James V. Warren

THE CARDIAC OUTPUT IN PATIENTS WITH CHRONIC ANEMIA AS MEASURED BY THE TECHNIQUE OF RIGHT ATRIAL CATHETERIZATION

Many patients with circulatory failure either from hemorrhage or heart failure have anemia. In these patients, the cardiac output may be within normal limits and yet the circulation may be inadequate. The question immediately arises as to what is the effect of anemia on the requirements of the tissues of the body for blood. Before it can be determined whether a given patient with anemia has an adequate circulation, it is necessary to know how anemia per se affects the cardiovascular system and what level of cardiac output should be expected for a given hemoglobin concentration. Studies on the circulation were, therefore, carried out on patients with chronic anemia in whom the picture was not complicated by shock and by the marked decrease in total blood volume which are so often present in the acute anemia produced by hemorrhage.

Vasodepressor Syncope Factors Influencing Cardiac Output

Vasodepressor syncope is characterized hemodynamically by a sudden fall in total peripheral resistance with little associated change in cardiac output. The failure of the cardiac output to compensate for the fall in peripheral resistance is a striking feature of the fainting reaction. Possible explanations for this phenomenon are the presence of neurogenic myocardial inhibition or markedly limited volume of blood available to the heart. The effects of atropine injections, inflation of antigravity suit, negative pressure breathing, and albumin infusions on the syncopal reaction were studied. Results favor the causative role of limited venous inflow in the cardiac output response.

CORRELATIVE OBSERVATIONS ON CEREBRAL METABOLISM AND CARDIAC OUTPUT IN MYXEDEMA

Patients with myxedema present an unusual opportunity for studying the effect of lowered metabolism on organ blood flow and for observing the effect of changes in peripheral circulation on cardiac output. Studies of cerebral metabolism in myxedema are of interest to the physician because changes in cerebral metabolism may be of importance in understanding the alterations in mental status which occur with this disease (1-3). The cerebral blood flow was measured by the nitrous oxide method of Kety and Schmidt (4) in eight patients with myxedema. The cardiac output was measured by the technique of right atrial catheterization in seven other patients with myxedema.

THE EFFECT OF VENESECTION AND THE POOLING OF BLOOD IN THE EXTREMITIES ON THE ATRIAL PRESSURE AND CARDIAC OUTPUT IN NORMAL SUBJECTS WITH OBSERVATIONS ON ACUTE CIRCULATORY COLLAPSE IN THREE INSTANCES

The mechanisms by which the body compensates for a decrease in blood volume have not been thoroughly studied in man. All physicians are aware that from 500 to 1000 ml. of blood can be removed from a person of average size without producing any symptoms, if the body is horizontal. If the blood is removed rapidly, hemodilution plays little part in the immediate adjustment. Do the arterioles constrict, maintaining the arterial pressure at a normal level at the expense of blood flow to the tissues? Is the atrial pressure maintained at the normal level by venous constriction? Or is it possible that up to a certain point, the heart can function effectively with a falling atrial pressure so that the circulation can be maintained without either arteriolar or venous constriction in spite of a moderate decrease in blood volume? The purpose of this paper is to describe the changes in the circulation in normal subjects caused by moderate loss of blood from the body, either as the result of venesection or by pooling blood in the extremities through the application of venous tourniquets. During the experiments, acute circulatory collapse (primary shock) occurred in three instances and quantitative observations were made on the changes occurring in the circulation.

The mechanism of cough syncope.

Abstract Although described in 1876 by Charcot, 1 the syndrome of cough syncope has until recently been considered a rare form of fainting. However, the excellent reports by Baker, 2 Sharpey-Schafer, 3 and Kerr and Derbes, 4 indicate that the condition may not be uncommon. Despite increasing recognition of the syndrome, the mechanism producing the syncope remains elusive. 4 Earlier investigators have suggested that this form of syncope is an epileptic equivalent 5–7 or the result of a laryngeal reflex. 6,8 These theories, however, have generally been abandoned in favor of a circulatory mechanism producing cerebral anoxia. 9 It has been suggested that the cerebral anoxia might be the result of marked reflex peripheral vasodilation 3 or a decreased cardiac output secondary to a reduced inflow or marked pulmonary vasoconstriction. 10 These theories, though attractive, fail to explain completely certain unique features of this form of syncope. For example, syncope may develop with remarkable rapidity (3 to 5 seconds) after the onset of cough. With the cessation of cough, consciousness is rapidly recovered without vasomotor or other sequelae. The syndrome is rarely observed in women and syncope may occur in the supine or standing subject. The present report, based on observations made on normal individuals and patients with cough syncope, suggests a more acceptable mechanism for this type of fainting.

Circulation of the Giraffe

Observations on the circulatory functions of 4 giraffes are recorded. Both the right and the left heart were catheterized under local anesthesia with a miniature manometer. Cardiac output was determined by employing both indicator dilution method and the Fick principle. Other parameters, such as the circulation time, blood volume, velocity, right and left ventricular pressure ascent as well as the changes in blood pressure occurring with changes in the Posture of the head were recorded. The difficulties of the experiments created certain limitations in their interpretation. The arterial blood pressure is high by human standards and adequate to maintain cerebral perfusion without other means of support. The arterial pressure pulse contour suggests a relatively lax vascular bed with considerable reserve distensibility. Values for cardiac output and blood volume were roughly comparable to those recorded in domestic cattle of the same approximate weight.

Effect of increasing the blood volume and right atrial pressure on the circulation of normal subjects by intravenous infusions

M ANY observations on the effects of decreasing the blood volume in man have been reported, but much less information is available on the effects of increasing the blood volume. It is known that an increase in blood volume caused by the rapid intravenous administration of fluid will produce a rise in venous pressure. The effects of this rise in venous pressure on the cardiac output and the size of the heart are of considerable importance to the physician. If, as the venous pressure rises, the normal heart is dilated and the cardiac output greatly increased, this would indicate that a considerable strain was being placed upon the heart. Such a reaction might explain the poor tolerance of patients with heart failure to intravenous fluids.

Circulatory changes produced by the Valsalva maneuver in normal subjects, patients with mitral stenosis, and autonomic nervous system alterations.

The cardiac output has been measured during the immediate post-Valsalva maneuver recovery period in normal subjects, patients with clinically significant mitral stenosis, and patients with alterations of the autonomic nervous system. When compared with the resting value, it was found that normal subjects had a decrease in cardiac output during the immediate post-Valsalva recovery period, while patients with mitral stenosis had an increased output following the same stress. Three patients with alterations of the autonomic nervous system had a variable response. Changes in total peripheral vascular resistance usually were directionally opposite to changes in the cardiac output. The difficulties of attaching clinical significance to a patients response to the Valsalva maneuver are considered.

CARDIORESPIRATORY DYNAMICS IN THE OX AND GIRAFFE, WITH COMPARATIVE OBSERVATIONS ON MAN AND OTHER MAMMALS*

Comparative mammalian physiology not only is important as an intellectual discipline in its own right, but it also provides a perspective which can contribute to the understanding of physiological processes in a given species. As an example, those functions of the organism which appear related to body weight or to body surface area can be studied over a wide range of animal size, providing more extensive data for the precise analysis of relationships than could be obtained from investigations confined to members of a single species. In recent years a strong increase in interest in physiological studies on large mammals has been evident.’-6 The discussion which follows is based on circulatory and respiratory observations obtained on four giraffe in South Africa a t an elevation of 2375 feet and on 26 domestic cows studied a t three centers in the United States a t 400 feet or less above sea level, as well as on data reported from other investigative groups. I n certain areas comparison of the findings in giraffe and cattle is made with those in man, dog, and other mammals. In the choice of material considerable selection has been exercised and preference given to findings providing new viewpoints for discussion or permitting direct comparison between species. The species of primary interest in this presentation-domestic cattle (cows) and giraffe-are large ruminants of approximately comparable body weight, namely, 650 to 1,450 pounds (295 to 659 kg.). Both of these animal groups belong to the same suborder (Pecora) but to different families, the Bovidae and Giraffidae, respectively. Although giraffe sometimes attain a height of 16 feet and are said to reach 20 feet rarely, the tallest animal in the present group was approximately 12 feet in height. FIGURE 1 shows this animal and a domestic cow of comparable weight in proper scale relationship. I t can be seen that although there is a striking difference in height (11’7.5” versus 4’6”) the position of the heart is roughly halfway between hoof and head in both animals. The heights of the other three giraffe, as measured

THE BLOOD VOLUME IN PATIENTS WITH ARTERIOVENOUS FISTULAS

There has been much controversy concerning the changes in blood volume which occur in the presence of arteriovenous fistulas. The large number of vascular injuries treated at Ashford General Hospital during the recent war offered an unusual opportunity to study this problem. This paper reports observations on the blood volume changes in a group of 41 such patients studied before and after operative removal of an arteriovenous fistula. In 1924 Holman (1) reported his studies on animals with arteriovenous fistulas. He used the brilliant vital red method of blood volume determination, obtaining a single dyed specimen four minutes after the injection of the dye. He found that the blood volume increased in the presence of a fistula. Later he reported similar blood volume studies in patients with arteriovenous fistulas (2, 3); in most instances there was a reduction in blood volume following removal of the fistula. In their studies on blood volume Rowntree and Brown (4) included seven patients with arteriovenous fistulas, three of whom had congenital lesions. Although the average blood volume was slightly above the normal value, in only one patient was there a distinctly increased blood volume. Pemberton and Saint (5) reported finding a slightly elevated value in a single patient with a congenital communication between artery and vein. Reid and McGuire (6) expressed doubt regarding the blood volume changes in view of their findings on three patients studied before and after operation. In one patient there was essentially no change in blood volume; in another, a postoperative decline of 600 cc.; and in the other, a post-