Plasma renin activity in end-stage kidney disease

Clinical and molecular correlation defines activity of physiological pathways in life-sustaining kidney xenotransplantation

Porcine kidney xenotransplantation is accelerating towards clinical translation. However, despite the demonstrated ability of porcine kidneys to remove metabolic waste products, questions remain about their ability to faithfully recapitulate renal endocrine functions after transplantation. Here we analyze xenograft growth and function of two kidney dependent endocrine pathways in seventeen cynomolgus macaques after kidney xenotransplantation from gene edited Yucatan minipigs. Xenograft growth, the renin-angiotensinogen aldosterone-system, and the calcium-vitamin D-parathyroid hormone axis are assessed using clinical chemistries data, renin activity and beta-C-terminal-telopeptide assays, kidney graft RNA-sequencing and serial ultrasonography. We demonstrate that xenografts transplanted from minipigs show only modest growth and do not substantially contribute to recipient RAAS pathway activity. However, parathyroid hormone-independent hypercalcemia and hypophosphatemia are observed, suggesting a need for close monitoring and timely intervention during human testing. Further study of these phenotypes is warranted in designing prospective clinical trials.

The perioperative management of simultaneous bilateral nephrectomy with renal transplantation: a case series

Purpose

Bilateral nephrectomy is performed at times with renal transplantation. Though surgical indications and timing of these two procedures have been described, there are no large case series describing the anesthetic management of these cases. We sought to describe our experience.

Methods

We performed a historical cohort study on 54 consecutive cases of simultaneous bilateral nephrectomy with renal transplantation at a single, tertiary-care medical centre. Descriptive statistics were used.

Results

The most common etiology of kidney disease involved was autosomal dominant polycystic kidney disease at 52/54 (96%) cases. All patients received grafts from living donors. An arterial line was placed in 44 (81%) and a central venous catheter in 16 (30%) subjects. At least one vasopressor infusion was used in 44 (81%) cases and 37 (69%) patients required admission to the intensive care unit (ICU). Of this subset, 30 (81%) were admitted for ongoing vasopressor support and six (16%) for hemodynamic monitoring. All patients were extubated in the operating room upon completion of the procedure. Median [interquartile range (IQR)] ICU length of stay (LOS) was 0.9 [0.7–1.4] days and total hospital LOS was 4.4 [4.3–5.4] days. There were no cases of mortality at 30 days or of postoperative dialysis.

Conclusions

Adult patients undergoing simultaneous bilateral nephrectomy with renal transplantation often developed perioperative hypotension requiring vasopressor infusions and postoperative transfer to the ICU. This is possibly due to a temporary loss of the renin-angiotensin system. Despite this, patients most commonly were transferred to the floor on postoperative day 1 and had successful outcomes with no mortality at 30 days.

Hypocholesterolemia is a risk factor for reduced systemic vascular resistance reactivity during hemodialysis

Intradialytic hypotension (IDH) is associated with high mortality. Peripheral vascular resistance and circulating blood volume are important factors in IDH; however, the effects of hemodialysis (HD) on vascular resistance in IDH remain unclear. We herein performed a retrospective observational cohort study to investigate changes in and factors related to vascular resistance during HD. A total of 101 HD patients were divided into two groups (Decreased blood pressure (BP) during HD group: N = 19, Nondecreased BP group: N = 82), and cardiac output was measured with electrical velocimetry (AESCLON) for 3 h. The systemic vascular resistance index (SVRI) was significantly decreased in the Decreased BP group, while the cardiac index was similar in both groups. A multivariate regression analysis identified hypocholesterolemia as a predictor of reduced vascular resistance reactivity during HD. Furthermore, a correlation was found between changes in the SVRI and cholesterol levels in patients with a higher Geriatric Nutritional Risk Index (GNRI) but not in those with a lower GNRI. The present results suggest that hypocholesterolemia contributes to reducing systematic vascular resistance reactivity during HD, which is an important predictor of a reduction in BP during HD. The relationship between hypocholesterolemia and vascular resistance may involve mechanisms other than malnutrition.

Intra-individual comparison of captopril and enalapril in patients undergoing regular haemodialysis

The acute and long-term efficacy, tolerance and safety of two orally active angiotensin converting enzyme (ACE) inhibitors, captopril (C) and enalapril (E) were compared in patients on regular haemodialysis (RHD). C and E were successively administered for 6 months to 8 RHD patients with hypertension unresponsive to fluid withdrawal and conventional antihypertensive therapy. The fall in blood pressure after a starting dose of 25 mg C or 5 mg E was of the same magnitude. It was not correlated with the initial PRA levels, which were normal in all patients. The mean daily dose of ACE inhibitor was 45 +/- 28 mg during the C period and 19.4 +/- 17.6 mg at the end of the E period. Three patients required additional treatment, comprising beta-blockers and/or calcium antagonists. The individual daily dose of ACE inhibitor, the need for additional treatment and the antihypertensive response achieved were highly correlated during both study periods. During C administration 4 out of 8 patients presented a taste disturbance, which disappeared 2 weeks after substituting E for C. Serum electrolytes, liver enzymes, haemoglobin concentration and white cell and platelet counts remained unchanged throughout both study periods. It is concluded that RHD patients with hypertension are responsive to ACE inhibitors, C and E being equally effective.

Adrenergic regulation of blood pressure in chronic renal failure

Previous investigations have suggested that significant hypotension during hemodialysis may result from abnormalities of sympathetic nervous system activity. To further evaluate these phenomena, plasma dopamine beta-hydroxylase (D beta H) and cold pressor test (proposed indexes of efferent sympathetic nervous system activity) and amyl nitrite inhalation (an index of the entire baroreceptor reflex arc) were studied in two groups of patients: group I, patients exhibiting a mean arterial pressure decrease to less than 70 mm Hg during less than 10% of dialyses; group II (hemodialysis hypotension), patients with a mean arterial pressure decrease to less than 70 mm Hg during more than 90% of dialyses. The groups were similar with respect to plasma renin activity, renin response to ultrafiltration, age, duration of dialysis, nerve conduction velocity, plasma protein concentration, hematocrit, dialysis weight change, resting heart rate, sex, race, blood pressure and heart rate response to cold pressor test, and 125I-albumin plasma volume. Supine mean arterial pressure was higher in patients with hemodialysis hypotension than in patients without hemodialysis hypotension (group I) both before and after dialysis. Plasma D beta H activity was significantly higher in patients with hemodialysis hypotension (group II) than in group I both before and after dialysis. Amyl nitrite inhalation, expressed as change in delta R-R interval/mean arterial pressure decrease, was less in hemodialysis hypotension patients. These results suggest that hemodialysis hypotension may result from a lesion in the baroreceptors, cardiopulmonary receptors, or visceral afferent nerves. Furthermore, elevated mean arterial pressure in patients with hemodialysis hypotension may be neurogenic in origin, as reflected by plasma D beta H activity, and appears similar to the hypertension that follows baroreceptor deafferentation of experimental animals.