Search

We developed a reliable system for the irradiation of xenografted tumors in mice which allows for accurate local irradiation under specific pathogen-free conditions. The system presented here consists of acrylic supports for mice and an acrylic box connected to a pump through 0.22 microns pore-sized filters. Mice with xenotransplanted tumors growing on their right hind legs were set on the supports and put into the box in a laminar flow hood. The tumors of 7 mice were irradiated simultaneously with X-rays of 6 and 10 MV generated by a linear accelerator at a dose rate of 3.1-4.7 Gy/min. The air was ventilated through filters during irradiation in the closed box. Microorganism tests confirmed that no bacteria entered or left the box. One of the significant characteristics of this setup is that it allows for irradiation under conditions of acute hypoxia, which is obtained using an integrated tourniquet. The dose variation among 7 tumors was less than 1%. The rest of the mouse's body was shielded effectively by a half-field technique and a lead block. As a result, the whole body dose for the mice was 0-4% of the total dose absorbed by the tumor. Due to the high dose rate and the ability to irradiate 7 mice simultaneously under specific pathogen-free conditions, this new system can be considered a time-saving and valuable tool for radiation oncology research.

The interhemispheric approach has been selected for clipping of the anterior communicating artery aneurysm located high above the sphenoidal plate, and in a posterior direction. However, this approach is sometimes complicated with postoperative hemorrhagic infarction due to excess brain retraction combined with damages of the cortical bridging veins. We have devised a modification in this approach to eliminate these complications. Our newly devised methods include the following; 1) Small bifrontal craniotomy performed, 2) Continuous ventricular drainage performed to minimize the effect of compression by the spatula during resection of interhemispheric fissure, 3) Bifrontal dural incision made along the frontal skull base, 4) Mobilization of the major cortical vein in the operated field, if necessary, by resection of the overlying arachnoid membrane with or without sacrificing its small tributaries, 5) Gradual dissection of the olfactory nerves according to the process of operation. We analysed the incidence of operative complications in thirteen consecutive cases with this approach. Major frontal ascending veins were carefully preserved in all cases. None showed hemorrhagic infarction, regardless of the cortical venous drainage patterns. The degree of smell preserved in 10% of the examined 11 cases was more than unilateral. In conclusion, this method is useful for the elimination of perioperative complications even in the acute stage of subarachnoid hemorrhage.

Twenty-two hydrocephalic patients with a ventriculoperitoneal shunt using a continuously variable flow resistance valve (Orbis-Sigma valve system; Cordis Corporation, USA) were reviewed to discuss usefulness of the shunt system. We divided the cases into two groups according to the demonstration of the cortical sulci in computed tomography (CT) as follows; A: progressive hydrocephalic cases mimicking simple brain atrophy, B: acute or subacute hydrocephalic cases with evidence of increased intracranial pressure. Patients in Group A had begun to present slowly progressive loss of activity, dementia and gait disturbance of various degrees after a long quiescent period following primary central nervous system injury. CT findings of these cases showed they were mimicking simple brain atrophy. Although the period of their deterioration was very long, ranging from 1 month to nine years, clinical signs improved in all cases after the shunt. None showed complications. Group B cases consisted of those with signs of increased intracranial pressure such as consciousness disturbance, nausea and vomiting. These cases showed poor demonstration of the cortical sulci in CT. Eleven out of thirteen cases showed satisfactory clinical improvement, though the size of the ventricle showed a slight decrease following shunt procedure. Only one case showed unilateral subdural effusion. In conclusion, this shunt system is useful for the management of ventricular enlarged cases mimicking simple brain atrophy as well as acute hydrocephalic cases. Troublesome consequences such as subdural effusion and hemorrhage rarely occur even in cases with low cerebrospinal pressure.

We have examined the total number of admitted cases to clarify the pathogenesis of hyponatremia during the management of neurosurgical patients. We experienced 32 cases of hyponatremia during the past year by measuring the sodium balance and atrial natriuretic peptide (ANP) level. According to these two factors, we divided the cases into three groups. The first group shows normal ANP levels in spite of hyponatremia. Low administration of the sodium was thought to be the cause in these cases. The second group shows the elevated ANP levels with a positive sodium balance. Elevated circulatory volume due to the inadequate level of antidiuretic hormone and mild heart and/or kidney failures cause these conditions. Water restriction and/or diuresis were effective methods in the management of the cases. The last group shows the elevated ANP levels with a negative sodium balance. There is a statistically significant negative correlation between sodium balance and the ANP level. Marked natriuresis due to the elevated ANP causes the decrement of the circulatory volume in these cases. Pathogenesis of the last group is very important in the management of neurosurgical patients in an acute state, especially in subarachnoid hemorrhage cases. The decrement of the systemic circulatory volume would jeopardize the patient's neurological condition. In this group, water restriction that has been commonly recommended is contraindicated. Satisfactory water and sodium replenishment seems to be the best recommended treatment for this group.

We have conducted a joint research project to investigate the incidence of ischemic heart disease in patients for noncardiac surgery and to define the risk of perioperative cardiac complications in these patients. From September to November 1997 we had 7288 patients scheduled to undergo noncardiac surgery in the 8 departments of anesthesiology. Of these patients, 228 (3.1%) patients had ischemic heart disease, and 30 of them (13.2%) developed perioperative cardiac events. Critical cardiac events, including perioperative myocardial ischemia and lethal arrhythmia, occurred in 7 of these patients. In our region of Japan, 3-4% of surgical patients tend to develop ischemic heart disease and 3.1% of them demonstrated severe cardiac complications perioperatively. Compared with United States we encounter fewer surgical patients with ischemic heart disease, but the risk of developing perioperative cardiac complications in such patients is almost the same for both countries.

We designed a joint research project to investigate the incidence of ischemic heart diseases in patients undergoing noncardiac surgery and to define the risk of perioperative cardiac complications in these patients. Of the 8358 surgical patients in the 8 departments of anesthesiology between March 1997 and June 1997, 328 (3.9%) had ischemic heart diseases. Among the 328 patients, 54 (16.4%) developed perioperative cardiac events, including myocardial infarction (3 patients) and either lethal or potentially dangerous dysrhythmias (51 patients). Preoperative cardiac assessments were performed while the anesthetic techniques including intensive monitoring and perioperative prophylactic therapy were also employed. Patients with ischemic heart diseases received various types of preoperative evaluation to identify the degree of coronary artery disease and to assess the overall cardiac function. The patients were monitored using a multilead electrocardiogram, an arterial line, a central venous catheter, a pulmonary artery catheter, and by transesophageal echocardiography intraoperatively. Therapeutically, isosorbide, nitroglycerin, beta-blockers, calcium channel blockers, and/or nicorandil were administered to prevent perioperative ischemia. So far, no generally accepted management strategies have been established in patients with cardiovascular disorders based on large-scale outcome trials in Japan. Therefore, nationwide large multicenter trials are awaited with interest in order to establish helpful guidelines to improve the perioperative management and to reduce ischemia in cardiac patients undergoing noncardiac surgery.