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Biomedical subjects

R von Kummer

Publications and source records attributed to R von Kummer.

At least 55 records · Page 3Linked to original sources
PubMed1998

Does NO regulate the cerebral blood flow response in hypoxia?

OBJECTIVES: To study whether nitric oxide (NO) affects the CBF response to hypoxic and carbon monoxide (CO) hypoxia. MATERIAL AND METHODS: We incrementally reduced arterial oxygen content in rats, by decreasing the concentration of inspired oxygen (20 rats) or by repeated CO inhalation (20 rats), and measured local CBF using the hydrogen clearance method. Ten animals of each group received 80 mg/kg NO synthase (NOS) inhibitor N-monomethyl-L-arginine intravenously prior to hypoxia, while 10 rats served as controls. RESULTS: Inhibition of NOS decreased mean CBF by 30% and increased cerebrovascular resistance by 70%. Under hypoxic hypoxia, mean oxygen reactivity of CBF (relative change of CBF to a change of arterial oxygen content) was 7.8%/vol% in control animals and 3.3%/vol% after NOS inhibition (P < 0.02). Under CO hypoxia, mean oxygen reactivity was 7.3%/vol% in control animals and 5.1%/vol% after NOS inhibition (P < 0.05). Inhibition of NOS diminished significantly the cerebral vasodilatory response during hypoxic hypoxia (P < 0.05) but only to a lesser extent during CO hypoxia. CONCLUSION: These observations suggest that NO is involved in cerebral oxygen vasoreactivity, particularly in severe hypoxia.

Animals↗
PubMed1998

Are iodinated contrast agents detrimental in acute cerebral ischemia? An experimental study in rats.

PURPOSE: To study the effects of iothalamate sodium and two dosages of iopromide in acute cerebral ischemia on infarction volume, neurologic performance, and mortality in a rat model of middle cerebral artery occlusion. MATERIALS AND METHODS: Sixty-four rats underwent endovascular occlusion of the middle cerebral artery. Four hours later, 16 animals received iothalamate sodium (588 mg iodine per kilogram); 16, iopromide as a single bolus (518 mg iodine per kilogram); and 16, iopromide as a double bolus (1,036 mg iodine per kilogram). Sixteen animals received equivolumetric saline (control group). Neurologic score and body weight were recorded every 8 hours. Twenty-four hours after occlusion, all animals were killed; brains were stained to assess the infarction size. RESULTS: Single and double doses of iopromide did not affect infarction volume or neurologic performance. Iothalamate caused an increase in infarction volume and worsening of the neurologic score (p < .05). Mortality rate was 25% in the iothalamate group, 12% in the control group, and 6% in the iopromide groups. CONCLUSION: Bolus injection of the nonionic iopromide does not statistically significantly affect infarction volume or cerebral ischemia symptoms. Nonionic rather than ionic contrast agents should be preferred during acute cerebral ischemia.

Acute Disease↗
PubMed1998

99m technetium-ethyl-cysteinate-dimer single-photon emission CT can predict fatal ischemic brain edema.

BACKGROUND AND PURPOSE: We sought to study the prognostic value of early 99mtechnetium-ethyl-cysteinate-dimer single-photon emission CT (99mTc-ECD SPECT) for fatal ischemic brain edema in patients with middle cerebral artery (MCA) stroke compared with the prognostic value of CT and of clinical findings. METHODS: We prospectively studied 108 patients clinically, with 99mTc-ECD SPECT, and with CT within 6 hours of symptom onset (Scandinavian Stroke Scale <40 points) appropriate to MCA ischemia. The follow-up consisted of Scandinavian Stroke Scale and CT on days 1 and 7, Barthel Index, and Modified Rankin Scale after 3 months. An activity deficit of the complete MCA territory on the SPECT scans and a parenchymal hypoattenuation of the complete MCA territory on CT scans were considered as predictors for a fatal MCA infarction due to mass effect and midbrain herniation. RESULTS: In 11 of 108 patients (10%), the MCA infarction was the cause of death. The sensitivity of SPECT for fatal outcome was 82% in both visual and semiquantitative analyses, while specificity was 98% and 99%, respectively. The sensitivity and specificity of baseline CT were 36% and 100%, respectively; the sensitivity and specificity of clinical findings (Scandinavian Stroke Scale, depressed level of consciousness, gaze deviation) varied from 36% to 73% and from 45% to 88%, respectively. In a multivariate logistic regression model, only SPECT findings were found to be independent predictors of malignant MCA infarction/death. CONCLUSIONS: We were able to identify patients with fatal MCA infarction with high accuracy by using 99mTc-ECD SPECT within 6 hours of stroke onset. This technique offers great potential to select stroke patients for specific therapies, eg, decompressive hemicraniectomy, soon after onset of symptoms.

Adolescent↗
PubMed1998

Effect of training in reading CT scans on patient selection for ECASS II.

Anticipating that patients with large ischemic lesions exceeding one-third of the middle cerebral artery (MCA) territory and detected on CT scans within 6 hours of stroke onset will not benefit from thrombolysis, we trained each participant of the second European Cooperative Acute Stroke Study (ECASS II) in the recognition of early ischemic lesions. Participants (n=532; neurologists, radiologists, neuroradiologists) were tested before and after each 4-hour CT reading training course. We asked the participants to estimate the extent of acute ischemic lesions on 10 CT scans, which we presented for 90 seconds without clinical information. Two sets of 10 CT scans each (A and B) were alternatively presented to each group, so that 254 participants evaluated set A before the training and 278 participants evaluated set B. We compared the numbers of correct estimates, underestimations, and overestimations before and after the course for each participant. The person who taught all courses (RvK) provided the reference estimates. We found that training significantly increased the number of correct estimates (p < 0.0001). Subsequently, we studied the incidences of large infarctions and parenchymal hemorrhages in the ECASS II population. In comparison with ECASS I investigators, the local investigators of ECASS II reduced the number of falsely included patients to an extent similar to that of the training courses. More remarkably, among the ECASS II patients, the proportion of patients with large infarctions or parenchymal hemorrhages was reduced to 50%. Careful CT reading may have contributed to this result.

Acute Disease↗
PubMed1997

[Computer tomographic diagnosis of acute cerebral ischemmia].

Computed tomography (CT) is the first step in the radiological diagnostics of brain emergencies. We intend to study which pathophysiological changes are detected by CT and how CT contributes to prognosis and patient management in acute cerebral ischemia. We review recent publications about the role of CT in acute cerebral ischemia. Ischemic brain edema is associated with a decreased X-ray attenuation. Computed tomography is thus highly sensitive in detecting irreversibly damaged ischemic brain tissue. Patients showing large volumes of ischemic edema, exceeding one third of the middle cerebral artery territory, do not benefit from thrombolysis and have an increased risk of brain hemorrhage. The brain territory at risk from ischemia can be detected by CT angiography. To combine CT with CT angiography is a pragmatic approach which enables carefully directed treatment in acute cerebral ischemia.

Acute Disease↗
PubMed1997

Acute stroke: usefulness of early CT findings before thrombolytic therapy.

PURPOSE: To determine whether the extent of subtle parenchymal hypoattenuation detected on computed tomographic (CT) scans obtained within 6 hours of ischemic stroke is a factor in predicting patients' response to thrombolytic treatment. MATERIALS AND METHODS: The baseline CT scans of 620 patients, who received either recombinant tissue plasminogen activator (rt-PA) or a placebo, in a double-blind, randomized multicenter trial were prospectively evaluated and assigned to one of three categories according to the extent of parenchymal hypoattenuation: none, 33% or less (small), or more than 33% (large) of the middle cerebral artery territory. The association between the extent of hypoattenuation on the baseline CT scans and the clinical outcome in the placebo-treated and the rt-PA-treated groups after 3 months was analyzed. RESULTS: In 215 patients with a small hypoattenuating area, treatment increased the chance of good outcome. In 336 patients with a normal CT scan and in 52 patients with a large hypoattenuating area, rt-PA had no beneficial effect but increased the risk for fatal brain hemorrhage. CONCLUSION: The response to rt-PA in patients with ischemic stroke can be predicted on the basis of initial CT findings of the extent of parenchymal hypoattenuation in the territory of the middle cerebral artery.

Acute Disease↗
PubMed1997

Hemorrhagic transformation in acute ischemic stroke. Potential contributing factors in the European Cooperative Acute Stroke Study.

BACKGROUND AND PURPOSE: Recent studies suggest that thrombolytic therapy may be of benefit to patients with acute ischemic stroke. However, the treatment also carries a significant risk of hemorrhagic transformation (HT). The purpose of this study was to select potential contributors to HT. METHODS: We provide an explanatory analysis of the European Cooperative Acute Stroke Study (ECASS) data. ECASS was a multicenter, placebo-controlled, randomized trial of recombinant tissue plasminogen activator in ischemic stroke, within 6 hours of symptom onset, which enrolled 620 patients. HTs were classified into either hemorrhagic infarction or parenchymal hemorrhage according to their CT scan appearance. We used logistic regression analysis to select potential contributing factors to each type of HT. RESULTS: The severity of initial clinical deficit (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.6 to 4.0) and the presence of early ischemic changes on CT scan (OR, 3.5; 95% CI, 2.3 to 5.3) were associated with increased risk of hemorrhagic infarction. Increasing age (in decades; OR, 1.3; 95% CI, 1.0 to 1.7) and treatment with recombinant tissue plasminogen activator (OR, 3.6; 95% CI, 2.1 to 6.1) were related to the risk of parenchymal hemorrhage. CONCLUSIONS: Since all potential contributing factors are readily discernible upon hospital admission, they should be used to improve selection of patients into future studies.

Acute Disease↗
PubMed1996

'Malignant' middle cerebral artery territory infarction: clinical course and prognostic signs.

BACKGROUND: Although the clinical features of space-occupying ischemic stroke are well known, there are limited prospective data on the clinical course of complete middle cerebral artery territory infarction and on the predisposing factors leading to subsequent herniation and brain death. METHODS: The clinical course of patients with complete middle cerebral artery territory infarction, defined by computed tomography and vascular imaging, was evaluated. Initial clinical presentation was assessed by the Scandinavian Stroke Scale and the Glasgow Coma Scale. Serial computed tomography with measurement of midline and septum pellucidum shift and data on the presence and location of vascular occlusion by angiography or Doppler ultrasound were obtained directly after admission. Time course and outcome were analyzed with regard to the clinical findings on admission and at follow-up. The functional status of surviving patients was assessed using the Barthel Index. RESULTS: Fifty-five patients with complete middle cerebral artery territory infarction caused by occlusion of either the distal intracranial carotid artery or the proximal middle cerebral artery trunk were studied. In all patients, embolic infarction was presumed. The mean Scandinavian Stroke Scale score on admission was 20, and the time course of deterioration varied between 2 and 5 days. Forty-nine patients required ventilator assistance during the acute stage of disease. Only 12 patients (22%) survived the infarct. The cause of death was transtentorial herniation with subsequent brain death in 43 patients. Survivors had a mean Barthel Index score of 60 (range, 45 to 70). CONCLUSIONS: The prognosis of complete middle cerebral artery territory stroke is very poor and can be estimated by early clinical and neuroradiological data within the first few hours after the onset of symptoms. A space-occupying mass effect develops rapidly and predictably over the initial 5 days after presentation. Herniation occurred as an end point in 43 (78%) of these patients.

Adult↗
PubMed1996

Detectability of cerebral hemisphere ischaemic infarcts by CT within 6 h of stroke.

To determine how early and how reliably ischaemic brain infarcts can be detected on CT within 6 h of the onset of cerebral hemisphere strokes, 44 such studies were interpreted by an experienced neuroradiologist blinded to clinical signs, but aware that the cohort was a stroke population. He was asked to detect and localise an area of parenchymal low density and/or focal brain swelling. A follow-up study showing the definite infarct served as a reference in each case. In 38 patients areas of slightly low density were seen, and in 36 follow-up CT confirmed infarcts in the locations indicated. In 2 patients the reading was false positive. In 6 patients no low density focus could be detected. In these 8 patients examined by CT within 180 min of the stroke, no low density could be identified, even in retrospect with the knowledge of the findings on follow-up. Thus, 42 readings (95%) were true positive or true negative; 2 were false positive; and none was a false negative. CT within 6 h of the onset of symptoms has a mean sensitivity of 82% (36/44) for ischaemic cerebral hemisphere infarcts. By contrast, its sensitivity to ischaemic parenchymal low density is low during the initial 2 h. The early development of hemispheric infarcts can be detected reliably if the radiologist is familiar with the signs.

Adult↗
PubMed1996

Thrombolytic therapy of acute basilar artery occlusion. Variables affecting recanalization and outcome.

BACKGROUND AND PURPOSE: Thrombolysis may reduce mortality after acute basilar artery (BA) occlusion. We intended to find variables affecting recanalization and clinical outcome in patients with BA occlusion undergoing thrombolytic therapy. METHODS: We analyzed in retrospect the clinical and angiographic data of a consecutive series of 51 patients treated with intra-arterial urokinase (n = 44; 0.3 to 1.5 mIU) or intravenous or intra-arterial recombinant tissue plasminogen activator (n = 7; 22 to 100 mg). We identified effective variables by multiple logistic regression analyses and univariate tests. RESULTS: Sites of occlusion were the caudal (n = 23), middle (n = 18), and distal (n = 10) segments of the BA. The pathogenesis was embolism in 35 and local atherothrombosis in 16 patients. Collateral circulation was good in 32 patients and poor or absent in 19 patients. Recanalization was achieved in 26 of 51 (51%) patients and was associated with occlusions of embolic etiology (P = .0025). Mortality was 46% (12/26) in the recanalization group and 92% (23/25) in the nonrecanalization group (P = .0004). Other independent variables affecting mortality were length of BA obstruction (P = .0011), age (P = .0008), and collateral state (P = .0454). After follow-up (median, 32 months), 10 of the 16 survivors were only minimally impaired, with a Barthel Index score of 95 or greater; 5 patients were moderately and 1 severely disabled. CONCLUSIONS: Recanalization of acute BA occlusion reduces mortality significantly. Length of BA obstruction and state of the collaterals are additional independent variables affecting survival. Young patients with monosegmental embolic occlusion of the BA seem to have the best chance to considerably profit from thrombolysis.

Adolescent↗