Severe hypertension induces disturbances of renal autoregulation.

Abstract

To study if the severity of hypertension could be associated with disturbances of the autoregulation of renal blood flow and glomerular filtration, we compared the renal hemodynamic and functional responses to acute blood pressure reductions of a group of patients with moderate essential hypertension (n=10) with those of a group of patients with severe hypertension (n=10). Blood pressure was reduced to normal levels by a stepwise infusion of sodium nitroprusside, and effective renal blood flow (by 131 I-hippuran), glomerular filtration rate (by endogenous creatinine clearance), and filtration fraction were determined. After acute blood pressure normalization, effective renal blood flow and glomerular filtration rate were significantly reduced in patients with severe hypertension (-41.6±8J% and -44.7±6.8%, respectively,/><0.01 for both) but not in those with moderate hypertension (+4.9±9.1% and +62±133%, respectively, NS). Filtration fraction remained unchanged in both groups. These results show that severe but not moderate essential hypertensive patients have a displacement to the right of the lower limit of the renal autoregulation curve due to impaired vasodilation to maintain adequate renal blood flow during acute reductions of blood pressure. This impairment may be due to anatomic or functional defects of preglomerular vessels, or to both. Furthermore, the inability to maintain adequate glomerular filtration in these circumstances shows that patients with severe hypertension also have an impaired ability to adjust postglomerular vasomotor tone in the face of reductions in glomerular blood flow. (Hypertension

From cardiac output to blood flow auto-regulation in shock

“…There is evidence that in severe hypertensive patients, the elevated levels of blood pressure induce a displacement of the normal renal auto-regulation curve to the right. Almeida et al [21] reported that although patients with severe hypertension can preserve the auto-regulatory capacity in the hypertensive range of arterial pressure, they showed substantial reductions of effective renal plasma flow during acute normalization of blood pressure. These reductions were accompanied by decreases of a similar magnitude in glomerular filtration.…”

Pathophysiology of Arterial Hypertension: Insights from Pediatric Studies

“…Medullary blood flow, renal interstitial hydrostatic pressure and renal autacoids as angiotensins, kinins, prostaglandins and nitric oxide play an important regulatory role in the regulation of pressurenatriuresis [22][23][24]. Animal models and clinical studies of primary and secondary hypertensive states have been shown an alteration of the renal perfusion pressure-sodium excretion control mechanism, which means that an excessive increase of blood pressure is necessary to trigger the natriuresis in these situations [22,25,26].…”

“…It is a protective mechanism that maintains nephron function within a narrow range even in the presence of significant blood pressure variation [25,26]. It is a protective mechanism that maintains nephron function within a narrow range even in the presence of significant blood pressure variation [25,26].…”

Chronic Renal Insufficiency

“…However, in the presence of diabetes, hypertension, or reduced renal mass, autoregulation of RBF is impaired. [19][20][21] Consequently, if systemic blood pressure decreases, the afferent arteriole cannot dilate appropriately, leading to an acute decline in GFR. In addition, patients with chronic renal disease have limited ability to abruptly curtail sodium excretion in the face of extrarenalvolumedepletion,thuspotentially exacerbating the salt loss.…”

“…Renal parenchymal disease is the most common cause of malignant hypertension 34 and a further acute chronic decline in renal function can occur because of myointimal proliferation and fibrinoid necrosis of the renal vascular bed. 34 Although reduction of blood pressure in these circumstances often causes a further transient decline in renal function attributable to impaired autoregulation of RBF, [19][20][21] continued good blood pressure control can improve renal function in the long-term. 35 In fact, some patients who require dialytic support have been able to discontinue dialysis with adequate blood pressure control.…”