Baroreflex Sensitivity in Patients on Long-Term Haemodialysis

Abstract

1. Serial studies of the baroreflex control of heart rate (baroreflex sensitivity) were made in thirty-two patients on long-term haemodialysis by relating the reflex slowing of the heart to the arterial pressure rise produced by repeated sudden injections of phenylephrine.2. Baroreflex sensitivity was less in the older patients and in those with higher pressures. The response was about 50% of that found previously for other subjects of comparable ages and arterial pressures without renal failure.3. Haemodialysis improved reflex sensitivity over the long term, but did not have any consistent immediate effect. 4. Patients who had malignant hypertension in the past had lower reflex sensitivities than others (with similar ages and pressures at the time of study) whose blood pressures had never been raised, but there were individual exceptions. 5. Reflex sensitivity changed very little with different blood pressures in any one subject.6. Three patients in whom hypertension was thought to have preceded renal failure had reflex sensitivities similar to eleven others in whom the hypertension was secondary to renal disease. 7. Reflex sensitivity was no different in three patients whose blood pressure could be controlled only by bilateral nephrectomy from that in others in whom the pressure could be controlled by salt restriction.8. Reflex sensitivity was slightly reduced in two patients studied in the diuretic phase of acute renal failure; it was markedly reduced in a third who was also pregnant.

Adrenergic regulation of blood pressure in chronic renal failure.

“…The results of previous studies of autonomic function in patients with chronic renal failure are limited and have yielded results which are difficult to compare with the present observations (5,6,9). Kersh (5,6,9).…”

“…There was no obvious localization of the autonomic defect and no description of blood pressure patterns before and after hemodialysis treatment. Other groups have reported a baroreceptor de-fect in all hemodialysis patients but failed to relate this proposed abnormality to blood pressure regulation during dialysis and the interdialytic interval (6,9). In the present investigation of a well-defined group of chronic renal failure patients, we have attempted to further localize an autonomic nervous system defect and to relate this abnormality to blood pressure patterns before, during, and after hemodialysis.…”

“…Investigations of the sympathetic nervous system are limited and have either failed to localize an autonomic lesion or neglected any possible relationship of the aforementioned defect with clinical behavior on hemodialysis (5)(6)(7)(8)(9). The results of two investigations suggest that severe hypotension during hemodialysis may be related to autonomic neuropathy, reduction in central blood volume, or lower plasma oncotic pressure (5,7).…”

Early Sympathetic Activation in the Initial Clinical Stages of Chronic Renal Failure

“…14,29 This hypothesis, however, is not supported by the finding that arterial baroreceptor modulation of adrenergic outflow is preserved in renal failure, 13 at variance from arterial baroreflex modulation of heart rate, which depends on the vagus and is markedly impaired in this condition. 30,31 It is, on the other hand, possible that other reflex mechanisms modulating adrenergic drive are involved. This may be the case for the reflex influences stemming from volume-sensitive receptors located within the cardiac chambers, of which the inhibitory function on sympathetic drive is drastically impaired in chronic renal failure.…”

Cardiovascular responses to upright tilting in hypertensive patients, with and without renal impairment and before and following nisoldipine treatment.

“…Patients with hypertension tend to have a lower baroreceptor reflex sensitivity than comparable normotensive subjects (Bevegard et al, 1980;Bristow et al, 1969;Pickering et al, 1972) and this may lead to an impaired orthostatic tolerance (Cuche et al, 1974;Esler & Nestel, 1973;Frolich et al, 1967;Lazarus et al, 1973). When hypertension is complicated by renal impairment, orthostatic tolerance may be even further reduced (Lilley et al, 1976).…”