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Biomedical subjects

A van Dieren

Publications and source records attributed to A van Dieren.

6 recordsLinked to original sources

End-to-side anastomosis of small vessels using an Nd:YAG laser with a hemispherical contact probe. Technical note.

A new technique is described which enables the surgeon to perform an end-to-side anastomosis between arteries with little (less than 2 minutes) or no occlusion of the recipient artery. The technique was developed in rabbits, but has recently been successfully used in a patient in whom an anastomosis between the superficial temporal artery and a proximal branch of the middle cerebral artery was created.

Aged

Combined use of subdural and intracerebral electrodes in preoperative evaluation of epilepsy.

For intracranial recording of partial seizures considered to originate from one of the temporal or frontal lobes, the team in the Utrecht Academic Hospital has used subdural, multicontact, flexible electrodes since 1972. These are introduced through bilateral, frontocentral trephine holes and are manipulated under fluoroscopy to cover most of the cerebral convexity. It became evident that in many patients, additional placements to record from intracerebral structures were indispensable. Therefore, using the same trephine holes, an additional 2 to 4 depth electrodes were stereotactically implanted in the mesial temporal and/or frontal structures, as appropriate. An extensive intra- and extracerebral spatial representation of the epileptogenic zone was thus obtained. We report here the methods for manufacturing and applying these electrodes and our clinical experience with 28 patients. The results obtained so far stress the value of combining subdural and depth electroencephalographic monitoring in the presurgical selection of patients suffering from medically refractory complex partial seizures. By miniaturizing the electrodes, extensive areas of the brain can be investigated without craniotomy or multiple burr holes.

Adult

New type of end-to-side anastomosis for small arteries: a technical and scanning electron microscopic study in rats.

A new type of end-to-side anastomosis between small arteries is described. The anastomosis is made for three-quarters of its circumference with a nonoccluded recipient artery. The recipient artery must be occluded for only 3 to 5 minutes to complete the anastomosis. The anastomosis site was studied with the scanning electron microscope at different times (1 hour to 3 months) after the operation in 20 rats. In every case, the anastomosis was widely patent and a gradual endothelialization of the anastomosis site was observed. After 7 to 10 days, the endothelialization was more or less complete and, during the following weeks, a further smoothing of the ridge protruding into the anastomosis was noted. As an addendum, the authors describe an improvement of this technique that was developed after the sapphire tip of the neodymium: YAG laser became available. Now the anastomosis is fully completed and the connection between the two vessels is made by the laser tip introduced via a side branch of the donor vessel. The recipient artery need not be occluded at all. The results are promising.

Anastomosis, Surgical

Interhemispheric steal. An experimental study.

In 21 cats the pressure in the occluded middle cerebral artery (MCA) was recorded by way of a catheter, introduced in the most proximal portion of this artery by way of the transorbital approach. The effect of temporary occlusion of the ipsilateral and contralateral common carotid artery on the pressure in the occluded MCA was studied. The results seem to prove the existence of the so-called "interhemispheric steal" syndrome.

Animals

A simple and non-invasive method to determine the ventilation-perfusion ratio of the lung and the effective lung perfusion.

A method is presented to obtain the ventilation-perfusion ratio non-invasively. To describe the properties of gasexchange over the lung we used the law of mass conservation. The use of sinusoidal changes in the concentration of a tracergas in the inspired mixture results in a simple formulation of the variation in the concentration in the expired mixture over the variation in the inspired mixture. A careful selection of tracergas and cycleperiod of the sinus enables us to neglect the influence of venous return leaving the ventilation-perfusion ratio as sole physiological variable in the formulation. The lungperfusion can be obtained by measuring the total ventilation and correcting this value for deadspace ventilation. The method can be used to evaluate the influences of techniques like positive end-expired pressure and increased carbon dioxyde levels on shunting. It is also suited for monitoring purposes.

Anesthesia, General