Claes von Essen

The cerebrospinal fluid pressure-volume curve was determined by measuring the pressure response to rapid injection of fluid into the cisterna magna of dogs, by means of a constant flow infusion pump. The shape of the curve is complex, with two plateaus at the levels of the venous and arterial pressures, respectively. The slope dP/dV is referred to as the elastance of the system (mmHg/ml). The elastance has a low value in the normal pressure range and shifts at a fluid pressure of about 15 mmHg to a value approximately 20 times higher, with a relatively minute change in the volume of the system.

Knowledge of the local incidence of aneurysm rupture permits the conclusion that almost every patient in the population of 933,800 persons served by the authors' institution who was stricken by this catastrophe and survived long enough to be transported was treated at this center (121 patients during 34 months). Of these, 9.1% were admitted late (greater than 72 hours after subarachnoid hemorrhage (SAH]; of the remaining cases, 94.5% were seen within 24 hours and 50% within 6 hours post-SAH. Of the 121 patients, 10% were neurologically devastated on arrival, a late operation was planned for 19%, and the earliest possible surgery and nimodipine administration was selected for 71%. In this latter group, 50% of the operations were begun within 24 hours and 76% within 48 hours post-SAH. Sixty percent of all mortality and morbidity could be linked to the initial aneurysm bleed. The remaining 40% could be ascribed to potentially avoidable causes of unfavorable outcome. No less than 9.6% of all patients admitted within 24 hours after SAH suffered from "ultra-early" rebleeding during transportation or preparation for operation. The mortality rate from such rebleeding was 7.4%, compared with the 9.1% combined mortality rate from complications and late ischemia.

The effect of dopamine on the cerebral blood flow was studied in anaesthetized dogs. Cerebral blood flow was measured by the radio-active gas elimination technique with external γ-registration. Dopamine was administered by continuous infusion. Dopamine was found to influence the cerebral blood flow in two different ways: first by exerting an α-adrenergic receptor stimulating effect, resulting in a blood flow decrease. This was found in response to very small doses of dopamine and then once again with larger doses. Secondly, dopamine was found to stimulate specific dopamine receptors in the cerebral vessels, resulting in vasodilatation, sometimes with a pronounced flow increase. This occurred mainly in response to medium doses of dopamine. Autoregulation functioned well both during stimulation and blockade of these receptors.

The purpose of this study was to analyse factors for interobserver disagreements in two scales used for the assessments of the amount of blood in subarachnoid space (Fisher grading) and of acute hydrocephalus on computerized tomographic (CT) scans. The assessments made by four neuroradiologists on 59 CT scans obtained in the acute stage after subarachnoid hemorrhage were analysed by a statistical method by Svensson and Holm. This method permits the separation of the inter-observer disagreements in their random and systematic components. The overall consistency of the assessments was significant (p < 0.0005) but the neuroradiologists disagreed on half of the CT-scans. The kappa values were 0.50-0.63. The analysis showed that the main reason for disagreements was systematic inter-observer differences in their use of the clinically most important parts of staging, i.e. subarachnoid clot or intraventricular blood (Fisher grading) and too low categories (hydrocephalus). The main conclusion from this study is that the proper remedy for Fisher grading and for grading of hydrocephalus is a sharpening of the criteria of specific category levels and given this improvement both grading systems will show a high level of reliability.