The effect of negative pressure breathing on urine flow

Hemodynamic Consequences of the Injection of Radiopaque Material

The hemodynamic changes resulting from injection of radiopaque material into the left heart in a series of patients undergong cineangiographic studies have been reported. The hypertonicity of radiopaque materials appears to be responsible for much of the observed reaction. The mechanism whereby hypertonic solutions produce the observed physiologic changes remains unknown.

Changes observed in patients could be reproduced in experimental animals. The combined experimental and clinical data show that left atrial pressure increases, left atrial pulse contour alters, stroke output increases, heart rate is much unchanged, peripheral artery pressure falls, hematocrit level falls, and myocardial contractile force decreases mildly and transiently.

The difference between the physiologic effects of injecting hypertonic media into the right and left sides of the circulation is discussed.

Because the pressure changes are easy to monitor and parallel the other features of the hemodynamic reaction, it is good to wait until pressures have returned to the pre-angiographic level before proceeding with the injection of more radiopaque material. This usually requires 15 minutes.

MECHANISMS OF THE RENAL RESPONSE TO PLASMA VOLUME EXPANSION

Expansion of the plasma volume by infusions either of plasma or iso-oncotic albumin solution resulted almost uniformly in diuresis and natriuresis in anaesthetized dogs. Although the clearance of para-aminohippurate (RPF) usually increased, changes in clearance of creatinine (GFR) were neither large nor consistent in direction, indicating that the renal response depended on altered tubular reabsorption. The usual temporal dissociation between the peak values for water and sodium output during the response was interpreted as evidence of operation of two effector mechanisms. Reasons are given for believing that the renal response was not due to a direct action of the infusate, but rather to activation of a reflex mechanism by expansion of vascular volume. Bilateral cervical vagotomy did not prevent either the diuresis or the natriuresis, again implying that receptors additional to those in the cardiac atria must contribute to the sensory limb of the reflex. The average magnitude of diuretic and natriuretic responses after cervical vagotomy was, however, less than a quarter of that before the denervation, supporting the contention that the vagi do contribute to the renal response to expansion of the plasma volume when plasma is infused. The diuresis and the natriuresis still occurred during infusion in adrenalectomized animals, indicating that inhibition of aldosterone secretion is not the only effector mechanism leading to a natriuretic response to expansion of vascular volume.

THE EFFECT OF VAGOTOMY AND DENERVATION OF THE CAROTID SINUS ON DIURESIS FOLLOWING PLASMA VOLUME EXPANSION

The hypothesis exists that afferent vagal fibers, arising in cardiac atrial stretch receptors, serve as the sensory limb of a reflex mechanism sensitive to variations in blood volume and producing corresponding changes in urine flow. Section of the vagi did not, however, prevent the diuretic and chloruretic response to expansion of the plasma volume with isotonic infusions. Carotid sinus denervation alone or combined with vagotomy also failed to prevent the diuresis and chloruresis following infusion in most experiments, although in a few cases the response was absent or diminished after the combined procedure. Reasons are given for believing that the bovine albumin infusion used did not act directly on the kidney to increase urine output, but rather through a reflex mechanism which could not have depended on the integrity of the vagi. It is concluded that receptors additional to those in the cardiac atria and the carotid sinus must contribute to the sensory component of a reflex mechanism regulating plasma volume.

THE EFFECT OF VAGOTOMY AND DENERVATION OF THE CAROTID SINUS ON DIURESIS FOLLOWING PLASMA VOLUME EXPANSION

The hypothesis exists that afferent vagal fibers, arising in cardiac atrial stretch receptors, serve as the sensory limb of a reflex mechanism sensitive to variations in blood volume and producing corresponding changes in urine flow. Section of the vagi did not, however, prevent the diuretic and chloruretic response to expansion of the plasma volume with isotonic infusions. Carotid sinus denervation alone or combined with vagotomy also failed to prevent the diuresis and chloruresis following infusion in most experiments, although in a few cases the response was absent or diminished after the combined procedure. Reasons are given for believing that the bovine albumin infusion used did not act directly on the kidney to increase urine output, but rather through a reflex mechanism which could not have depended on the integrity of the vagi. It is concluded that receptors additional to those in the cardiac atria and the carotid sinus must contribute to the sensory component of a reflex mechanism regulating plasma volume.

MECHANISMS OF THE RENAL RESPONSE TO PLASMA VOLUME EXPANSION

Expansion of the plasma volume by infusions either of plasma or iso-oncotic albumin solution resulted almost uniformly in diuresis and natriuresis in anaesthetized dogs. Although the clearance of para-aminohippurate (RPF) usually increased, changes in clearance of creatinine (GFR) were neither large nor consistent in direction, indicating that the renal response depended on altered tubular reabsorption. The usual temporal dissociation between the peak values for water and sodium output during the response was interpreted as evidence of operation of two effector mechanisms. Reasons are given for believing that the renal response was not due to a direct action of the infusate, but rather to activation of a reflex mechanism by expansion of vascular volume. Bilateral cervical vagotomy did not prevent either the diuresis or the natriuresis, again implying that receptors additional to those in the cardiac atria must contribute to the sensory limb of the reflex. The average magnitude of diuretic and natriuretic responses after cervical vagotomy was, however, less than a quarter of that before the denervation, supporting the contention that the vagi do contribute to the renal response to expansion of the plasma volume when plasma is infused. The diuresis and the natriuresis still occurred during infusion in adrenalectomized animals, indicating that inhibition of aldosterone secretion is not the only effector mechanism leading to a natriuretic response to expansion of vascular volume.