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Biomedical subjects

M Vermeulen

Publications and source records attributed to M Vermeulen.

At least 181 records · Page 10Linked to original sources
PubMed1987

Digoxin-like immunoreactive substance in patients with aneurysmal subarachnoid haemorrhage.

Digoxin was measured by radioimmunoassay in the plasma of 25 patients with aneurysmal subarachnoid haemorrhage who had not received digoxin treatment. After heating the plasma an endogenous substance cross reacting with antibodies to digoxin was identified in 18 cases. The presence of this substance was significantly related to the total amount of blood and to the presence of blood in the frontal interhemispheric fissure and could not be explained by hypertension or intake of water and sodium. A negative sodium balance and volume depletion occurred more often in patients who were positive for digoxin, but this relation did not reach statistical significance. It is concluded that a digoxin-like natriuretic factor is released in response to a subarachnoid haemorrhage, probably as a result of hypothalamic damage.

Aged↗
PubMed1987

Evaluation of electrical conductivity-temperature curves using a mathematical model: temperature-dependent changes during thawing of frozen aqueous pharmaceuticals.

The information contained in the electrical conductivity curves of pharmaceuticals measured as a function of temperature can be represented by a small set of parameters. This is achieved by approximating the electrical conductivity curve as a number of consecutive steps, using a suitable empirical model. The three parameters describing each step are: transition temperature, slope factor and step height. The validity of the calculated transition temperatures was established by applying the model to electrical conductivity curves measured on aqueous solutions of KCl, NaCl and on a KCl-NaCl mixture. It appears that the transition temperatures calculated for these inorganic salts are in good agreement with the respective eutectic temperatures reported in the literature. Subsequently, the method was applied to the corticosteroids prednisolone sodium succinate and prednisolone disodium phosphate. The mathematical model yields a satisfactory fit for both experimental conductivity curves. The actual consequences of freeze-drying an aqueous solution of prednisolone sodium succinate below and above the respective transition temperatures calculated are discussed in relation to the experimental conductivity data.

Chemistry, Pharmaceutical↗
PubMed1987

Clinical significance of antibodies against peripheral nerve tissue in inflammatory polyneuropathy.

With the use of a mixed hemagglutination test (MHT), circulating antibodies against human peripheral nerve tissue (PNT) were found in 22 of 38 patients with Guillain-Barré syndrome (GBS) or chronic relapsing demyelinating inflammatory polyneuropathy (CR-DIP). The antibodies were found in only 1 of 34 patients with polyneuropathy of other origin, and in 3 of 32 patients without polyneuropathy. The presence of antibodies was related to response to intravenous gamma globulin treatment in CR-DIP patients. Antibodies against PNT may be pathogenic.

Antigen-Antibody Complex↗
PubMed1987

Rerupture of intracranial aneurysms: a clinicoanatomic study.

In a series of 176 prospectively studied patients who survived for at least 24 hours after aneurysmal subarachnoid hemorrhage, 39 had at least one computerized tomography (CT)-proven rebleed within 4 weeks after the first rupture. There were peaks in the incidence of rebleeding at the end of the 2nd and 3rd weeks. Sudden loss of consciousness occurred in 35 patients, preceded in one-third of them by headache. A sudden increase in headache was a symptom of rebleeding in only one patient. Loss of brain-stem reflexes was recorded in 13 patients, respiratory arrest in six, and both symptoms in eight patients. Apnea was temporary in 11 patients. Rebleeding occurred as gross intraventricular hemorrhage in 20 patients, as a space-occupying hematoma in four, as both types of hemorrhage in three, and as a purely subarachnoid hemorrhage in 12. The location of the rebleed could not be inferred from the clinical features. Rebleeding was fatal in 51% of cases (two of 12 patients with a purely subarachnoid hemorrhage, and 18 of the other 27 patients (p less than 0.005)). The risk of rebleeding could not be predicted from the patients' clinical condition on admission or from the amount of subarachnoid blood identified on the initial CT scan. The risk of further rebleeding was significantly increased in survivors of a first rebleed (47%: p less than 0.01). Only seven (18%) of the 39 patients with rebleeding had survived at 3 months after the initial hemorrhage.

Adolescent↗
PubMed1987

[Recovery following CVA: caused by effective therapy or by the natural course of the disease?].

The efficacy of treatment of cerebrovascular disorders is difficult to establish. Treatment effects may be confounded by the natural course of the disease, or they may be misjudged by bias and can not be compared with the results of treatments in other hospitals or with previous results. Pathophysiological knowledge does not always lead to the right or the most practical treatment, neither the results of in vitro or animal experiments, nor the experience with related disorders. The randomized clinical trial is the right method to investigate treatment effects, but is not faultless and explanatory experiments ought to be distinguished from pragmatic studies.

Aspirin↗
PubMed1987

Lack of relation between the ventricular refractory period prolongation by amiodarone and the thyroid state in rats.

We investigated the possibility that the prolongation of the ventricular effective refractory period (VERP) by amiodarone might be mediated, at least in part, by inhibition of thyroid influence on the heart. VERP values were measured in vitro in isolated septal preparations obtained from control, thyroidectomized and thyroxine (tetraiodothyronine; T4)- or triiodothyronine (T3)-treated rats. Differences in thyroid influence on the heart between these groups were assessed by changes in the myosin isozyme (V1, V2, V3) pattern. VERP measurements were also done in similar groups treated with amiodarone for 7 days (50 mg/kg/day i.p.). VERP tended to be increased by thyroidectomy and was significantly reduced by T4 or T3 treatment when compared with the control group. Amiodarone treatment significantly prolonged VERP in control (33.4 +/- 1.9 to 45.0 +/- 4.5 msec), thyroidectomized (39.9 +/- 1.7 to 48.3 +/- 2.8 msec), T4-treated (26.2 +/- 1.0 to 37.4 +/- 1.3 msec) and T3-treated rats (25.6 +/- 1.1 to 34.3 +/- 1.3 msec). However, the magnitudes of the VERP prolongation by amiodarone were not significantly different among the four groups. The action of amiodarone on action potential duration was similar to its action on VERP. The myocardial concentrations of amiodarone and desethylamiodarone were not significantly different among the four groups. Amiodarone treatment produced a significant reduction of serum T3 levels in the control and in the T4-treated groups and an increase in reverse T3 levels. Thus, the class III action of amiodarone was not affected, in the present model, by experimental modification of thyroid influence on the heart.

Action Potentials↗
PubMed1986

Cerebral borderzone infarcts after phlebotomy.

We describe a 68-year-old patient with cerebral ischaemia who underwent a phlebotomy to lower an elevated haematocrit (0.61 l/l. The procedure was complicated by the development of a total hemiplegia after two hours. CT scanning showed two borderzone infarcts. We conclude that the plasma volume of patients with cerebral ischaemia and a high haematocrit may be contracted to such an extent that venesection is hazardous. The most appropriate treatment in these patients is expansion of the plasma volume.

Aged↗
PubMed1986

Characterisation of unipolar waveform alternation in acutely ischaemic porcine myocardium.

The relation between electrical alternans recorded in acutely ischaemic myocardium, ventricular arrhythmias, and changes in the activation sequence was studied. Sixty three unipolar electrograms, simultaneously recorded from the epicardial surface of the in situ porcine heart during 6 min periods of coronary occlusion, were converted to a digital format and analysed by computer. The time integrals of the electrograms during their QRS complex, ST segment, and T wave were measured. Unipolar waveform alternation was then quantified by subtracting the values obtained for two consecutive beats showing alternans. The spatial distribution of unipolar waveform alternation was illustrated by isoarea difference maps. Isochronal maps of the local excitation detected on each electrogram were constructed. Of 52 occlusions in 27 preparations, unipolar waveform alternation was detected in 42 and was promptly followed by ventricular arrhythmias in 37. The magnitude of unipolar waveform alternation increased from the margin to the inner portion of the ischaemic zone but its correlation with activation delay was poor, and there was no change in the activation sequence. These results suggest that beat to beat alternation of the unipolar waveform is related to changes in the action potential configuration rather than to changes in the activation sequence. Furthermore, unipolar waveform alternation appears to be associated with the development of early post-occlusion ventricular arrhythmias.

Action Potentials↗
PubMed1986

Delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage: clinicoanatomic correlations.

Fifty-seven of 176 prospectively studied patients with aneurysmal subarachnoid hemorrhage (SAH) developed delayed cerebral ischemia. Clinical features included hemispheric focal signs (13), decrease in level of consciousness (14), or both (30), and mutism (15). Forty-seven patients showed hypodense lesions on CT in one (19) or multiple vascular territories (22), or diffusely in one or both hemispheres (6). Twenty-eight had symmetric decrease in ventricular size. Of 18 autopsied patients, only 1 had a purely univascular lesion. The clinical, CT, and pathologic features suggest that delayed cerebral ischemia after SAH is a multivascular or diffuse process in most patients.

Adult↗
PubMed1986

Effect of the induction of amiodarone biotransformation on ventricular refractory periods in rats.

Amiodarone is a potent class III antiarrhythmic agent that has a slow onset of action in patients (ca. 20 days). To determine if myocardial accumulation of desethylamiodarone (DEA), its main metabolite, influences its antiarrhythmic activity, three groups of six Wistar rats were given amiodarone, 50 mg/kg/day i.p. (A groups), and three groups received the same dose of amiodarone in combination with 80 mg/kg/day of phenobarbital to induce hepatic biotransformation (AP groups). After 3, 7 or 21 days, the rats were sacrificed and the ventricular effective refractory period (VERP) was determined by the extrastimulus technique in endocardial preparations superfused in the tissue bath. Control measurements of VERP were done in untreated rats. Myocardial concentrations of DEA measured by high-performance liquid chromatography were significantly higher in the AP groups than in the A groups (7.5 +/- 0.83 vs. 2.27 +/- 0.11 micrograms/g at 3 days, 6.09 +/- 0.70 vs. 2.82 +/- 0.30 micrograms/g at 7 days and 11.93 +/- 1.22 vs. 4.79 +/- 1.84 micrograms/g at 21 days: mean +/- S.E.). Control VERP value was 33.4 +/- 1.2 msec and was increased by 9, 35 and 42% after 3, 7 and 21 days in the A groups, and by 9, 38 and 39% in the AP groups. After 7 days of DEA administration yielding myocardial concentrations similar to those obtained after amiodarone treatment, there was a slight but nonsignificant prolongation of the VERP (12%). Thus, the prolongation of VERP after amiodarone administration did not appear to depend on myocardial DEA accumulation, suggesting that the slow onset of amiodarone class III action may not be related to DEA disposition.

Action Potentials↗
PubMed1985

Hyponatremia and cerebral infarction in patients with ruptured intracranial aneurysms: is fluid restriction harmful?

We studied retrospectively the relationship between hyponatremia and cerebral infarction in 134 consecutive patients with aneurysmal subarachnoid hemorrhage. In 44 patients sodium levels fell below 135 mmol/L on at least two consecutive days between the second and the tenth day after the hemorrhage. Twenty-five of these patients fulfilled the criteria for the syndrome of inappropriate secretion of antidiuretic hormone. Cerebral infarction developed in 27 of the 44 patients with hyponatremia and in 19 of the 90 patients with normal serum sodium levels (p less than 0.001). Cerebral infarctions were more often fatal in patients with hyponatremia (p less than 0.01). Twenty-six of the 44 patients had been treated with fluid restriction to correct the serum sodium levels, and infarctions developed in 21. Fluid restriction to correct hyponatremia appears to be potentially dangerous in patients with aneurysmal subarachnoid hemorrhage.

Cerebral Infarction↗
PubMed1985

Volume depletion and natriuresis in patients with a ruptured intracranial aneurysm.

We studied the sodium balance and changes in plasma volume by an isotope dilution technique in the first week after an aneurysmal subarachnoid hemorrhage in 21 patients. In 11 of the patients, the plasma volume decreased by more than 10%. This was accompanied by a negative sodium balance and hyponatremia in 6 patients, a negative sodium balance without hyponatremia in 4 patients, and a positive sodium balance in 1 patient. Together with a decrease in plasma volume, blood urea nitrogen content increased and body weight decreased. Three patients developed hyponatremia without a decrease in plasma volume. Serum vasopressin was measured in 14 of the 21 patients. The values were elevated on admission and declined in the first week, regardless of the presence of hyponatremia. These findings indicate that natriuresis and hyponatremia in aneurysmal subarachnoid hemorrhage reflect salt wasting and not inappropriate secretion of antidiuretic hormone and that these changes should be corrected by fluid replacement rather than by fluid restriction.

Arginine Vasopressin↗