Howard K. Thompson

Determination of regional cerebral blood flow by inhalation of 133-Xenon.

A method for estimating regional cerebral blood flow is described in which tracer amounts of 133Xe are inhaled for 2 min and monitored extracranially over the next 45 to 60 min. A three-compartment model used to analyze the resulting clearance curves provided separate blood flows for “gray” and “white” matter, plus a decay constant for a slow third component, believed to arise from extracerebral tissue. The analysis included a correction for recirculation of all three components, based on radioisotope concentration of the expired air or arterial blood. Results from the analysis were compared with those obtained by the more traditional two-compartment approach, using data from 15 healthy young males. Whereas the three-compartment method yielded measurements comparable with those obtained by established techniques (average CBF = 54.7 ml/100 g/min), the two-compartment analysis gave consistently lower values (average CBF = 30.2). Comparison of results based on expired air and arterial sampling suggested that end-expiratory air is a reasonable substitute for arterial blood. Although the 133Xe inhalation method is technically simpler and less traumatic than other methods, complex analytic treatment of the data is necessitated by the presence of appreciable recirculation and extracerebral contamination.

Components of delay in the pre-hospital phase of acute myocardial infarction☆

Abstract One hundred sixty patients from a defined population with acute myocardial infarction were questioned about their activities before hospital arrival. Hospital arrival time was divided into prodromal period, patient decision time, lay consultation period, medical decision time and travel time. Forty-eight percent experienced prodromal chest pain before the acute onset of symptoms. The median hospital arrival time for all patients was 2 hours, 45 minutes. Hospital arrival time was significantly prolonged in patients experiencing an increase in the severity of angina pectoris, and in those with a physician decision time of more than 1 hour. Implications for intervention techniques are discussed.

Permanent Ventricular Pacemakers Comparison of Transthoracic and Transvenous Implantation

In the series of 86 patients with the Stokes-Adams syndrome or with symptomatic bradycardia managed with permanently implanted ventricular pacemakers reported on, 35 patients had primary implantation of epicardial leads at thoracotomy and 51 had transvenous endocardial electrodes passed via the jugular venous system for permanent ventricular pacing. The transvenous method of permanent pacemaker implantation appears to be easier to apply with less serious complications and provides the same overall mortality as the transthoracic approach. However, pacemaker failure, both permanent and temporary, is more likely to occur with the transvenous approach.A series of unique complications and findings noted in the transvenous group were thought to be related to the permanent pacing electrode catheter. These included myothought cardial perforation, pericardial friction rubs, intermittent ventricular pacing, and diaphragmatic stimulation.The experience suggests that it is reasonable to employ a transvenous pacemaker initially, recognizing that replacement with a transthoracic pacemaker will be necessary in approximately 16% of the patients and remanipulation of the electrode catheter will be needed in another 13%. Therefore, to undertake transvenous permanent implantation of a pacemaker, one must also be prepared to employ the transthoracic approach in a small but significant number of patients.

Reproducibility of Results obtained with Indicator-Dilution Technique for Estimating Cardiac Output in Man

The reproducibility of the indicator-dilution estimation of cardiac output was assessed by evaluating pairs of indicator-dilution curves recorded simultaneously from normal subjects and patients by two similar linear densitometers. Measurement error was defined by comparison of 90 simultaneous measurements obtained from the same needle; two standard deviations of the difference equaled 430 ml./min. (6 per cent of the mean cardiac output). A much larger variation resulted when 159 simultaneous cardiac output determinations, sampling from the brachial and femoral arteries, were compared (two standard deviations of the difference equaled 1,200 ml./min. or 20 per cent of the mean cardiac output). Intermediate values were obtained in a comparison of 29 simultaneous measurements from the radial and brachial arteries of the same arm. The larger deviations between the simultaneous measurements from different arteries suggested nonuniform distribution of dye. The discrepancies between the paired cardiac output determinations were larger and more frequent when peripheral blood flow alterations were produced. However, the nature of dye-distribution abnormalities and the mechanisms whereby peripheral arterial flow influence the dye-dilution cardiac output measurement were not evident.

The Hemodynamic Effects of the Injection of Contrast Medium (Isopaque)

This study was supported in part by Research Grants HE-07563-03 and HE-04807 from the National Heart Institute of The National Institutes of Health, U.S. Public Health Service and Grants-in-Aid from The John A. Hartford Foundation, Inc., The Winthrop Laboratories and The US Council for Tobacco Research. * This study was completed during the tenure of a U.S. Public Health Service Postdoctoral Research Fellowship. 1 Generously supplied as Isopaque® 440, by the late W. Wesley Herndon, M.D., Associate Director, Department of Medical Research, Winthrop Laboratories, New York, New York. INTRODUCTION

A generalized medical information system (GEMISCH) for practicing physicians

Here is described an information system for the accumulation, storage, analysis, retrieval and output of medical data. Particular attention has been given to flexibility of input devices, and to readability of output. Primary emphasis has been on making the computer a more accessible tool to the physician.

Effects of acetazolamide on cerebral blood flow of dogs during hyperbaric oxygenation

Abstract The effect of acetazolamide in improving cerebral blood flow and counteracting hyperoxic cerebral vasoconstriction was evaluated in 7 dogs breathing room air at ambient pressure and in 5 dogs breathing 100 per cent oxygen at 2.3 atmospheric pressure. Cerebral blood flow, measured with the radioactive xenon clearance method, was determined serially before and after administration of 5 mg. per kilogram of acetazolamide intravenously. Following the administration of acetazolamide at ambient environment, the mean fast flow increased from a base-line level of 60.8 to 112.4 ml. per 100 Gm. per minute and slow flow from 16.2 to 24.6 ml. per 100 Gm. per minute with the arterial pCO 2 and arterial blood pressure remaining relatively constant. The cerebral blood flow was markedly increased at 10 minutes, it attained a peak at 30 minutes, and tended to remain elevated throughout the two hour observation period. Hyperbaric oxygenation (arterial pO 2 = 1,548 mm. Hg) reduced the mean fast flow from 66.4 to 55.9 ml. per 100 Gm. per minute and mean slow flow from 17.2 to 15.3 ml. per 100 Gm. per minute. Administration of acetazolamide during hyperbaric oxygenation raised the mean fast flow to 134.8 and slow flow to 24.7 ml. per 100 Gm. per minute. This increase of cerebral blood flow was not observed in the 3 control animals which were subjected to only hyperbaric oxygenation without receiving acetazolamide. These studies demonstrate that acetazolamide in a small amount not only effectively counteracts the cerebral vasoconstricting effect of hyperoxia, but also significantly increases cerebral blood flow at both ambient and hyperbaric conditions.

Coronary occlusion during right heart catheterization

Abstract A case of tetralogy of Fallot in a 17 year old boy is described. A catheter inadvertently became lodged for nine minutes in the left coronary artery during right heart catheterization. During the period of occlusion, electrocardiographic changes of subendocardial ischemia promptly appeared and were followed after three or four minutes by pressing anterior chest pain that radiated to the left arm. Subsequent follow-up studies revealed evidence of myocardial infarction.

Problems and complications with the use of side-hole cardiac catheters

W hen Forssman catheterized himself in 1928,’ he used a “well greased” urethral catheter. Since then, in order to improve the facility and safety of intravascular catheterization, a variety of catheters of different designs have been fabricated. One such modification was the incorporation of holes in the side of the catheter near its tip. The purpose of such side-hole catheters is to: (1) permit sampling or adequate recording of pressure when the tip is against the wall of a vessel or chamber, and (2) permit rapid and wide dispersion of contrast medium and minimize catheter recoil during the injection of contrast medium. Although the side holes usually serve these intended purposes, they may cause several problems and complications. Some of these problems and the suggested methods for obviating them will be presented in this report. Artifacts in pressure tracings. Although the side holes near the tip of the catheter prevent complete damping of the pressure tracing when the end hole becomes obstructed, they may result in erroneous pressure tracings under certain circumstances. When a catheter is advanced or withdrawn slowly across a cardiac valve or septum, a point can be reached at which some of the lateral pressure holes are exposed to pressures in one chamber while other side holes or the end hole are exposed to pressures in the adjacent chamber. Under these circumstances the pressure recorded by the manometer will be an artifactual average pressure somewhere between the actual pressures in the two chambers. A left atria1 pressure recorded at the time of transseptal catheterization might be considerably reduced by this technique if some of the lateral taps are still in the right atrium, or the recorded left ventricular systolic pressure might be incorrectly low in a patient with aortic stenosis if the openings of the transseptal catheter are simultaneously sensing pres-

Using a decision support optimisation software tool to maximise returns from an overall marketing budget: A case study from a B-to-C marketing company

Most marketers go through an annual budget-setting round in which they allocate sums of money to a number of different marketing activities. This process is usually undertaken using historic experience of results, combined with last years budget, to arrive at a decision about how the money should be distributed. The authors have used a new approach to solving the budget-allocation problem, using a decision support system that they have developed using integer linear programme techniques. This article is a case study of one application of this technology in the B-to-C field; it describes the problems that were encountered in getting the right metrics to go into the system, and the ways in which these were overcome. It goes on to show how the optimised outputs differed from business as usual, and the types of scenario outcome that resulted.