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Biomedical subjects

A M Renou

Publications and source records attributed to A M Renou.

At least 19 recordsLinked to original sources
PubMed1978

Comparative results of 99mTc-pertechnetate scintigraphy and computerized tomography after contrast injection in cerebral pathology.

Fifty-six patients presenting acute cerebral ischemia were investigated by means of 160 CT and 90 RN scans. CT was positive before contrast injection in 90% of cases. A total of 120 CTs were done before and after contrast injection. Only 31% of the ischemic areas were enhanced. Out of 90 RN scans, 50 showed localized uptake. The peak of scintigraphic detection was found on the 15th day of evolution, while enhancement at CT was more frequent between the 15th and 21st days. For the hematomas (13 cases) detection by RN scan depends on the size of the lesion. Among the 47 patients presenting cerebral tumor, the RN uptake depends above all on the intensity of the BBB lesion. RN uptake and CT enhancement both show the same blood-brain barrier disturbance.

Brain↗
PubMed1978

Prognostic value of rCBF measurements and CT in focal cerebral ischemia.

CT is the most effective examination technique for studying the evolution of ischemic attacks, but if performed within the first 3 weeks it does not allow prognosis of possible evolution towards necrosis. CBF measurement and vasoreactivity tests under Althesin do allow this prognosis. Thirty patients whose evolution was checked clinically and by repeated CT examinations (89 in all) underwent CBF measurements (intra-arterial xenon 133) and vasoreactivity tests. In all cases (17 patients) where vasoreactivity had completely disappeared (inverse steal), the infarct evolved towards necrosis.

Brain↗
PubMed1978

Vascular thrombosis induced by direct electric current. A new technique for therapeutic embolisation; animal experimentation; first clinical applications.

A first series of experiments showed that the passage of a direct current along a positive electrode immersed in heparinised blood caused the formation of an adhering clot whose diameter increased with time and current intensity. A second series of experiments was done on 10 rabbits as follows: under general anaesthesia, a catheter used as a guide to the positive electrode was surgically inserted in the abdominal aorta. The negative electrode was placed on the thigh. A direct current (10 mA, 10V) was applied for 10-20 min. The first two clinical applications in man of this new method of treatment by electric current thrombosis were carried out using catheterisation of branches of the external carotid and cervical arteries.

Adolescent↗
PubMed1978

Cerebral blood volume and water extraction from cerebral parenchyma by hyperosmolar contrast media.

The attenuation coefficients of cerebral parenchyma and systemic blood were simultaneously measured at varying times after injection of two contrast agents with differing osmolarities. Cerebral parenchyma was in fact denser than the theory would predict. The osmolarity of the iodinated contrast agents seems to play only a very minor part. However, liposolubility could perhaps explain the leakage of iodine across the BBB and thus the increase in the attenuation coefficient of cerebral parenchyma.

Blood Volume↗
PubMed1978

Variations in the measurement of regional cerebral blood volume by CAT.

The cerebral blood volume (CBV) has been measured by transverse axial tomography. The attenuation coefficient of 100 "pixels" located in a well determined region was measured before and after injection of a contrast material (Telebrix 38). The attenuation coefficient of blood samples was measured by CT in a phantom. Blood samples were drawn before and after injection at the same time as the tomographic section (time: half rotation of the scanner). The volume was calculated by the (formula: see text). The values obtained with very early measurements (1--5 min after injection), were very close to those measured by other methods (3--5 ml/100 ml). For 5 patients, the CBV was measured by the same method at different times: 20 measures between 2 and 50 min after the injection. The CBV seemed to vary in function with time according to the equation: CBV in ML%: ate-bt + Vo (t = time in minutes: a = integration constant, a = 1.94; b = time constant, b = 0.089; Vo = real CBV). The apparent variation of CBV was the result of two factors related to the blood-brain barrier, (1) water movement from the extravascular space towards the intravascular space, related to the hyperosmolarity of the contrast medium. The variations of osmolarity and haematocrit values measured after contrast injection did confirm this hypothesis; and (2) iodine movement from the intravascular space towards the extravascular space, due to the toxicity of the material (hyperosmolarity, Na ions, etc). The measurement of CBV by CT is only possible if the contrast materials do not modify the blood-brain barrier. The use of actual materials allows the study of the blood-brain barrier behaviour and enables to make an estimate of the cerebral extra-cellular space. But CT is not a right method of CBV measurement with the contrast medium in use nowadays.

Blood Volume↗
PubMed1978

Cerebral blood flow and metabolism during etomidate anaesthesia in man.

The effects of etomidate on regional cerebral blood flow (rc.b.f.) and cerebral metabolic rate for oxygen (CMRo2) were studied in seven patients undergoing diagnostic carotid angiography. Following determination of baseline rc.b.f. while awake, the patients were anaesthetized with a single dose of etomidate 15 mg. Thereafter, an infusion of etomidate (2 or 3 mg min-1) was administered. Etomidate decreased both rc.b.f.10 (mean decrease 34%) and CMRo2 (mean decrease 45%). It was concluded that etomidate is a potent cerebral metabolic depressant. Furthermore, the cerebrovascular reactivity to carbon dioxide was maintained under etomidate anaesthesia.

Adult↗
PubMed1978

Effects of a diazepam-fentanyl mixture on cerebral blood flow and oxygen consumption in man.

The effects of a mixture of diazepam and fentanyl on cerebral blood flow (c.b.f.) and cerebral metabolism of oxygen (CMRo2) were studied in eight normal subjects and 13 patients with organic brain disease. The coupling of flow and metabolism and the carbon dioxide responsiveness of the c.b.f. were studied also. In the normal subjects the injection of the mixture resulted in a significant decrease in c.b.f. (34%), and a similar decrease in CMRo2 (34.5%). The vasoreactivity of the brain to carbon dioxide was maintained. C.b.f. decreased in all patients with intracranial pathology.

Brain↗
PubMed1978

[Electrophysiologic aspects of the effects of etomidate in man].

Recordings were electroencephalographical (EEG with spectral analysis), polygraphical (EMG, EKG, breathing). Visual and Auditory Cerebral Evoked Responses were also recorded. The depth of narcosis was quantified upon EEG data. The reactivity during the narcosis and the mechanisms of action of Etomidate on the "non specific structures" are discussed. Cautions should be taken with the use of tomidate in anesthesiology with epileptic and arteriopathic patients.

Adult↗
PubMed1978

[Effect of etomidate on cerebral blood flow and oxygen metabolism in man].

The effects of Etomidate on cerebral blood flow (C.B.F.) and cerebral oxygen consumption (C.02 C.) were studied in 13 patients in a neuroradiology department. Induction of anaesthesia was ensured using a standard dose of 15 mg of Etomidate, followed by a constant rate infusion (2.8 mg/kg/hour). Seven subjects were considered to be normal whilst six were suffering from tumour pathology. Under the influence of Etomidate, C.B.F. in the normal subjects decreased by 34 p. 100 and C.02 C. by 46.7 p. 100. The relationship between C.B.F. and arterial PC01 was studied under the influence of Etomidate: cerebral vasoactivity to C02 was maintained. A special study was made of focal changes in flow in patients with tumour pathology. Under the influence of Etomidate, there were zones of adaptation of flow, indicative of vasoparalysis situated opposite the tumour.

Anesthesia, General↗
PubMed1977

Cerebral ischemia with CT.

One hundred fifty-eight patients with cerebral ischemia, and divided into four clinical groups were studied with CT. The results were correlated with those of angiography, scintigraphy and regional cerebral blood flow measurement. CT evolution was closely correlated with clinical and anatomical evolution. Changes in cerebral parenchyma density, in relation to the ischemic lesion, are the result of two phenomena: first, edema showing a fairly stable peak of intensity in the 2nd week and disappearing totally before the 20th day; and second, necrosis, variable in extent from patient to patient at the onset with subsequent evolution towards cavitation and thus a density similar to that of cerebro-spinal fluid.

Adolescent↗
PubMed1977

Cerebral metastasis--a study of computerized tomography.

Sixty-eight cases of metastases affecting 34 patients were studied by computerized tomography (CT) before and after the injection of an iodinated contrast medium. CT data provided a diagnosis in most cases. After injection of the contrast medium, a ring aspect was found in half the cases. This morphological feature is a sign of blood-brain barrier impairment crossed by the contrast medium. The low density area inside the ring is not caused by central necrosis, nor is it caused by too little contrast medium. The increase in density is a sign of extra-vascular loss of iodinated molecules in the peritumoral cerebral tissue. Performance of CT should be improved using specific tracers of the tumoral cells.

Brain Neoplasms↗
PubMed1977

[Study of a new anesthetic agent: etomidate (R 26490). Electroencephalographic aspects].

Etomidate or R 26490 is a new hypnotic agent produced by JANSSEN and al. in 1971. The first human experimentation was performed in 1972. The authors used Etomidate for 300 anaesthetics given for neuroradiological investigations. Two protocols were used for study: 25 anaesthetics were given with Etomidate as sole anaesthetic to outline its specific properties; 275 angiographies were performed with a combination of Etomidate and fentanyl. In protocol no. 1, the mean consumption was for 1,85 mg/kg/h, in protocol no. 2, the mean consumption was of 0,9 mg/kg/h. Pharmacological study of this drug defines it as a short acting hypnotic agent of low toxicity. Clinical observation shows cardiovascular and respiratory stability. However, frequent myoclonias were noted, when Etomidate was given as a sole anaesthetic. EEG recording and evoked response encephalography helped to outline some effects of Etomidate on central nervous system.

Adolescent↗
PubMed1977

[Effects of high doses of morphinomimetics (fentanyl and fentathienyl) on the cerebral circulation in normal subjects].

The effects of large doses of morphinomimetics on the cerebral circulation were studied in 12 normal subjects (fentanyl 16 microgram/kg in 6 patients and fentathienyl 1.9 microgram/kg in 6 others). Mean hemispheric flow (corrected to a pCO2 of 40) changed from 50.8 +/- 4.4 ml/100 g/min in the conscious state to 50.3 +/- 25.1 under the influence of fentanyl, and flow in the grey matter from 78.8 +/- 10 to 84.3 +/- 65 ml/100 g/min. Mean flow changed from 49 +/- 3.1 ml/100 g/min in the conscious state to 55.5 +/- 10 under the influence of fentathienyl, flow in the grey matter increasing from 75 +/- 9 to 81.8 +/- 14.4. Whilst there was no variation in mean flow rates under the influence of morphinomimetics, individual behaviour was very variable, in particular in the case of fentanyl, the changes produced by fentathienyl being much more homogeneous. There was no obvious modification in the distribution of regional flow by these morphinomimetics. Individual variations in flow correlated perfectly with individual variations in cerebral oxygen consumption. Vascular reactivity to CO2 was increased b morphinomimetics. In one subject, fentanyl produced a very marked increase in cerebral blood flow (+ 104 p. 100) for which no explanation could be found.

Adolescent↗