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Biomedical subjects

C M Loftus

Publications and source records attributed to C M Loftus.

At least 37 records · Page 2Linked to original sources
PubMed1997

Hypoplastic internal carotid artery mimicking a classic angiographic "string sign". Case report.

The authors report the case of a patient with transient ischemic attacks who was evaluated by duplex scanning, which demonstrated total carotid artery occlusion. Arteriography revealed what appeared to be a classic "string sign" in the cervical carotid artery, and a standard endarterectomy was planned. At surgery the internal carotid artery was found to be congenitally atretic, accounting for the string appearance of the arteriogram. The etiology, associated anomalies, differential diagnosis, and diagnostic evaluation of such lesions are discussed.

Angiography↗
PubMed1997

Effects of serotonin on cerebral circulation after middle cerebral artery occlusion.

Serotonin (5-HT) produces constriction of peripheral collateral blood vessels. Using an animal model, the authors tested the hypothesis that 5-HT constricts collateral vessels in the cerebrum. A branch of the middle cerebral artery (MCA) was occluded proximally and cannulated distally in anesthetized dogs. Blood flow to the area at risk for infarction was detected by perfusing the cannulated MCA branch with microsphere-free blood during systemic injection of radioactive microspheres (shadow flow technique). Blood flow to collateral-dependent and normal cerebrum was measured during intravenous infusion of 5-HT (10 and 40 mg/kg/minute). Serotonin produced a dose-related reduction of blood flow to collateral-dependent cerebrum, increased collateral vessel resistance in large cerebral arteries and collateral vessels, and decreased cerebral artery perfusion pressure. In contrast, blood flow to normal cerebrum was not altered because a decrease in small vessel resistance effectively compensated for a decrease in MCA perfusion pressure. These findings indicate that 5-HT produces constriction of collateral vessels in the cerebrum. This response is clearly different from normal small cerebral vessels, which dilate during 5-HT infusion.

Animals↗
PubMed1997

Pre- and postischemic effects of the NMDA receptor antagonist dizocilpine maleate (MK-801) on collateral cerebral blood flow.

The authors studied the effects of pre- and postischemic administration of dizocilpine maleate (MK-801) on collateral and regional cerebral blood flow (CBF). The ischemic penumbra appears to benefit most from the neuroprotective effects of MK-801. The precise mechanism by which MK-801 provides this neuroprotection remains controversial. Alterations in CBF have been demonstrated with MK-801 administration, but whether the response is an increase or decrease in flow has remained unclear. A left-sided craniectomy was performed in 20 dogs. A branch of the middle cerebral artery (MCA) was cannulated and collateral blood supply-dependent tissue (CDT) was identified using the "shadow flow" technique. Regional CBF was measured using radiolabeled microspheres. Six dogs received MK-801 (1 mg/kg administered intravenously) before they underwent MCA branch occlusion; the remaining 14 dogs received MK-801 after they underwent MCA occlusion. Cerebral blood flow and vascular pressures were measured 30 and 60 minutes after MK-801 administration. In animals that received MK-801 before MCA occlusion, CBF did not change significantly from baseline values before or after occlusion. In contrast, in animals that received MK-801 after MCA occlusion, CBF was significantly reduced in all regions of the brain, including the CDT. Collateral blood supply-dependent tissue showed a 51.7% reduction in flow, whereas normal CBF was reduced by 29.7%. The MK-801 induced cerebral vasoconstriction in both groups. The neuroprotective effects of MK-801 do not appear to be caused by the augmentation of collateral or global cerebral circulation and, in fact, may block the glutamate-mediated vasodilation that occurs during ischemia.

Animals↗
PubMed1997

Diagnosis of spontaneous subarachnoid hemorrhage.

Spontaneous subarachnoid hemorrhage is usually the result of rupture of an intracranial saccular aneurysm or arteriovenous malformation. The hemorrhage is typically a cataclysmic event, heralded by severe headache, meningeal signs and neurologic dysfunction. About one-half of patients with aneurysmal rupture experience "sentinel headaches" days to weeks before a major hemorrhage. Diagnosis at this stage may permit treatment before the occurrence of a devastating neurologic event. Clinical suspicion of subarachnoid hemorrhage should be confirmed by computed tomographic evaluation. Initial treatment of patients with spontaneous subarachnoid hemorrhage includes resuscitation and/or stabilization, management of acute effects of the hemorrhage, and prompt referral for neurosurgical treatment.

Algorithms↗
PubMed1997

Acute surgical therapeutic interventions in stroke patients.

Surgical presence in the treatment of acute stroke patients is becoming increasingly aggressive. This article presents the current standards for stroke surgery in the acute setting, and defines those patient groups that represent appropriate candidates for such intervention.

Anastomosis, Surgical↗
PubMed1995

Effects of adenosine and 2-chloroadenosine on cerebral collateral vessels.

Adenosine is a potent cerebral vasodilator. We tested the hypothesis that dilatation of collateral vessels in cerebrum, in response to topical adenosine and 2-chloroadenosine (2-CAD), would increase blood flow to collateral-dependent cerebrum. In dogs anesthetized with halothane, a branch of the middle cerebral artery (MCA) was occluded proximally and cannulated distally. The collateral-dependent area at risk for infarction was perfused from a reservoir with microsphere-free blood, and blood flow to normal cerebrum and to cerebrum dependent on collateral flow was measured with radioactive microspheres injected into the left ventricle through a femoral artery catheter. Perfusion through the cannulated MCA branch was stopped, and flow to normal and collateral-dependent cerebrum was measured after adenosine (10(-2) M) or 2-CAD (10(-4) M) was added to the superfusate over the cerebrum. In normal cerebrum, topical application of adenosine increased flow to outer but not inner layers. Topical application of adenosine had little effect on flow to collateral-dependent tissue. In normal cerebrum, 2-CAD increased flow to outer layers, whereas flow to inner layers tended to increase. During 2-CAD, flow to outer cortical layers of collateral-dependent cerebrum increased from 140 +/- 20 ml/100 g/min (mean +/- SD) to 231 +/- 68, whereas flow to the inner collateral-dependent tissue did not change. The findings indicate that, after occlusion of a cerebral artery, topical 2-CAD increases blood flow to outer layers of collateral-dependent and normal cerebrum.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Chloroadenosine↗
PubMed1995

Technical issues in carotid artery surgery 1995.

In reviews in the 1980s, we discussed both indications for and surgical techniques in carotid endarterectomy. Significant changes in the practice of extracranial cerebrovascular reconstruction have occurred over the past few years. The newest indications and cooperative study data have recently been discussed by Camarata and Heros in this topic review series. In this article, we aim to review the advances in operative monitoring and surgical techniques of the last decade. We would be remiss, however, not to note that the latest Asymptomatic Carotid Atherosclerosis Study data, released in September 1994, indicate that carotid endarterectomy is significantly superior to medical therapy for asymptomatic stenosis of > 60%. These data, along with the North American Symptomatic Carotid Endarterectomy Trial results, will revitalize and lend scientific validity to carotid artery reconstruction.

Arteriosclerosis↗
PubMed1995

Posterior interosseous nerve palsy after brachiocephalic arteriovenous fistula construction: report of two cases.

Two cases of delayed posterior interosseous nerve palsy after brachiocephalic arteriovenous fistula creation are presented. Both patients suffered from end-stage renal disease, necessitating chronic hemodialysis. After fistula construction, both developed progressive weakness of the muscles innervated by the posterior interosseous nerve. One patient also demonstrated sensory loss in the distribution of the superficial radial nerve. Electrophysiological studies confirmed posterior interosseous mononeuropathies in both cases. Surgical exploration demonstrated posterior interosseous nerve continuity, with severe compression from the hypertrophied venous limb of the arteriovenous fistula. The superficial radial nerve was also compressed in one patient. After neurolysis and fistula revision, both patients recovered neurological function.

Aged↗
PubMed1994

Augmentation of blood flow through cerebral collaterals by inhibition of nitric oxide synthase.

We examined the influence of nitric oxide (NO) on normal and collateral cerebral blood flow after occlusion of the middle cerebral artery (MCA). Effects of NG-nitro-L-arginine (nitroarginine), an inhibitor of NO synthase, were examined during normotension and hypotension (arterial pressure, 50 mm Hg) in 49 anesthetized dogs. Following a craniotomy, a branch of the MCA was cannulated, and collateral-dependent tissue was identified using the shadow-flow technique. Regional cerebral blood flow was measured with microspheres, and pial artery pressure was measured with a micropipette. Intravenous nitroarginine reduced blood flow to normal cerebrum by approximately 40% (p < 0.05) during normotension and hypotension, with aortic pressure maintained constant after nitroarginine administration. Injection of nitroarginine during hypotension, without control of pressor effects, increased aortic and pial artery pressure approximately twofold. Concurrently, blood flow to normal cerebrum decreased (p < 0.05), while flow to collateral-dependent cerebrum increased (p < 0.05). Phenylephrine was infused during hypotension to increase arterial pressure to values similar to those achieved following nitroarginine. Blood flow to collateral-dependent cerebrum increased (p < 0.05), but flow to normal cerebrum was not altered during infusion of phenylephrine. Thus, inhibition of NO synthase during hypotension increases arterial pressure, decreases blood flow to normal cerebrum, and increases blood flow to collateral-dependent cerebrum. Phenylephrine also increases perfusion pressure and blood flow to collateral-dependent cerebrum, but in contrast to nitroarginine, it does not redistribute blood flow from normal cerebrum.

Amino Acid Oxidoreductases↗
PubMed1994

Mechanism of redistribution of cerebral blood flow during hypercarbia and seizures.

After occlusion of an artery to the brain, hypercarbia and seizures may produce a paradoxical reduction in cerebral blood flow to the region supplied by collateral vessels. We measured pressure in an occluded branch of the middle cerebral artery and measured regional cerebral blood flow (rCBF) to collateral-dependent cerebrum in dogs (n = 25) to examine hemodynamic mechanisms that account for the reduction in flow. During hypercarbia (arterial PCO2 = 70 +/- 5 mmHg), rCBF to collateral-dependent cerebrum, measured with microspheres and identified using the shadow flow technique, decreased from 95 +/- 6 (mean +/- SE) to 71 +/- 9 ml.100 g-1.min-1 (P < 0.05), while flow to normal brain increased from 105 +/- 9 to 281 +/- 15 ml.100 g-1.min-1 (P < 0.05). Pressure in a branch of the middle cerebral artery decreased during hypercarbia from 50 +/- 6 to 25 +/- 3 mmHg (P < 0.05), concurrent with a significant increase in resistance of collateral vessels. Small vessel resistance was the same in collateral-dependent and normal brain. During bicuculline-induced seizures, with blood pressure maintained at control levels by withdrawal of blood, rCBF decreased in collateral-dependent cerebrum from 128 +/- 16 to 67 +/- 11 ml.100 g-1.min-1 (P < 0.05), and flow to normal brain increased from 169 +/- 14 to 418 +/- 17 ml.100 g-1.min-1 (P < 0.05). Small vessel resistance decreased in both regions, but the decrease was much greater in normal cerebrum. Changes in cerebral artery pressure and resistance of collateral vessels during seizure were similar to those during hypercarbia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Pulmonary embolization and infarction. An iatrogenic complication of transcatheter embolization of a cerebral arteriovenous malformation with polyvinyl alcohol sponge.

Transcatheter embolization therapy of vascular abnormalities is a well-accepted technique. It is particularly useful in the preoperative management of cerebral arteriovenous malformations, in which the risk of significant hemorrhage at surgery would otherwise be unacceptably high. A patient developed symptomatic pulmonary emboli and infarction following an uneventful embolization using polyvinyl alcohol particles. The authors believe this to be the first reported case of this complication of embolic therapy using polyvinyl alcohol.

Adult↗
PubMed1992

Stem pressure at the origin of intracranial collateral vessels.

The relationship between pressure at the functional site of origin of intracranial collateral channels (Pstem) and systemic pressure allows an estimation of the size of vascular channels from which collateral vessels originate. In this study, Pstem was determined in anesthetized dogs. A branch of the middle cerebral artery was perfused through a closed system with autologous blood. Tissues with regional cerebral blood flow (rCBF) less than or equal to 10 ml.100 g-1.min-1 (collateral-dependent zone) were identified using radioactive microspheres. Sequential injections of nonradioactive microspheres were made into the cannulated vessel to progressively occlude the terminal capillary bed. Injection of nonlabeled spheres was terminated when backpressure no longer increased, and the final rCBF measurement was made. There was a linear relationship between backpressure and flow to the collateral-dependent tissues. When rCBF within these tissues was zero, the corresponding value for backpressure (Pstem) was 79 +/- 4% (mean +/- SD) of mean arterial pressure. The high value for Pstem suggests that cerebral collateral channels arise in part from large vessels.

Animals↗
PubMed1992

Pressure-flow relations in canine collateral-dependent cerebrum.

BACKGROUND AND PURPOSE: The pressure-flow relation has been characterized in normal cerebrum, but it has not been studied in cerebrum dependent on collateral flow. The purpose of this investigation was to examine the relation between systemic pressure, regional cerebral blood flow, and middle cerebral artery branch pressure in collateral-dependent and normal brain. METHODS: In 10 anesthetized dogs, we cannulated a branch of the middle cerebral artery and identified collateral-dependent tissues using the shadow flow technique. We measured pressure in normal and cannulated branches of the middle cerebral artery and regional cerebral blood flow. The common carotid arteries were occluded, and hemorrhage reduced mean arterial pressure to 50 and 25 mm Hg. RESULTS: When aortic pressure was 25 mm Hg, blood flow to the collateral-dependent zone decreased from a baseline of 87 +/- 5 to 6 +/- 1 ml/100 g per minute (mean +/- SE), and pressure in the cannulated branch of the middle cerebral artery decreased from 49 +/- 4 to 2 +/- 0.4 mm Hg (p less than 0.05). Small-vessel resistance in the collateral-dependent region decreased from 0.56 +/- 0.09 to 0.38 +/- 0.04 mm Hg/ml/100 g per minute (p less than 0.05) after carotid occlusion but did not change significantly during hypotension. In normal brain, however, small-vessel resistance continued to decrease as systemic pressure was reduced. CONCLUSIONS: This study provides pressure-flow relations in normal and collateral-dependent cerebrum during carotid occlusion and progressive hypotension. In collateral-dependent tissue, concurrent occlusion of middle cerebral and carotid arteries produces autoregulatory dilatation of small vessels, resistance fails to decrease as mean arterial pressure is reduced to 25 mm Hg, and profound focal hypoperfusion is produced.

Animals↗
PubMed1992

Diagnosis and management of brain abscess.

Over the past 20 years, the diagnosis and management of brain abscess has been facilitated by a number of technologic advances that have resulted in a significant reduction in mortality. Despite these advances in technology, however, brain abscess remains a serious disease. In this article the nature, pathogenesis, and diagnosis of brain abscesses are discussed. Issues regarding surgical versus nonsurgical management, optimal surgical therapy, choice and duration of antibiotics, and the use of corticosteroids are examined in terms of their impact on mortality and long-term neurologic sequelae.

Adrenal Cortex Hormones↗
PubMed1991

Diagnosis and management of nontraumatic subarachnoid hemorrhage in elderly patients.

Subarachnoid hemorrhage is a significant problem in the geriatric population. The most common causes of nontraumatic subarachnoid hemorrhage in elderly patients are ruptured aneurysms or arteriovenous malformations. Aggressive therapy for aneurysmal subarachnoid hemorrhage is warranted in many patients whereas conservative treatment of arteriovenous malformations is customarily warranted in this age group. Less common causes of subarachnoid hemorrhage in geriatric patients include tumor bleeding, bleeding diathesis, and systemic illnesses. A number of these considerations must be kept in the differential diagnosis of any subarachnoid hemorrhage in a geriatric patient.

Aged↗
PubMed1990

Carcinoma metastatic to a cerebellar vascular malformation: case report.

A 73-year-old woman with a spontaneous intracerebellar hemorrhage was seen and was found to have metastatic adenocarcinoma within a vascular malformation. There was no evidence of other metastatic disease. The association of these two lesions is uncommon and has rarely been reported. The rich vascularity of the malformation may explain the hematogenous deposition of metastatic neoplasm at this site.

Adenocarcinoma↗