The blood flow in the forearm in patients with cardiac failure. I. The relationship between the cardiac output and the blood flow in the forearm

[Kidney in heart failure (author's transl)]

The adaptability of the kidney in heart-failure is restricted. This is due to a sympathetically mediated renal vasoconstriction, forming part of a sympathetically induced general rearrangement of haemodynamics. This is reflected in a rise of the total peripheral vascular resistance and of the right auricular pressure and can be normalized to a large extent by sympathetic gamma-blockade. The renal vasoconstriction reduces the glomerular filtration rate and, thus, the tubular sodium load. Simultaneously, possibly by the same sympathetic stimulus, more renin is liberated from the juxtaglomerular apparatus. This increases the production of angiotensin and in turn, raises the production of aldosterone. By the combined effect of the reduced glomerular sodium load and aldosterone-mediated increase in tubular reabsorption of sodium, sodium and water will be retained in the body. During the night-rest the load on the circulatory system diminishes. In the early stages of heart-failure this emergency circulatory reaction, therefore, subsides and the rise of the renal fraction of the cardiac output leads to the excretion of the retained fluid and is the basis of nocturia.

Evaluation of skeletal muscle capillary basement membrane thickness in congestive heart failure

Although it has been demonstrated that during isotonic grip exercise patients with chronic congestive heart failure have an abnormally reduced forearm oxygen consumption resulting from a depressed forearm flood flow, there may be additional etiologies of this abnormality. To explore this possibility biopsies of the pronator teres muscle were taken in eight control subjects with normal cardiac hemodynamics and in seven severely decompensated chronic congestive heart failure subjects. Each sample was fixed, stained, and photomicrographs of the sections were obtained and the capillary basement membrane thickness determined. The control capillary basement membrane thickness was 3028 plus or minus 187 A (mean plus or minus SEM) compared to the congestive heart failure thickness of 4924 plus or minus 538 A (pless than .01). It is possible that the increased basement membrane thickness in congestive heart failure may result from or actually cause the depressed oxygen consumption by altering diffusion.

Influence of experimental edema on metabolically determined blood flow

To evaluate the effects of edema and elevated tissue pressure on metabolically determined blood flow, forelimb vascular resistance was determined by two techniques. Peak reactive hyperemic blood flow after release of a 5-minute arterial occlusion was bilaterally measured in the brachial arteries of 11 dogs before and after venous congestion of one limb for 4 hours at 70 mm Hg and after infusion of 1,000 ml of 6% Dextran 70. Before determining peak reactive hyperemic blood flow, congestion was released; venous pressure was then similar in both limbs. Congestion reduced peak reactive hyperemic blood flow from 23.9 ± 5.7 (SE) to 16.0 ± 3.6 ml/min 100 g -1 ( P < 0.05). Peak reactive hyperemic blood flow was unchanged in the uncongested control limb (21.2 ± 5.2 to 20.4 ± 4.5 ml/min 100 g -1 , P > 0.5) at the time when it was reduced in the congested limb. Total tissue pressure measured with a needle was greater in the congested limb (9.1 ± 1.7 mm Hg) than it was in the uncongested limb (2.5 ± 1.5 mm Hg, P < 0.01). Likewise, pressure in a chronically implanted perforated capsule was -2.1 ± 2.0 mm Hg in the control limb but was +7.2 ± 1.5 mm Hg ( P < 0.01) in the contralateral limb following congestion. Dextran 70 was infused after venous congestion; this procedure produced peak reactive hyperemic blood flows and tissue pressures which were similar in both limbs. Similarly, minimum vascular resistance following an ischemic stimulus in an isolated, denervated constant-perfused forelimb was increased from 17.7 ± 2.2 to 23.9 ± 1.8 mm Hg/ml min -1 100 g -1 ( P < 0.01) following congestion in five dogs. Brachial arterial sodium content was unchanged in four dogs following 4 hours of congestion. These data suggest that, in the presence of edema, metabolic arteriolar dilation may be impaired.

Pathogenesis of cardiac oedema

When the heart ceases to meet the requirements of the body for oxygen, the sympathetic-adrenal system is activated. This occurs in people with a healthy heart when the demands for oxygen are excessive-for example, in heavy muscular work-and in subjects with a failing heart when the demands are normal or small. Eventually, when the heart is unable to meet even the ordinary requirements of everyday life, the sympathetic activity becomes more or less continuous. It may lessen during rest at night, but with a further failing of the heart its output may become inadequate even in complete rest.The sympathetically-medicated renal vasoconstriction, with reduction of the glomerular sodium load, redistribution of the blood flow in the renal cortex to the juxtamedullary glomeruli, and the mobilization of the renin-angiotensin-aldosterone system, is responsible for the salt and water retention which will ultimately become clinically manifest as oedema-especially when it is no longer counteracted by the tidal output of water and sodium at night. A by-product of this continuing dehydration reaction is a cumulative potassium loss which may lead to disastrous consequences if untreated.