Hypertension on the Hallucal Circulation

Transcription

1 Downloaded from by on November 18, 218 The Effect of Sympathectomy for Essential Hypertension on the Hallucal Circulation By MILTON MENDLOWITZ, MD, AND ARTHUR S WV TOUROFF, MD The effects of sympathectomy on the hallucal circulation were studied in patients with essential hypertension Return of sympathetic nerve function of variable degree could be demonstrated in every patient An increase in nonneurogenic or intrinsic resistance was also found to he attributable to the symmpathectomy This could not be reversed by benzodioxane and was therefore probably not produced by circulating epinephrine The possible mechanisms of this phenomenon are discussed IT IS generally agreed that sympathectomy produces an increase in blood flow in a normal extremity This is manifested by an increase in skin temperature when comparison is made with the contralateral extremity not subjected to sympathectomy' It also has been demonstrated in animals that, to a variable extent, sympathetic nerve tone returns after sympathectomy' In addition, the maximal blood flow obtainable after release of residual sympathetic nerve tone often declines gradually to a point somewhere between previous maximal and extreme vasoconstrictive levels1 Thus when the body is warm, blood flow may be less on the sympathectomized than on the normal side, whereas the opposite may be true when the body is cool This decline in maximal blood flow after sympathectomy has been attributed to the effect of circulating epinephrine and it can be demonstrated by epinephrine perfusion experiments that denervated blood vessels react to epinephrine by constricting' There is controversy, however, as to whether these reactions are greater than normal3' 4 There is, in addition, no conclusive evidence that sufficient epinephrine is in the circulation to account for the postsympathectomy decrease in maximal blood flow as it is usually measured To clarify these points, 21 patients who had been subjected to operation for hypertension From the First Medical Service and Surgery B, The Mount Sinai Hospital, New York, N Y Presented before the Twentyfourth Annual Scientific Session of the American Heart Association, Atlantic City, June 9, 1951 Aided by a Grant from the National Heart Institute, United States Public Health Service 577 were studied Standard thoracolumbar sympathectomies had been carried out in these patients from two to five years prior to these studies Brachial blood pressure and blood flow in the great toe were measured with the patient at rest in a quiet room These determinations were repeated after the application of indirect heat with a cradlebaker over the trunk for 3 to 6 minutes, supplemented by the intravenous administration of 5 mg per kilogram of tetraethylammonium chloride The measurements were repeated again after the intravenous injection of 1 mg of benzodioxane per square meter of body surface Brachial blood pressure was measured by the standard method with a mercury manometer and cuff, whereas blood flow in the great toe was measured calorimetrically5 The drugs were injected slowly via the tubing of an intravenous apparatus containing physiologic salt solution The results are presented in table 1 Dimensional changes in the digital vessels were estimated crudely from changes in the vascular volume index6 This is the flowmean pressure ratio multiplied by a constant and is the reciprocal of resistance in dyne seconds per cm' These determinations cannot be made more precisely because digital blood pressure measurement, especially of the diastolic phase, is inaccurate in the toe Directional changes in blood pressure, however, are determined largely by chancres in the systemic resistance as a whole rather than by local changes in any vascular bed, and the error introduced by the use of brachial arterial blood pressure is probably small Atmospheric conditions were kept as uniform as possible in a quiet room in which Circulation, Volume V, April 1952

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4 58 EFFECT OF SYMPATHECTOMY ON HALLUCAL CIRCULATION automatic controls of temperature and humidity were not available In the resting state, the emotions of the individual tended to cause neurogenic vasoconstriction, the other factor that acted oppositely, being the degree of "success" of the sympathectomy Despite these complexities, the figures clearly demonstrate residual sympathetic nerve tone of varying degree in every patient (fig 1) It should also be noted that sympathectomized patients with hypertension had blood flow readings, after release of sympathetic nerve A IE AND TEAC nerve tone must represent a sharp increase in intrinsic resistance caused by the sympathectomy Such changes have been described after sympathectomy for a variety of diseases including hyperhidrosis,' and are confirmed in these observations The results are unequivocal (fig 3) in iiidicating no decrease in intrinsic resistance after the administration of benzodioxane Resistance was either unchanged, slightly increased, or slightly ,8m POST NEAT 24 AND TEAC 21 >2 CASES HYPERTENSION) A Downloaded from by on November 18, 218 CASES (HYPERTENSION AFTER SYMPATNECTOMY) FIG 1 Vascular volume index (flowpressure ratio) before and after release of residual sympathetic nerve tone by indirect heating and tetraethylammonium chloride (5 mg per kilogram) Black bars: Mean 153 Standard deviation 86 Standard error of the mean 19 White bars: i\ean 245 Standard deviation 17 Standard error of the mean 24 Standard error of the difference of the means 31 Significance ratio 3 tone, which were lower than similar flow readings in a comparable group of patients with established uncomplicated hypertension (fig 2) This would indicate that the operation produced an increase in nonneurogenic, or intrinsic, resistance in the toe The general effect of this would be to increase the blood pressure "floor" after heat and tetraethylammonium chloride7 moderately, so that any change in "floor" blood pressure would be upwards Advance of underlying renal and vascular disease would also tend to raise rather than lower "floor" blood pressure Unless there were an extreme decrease in the blood pressure "floor," which thus is unlikely, the decreased blood flow in the toe after release of sympathetic CASES(HYPERTENSION AFTER SYMPATHECTOMY) B FIG 2 Blood flow after release of syom)ath~tic nerve tone by indirect heating and tetrat hylammonium chloride (5 mg per kilogram) A Mean 214 Standard deviation 66 Standard error of the mean 15 B Mean 158 Standard deviation 55 Standard error of the mean 12 Standard error of the difference of the means 19 Significance ratio 29 decreased, even in those patients with a demonstrable increase in intrinsic resistance after operation In several cases, the increase in resistance produced by benzodioxane was associated with an alarming increase in heart rate, an effect already described9 In figure 4, the extent of the return of sympathetic nerve function, as manifested by the difference in vascular volume indexes before and after release of residual sympathetic nerve tone, are plotted against the degree of increase in intrinsic resistance produced by the sym

5 MILTON MIENDLOWITZ AND ARTHUR S W TOUROFF pathectomy as measured by the level of blood flow after release of sympathetic nerve tone The correlation is marred by the variable factor of emotion in the "resting" state but still is suggestive of a trend toward greater increase in intrinsic or nonneurogenic resistance in those cases with the least residual sympathetic nerve tone The more "successful" the operation, then, the greater the apparent tendency to counteract neurogenic vasodilatation by the development of intrinsic, or nonneurogenic vasoconstriction There is no significant cor 581 interrupt sympathetic nerve outflow to the lower extremities permanently This may be due in part to some bridging of the nerve gaps, but also may be caused by the assumption of function of small nests of sympathetic ganglion cells in the anterior spinal nerve roots, the preand postganglionic fibers of which are not interrupted by the operation2 What is more, the degree of sympathetic nerve tone which returns is probably variable, if one can safely disregard the factors of atmospheric variation and emotion It is also clear that sympathectomy in some manner often produces an increase in nonneurogenic or intrinsic vascular resistance If the failure of these vessels to dilate after the Downloaded from by on November 18, 218 CASES (HYPERTENSION AFTER SYMPATHECTOMY) FIG 3 Vascular volume index (flowpressure ratio) after release of residual sympathetic nerve tone by indirect heating and tetraethylammonium chloride (5 mg per kilogram) compared with index after benzodioxane (1 mg per square meter of body surface) Black bars: Mean 245 Standard deviation 17 Standard error of the mean 24 White bars: Meals 215 Standard deviation 94 Standard error of mean 21 Standard error of difference of means 32 Significance ratio 9 relation between the difference in blood pressure before and after release of residual sympathetic nerve tone and the intrinsic resistance as measured by the blood flow level after indirect heating and tetraethylammonium chloride This tends to exclude incomplete release of sympathetic nerve tone as an important factor It is also unlikely that sympathetic nerve tone was more completely released in the hypertensive group than in the patients subjected to sympathectomy DISCUSSION It is clear that sympathectomy as ordinarily performed for hypertension does not totally s D <28, z2 2 2 :E 8 16C a > 8,6 4 2 L " BLOOD FLOW IN CC 1CM*ININ FIG 4 Difference in vascular volume index before and after release of sympathetic nerve tone correlated with blood flows after release of sympathetic nerve tone Correlation index is 7 administration of benzodioxane signifies the absence of sufficient circulating epinephrine to account for this intrinsic vascular narrowing, whether or not the denervated vessels are more sensitive to such stimulation, some other explanation must be sought for the phenomenon The possibilities are (a) sensitization of the denervated vessels to some circulating substance other than epinephrine, (b) changes produced by the operation in such components of tissue metabolism as hydration, salt content, or oxidation with a corresponding influence on vascular caliber and reactivity and (c) the development because of decreased nervous stimulation of atrophy of disuse and hence shortening of the circular arteriolar smooth muscle Although (a) and (b) are not completely excluded, the fact that the increased

6 582 5,EFFECT OF SYMPIATHECTOMY ON HALLUCAL CIRCULATION Downloaded from by on November 18, 218 intrinsic resistance develops gradually' and seems to be greater in those patients with less residual sympathetic nerve tone favors the third hypothesis, namely, that the greater the "success" of the sympathectomy the greater the increase in intrinsic resistance because of disuse atrophy and shortening of the circular smooth muscle of arterioles SUMMARY AND NCLUSIONS The hallucal circulation of patients subjected to sympathectomy for hypertension was studied Sympathetic nerve tone always returned to a variable extent after operation The sympathectomy, in addition, often produced an increase in intrinsic nonneurogenic vascular resistance This increase in resistance could not be reversed by benzodioxane and hence was probably not attributable to the effect of circulating epinephrine Since there was a tendency for greater increase in intrinsic vascular resistance when there was less return of sympathetic nerve function, such increase might have been caused by relative disuse atrophy and shortening of the circular smooth muscle of arterioles ACKNOWLEDGMENT The advice of Dr S Feitelberg and the technical assistance of Mr Ralph E Schwartz are gratefully acknowledged REFERENCES 1 LEWIS, T, AND PICKERING, G W: Circulatory changes in the fingers in some diseases of the nervous system, with special reference to the digital atrophy of peripheral nerve lesions Clin Sc 2: 149, RANDALL, MW C, ALEXANDER, W Fal, HERTZMAN, A B, Cox, J,W, AND HENDERSON, W P: Functional significance of residual sympathetic pathways following verified lumbar sympathectomy Am J Physiol 16: 441, 195 GRANT, R T: Further observations on the vessels and nerves of the rabbit's ear, with special reference to the effects of denervation Clin Sc 2: 1, JUDSON, W E, CULBERTSON, J W, TINSLEY, C M\I, LITTER, J, AND WILKINS, R W: The comparative effects of small intravenous doses of epinephrine upon arterial pressure and pulse rate in normotensive subjects and in hypertensivre patients before and after thoracolumbar sympathectomy J Clin Investigation 29: 145, MENDLOWITZ, M: Observations on the calorimetric method for measuring digital blood flow Angiology 1: 2417, : D)igital vascular resistance in normal, polycythemic and hypertensive states Circulation 3: 694, STEAD, W W, REISER, MI F, RAPOPORT, S, AND FERRIS, E B: The effect of sodium chloride depletion on blood pressure and tetraethylammonium chloride response in hypertension J Clin Investigation 27: 766, BARCROFT, H, AND WALKER, A J: Return of tone in blood vessels of the upper limb after sympathectomy Lancet 256: 135, W'ILKINS, R Mr, GREER, W E R, CULBERTSON, J W, HALPERIN, AI H, LITTER, J, BURNETT, C H, AND SMITHWICK, R H: Extensive laboratory studies of a patient with pheochromocytoma before and after successful operation Arch Int Med 86: 51, 195