The Effects of Spinal Anesthesia on the Circulation in Normal, Unoperated Man With Reference to the Autonomy of the Arterioles, and Especially Those of the Renal Circulation

Abstract

The present study, comprising observations on 21 subjects given high spinal anesthesia, is an investigation of the effects of anesthetic denervation in normal man, uncomplicated by surgical intervention, on the circulation with particular reference to the vascular bed of the kidney. It is concluded that the renal arterioles are distinctly autonomous, in the sense that under basal conditions the renal vascular tone is not affected by anesthetic denervation. Our observations further suggest that the arteriolar bed generally (apart from the skin) possesses considerably more autonomy than is usually attributed to it-sufficient, in fact, in the normal supine individual at rest, to maintain an essentially normal arterial pressure. We find no evidence of significant arteriolar dilatation during high spinal anesthesia, such reduction in blood pressure as occurs being attributable, we believe, to diminished circulating blood volume in consequence of dilatation of the capillaries, venules, and veins.Part I deals with the following topics: (1) Methods; (2) the effects of spinal anesthesia on renal blood flow; (3) on the arterial pressure, and (4) on the reflex responses to posture, hypercapnia, and anoxemia. Part II consists of a review of the evidence on (5) the existence of tonic vasoconstrictor activity and on (6) the existence of autonomy in the peripheral arterioles generally, and (7) in the kidney in particular, and (8) the peripheral effects of hypercapnia and anoxemia. In (5) it is brought out that the notion of tonic vasoconstrictor activity in the sympathetic nervQus system, apart from the skin, is based largely upon animal experiments which are seriously complicated by general anesthesia, venous dilatation, etc., and that the information so obtained cannot be transferred with confidence to normal animals, and certainly not to man.PART I MethodsThe subjects were male convalescent patients ranging in age from 18 to 50 years who, with a single exception, presented no abnormal signs contraindicating selection for this study. They were examined in the morning in the basal, fasting condition, and were prepared for the measurement of renal blood flow and filtration rate by the clearance method, as described by Smith, Goldring, and Chasis (93). In the earlier observations the phenol red and inulin (35) clearances were followed, but after the introduction of the diodrast clearance (93), all three clearances were used. The phenol red clearance serves as a check on the diodrast clearance, the constancy of the phenol red/diodrast clearance ratio before and after anesthesia demonstrating that procaine per se has no effect upon the tubular excretory mechanism. The infusions corresponded to the typical infusion cited by Chasis, Ranges, Goldring, and Smith (18). Zero time was taken as the beginning of the priming infusion, which occupied about 10 minutes; the infusion was then changed to the sustaining infusion, the first urine collection period being started at about 30 minutes. The sustaining infusion was usually interrupted ...

Dependency of Renal Blood Flow on Prostaglandin Synthesis in the Dog

“…The chromatographic mobilities of the biosynthesized PGF, a and PGE 3 ml/g min 1 , which is within the range of values reported for resting renal blood flow in unanesthetized dogs (14, p 1483) ( Table 1). Fifteen minutes after administration of either drug, the mean concentrations of PGE-and PGF-like substances in renal venous blood decreased to 0.08 ±0.02 (P<0.01) and 0.01 ± 0.01 ng/ml, respectively, from control levels of 0.34 ± 0.10 and 0.10 ± 0.03 ng/ml (Table 2).…”

Renal Blood Flow, Glomerular Filtration Rate, Renal PAH Extraction Ratio, and the Role of the Renal Vasomotor Nerves in the Unanesthetized Rabbit

“…3 ' 18 The mean filtration fraction was 22% in the rabbit, closely similar to values observed in man, and somewhat below the average values reported for the dog. 3 The demonstration of a low degree of sympathetic constrictor tone in the resting renal circulation of the rabbit is similar to the findings obtained in man, 19 and suggests that under the present experimental conditions the rabbit did not exhibit tbe degree of autonomie instability traditionally ascribed to this species.…”

The Behavior of Renal Blood Flow After Partial Constriction of the Renal Artery

“…In no instance was renal blood flow observed to fall before that through other arteries. These observations confirm those of other investigators and afford evidence for "the autonomous control of the renal vascular bed" (18). They also suggest that the kidneys take little part in the general vasoconstriction induced by shock.…”