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Biomedical subjects

R von Kummer

Publications and source records attributed to R von Kummer.

At least 19 recordsLinked to original sources
PubMed1992

Safety and efficacy of intravenous tissue plasminogen activator and heparin in acute middle cerebral artery stroke.

BACKGROUND AND PURPOSE: There is little reported of the safety and efficacy of high-dose intravenous recombinant tissue plasminogen activator (alteplase) in combination with heparin anticoagulation in patients presenting with acute ischemic stroke. METHODS: Thirty-two patients with severe hemispheric stroke syndrome caused by angiographically proven middle cerebral artery and/or intracranial internal carotid artery occlusion were treated with 100 mg alteplase by intravenous infusion over 90 minutes within a mean +/- SD of 226 +/- 68 minutes after symptom onset. Recanalization was assessed by digital subtraction angiography in all patients immediately after treatment and by transcranial Doppler monitoring (n = 30) and/or a third angiogram (n = 5) 12-24 hours later. RESULTS: Complete or partial reperfusion was observed in 11 patients (34%) 90 minutes after the initiation of alteplase infusion and in 17 patients (53%) within 12-24 hours. Hemorrhagic infarction without clinical deterioration was detected by follow-up computed tomography in nine patients (28%). Fatal parenchymal hemorrhage occurred in three patients (9%) with huge middle cerebral artery infarcts. Serious hemorrhage from the puncture site occurred in two patients (6%). Good clinical outcome correlated with reperfusion (p less than 0.05) and the presence of grade 2 collateral blood flow (p less than 0.01). CONCLUSIONS: When 100 mg of recombinant tissue plasminogen activator was given within the first 6 hours of acute stroke together with heparin the incidence of deleterious hemorrhage was less than 10%. Reperfusion and effective collateral blood flow seem to be two important factors associated with a small infarct volume and good clinical outcome.

Adult↗
PubMed1992

Advantages and disadvantages of using the hydrogen clearance technique to measure pancreatic blood flow.

This study was undertaken to identify the advantages and disadvantages of using the hydrogen clearance technique (HCT) to measure pancreatic blood flow (PBF) in the opossum over short and long periods. An open study was performed on 8 opossums. A total of 72 platinum electrodes were implanted into the pancreas. On the fifth day 41 additional electrodes were implanted. All implantation sites were examined histologically after five days. Measurements of pancreatic blood flow were taken every other day for five days. Three measurements were taken from each electrode and the mean of the three was used for analysis. In the anaesthetized animal mean PBF (SD) was 63.5 (12.8) ml min-1 100 g-1 immediately after electrode implantation and 34.3 (11.4) ml min-1 100 g-1 on the 5th postoperative day. Of the implanted electrodes, 35% failed during the experimental course, mainly as the result of proliferation of scar tissue around the electrodes. Mild to moderate fibroproliferation had taken place around the platinum tips of the remaining 65%. Primary electrode implantation caused no or negligible trauma to the pancreas. We recommend the HCT only for short-term measurements of PBF. Implantation of electrodes for any length of time leads to inflammatory changes around the platinum tips that cause proliferation of scar tissue and lead to failure of the electrodes, misleadingly low PBF recordings, and fewer monoexponential clearance curves.

Animals↗
PubMed1991

Cerebrovascular CO2 reactivity in migraine: assessment by transcranial Doppler ultrasound.

Cerebrovascular reactivity to CO2 inhalation was studied by transcranial Doppler sonography in 30 patients with classic or common migraine and 39 healthy controls without clinical or ultrasonic signs of arteriosclerosis. Systolic and diastolic Doppler frequencies of the middle cerebral artery were plotted against end-tidal CO2 partial pressure; the reactivity index (I x R) was defined as relative frequency change during a PCO2 increase of 5 mmHg. In the normal subjects, I x R was 20.0 +/- 6.3 for systolic velocities, and 26.0 +/- 8.2 for diastolic values. Migraineurs during their headache-free interval had significantly higher I x R values on the affected side (mean: 41.6 systolic, 61.2 diastolic), compared with either controls (P less than 0.01) or the contralateral side (mean: 28.3 systolic, 30.8 diastolic; P less than 0.01). During the headache attack, CO2 reactivity was significantly lower than normal only for systolic velocities (mean: 8.3; P less than 0.05). Increased CO2 reactivity is thought to be one phenomenon of migraine. Transcranial Doppler CO2 testing of cerebrovascular reactivity is a reliable method that may be of interest for the diagnostic evaluation and management of migraine patients.

Adult↗
PubMed1990

Controlled-release levodopa/benserazide (Madopar HBS): clinical observations and levodopa and dopamine plasma concentrations in fluctuating parkinsonian patients.

In five levodopa (L-dopa)-treated patients with Parkinson's disease with severe fluctuations of motor performance, plasma L-dopa as well as dopamine levels were measured during 2 days, first under optimal standard L-dopa with peripheral decarboxylase inhibitor (PDI) and then after a dose adjustment period using slow-release L-dopa/benserazide (Madopar HBS) in an open inpatient trial. Three patients benefited from the slow-release preparation; two patients deteriorated with a tendency to have an unpredictable response, a delay to turn "on" with the first dose in the morning, as well as an increase in dyskinesia corresponding to L-dopa cumulation during the day. These problems were subsequently also seen during the follow-up period of 1 year in those patients who benefited from Madopar HBS as inpatients. This might indicate that patient compliance is more difficult with the new formulation. After 1 year all patients had returned to their previous standard L-dopa/PDI treatment. L-Dopa levels continued to fluctuate, but to a lesser degree with Madopar HBS. The equivalent L-dopa dosage had to be increased by 56% (29-100%) with Madopar HBS while mean dopamine levels increased in four patients (by 47-257%) without the occurrence of peripheral side-effects. This implies that with the new formulation more L-dopa is metabolized to dopamine and explains the necessity to increase the equivalent L-dopa dosage.

Aged↗
PubMed1990

[Intracranial MR flow signal changes in extracranial occlusions of the internal carotid artery].

Spin-echo sequences allow an identification of the basal brain vessels because of their typical signal void. The increasing use of MRI also in clarification of cerebrovascular disease requires a good knowledge of intracranial flow alterations. We saw characteristic signal pattern in the carotid siphon in 22 prospective examined patients with occlusion of the internal carotid artery confirmed by ultrasound. The lower siphon showed a loss of flow void and a brain isointense signal. The signal in the upper siphon was identical or showed a flow void with significant calibre reduction, probably because of collateral filling. This diagnostic potential of MRI is a remarkable advantage in comparison to CT and should be routinely considered in patients with cerebrovascular disease.

Arterial Occlusive Diseases↗
PubMed1989

Haemodilution with dextran 40 and hydroxyethyl starch and its effect on cerebral microcirculation.

The effect of haemodilution with Ringer's solution, hydroxyethyl starch (HAES) 200/0.5 10% and dextran 40 on cerebral blood flow (CBF) was measured in ten cats by means of the hydrogen clearance technique. As expected from theoretical considerations the haemodilution effect was short and not significant with Ringer's solution, but was 25% with HAES and 35% with dextrane 40. The corresponding rise in CBF was significant in both the latter but not with Ringer's solution. CBF was similarly highly correlated with diminution of haematocrit (Hct). The different effects of the substances on CBF could all be explained by their different effects on the Hct. Data analysis, together with recent literature, suggests that the dominating factor determining CBF was the O2-transport capacity, which in these experiments was in close relation to Hct. The results support the assumption that the increase of CBF by haemodilution is caused by a regulatory mechanism and not by a change of rheological parameters.

Animals↗
PubMed1988

Autoregulatory capacity and the effect of isovolemic hemodilution on local cerebral blood flow.

The effect of isovolemic hemodilution with dextran 40 on local cerebral blood flow was measured in eight cats by means of the hydrogen clearance technique. Under normotension the decrease of hematocrit from 35% to 25% causes a sudden increase of up to 30% in local cerebral blood flow. After lowering the mean arterial blood pressure from 140 to 80 mm Hg, hemodilution did not alter cerebral blood flow significantly. From this observation it is concluded that the increase of cerebral blood flow following hemodilution is caused by compensatory vasodilatation and not by reduction of blood viscosity. This could imply that hemodilution cannot improve blood flow in areas of impaired autoregulation.

Animals↗
PubMed1987

[Value of oligoclonal IgG fractions in the cerebrospinal fluid and blood in neurologic diseases].

CSF and serum from 700 patients were analysed by isoelectric focusing (IEF). Oligoclonal bands in the high alkaline range were detected in 156 cases. Ninety-five patients were diagnosed as having multiple sclerosis (MS), 38 various CNS inflammatory disorders, 18 vascular, neoplastic or degenerative and 5 patients other neurological diseases. IEF was positive in 98% of clinically definite and 85% of clinically probable MS cases and was found to be more sensitive as compared to intrathecal IgG production and evoked potentials. Neither the presence of oligoclonal IgG nor the banding distribution pattern is specific for any disease. Further characterization may be obtained by immunofixation if the antigen is known.

Blood-Brain Barrier↗
PubMed1986

Hydrogen clearance method for determining local cerebral blood flow. I. Spatial resolution.

To define the effective spatial resolution of the hydrogen clearance method, serial local CBF (LCBF) measurements were performed at different distances from the cortico-white matter junction of the cat brain. Twenty-five platinum-wire microelectrodes with a sensitive surface of 0.07 mm2 were inserted into the cerebral cortex of three cats through burr holes in the skull and advanced toward the ear-to-ear level in 1- or 0.1-mm steps. Most electrodes passed from high-perfusion regions into low-perfusion areas, indicating that the cortico-white matter junction had been traversed. Whereas within the gray and white matter the LCBF values were fairly constant, a striking decrease of CBF was registered at the cortico-white matter junction. Here the mean LCBF from 12 electrodes showed significant differences in flow between two locations 1 mm apart. On two occasions, a significant difference in CBF was found for locations only 0.1 mm apart. Despite this high spatial resolution, monoexponential clearance curves were detected only in the vicinity of the cortico-white matter junction. It is therefore assumed that factors other than flow might influence H2 clearance.

Animals↗
PubMed1986

Hydrogen clearance method for determining local cerebral blood flow. II. Effect of heterogeneity in cerebral blood flow.

The time course of hydrogen uptake and washout was followed simultaneously in extracranial arterial blood, cortex, subcortical white matter, and caudate nucleus of the cat brain to study intercompartmental hydrogen concentration differences. A clear delay of 1-2 min was seen between the onsets of concentration increase in arterial blood and low-flow brain tissues. Equilibration time was dependent on local CBF and varied between 3 and 34 min. Hydrogen was not cleared simultaneously from the regions under detection. This led to considerable concentration differences within the cerebral tissue during washin and washout phases. Analysis of the clearance curves revealed that secondary equilibration occurs during washout. Hydrogen concentration in the external carotid artery was not a reliable reflection of tracer input in the brain tissues. The consequences of these observations for other techniques of CBF measurement using less diffusive gases and external detection are discussed.

Animals↗