndrome underwent surgical correction without mortality. Ten patients were relieved from their symptoms. Two vessels reoccluded, two months and three years postoperatively, with reappearance of symptoms. One patient was hemiplegic after the operation. Associated lesions of other precerebral vessels were found in 7 patients, and surgical correction of two or three stenosed or occluded arteries was performed in 5 of them. Satisfactory and complete preoperative angiographic study of all precerebral vessels is therefore important. In 4 patients studied, the vertebral artery flow changed from a mean retrograde flow of 91 ml/min to a mean forward flow of 64 ml/min.
Blood Flow Velocity↗
Intraoperative evaluation of cerebral hemodynamics using directional Doppler technique. Part 1: Arteriovenous malformations.
The use of a pulsed echo Doppler technique during surgery for cerebral arteriovenous malformation is described. The equipment and the methods employed are presented. The main advantages are easy determination of flow direction and pattern of the vasculature involved, allowing a precise discrimination between inflow and outflow channels. Deep-seated malformations, not visible at the brain surface, can be located with the Doppler technique. The ultrasound probe was placed on the brain surface with a slight pressure on the intact pia mater. The precise direction and depth of the malformation could be determined in relation to the recording site. This facilitated the planning of cortical incisions, identification of vessels involved, and the vascular procedure to be employed.
Adolescent↗
Intraoperative evaluation of cerebral hemodynamics using directional Doppler technique. Part 2: Saccular aneurysms.
The use of a pulsed echo Doppler technique during procedures for occlusion of intracranial aneurysms is described. Saccular aneurysms can be located with reference to probe position and depth setting. Tracings of intra-aneurysmal flow are presented, and the characteristic flow pattern is disucssed. Special emphasis has been placed on the parent artery flow, particularly the effect of lumen reduction on flow velocity. Results of flow velocity studies on the cognate (direct) and collateral flow in the middle cerebral artery and the proximal anterior cerebral artery are presented and discussed.
Blood Flow Velocity↗
Results of microsurgical management of intracranial aneurysms.
This paper presents the results of a total of 468 aneurysm operations performed on a consecutive series of 463 patients in an 8-year period, using microsurgical techniques. About two-thirds of the patients were operated on within the first 2 weeks after hemorrhage. The postoperative mortality was 4.5%. A good result was obtained in 74.5% of cases, and a fair result in 11.8%, whereas 9.2% were permanently disabled. Hypothermia was used in 142 operations, and 326 were carried out under induced hypotension. Immediate and late results of surgery are discussed with reference to selection of patients, timing of surgery, and the anesthetic and operative procedures.
Adolescent↗
Cerebral arterial flow dynamics during aneurysm haemorrhage.
A case of intraoperative early rupture of an infraclinoid aneurysm is reported with data showing the specific dynamics of cerebral arterial flow during aneurysm haemorrhage. Internal carotid artery flow and arteriial blood pressure were recorded throughout the surgical procedure. The rupture took place during preparations for dural opening at a mean blood pressure of 160 mmHg and at a low intracranial pressure of 5 to 6 mmHg. The dura became instantly tight, and was non-pulsatile within 10 seconds. The parietal epidural pressure rose rapidly to 110 mmHg. There was a brief initial increase in flow as the haemorrhage started, followed by a marked reduction within seconds. End-diastolic blood flow arrest was observed at this stage, demonstrating the self-limiting effect of a subarachnoid haemorrhage. This impaired cerebral perfusion pressure, or transmural pressure, is discussed with regard to the risk of cerebral damage as well as the beneficial effect in the staunching of haemorrhage. Carotid artery flow showed a moderately impaired autoregulation and an increased vascular resistance suggesting a no-reflow phenomenon subsequent to these events.
Blood Pressure↗
Internal carotid artery blood flow during cerebral angiography.
A total of 13 contrast injections of Isopaque Cerebral (meglumine metrizoate) were made into the precerebral arteries or the aortic arch in 6 patients and the bilateral internal carotid artery blood flow monitored continuously using implanted electromagnetic blood flow probes. The most frequent causes of flow changes were found to be due to sudden changes in arterial blood pressure or ventilation which caused a simultaneous and generally identical flow pattern in the two arteries. In 4 patients a slight increase in flow in the artery receiving contrast medium was observed; the increase ranged from 10 to 20% above control level. In one patient the ICA receiving contrast medium showed an initial drop in blood flow to about 85% within 15 sec while the contralateral side showed an increase in flow to about 110%. This sequence was followed by a 6 minute period of slightly increased blood flow on the injection side while the other side showed a slight decrease. A discrepancy in carotid vasomotor response was seen after the injection of 50 ml of contrast medium into the aortic arch with filling of both carotids in the angiogram. Flow changes thought to reflect "arterial spasm" (increased vascular resistance) were observed during attempts to puncture the common carotid artery. The risks connected with this method are discussed. Repeat flow recordings throughout the 24 hours following angiography did not show flow changes attributable to the angiographic investigation.
Adult↗
Intracranial pulse pressure dynamics in patients with intracranial hypertension.
The pulsative inflow of blood to the brain causes fluctuations in the cerebral blood volume, and this is considered to be the main cause of the pulsations of the intracranial pressure (ICP). This statement allows discrimination between two different factors that influence the pulse amplitude of the ICP: 1. The pulsatile pattern of the cerebral arterial blood flow. 2. The slope of the intracranial pressure-volume curve. In order to clarify the relative contributions of the two factors we have developed a simulation model of the intracranial pressure-volume curve and the cerebral blood flow. Measurements from clinical practice and data from other authors can be interpreted with reference to this model. The increase in the pulse amplitude due to a moderate increase in the ICP is mainly explained by the decrease of the intracranial compliance. However, it is recognized that, when the ICP approaches the arterial blood pressure, the ICP amplitude increases disproportionally with increasing ICP. In this situation the transmural pressure of the cerebral arteries approaches zero, and the compliance relevant to the arterial flow system is no longer that of the vessel wall but the compliance of the craniospinal compartment.
Adult↗
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.
Adult↗
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.
Adult↗
Cerebral arterial blood flow and aneurysm surgery. Part 2: Induced hypotension and autoregulatory capacity.
A study of 21 patients was conducted to clarify the autoregulatory capacity in patients subjected to induced hypotension during intracranial surgery for saccular aneurysms. Trimethaphan camsylate (Arfonad) was used for induced hypotension and arterial blood flow was measured with an electromagnetic flow probe on the internal carotid artery or one of its main intracranial branches. In Grade I and II patients the control arterial blood pressure (ABP) ranged from a mean of 90 to 135 mm Hg (average 110 mm Hg), with a lower level of autoregulation (LLAR) from 35 to 85 mm Hg (average 62 mm Hg). Grade III patients had a control ABP of between 105 and 145 mm Hg (average 124 mm Hg) and the LLAR was found to be between 60 and 95 mm Hg (average 76 mm Hg). There was a significant difference between the two groups with regard to both the control ABP and the LLAR. A surprising result obtained from these data was that the average lower autoregulatory range (the difference between control ABP and LLAR) is practically the same in the two groups. A systematic investigation of the upper limit of autoregulation was not possible for ethical reasons. In those few patients in whom spontaneous increase in the ABP made such observations possible, upper limits up to 150 mm Hg with a total autoregulatory capacity of about 75 mm Hg were observed. In some patients, however, lower limits and cing that the upper limit of autoregulation is markedly influenced by several factors.
Blood Pressure↗
CBF autoregulatory capacity during aneurysm surgery with induced hypotension.
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Cerebrovascular Circulation↗
Cisternography with metrizamide in cerebellopontine angle tumors.
The technique and results of cerebello-pontine angle cisternography with metrizamide (Amipaque) in 34 patients are reported. Fourteen tumors were diagnosed. The internal auditory canal was normal in 19 patients, and in all of them the facial and statoacoustic nerves were visible. One examination was unsuccessful. No serious complications occurred. Headache was recorded in 76 per cent and transient EEG disturbance in 32 per cent of the patients.
Adult↗
Increased intracranial pressure in so-called 'normal-pressure hydrocephalus'.
Five patients exhibited an apparently communicating hydrocephalus -- type of disorder, with ventricular reflux on the cisternograms, lack of air-encephalographic parasagittal air-filling and clearly enlarged temporal horns. The group seemed heterogeneous, with regard to age distribution; possible etiological factors and duration of the hydrocephalic process. In all 5 patients increased intracranial/intrathecal pressure was observed: in 2 patients, only with intrathecal measurement in the lumbar area, but in the remaining 3 patients with epidural/ventricular fluid pressure monitoring. Continuously increased pressure extending over 1 or more days was observed in these patients. This pressure increase may seem different from the episodic pressure increase previously reported in normal-pressure hydrocephalus. These patients seem to be cases of so-called normal-pressure hydrocephalus according to the commonly accepted criteria. It is therefore suggested that the term normal-pressure hydrocephalus should be abandoned, and replaced by, e.g., low-pressure hydrocephalus, malresorptive or malabsorptive hydrocephalus.
Adult↗
Electromagnetic blood flowmetry in small vessel surgery. An experimental study.
The aim of this work was to study problems in microvascular flowmetry. Special emphasis was placed on the meticulous preparation of the vessel wall in order to improve zero-line stability and on the problems related to the calibration of small electromagnetic flow probes. Electromagnetic flow probes with an inner diameter of 2, 1.5 and 1 nm were used for studies on zero-line drifting and for calibration procedures in a series of rats and rabbits. Principles and tools derived from microvascular surgery, including the binocular microscope, were employed in the preparation of the vessel wall and in the application of the probes. The results obtained indicate an improvement in flow uptake and in zero-line stability following this procedure. Precalibration of small flow probes using laboratory animals should be considered if calibration is not feasible at the time of the flow measurement. Use of the microsurgical technique for vessel preparation is recommended.
Animals↗