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Biomedical subjects

H Nornes

Publications and source records attributed to H Nornes.

At least 55 records · Page 3Linked to original sources
PubMed1986

Evaluation of cerebral AVM's using transcranial Doppler ultrasound.

Blood flow velocities in basal cerebral arteries were recorded noninvasively in 28 patients with cerebral arteriovenous malformations (AVM's) and were correlated with the angiographic findings. In normal arteries remote from the AVM, flow velocities ranged from 44 to 94 cm/sec (median 65 cm/sec) with pulsatility indexes from 0.65 to 1.10 (median 0.87). This is consistent with findings in normal individuals. Arteries feeding the AVM's were identified by the high flow velocities (ranging from 75 to 237 cm/sec, median 124 cm/sec). The pulsatility index ranged from 0.22 to 0.74 (median 0.48). The difference of these results from findings in normal remote arteries was highly significant (p less than 0.001). Hyperventilation tests illustrated the hemodynamic difference between an AVM and normal cerebrovascular beds. Flow velocity measurements permitted noninvasive diagnosis of AVM's in 26 of the 28 patients. Furthermore, the identification of individual feeding arteries permitted good definition of the anatomical localization of individual AVM's. Flow velocity measurements combined with computerized tomography scans are useful in the diagnosis of AVM's. With the feeding artery's configuration identified on angiography, flow velocity measurements permit a new insight into the "hemodynamic dimension" of an AVM and its possible effects on adjacent normal brain-tissue perfusion in the individual patient.

Adolescent↗
PubMed1986

A non-invasive Doppler ultrasound method for the evaluation of patients with subarachnoid hemorrhage.

Measurements of flow velocity in the basal cerebral arteries can be obtained non-invasively through the intact skull using 2 MHz pulsed Doppler ultrasound. We investigated 47 patients with subarachnoid hemorrhage and compared flow velocity with angiography. Flow velocity in the middle and posterior cerebral arteries (MCA and PCA) was inversely related to the lumen diameter. Further clues to diagnose MCA spasm were obtained from the ratio of MCA flow velocity divided by the velocity in the distal extracranial internal carotid artery. In the individual patient, the two anterior cerebral arteries should be considered together, since this communicating system often has unique possibilities for collateral flow. Recordings from large MCA aneurysms were obtained before angiography in 4 patients.

Adult↗
PubMed1985

Transmitter expression and morphological development of embryonic medullary and mesencephalic raphé neurones after transplantation to the adult rat central nervous system. I. Grafts to the spinal cord.

Suspensions of cells derived from the mesencephalic raphé or medullary raphé regions of the 13-14 day old embryonic rat brain were injected into the spinal cord of adult rats which had been previously denervated with 5,7-dihydroxytryptamine. At periods of up to 12 months after grafting, the spinal cords were taken for immunohistochemical analysis of 5-hydroxytryptamine (5HT), substance P (SP) and thyrotropin releasing hormone (TRH). In nearly all cases, surviving transplants were found. The grafts derived from mesencephalic raphé cells contained neurones which were immunoreactive to 5HT, or SP, but not both together. On average 4% of the total possible number of the available embryonic mesencephalic serotoninergic cells were found. A very dense outgrowth of 5HT positive fibres from the transplant was observed, extending up to 1.5 cm in both the caudal and rostral directions from the graft locus. Some SP immunoreactive fibres were also apparent near the implant. The grafts derived from the medullary transplant also contained 5HT-immunoreactive cells, comprising on average 25% of the total 5HT neurones available from the embryonic medullary primordium. In addition, neurones co-localizing 5HT together with SP and TRH were visible, closely reflecting the situation found in the medullary raphé in situ. Dense plexi of fibres containing 5HT-LI extended both caudally and rostrally up to 12-15 mm from the transplant. Outgrowth of SP and TRH varicose fibres was also demonstrable, although to a lesser degree than for 5HT. It was also possible to find many motoneurones surrounded by varicose fibres containing both 5HT and SP, in contrast to the situation with the mesencephalic grafts, where no such patterns of innervation were seen. The experiments indicate that the milieu of the spinal cord may compromise the survival of mesencephalic raphé 5HT neurones far more than of medullary serotonin cells. However, despite this effect on cell survival, the outgrowth of fibres from the remaining mesencephalic 5HT neurones was apparently unaffected by their ectopic position. Similarly, the transmitter content of both classes of raphé cells was largely unaltered, either by the transplantation process or by the environment into which they were placed. It is concluded that although the adult denervated spinal cord can selectively affect neuronal survival, it is incapable either of inducing in other serotoninergic cells placed within it the transmitter phenotype typical of medullary raphé neurones, or of causing those ectopically located 5HT cells to form connections appropriate to the descending serotonin fibres.

Animals↗
PubMed1985

Cerebral perfusion during nonpulsatile cardiopulmonary bypass.

The recording of middle cerebral artery (MCA) flow velocity by the transcranial Doppler method offers a new, noninvasive, continuous technique for studies of cerebral circulation. Comparative studies of electromagnetic internal carotid artery (ICA) flowmetry and MCA flow velocity by the transcranial Doppler technique have demonstrated that observed changes in MCA flow velocities reflect concomitant changes in cerebral circulation. Eleven high-risk patients undergoing cardiopulmonary bypass (CPB) procedures were included in a pilot study. Arterial blood pressure (BP), central venous pressure, and epidural intracranial pressure (EDP) were recorded during CPB. Cerebral electrical activity was recorded by a cerebral function monitor. Flow velocity in the MCA was increased during nonpulsatile CPB in 10 of the 11 patients. This increase was related to the degree of hemodilution, and the flow velocity during steady-state CPB was 80 to 300% of the prebypass value. The MCA flow velocity changed, however, in a pressure-passive manner with the cerebral perfusion pressure (CPP = BP - EDP) in the individual patient, which indicates that cerebral autoregulation was not operative. During the first 15 minutes after termination of bypass, the MCA flow velocity was reduced, but remained higher than the prebypass level, 110 to 210% of the level during the last 5 minutes preceding CPB.

Adult↗
PubMed1985

Dissociation between cerebral autoregulation and carbon dioxide reactivity during nonpulsatile cardiopulmonary bypass.

Five patients undergoing cardiopulmonary bypass (CPB) procedures were extensively monitored because of anticipated high risk for neurological complications. Arterial blood pressure (BP), central venous pressure, and epidural intracranial pressure (EDP) were continuously recorded throughout CPB; thus, information on the cerebral perfusion pressure (CPP) was also continuously available (CPP = BP - EDP). Cerebral electrical activity was recorded by a cerebral function monitor. The flow velocity in the middle cerebral artery (MCA) was recorded using a transcranial Doppler technique. During steady-state CPB (constant hematocrit, constant temperature, and constant flow from the heart-lung machine) partial pressure of arterial carbon dioxide (PaCO2) was repeatedly changed to study the effect of changes in this variable on MCA flow velocity during nonpulsatile bypass. During CPB with constant temperature, hematocrit, and PaCO2, the effect of changes in CPP on MCA flow velocity was recorded and analyzed. During nonpulsatile, moderately hypothermic (28 degrees to 32 degrees C), low-flow (1.5 L/min/m2) CPB, there was no evidence of cerebral autoregulation, with CPP levels ranging from 20 to 60 mm Hg. The CO2 reactivity, however, was clearly present and in the range of 1.9 to 4.1%/mm Hg, indicating that there was a dissociation between cerebral autoregulation and CO2 reactivity under these circumstances.

Aged↗
PubMed1985

Some observations on cerebral perfusion during cardiopulmonary bypass.

Blood flow was recorded with an electromagnetic flow probe on one internal carotid artery (ICA) during cardiopulmonary bypass (CPB) in 5 patients. The ICA flow was monitored continuously along with arterial blood pressure, epidural intracranial pressure, and cerebral electrical activity using a cerebral function monitor (3 patients). The ICA flow increased by 50 to 100% at the inception of extracorporeal circulation. This rapid enhancement of flow occurred within a thirty-second period and was due to rapid arterial hemodilution caused by introduction of the priming solution. A transitory fall in ICA flow was observed during subsequent minutes when the well-recognized drop in blood pressure took place and the cerebral perfusion pressure (CPP = blood pressure - epidural intracranial pressure) was reduced to less than 30 mm Hg. In only one instance, however, when CPP fell to 15 mm Hg, was the fall in flow lower than the prebypass level. Throughout the rest of CPB, with steady-state hemodilution and CPP levels in the range of 30 to 50 mm Hg, ICA flow was markedly enhanced (50 to 100% above the prebypass level). The flow pattern, however, disclosed a pressure-passive system, indicating that cerebral autoregulation was impaired or that the CPP levels were lower than the individual lower limit of cerebral autoregulation during the period of steady-state hemodilution on CPB. A transient depression of cerebral electrical activity was seen in 2 patients shortly after the introduction of CPB. This phenomenon is suggestive of qualitatively insufficient perfusion and was observed even when ICA bulk flow was increased (hematocrit values, 13 to 17%).

Adult↗
PubMed1985

Assessment of intracranial hemodynamics in carotid artery disease by transcranial Doppler ultrasound.

Noninvasive transcranial Doppler recordings were correlated to the angiographic findings in 77 patients with carotid artery disease. Stenoses reducing the luminal area of the internal carotid artery by 75% or more also reduced the pulsatility transmission index (PTI) of the ipsilateral middle cerebral artery (MCA). The PTI is the pulsatility index of the artery under study expressed as a percent of the pulsatility index of another intracranial artery with presumed unimpeded inflow in the same individual. For stenoses in the 75% to 89% category. PTI reduction was significantly greater in patients with bilateral carotid stenosis, indicating an impaired potential for collateral flow in these patients. The PTI reduction probably reflects both the pressure drop across the stenosis and the cerebral autoregulatory response. Two criteria proved useful in demonstrating collateral MCA supply through the circle of Willis. On the recipient side, retrograde flow in the proximal anterior cerebral artery was demonstrated in 29 of the 31 patients when this flow pattern was disclosed angiographically. In 26 of these patients, the anterior cerebral artery on the supplying side also had clearly increased flow velocity. Increased flow velocities in the proximal posterior cerebral artery were present in 26 of the 30 vessels that were acting as a collateral channel to the ipsilateral MCA.

Adult↗
PubMed1984

Musical murmurs in human cerebral arteries after subarachnoid hemorrhage.

A transcranial ultrasonic method for the recording of murmurs from cerebral vessels is described. Using the new approach the authors have observed musical murmurs of pure tone quality in 15 patients with increased flow velocities in the cerebral arteries after spontaneous subarachnoid hemorrhage (SAH). The frequency range of the pure tones was from 140 to 820 Hz, corresponding to flow velocities between 73 and 215 cm/sec. The musical murmurs occurred as a transitional state between silent flow and the well known phenomenon of bruit. They were observed between the 4th and the 20th day after SAH. The most likely cause of the musical murmur is a periodic shedding of vortices in the cerebral arteries, commonly referred to as "a von Kármán vortex street." Clinically the presence of musical murmurs indicated that pathologically increased blood velocities were present in the artery under investigation. This probably reflected the degree of spasm.

Adult↗
PubMed1984

Evaluation of cerebrovascular spasm with transcranial Doppler ultrasound.

The use of an ultrasonic transcranial Doppler technique for noninvasive evaluation of cerebral vasospasm is described. Middle cerebral arteries (MCA's), classified as spastic on angiography, demonstrated blood-flow velocity between 120 and 230 cm/sec. The flow velocities in these arteries had a clear inverse relationship to the diameter as measured from angiograms in 38 patients with recent subarachnoid hemorrhage. This relationship in the proximal anterior cerebral artery (ACA) was found to be more complicated to assess, due to the collateral channels in the anterior part of the circle of Willis. The authors conclude, however, that the new method of measuring vasospasm will also detect spasm in the ACA if it has a hemodynamically significant effect upon flow resistance.

Blood Flow Velocity↗
PubMed1983

Reinnervation of the denervated adult spinal cord of rats by intraspinal transplants of embryonic brain stem neurons.

Previous studies have revealed a remarkable capacity of intracerebral grafts of embryonic brain tissue to establish extensive axonal connections with denervated areas in the brains of adult rats. In the present study we have explored the possibilities of using grafts in the spinal cord to substitute for the loss of noradrenergic brain-stem inputs to the severed spinal cord. Intraspinal grafts of embryonic pontine noradrenergic neurons were made into the lower thoracic region of adult rats. Three different surgical techniques were tested: (i) grafting to a small central cavity in the spinal-cord grey matter; (ii) grafting to a small subpial cavity involving removal of the dorsolateral third of the spinal-cord matter; (iii) grafting to the gap between the rostral and caudal stumps of the spinal cord after a nearly complete subpial transection. The results indicate that direct contact with the vessel-rich pia is essential for good survival of the grafts. Provided that the pia was left intact, the scarring around the grafts was minimal and the grafts fused well with both the grey and white matter of the cord. In the subpially transected cord, a brain-stem graft taken from a young embryonic donor fused well with both the rostral and the caudal stumps of the severed cord and thus restored tissue continuity across the gap. Large numbers of catecholamine (CA)-containing and non-monoaminergic cells were present in the transplants after 3-6 months. CA fluorescence histochemistry in combination with injections of fluorescent retrograde tracers revealed that both noradrenergic and non-monoaminergic neurons in the grafts had grown to reinnervate large segments of the host spinal cord. In those cases where the transplant had fused well with the cord, abundant CA-fluorescent axons could be traced across the graft-cord junction. They course along the grey and white matter of the host cord to reestablish a new CA terminal plexus in the grey matter as far as 12 mm from the graft.

Animals↗
PubMed1983

Effects of carotid endarterectomy on blood flow in the internal carotid artery.

A retrospective study of patients operated upon for carotid stenosis was undertaken with special emphasis on the internal carotid artery (ICA) blood flow. A total of 212 endarterectomies were performed in 198 patients. The overall operative mortality was 1.4%, and the cerebral morbidity was 2.8%. A temporary inlying shunt was used routinely during endarterectomy. In two of 198 endarterectomies the shunt itself could not be excluded as a possible cause of postoperative neurological deficits. The ICA blood flow before and after endarterectomy was determined by electromagnetic flowmetry in 160 operations. Flow measurements were compared in TIA and stroke patients, in patients with high and low degrees of luminal constriction, and in patients with occluded or "open" (minimal stenosis) contralateral ICA. The results indicate that the preoperative blood flow, as well as the increase in blood flow after removal of the stenosis, is determined not only by the degree of luminal constriction, but also by the magnitude of blood flow from all precerebral feeding arteries and their intracranial collateral circulation. In treatment of carotid stenosis critical evaluation of symptoms, angiography, and haemodynamics are essential. Endarterectomy is beneficial because an embolic source is removed, and probably because perfusion is improved to areas of the brain with marginal circulation. The main factors regulating the normal cerebral perfusion are cardiac output (mean perfusion pressure), arterial pCO2 and PO2, haematocrit, and the arterial and venous blood pressures. Comparatively few investigations have been published on the effect of endarterectomy upon internal carotid artery (ICA) blood flow 4, 12, 14, 27. Since 1970 we have routinely measured the ICA blood flow before and after endarterectomy. This paper reviews the clinical and haemodynamic results of our patients operated on for carotid stenosis.

Adult↗
PubMed1983

Cerebral damage following open-heart surgery in deep hypothermia and circulatory arrest.

Six patients undergoing aortic arch replacement during deep hypothermia and circulatory arrest were subjected to studies including serial determinations of total creatine kinase (CK) activity in the cerebrospinal fluid (CSF), monitoring of the intracranial epidural pressure and the cerebral perfusion pressure and clinical neurological evaluation. In two of four patients with postoperative pressure monitoring, a marked increase in pressure was seen. In one case this pressure rise terminated in brain tamponade six days postoperatively, despite aggressive treatment with steroids, mannitol and barbiturate. In comparison with patients undergoing surgery for valve replacement or aorto-coronary by-pass, some of the patients with aortic arch replacement clearly sustained more severe cerebral damage, as judged by clinical examination and autopsy findings as well as by assessment of the degree or extent of the neuronal damage from CK activity in CSF. Patients of this type are obvious candidates for postoperative neuro-intensive monitoring and care. Repeated pulsed Doppler flow velocity determinations in precerebral arteries, performed bedside, combined with monitoring of the cerebral perfusion pressure, provide a useful indication of the cerebral circulatory state in such situations.

Adult↗
PubMed1983

Monitoring of intracranial pressure after open-heart surgery.

Brain damage following open-heart surgery is receiving increasing attention. Efforts are being made to improve the setting for cardiac surgery so as to avoid such complications. When they occur, their recognition is retrospective, when the cerebral lesion is inevitable. Because heavy sedation is necessary, clinical supervision with respect to brain function is both difficult and unreliable in the early postoperative period. We therefore submitted 34 selected patients to neurosurgical intensive care supervision. The measures included postoperative monitoring of intracranial epidural pressure (EDP), of arterial blood pressure (BP) and of central venous pressure (CVP). In 25 patients there was rise in EDP during the first postoperative hours. Six of these patients received mannitol treatment and in three of them barbiturate was additionally given, in order to reduce EDP and improve the cerebral perfusion pressure (CPP = BP-EDP). Nevertheless EDP progressed to brain tamponade six days postoperatively in one case. In patients with raised EDP, weaning from the ventilator should be postponed until EDP has almost normalized. The EDP recording is a valuable guide in the postoperative management of the individual patient.

Blood Pressure↗
PubMed1983

The clinical significance of changes in cerebral perfusion pressure during open-heart surgery.

In 34 high-risk patients, the intracranial epidural pressure (EDP) and the cerebral perfusion pressure (CPP) were monitored in connection with open-heart surgery. The findings were clinically evaluated, with special attention to affection of the central nervous system. Reduction of EDP to 10-30 mmHg for periods up to 10 min at the start of extracorporeal circulation and transient rise of EDP in the early postoperative period were relatively well tolerated. Late postoperative EDP rise, on the other hand, denoted an unfavourable trend, associated with permanent cerebral damage. Mannitol and/or barbiturates are indicated when an early rise in postoperative EDP persists or a late rise occurs. Covariation of EDP and arterial blood pressure (BP) should be regarded as a warning sign, especially if it is pronounced or appears during the postoperative course. In such conditions it seems important to stabilize the CPP by reducing a high EDP and by careful management of BP variations, i.e. with use of vasopressors. Postoperative epileptiform seizures seem to be prognostically unfavourable.

Adolescent↗
PubMed1982

Aspects of cerebral perfusion in open-heart surgery.

A selected series of 25 patients undergoing open-heart surgery were subjected to continuous monitoring of arterial blood pressure (BP), central venous pressure (CVP) and intracranial epidural pressure (EDP). This gave continuous information on the cerebral perfusion pressure (CPP = BP-EDP). In all patients the start of the extracorporeal perfusion caused a rapid fall in CPP (30 mmHg or less in 22 patients, less than 10 mmHg in 5 patients). The combination of grave systemic hypotension and increased EDP contributed to these low CPP states, which varied in duration from 2 to 15 min. Spontaneous, as well as vasopressor-induced BP recovery was accompanied by a concomitant increase in EDP in 15 patients. This prolonged the low CPP state, making an evaluation of CPP from BP alone misleading under such conditions. Increasing EDP secondary to a rise in BP was also observed during termination of the extracorporeal circulation, particularly in 6 patients requiring an intra-aortic balloon pump in addition to large doses of vasopressors to obtain an acceptable BP. An increase in CVP to levels above EDP is transmitted intracranially, thus reducing the CPP. The recordings may improve insight into pathogenic mechanisms leading to harmful effects on the brain in connection with open-heart surgery.

Blood Pressure↗
PubMed1982

Noninvasive transcranial Doppler ultrasound recording of flow velocity in basal cerebral arteries.

In this report the authors describe a noninvasive transcranial method of determining the flow velocities in the basal cerebral arteries. Placement of the probe of a range-gated ultrasound Doppler instrument in the temporal area just above the zygomatic arch allowed the velocities in the middle cerebral artery (MCA) to be determined from the Doppler signals. The flow velocities in the proximal anterior (ACA) and posterior (PCA) cerebral arteries were also recorded at steady state and during test compression of the common carotid arteries. An investigation of 50 healthy subjects by this transcranial Doppler method revealed that the velocity in the MCA, ACA, and PCA was 62 +/- 12, 51 +/0 12, and 44 +/- 11 cm/sec, respectively. This method is of particular value for the detection of vasospasm following subarachnoid hemorrhage and for evaluating the cerebral circulation in occlusive disease of the carotid and vertebral arteries.

Adult↗