Gustavo Bounous

Blood Pressure and Renal Blood Flow Response to Occlusion of Visceral Arteries '

MARIO ONNIS, M.D., HARms B. SHUMACKER, JR., M.D., GUSTAVo BOUNOUS,

M.D.

From the Department of Surgery and the Heart Research Center, Indiana University School of Medicine, Indianapolis, Indiana

the 30-minute period of arterial occlusion and every five minutes during a 15-minute period after release of the clamp. Four groups of eight dogs each were studied. In the first the superior mesenteric artery was occluded, in the second the celiac axis, in the third the hepatic artery, and in the fourth both inferior and superior mesenteric arteries and the celiac axis. In an additional group of four dogs thoracolumbar sympathectomy and splanchnicectomy were performed in two stages by a technic described previously.4 Approximately eight days later arterial pressure and renal blood flow were studied before, during, and after clamping of both mesenteric arteries and the celiac axis.

THE PRESENT study was undertaken in order to investigate systemic blood pressure and renal blood flow responses to acute clamping of the major abdominal visceral arteries.

Materials and Methods Adult mongrel dogs varying in weight from 11.8 to 17.3 kilograms were used. They were anesthetized by the intravenous injection of 5.0 per cent thiopental sodium. An endotracheal tube was inserted and oxygen was administered rhythmically by means of a mechanical respirator. Mean arterial blood pressure was monitored by a U-tube mercury manometer connected with a plastic catheter inserted into the aorta via a femoral artery. Temperature was measured by a telethermometer placed in the mid portion of the esophagus. Renal blood flow was determined by a direct method which has been described previously.2 The arteries to be occluded were dissected free using nonsterile technic. After renal blood flow and arterial pressure had been measured during a ten-minute control period, the arteries were clamped with a noncrushing arterial clamp. Renal blood flow and systemic arterial pressure were measured every five minutes during

Results Clamping of the Superior Mesenteric Artery. In this group the mean arterial blood pressure during the control period varied from 110 to 140 and averaged 124 mm. Hg (Fig. 1). A mild increase in arterial pressure occurred during the period of superior mesenteric arterial clamping in seven of the eight animals. Blood pressure remained essentially unchanged in the exceptional instance. On the average the arterial blood pressure rose 15 mm. Hg. The blood pressure fell in every instance when the clamp was removed from the mesenteric artery. Renal blood flow values during the control period ranged from 18.9 to 27.2 and averaged 21.9 cc./kg./min. A

* Submitted for publication January 17, 1962. Aided by PHS research grant (H-203 C5) from the National Heart Instituite, National Institutes of Health, Public Health Service, and by grants from the American Heart Association and James Whitcomb Riley Memorial Association.

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Volume 157 Number 1

very slight increase in renal flow occurred during the period of clamping in each animal. The average increase was little, only approximately 10 per cent above the control values. Upon release of the clamp a very slight decrease in the renal blood flow was observed in six of the eight dogs. The average renal blood flow returned to the control level. Clamping of the Celiac Axis. In this group the mean arterial blood pressure during the control period varied from 120 to 155 mm. Hg and averaged 130 (Fig. 2). In seven of the eight animals the blood pressure began to fall slightly shortly after the clamp had been placed on the celiac axis. In the exceptional case the blood pressure remained the same throughout. On the average the blood pressure fell about 15 mm. Hg. It fell somewhat more after the clamp was released in five of the eight animals. In the other three the blood pressure tended to remain at about the

1505 N

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FIG. 1. Chart showing response of arterial blood and renal blood flow to clamping of superior mesenteric artery. In this figure and in Figures 2-6 the continuous line represents the average mean arterial blood pressure, the broken line the average renal blood flow. The cross matched areas show the range of values. The arrow pointing down signifies time of application of clamp, the arrow pointing lp, time of its release.

pressure

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FIG. 2. Chart showing response to clamping of celiac axis.

same level as during the terminal period of aortic clamping. In this group the renal blood flow values during the control period ranged from 19.5 to 32.5 cc/kg/mm. and averaged 23.7 cc./kg./min. A slight fall in renal blood flow was observed in all animals during the period of clamping. The average renal blood flow gradually fell to 18.5 cc./kg./mmn., or a little less than 80 per cent of the control value. WVhen the clamp was released the changes in renal flow were inconsistent. A slight increase occurred in six and a decrease in two. On the whole no appreciable change took place in mean values. Clamping of Hepatic Artery. The mean arterial blood pressure during the control period varied from 100 to 145 and averaged 134 mm. Hg (Fig. 3). The response of blood pressure and renal flow was somewhat similar to that in the previous group. Some mild decrease in blood pressure during the period of clamping was observed in six of the eight animals. On the average it fell to a level only approximately 10 mm.

ONNIS, SHUMACKEFI AND BOUNOUS

58

15 5 10 T I M E I N

25 30 5 20 M I N U T E S

10

15

FIG. 3. Chart showing response to clamping of hepatic artery.

below the control value. The renal blood flows in the control period varied from 17.5 to 27 and averaged 21.3 cc./kg./min. Some decrease was observed during the period of clamping in all animals. The average renal blood flow at the end of the period was 14.5 cc./kg./min., or a little less than 70 per cent of the control value. After the clamp was released the blood pressure tended to fall a little in all instances and the renal blood flow to increase slightly or to remain at approximately the same level. Clamping of Celiac Axis and Both Mesenteric Arteries. In this group a substantial rise in blood pressure and fall in renal flow was observed during the period of clamping. (Fig. 4). During the control period the blood pressures ranged from 110 to 145 and averaged 125 mm. Hg. Increase in blood pressure was observed during the period of clamping in each instance. The average blood pressuire increased to a level t approxil nately 30 m11. al)Ove the (onrl valtie. 'Whlenl the clamp was released a pronounced fall occurred in each animal. On the average the blood pressure fell

Annals of Surgery January 1963

about 60 mm. Hg. The renal blood flow during the control period in this group varied from 18.5 to 26.2 and averaged 21.5 cc./kg./min. A decrease was observed during the period of clamping in every instance. The average renal blood flow fell to 8.5 cc./kg./min. or approximately 40 per cent of the control value. When the clamp was released, an increase in renal flow was observed in each animal. On the whole the renal flow increased to almost twice the level observed during the terminal period of clamping (to 15.5 cc./kg./ min.). Clamping of Mesenteric Arteries and Celiac Axis in Sympathectomized Animals. A striking difference in renal blood flow response was noted in this group in spite of a similar, though less marked, response in blood pressure. (Fig. 5). In these animals the average blood pressure during the control period was only 82 mm. Hg.

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FIG. 4. Chart showing response to cla.mping of celiac axis and superior and inferior mesenteric arteries.

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OCCLUSION OF VISCERAL ARTERIES

It increased during the period of clamping a maximal value of 114 mm. Hg. After the clamps were released the average arterial blood pressure fell precipitously to a level of around 40 mm. Hg and then rose to a final value of 55. The average renal blood flow was 20.7 cc./kg./min. during the control period. It rose to 26 cc./kg./min. during the period of clamping, fell upon release of the clamp to 17.1 and then rose to nearly the control level (19.7 cc./kg./ min ). In Figure 6 the arterial blood pressure and renal flow responses in the normally innervated and sympathectomized animals are contrasted. Figure 7 summarizes the pressure and renal flow values in all groups at the end of the period of arterial occlusion. Comments

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5. Chart showing response clamping of lomy Incnrs,tebl6 and superior and inferiorrsuefl Fic.

celiac

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axis

mesenteric

(left).

arteries

In our studies the mean arterial blood pressure increased slightly when the superior mesenteric artery was occluded and more so when the superior and inferior mesenteric arteries and celiac axis were occluded. This was true regardless of whether the

animal had normal innervation

subjected previously to lumbar sympathectomy

or

had been

bilateral and

thoraco-

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tomy. In contrast, the blood pressure fell in

those animals in which the celiac axis

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those in which

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FIG. 6. Chart comparing responses in normal dogs and in those previously suibjected to thoracolutmbar sympathectomy and splanchnicectomy (right) to clamping of celiac axis, superior aInd inferior

mesenteric arteries.

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ONNIS. SHIU\l \CKER AND) BOU\OUS

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lhepatic artery- alone as occlidecd. Beninati andcl Ghigginio I haid noted a sliglht increase in systemic

lbl1o0(

) pressure i1poi( occluision miesenteric artery. 'More

of the stuperior recently Ilevmiiains andl hiis associates ald

observed that the 1lood pressuire increasedl fromii 20 to 44 mim. Hg ( average 28 ) uipon clamllpinlg of the suiperior meseniteric artery. 0 They foundi(I the inierease axeraged 130Mm. HIg xvleni the celiac axis an(1 superior an(I iniferior meselnteric arteries Nx7ere occltu(led.

their opinion that this lhpertensive response slhoulcl Inot 1)e considered of reflex origin siince it xvas niot affected 1)v the adminiistratioli of helxamiietlhomliiim. Selkiurt average ineerase nd Rotle observed of 13 min. Hg uiponi oceluisioi) of the suiperior mesenteric arterx anid the celiac axis. It

xxwas

an

They

(licl Inot

find(I

that this

appreciably affected

l)v

response

xvas

vagal sectioni and(I

believed it could be better explainedI on reflex basis. hv(1rodvnamic rathlr thian1 In oulr exper-iien1ts, the hix pertensix e response xv-as quiite simnilar folloxing clamipinig of imiesenter-ic ar-ter-ies an(I( the celiac a

a

axis in normal (logs auijI in those pleviouslv subjected to exteinsive thoraco-lumbar svmlsplanchnicecttomy. This pathectomy an(I

o.bservation x-mould lend xw eight to thle belief that the hypecrtensive reaction (1()es not resuilt fIro mil xasocouistr-ictionl

plainedI

tIpon

a

ani(d is

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hasis

ex-

as

a

conse(quienice of a studden clhanige in the distribuition of blood flow aind reduction in effective xvascuilar- bed. Any rncal xvasoconstriction occtirriiig dutrinig

C.ombincld

meseii-

teric anil celiac clamping, is not felt responsible for elevation in blood piressture sinc-e ympatlectomy al)olishes the formiiier l)llt does niot affect the latter. Otlher interesting ob)servations w ere imalde concerning the behavior of renal b0loo0d flowx during occlusion of the v'arious abdomIinal xisceral ar-teries. Clamping of the s

suiper-ior

mlecseniteric artery brought about

only a questional)le increase in renal blood flow. In contrast, claim1pin1g of the cCeliac axis or of the hlepatic artery alonle brought al)out a dlefiniite signiific-anit decrease in reinal 1)l00(1 flowx This r-esponse was exaggerated xw hen the celiac, axis and(i both occlut(led, the mileseniter-ic aIrterieis 1)lood0 flow falling', abruptly to atppr-oxialue. mnately 4() per cent of the molltrl The reducltionl in flowx whichl occurred xhilil the hepatic artery or the c eliac axis xere

xvas

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OCCLUSION OF VISCERAL ARTERIES

occluded in contrast to the slight increase which followed occlusion of the superior mesenteric artery alone makes it evident that depression in renal function is at least in part related to decrease in hepatic artery flow. This provides experimental support for the clinical observations of depressed renal function in certain states in which hepatic function is reduced. No obvious explanation is available for the intensification of the reduction in renal blood flow when occlusion of superior and inferior mesenteric arteries was added to occlusion of the celiac axis. The fact that under these circumstances renal blood flow did not fall but indeed increased a little in animals previously subjected to sympathetic denervation and splanchnicectomy makes it evident that the reduction in renal blood flow observed in normal dogs is related to increased renal vascular tone during the period of arterial occlusion. This observation would suggest that efforts to abolish increased renal vascular tonus might conceivably be worthwhile in clinical states characterized by reduced hepatic and renal function. Summary Mean arterial blood pressure and renal blood flow responses to clamping of visceral arteries were studied. Mean blood pressure increased slightly when the superior mesenteric artery was occluded. It increased more when both mesenteric arteries and the celiac axis were occluded both in normal dogs and in those previously subjected to thoraco-lumbar sympathectomy and splanchnicectomy. This suggests that the hypertensive reaction is not due to reflex vasoconstriction but to a change in the distribution of blood flow

61 6

and a reduction in the effective vascular bed. Blood pressure fell when the celiac axis or the hepatic artery was occltuded. Only questionable increase in renal blood flow was observed during clamping of the superior mesenteric artery. Renal flow, in contrast, decreased when the celiac axis or the hepatic artery was occluded. This decrease was exaggerated when the mesenteric arteries were occluded as well as the celiac axis. The observed decrease in renal flow was at least in part related to decreased hepatic artery flow and lends some experimental support to observed clinical states of reduced renal function in cases of reduced hepatic function. The fact that sympathectomy and splanchnicectomy abolish the fall in renal flow otherwise observed with clamping of the mesenteric arteries and celiac axis indicates that this reaction results from increased renal vascular tonus.

Bibliography 1. Bennati, D. and C. W. Ghiggino: Effecto de Hypertension Arterial Provocado por la Occlusion Temporara de Arterias de l'area Splannica. An. Fac. Med. Montev., 41:53,

1956. 2. Bounous, G., H. B. Shumacker, Jr. and H. King: Studies in Renal Blood Flow I. Some General Considerations. Ann. Surg., 151:1, 1960. 3. Heymans, C., A. F. De Schaepdryver and G. R. De Vleeschouwer: Abdominal Baro-Chemosensitivity in Dogs: Circulation Research, 8:347, 1960. 4. Jontz, J. G., C. S. Su, H. B. Shumacker, Jr. and G. Bounous: Influence of Renal Denervation Upon Renal Blood Flow. Surg. Gynec. & Obst., 110:622, 1960. 5. Selkurt, E. E. and C. F. Rothe: Splanchnic Baroreceptors in the Dogs. Am. J. Physiol., 99:335, 1960.