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H Landolt

Publications and source records attributed to H Landolt.

At least 37 records · Page 2Linked to original sources
PubMed1995

Experimental and clinical monitoring of glucose by microdialysis.

The aim of this investigation was to assess the use of cerebral extracellular glucose as a parameter for microdialytic monitoring in neurosurgical critical care patients. Samples were collected from four patients with severe head injury and one with subarachnoid haemorrhage for periods of 4.5-67 h. Glucose and lactate were analysed in the dialysates. The ratios of glucose to lactate were calculated to partially allow for changes in microdialytic conditions over time. On-line pH was measured for up to 3 days in three patients. In experiments with spontaneous hypertensive rats we found that extracellular glucose became unmeasurable in the ischemic zone after middle cerebral artery occlusion. Similarly, in 3 patients glucose became undetectable for several hours, and glucose/lactate tended to decrease during measurement. This was accompanied by high ICP in one patient, and by a hypoxic episode in another. In the two other patients glucose/lactate ratios showed a rising trend. Findings indicate that glucose, and the glucose/lactate ratio show some correlations with clinical course and are promising parameters for cerebral monitoring and therapeutic decision making.

Adult↗
PubMed1994

Neurochemical monitoring and on-line pH measurements using brain microdialysis in patients in intensive care.

We will report on our preliminary findings using microdialysis to monitor three patients in intensive care with either severe head injury (SHI) or severe subarachnoid hemorrhage (SAH) for up to 72 hours. In addition, basal levels in uninjured brain were assessed during an extra-intracranial bypass operation. Samples were collected hourly or half-hourly (flow rate 2 microliters/min, perfusion medium 0.9% saline). Parameters measured were the antioxidants ascorbic acid, uric acid, glutathione and cysteine. In 2 patients, the pH of the dialysate (pHD) was also measured on-line with a specially constructed flow-through meter, and glucose and lactate levels were assessed in the dialysate. In patient 1 (SHI), there was practically no cerebral perfusion pressure because of high ICP; cysteine and lactate levels were very high and glucose not measurable. In patient 2 (SAH) a hypoxic episode was accompanied by increased uric acid and decreased glucose. In patient 3 (SHI), the pHD reflected normalisation of blood gases after hyperventilation. Results indicate that parameters are in the range known from experimental studies, and can be correlated with clinical situations. The pHD as valuable indicator of metabolic changes is also feasible bedside.

Acid-Base Equilibrium↗
PubMed1994

Levels of water-soluble antioxidants in astrocytoma and in adjacent tumor-free tissue.

The aim of the present study was to investigate the oxidative status in astrocytoma. Samples of brain tissue from the centre to the periphery of the tumor were obtained from 11 astrocytoma patients undergoing computer tomography-guided stereotaxic operation, who had been previously treated with the corticosteroid dexamethasone. Part of the sample was investigated histologically for clarification of tumor type, and the presence of neoplastic and non-neoplastic tissue and necrosis. The rest was used for the quantification of the antioxidants ascorbic acid, uric acid, glutathione and cysteine by high performance liquid chromatography, and for quantification of DNA. Levels of antioxidants were calculated as micrograms/g fresh tissue and mumol/g DNA, a parameter related to cell content. There was significantly more DNA in neoplastic samples than in non-neoplastic ones, indicating increased cell density. Uric acid (micrograms/g fresh tissue) was significantly increased in neoplastic compared with non-neoplastic tissue, and levels were even higher in necrotic tissue. There were no significant differences between neoplastic and non-neoplastic tissue levels of ascorbic acid, glutathione or cysteine, expressed as micrograms/g fresh tissue. However, when levels of these three compounds were expressed as mumol/g DNA, i.e. taking into account the higher cell density, ascorbic acid, glutathione and cysteine were significantly reduced in neoplastic samples compared with non-neoplastic ones. Results thus show that there are differences between the antioxidant levels in astrocytoma and non-neoplastic tissue, providing additional support for the hypothesis that free radicals play a role in tumor growth.

Adult↗
PubMed1994

Diagnosis and management of abscesses in the basal ganglia and thalamus: a survey.

A review is made of the current management strategies of abscesses in basal ganglia and thalamus, based on a review of the literature and three of our own cases. Clinical picture, aetiology, diagnostic, surgical treatment and outcome are discussed. Stereotactic abscess puncture in combination with temporary drainage and rinsing of the abscess cavity in combination with systemic medication of antibiotics has become the management of choice with satisfactory results.

Adult↗
PubMed1993

[Cerebral microdialysis in neurological and neurosurgical research and clinical application in neurology and neurosurgery].

Microdialysis of the cerebral extracellular space (CES) provides information on the cortical metabolic state by measurement of the concentrations of metabolites and transmitters as well as of the extracellular pH. In trauma patients, this kind of monitoring should reveal damage from secondary cortical ischemia in an early, hopefully reversible state. The method further allows in vivo measurement of drug levels in the CES and investigation of their effect on metabolism. Although microdialysis has mainly been used experimentally, it is now beginning to be applied clinically. We report on our experience with both experimental and clinical work.

Animals↗
PubMed1993

Penetration of rifampicin into the brain tissue and cerebral extracellular space of rats.

Rifampicin is used to treat neurosurgical shunt infections because of its excellent in-vitro activity against staphylococci and its adequate penetration into the CSF. However, nothing is known about rifampicin concentrations in the cerebral extra-cellular space (CES). We measured the penetration of rifampicin into the CES of anaesthetized rats by microdialysis using low-flow and equilibrium methods. Depending on the method, rifampicin concentrations in the CES were 0.3-1% of the serum concentration or 3-8% of brain tissue concentration, respectively. These experimental data in animals suggest that the recommended dose of rifampicin in man might be inadequate for treatment of some brain infections.

Animals↗
PubMed1993

On-line monitoring of cerebral pH by microdialysis.

An on-line pH meter that can be mounted in microdialysis systems is described. The pH monitoring system was tested in rat cortex before and after middle cerebral artery occlusion (focal ischemia model). After probe implantation, pH values in the dialysate quickly reached a stable level that depended on perfusion medium (6.72, Ringer; 6.47, 0.9% saline) and flow rate (2 microliters/min). During ischemia, pH values sank rapidly and significantly, whereas lactic and ascorbic acid levels in the dialysate increased 9- to 12-fold. The pH of the dialysate is lower than that of the extracellular fluid because the relative recovery of carbon dioxide is about twice that of bicarbonate at the flow rate used, as shown in in vitro experiments. The pH meter would provide useful additional information during monitoring for ischemia, not only in experimental situations but also during neurosurgical intensive care. In the latter case, the on-line pH value would be a bedside parameter enabling fast feedback for setting analytical priorities and making therapeutical decisions.

Acid-Base Equilibrium↗
PubMed1992

Extracellular antioxidants and amino acids in the cortex of the rat: monitoring by microdialysis of early ischemic changes.

Extracellular concentrations of ascorbic acid, glutathione, cysteine, uric acid, tyrosine, and tryptophan were monitored using intracerebral microdialysis in the left frontoparietal cortex of spontaneous hypertensive rats before, and for 3 h after, either focal ischemia [left middle cerebral artery occlusion (MCAO)] or sham operation. The size of the ischemic area and the position of the microdialysis probe were checked using the enzyme histotopochemical acid phosphatase reaction. The probe was always located in the cortex inside the stained area. Ascorbic acid levels rose immediately after MCAO and remained at about 12-fold for 3 h. There was a transient release of glutathione during 1-1.5 h. Uric acid concentrations were also increased but the differences did not reach significance. The levels of the amino acids tyrosine and tryptophan increased steadily after MCAO. The increases in cysteine were variable but significant. In some experiments, the pH of the dialysate was measured online. The parameters ascorbic acid, glutathione, cysteine, and pH are suitable for the early detection of cortical ischemic events by microdialysis.

Animals↗
PubMed1991

Levels of low molecular weight scavengers in the rat brain during focal ischemia.

Ascorbic acid, cysteine, glutathione, uric acid, tyrosine and tryptophan were quantified in samples of frontoparietal cortex, striatum, hippocampus and cerebellum from both sides of rat brain 0.5 h, 4 h and 24 h after focal ischemia. Cysteine, tyrosine and tryptophan were increased in cortex and striatum at 0.5 h, returning afterwards to normal. Uric acid was increased, whereas ascorbic acid and glutathione were correspondingly decreased. Although changes can be explained primarily by energy failure they are also consistent with free radical activity during early stages of ischemia.

Amino Acids↗
PubMed1991

[The diagnosis of Cushing's syndrome. Results of diagnostic assessment of 20 patients with Cushing's syndrome of variable etiology (1979-1989)].

In the light of 20 cases of Cushing's syndrome the currently used diagnostic strategies are presented. For initial screening the classical dexamethasone suppression test using 1 mg dexamethasone p.o. and 24-hour urinary extraction of free cortisol were used, and diagnosis was confirmed using the 2 mg dexamethasone suppression test for two days. All three tests had a sensitivity of 100% in these 20 patients. Etiological evaluation was performed using basal ACTH plasma concentration measurement and the more recently available stimulation tests using corticotropin-releasing factor (CRF): in cases with suspected pituitary-hypothalamic etiology, selective catheterisation of the sinus petrous inferior with simultaneous blood sampling for measurement of plasma ACTH concentration was performed. Detailed etiological diagnosis is important in Cushing's syndrome since therapeutic measures differ widely: the etiologies in the 20 patients with Cushing's syndrome were: central Cushing's disease (microadenoma in 11, pituitary carcinoma in 1), adrenal carcinoma (3), adrenal adenoma (1), adrenal hyperplasia (1), ectopic ACTH production (2) and alcohol-induced Cushing's syndrome (1). The stepwise procedure in screening and diagnosis of the various etiologies of Cushing's syndrome are presented and the results of the 20 patients compared with the literature.

Adrenal Cortex Function Tests↗
PubMed1989

[Frontobasal fractures in children].

In 1987, four children between 5 and 13 years of age with severe frontobasal trauma and dural tears were treated operatively. A CSF rhinorrhea was manifest clinically in only two cases. In addition high-resolution computerised tomography was essential in diagnosis and planning of the operation. In each of the cases an intracranial pneumatocele indicating dural laceration was shown. The fractures were confirmed during surgery in: Case 1. The roof of the ethmoid sinus and the roof of the orbit. Case 2. Both the sphenoid sinuses. Case 3. The roof of the ethmoid sinus and the posterior wall of the frontal sinus. Case 4. The roof of the ethmoidal sinus and the posterior wall of the frontal sinus. The ontogenetically oldest part of the paranasal sinuses in the floor of the anterior cranial fossa forming the anterior part of the roof of the ethmoid bone is the site of predilection for fractures, even in children. The anterior cranial fossa was exposed in each case through a paranasal subfrontal access, in the first case combined with a frontal craniotomy by a neurosurgeon, because of the fracture of the roof of the orbit. In the second case the dural injury had to be closed at a second neurosurgical operation, because of a recurrence of the CSF leak. The third and fourth cases were treated by nasal surgery alone.

Adolescent↗
PubMed1989

CT-guided "real time" stereotaxy.

Starting from a previously developed 3-D digitizer for a CT correlated topographic orientation during open brain surgery a computerized targeting device was constructed specially designed for stereotaxy. CT and later MRI data are transferred to an IBM compatible personal computer. The spatial information is registered by a multi-axis measuring arm. Advantages and future development of computerized stereotaxy are discussed.

Biopsy, Needle↗
PubMed1988

Intravenous phenytoin loading in patients after neurosurgery and in status epilepticus. A population pharmacokinetic study.

In 49 patients treated with intravenous phenytoin after a neurosurgical procedure or because of repetitive frequent seizures, the serum concentration was measured before and 2 hours after an intravenous bolus injection. Based on these data the apparent volume of distribution and intra- and interpatient variability were determined in this representative patient population, using the statistical package NONMEM. From 5 characteristics tested (age, sex, bodyweight, serum albumin, renal function) only bodyweight was found to significantly influence the apparent volume of distribution of phenytoin. The population average was estimated as 1.0 +/- 0.04 L/kg (estimate +/- SE) and interindividual variability, expressed as coefficient of variation, was 23 +/- 6%. By means of Monte Carlo simulations an optimal dosing scheme for phenytoin loading has been calculated. Based on these results, a dose of 15 mg/kg divided into 3 intravenous injections administered 2 hours apart at a maximum rate of 50 mg/min is recommended. This loading regimen should result in therapeutic concentrations (10 to 20 mg/L) in 90% of patients within 6 hours.

Adolescent↗