Secondary Hyperparathyroidism in Chronic Kidney Disease: Focus on Clinical Consequences and Vitamin D Therapies

Evaluation of alterations in length and calcification of the styloid process in patients with end-stage renal failure

OBJECTIVE

This study compared alterations in length and types of elongation and calcification of the styloid process (SP) between patients with end-stage renal failure (ESRF) who received renal transplantation, patients with ESRF undergoing dialysis, and a healthy control group.

STUDY DESIGN

The SPs of 58 patients who had undergone renal transplants, 58 patients who received dialysis treatment, and 58 healthy individuals were examined with panoramic radiographs. Length measurements were made from the apex to the base of the SP. Elongation types were classified into 5 groups: normal, non-segmented, pseudo-segmented, segmented, and non-continuous. Calcification types were classified into 4 groups: external, partial, nodular, and complete.

RESULTS

SP length was significantly greater in the renal transplantation and dialysis groups than in the control group (P < .001) and significantly longer in the renal transplantation group than in the dialysis group (P < .001). There was a significant difference between the groups regarding elongation types (P < .001), with the non-segmented type more frequent in the dialysis and renal transplant groups than in the control group. There was no significant difference in calcification types between groups (P = .225). Elongation and calcification types differed between sexes (P ≤ .008) CONCLUSIONS: Orofacial pain complaints in patients with ESRF should raise the suspicion of abnormal elongation and calcification of the SP, perhaps a manifestation of Eagle syndrome. It would be useful to evaluate the SPs of these patients clinically and radiographically.

Perioperative Concerns for Profound Metabolic Alkalosis During Kidney Transplantation: A Case Report

Introduction

Profound metabolic alkalosis is an uncommon consideration for the anesthetic management of kidney transplantation. Serum total carbon dioxide content and complex electrolyte abnormalities might be important diagnostic clues for the presence of metabolic alkalosis in the absence of arterial blood gas analysis.

Case Presentation

A 34-year-old female visited Gachon University Gil Medical Center, Incheon, South Korea during year 2015. She experienced aggravated renal function due to chronic hypokalemia and severe hypochloremic metabolic alkalosis, induced by laxative abuse, and underwent ABO incompatible kidney transplantation. Serum total carbon dioxide content remained high (about 60 mEq/L) over eight months of monthly follow-up prior to kidney transplantation.

Conclusions

The authors described their anesthetic experience of profound metabolic alkalosis with complex electrolyte abnormalities and provided a review of relevant literature.

Paricalcitol versus Calcitriol in the Treatment of Secondary Hyperparathyroidism in Hemodialysis Patients

Purpose

A mainstay treatment of secondary hyperparathyroidism has been the administration of vitamin D analogs. Paricalcitol is a vitamin D analog thought to reduce parathyroid hormone (PTH) levels with fewer effects on calcium (Ca) and phosphorous (P) levels than intravenous calcitriol. However, there are limited data directly comparing the 2 agents. The primary objective was to compare the efficacy of paricalcitol to calcitriol in hemodialysis patients. Secondary objectives evaluated the safety and direct costs associated with these agents.

Methods

This was a retrospective study of hemodialysis patients who received at least 8 weeks of both therapies from 2002 to 2004. Primary outcomes included the percentage of patients achieving greater than or equal to 50% reduction in baseline PTH levels; the change in PTH levels from baseline to the end of therapy; and time to achieve greater than or equal to 50% reduction in baseline PTH concentrations. Secondary outcomes included the percentage of patients experiencing hypercalcemia, hyperphosphatemia, or elevated Ca and P product; and the percentage of patients hospitalized secondary to these side effects.

Results

Calcitriol-treated patients showed a median reduction in PTH concentrations from baseline to the end of treatment phase of 8.3% versus paricalcitol reduction of 1.5%. This result was not statistically significant ( P = 0.08); however, it should be examined in a study powered to detect this difference. A similar number of patients in both treatment groups were able to achieve a greater than or equal to 50% reduction in baseline PTH concentrations but calcitriol-treated patients were more likely to achieve this primary end point faster than the paricalcitol-treated group (166 days vs 207 days, respectively, P = 0.18). The incidence of side effects between the agents was similar. There was a substantial difference in the annual drug cost between paricalcitol and calcitriol.

Conclusion

Paricalcitol did not seem to result in clear efficacy and safety benefit over calcitriol in this study. However, due to the study's retrospective design and potential for a type 2 error, as well as limited published data comparing this agent to calcitriol, additional research is required before paricalcitol becomes the standard of care in patients with chronic kidney disease and secondary hyperparathyroidism.

Vitamin D receptor activator selectivity in the treatment of secondary hyperparathyroidism: understanding the differences among therapies

Secondary hyperparathyroidism (SHPT) is a common and serious consequence of chronic kidney disease (CKD). SHPT is a complex condition characterised by a decline in 1,25-dihydroxyvitamin D and consequent vitamin D receptor (VDR) activation, abnormalities in serum calcium and phosphorus levels, parathyroid gland hyperplasia, elevated parathyroid hormone (PTH) secretion, and systemic mineral and bone abnormalities. There are three classes of drugs used for treatment of SHPT: (i) nonselective VDR activators or agonists (VDRAs); (ii) selective VDRAs; and (iii) calcimimetics. The VDRAs act on the VDR, whereas the calcimimetics act on the calcium-sensing receptor. Calcimimetics are commonly used in conjunction with VDRA therapy. By virtue of the differences in their chemical structure, the nonselective and selective VDRAs differ in their effects on gene expression, and ultimately parathyroid gland, bone and intestine function. Medications in all three classes are effective in suppression of PTH; however, clinical studies show that calcimimetics are associated with an unfavourable tolerability profile and hypocalcaemia, whereas nonselective VDRAs, and to a lesser extent selective VDRAs, are associated with dose-limiting hypercalcaemia and hyperphosphataemia. Selective VDRAs also have minimal undesirable effects on calcium absorption in the intestine, and calcium and phosphorus mobilisation in the bone compared with nonselective VDRAs. Calcium load in patients with CKD can lead to vascular calcification, accelerated progression of cardiovascular disease and increased mortality. High serum phosphorus levels are also associated with adverse effects on cardiorenal function and survival. Recent evidence suggests that VDRAs are associated with a survival benefit in CKD patients, with a more favourable effect with selective VDRAs than nonselective VDRAs. Paricalcitol, a selective VDRA, is reported to exert specific effects on gene expression in various cell types that are involved in vascular calcification and the development of coronary artery disease. This article examines the molecular mechanisms that determine selectivity of VDRAs, and reviews the evidence for clinical efficacy, safety and survival associated with the three drug classes used for treatment of SHPT in CKD patients.

Nonclassical Aspects of Differential Vitamin D Receptor Activation

The 'classical' effects of vitamin D receptor activator or agonist (VDRA) therapy for the treatment of secondary hyperparathyroidism in patients with chronic kidney disease primarily involves suppressive effects on the parathyroid gland, and regulation of calcium and phosphorus absorption in the intestine and mobilisation in bone. Observational studies in haemodialysis patients report improved cardiovascular and all-cause survival among those receiving VDRA therapy compared with those not on VDRA therapy. Among VDRAs, the selective VDRA paricalcitol has been associated with greater survival than nonselective VDRAs, such as calcitriol (1,25-dihydroxyvitamin D(3)). The survival benefits of paricalcitol appear to be linked, at least in part, to 'nonclassical' actions of VDRAs, possibly through VDRA-mediated modulation of gene expression. In cardiovascular tissues, VDRAs are reported to have beneficial effects such as anti-inflammatory and antithrombotic effects, inhibition of vascular smooth muscle cell proliferation, inhibition of vascular calcification and stiffening, and regression of left ventricular hypertrophy. VDRAs are also reported to negatively regulate the renin-angiotensin system, which plays a key role in hypertension, myocardial infarction and stroke. The selective VDRAs, paricalcitol and maxacalcitol, are associated with direct protective effects on glomerular architecture and antiproteinuric effects in response to renal damage. Paricalcitol regulates several cardiovascular and renal parameters more favourably than nonselective VDRAs. Complex nonclassical effects, which are not clearly understood, possibly contribute to the improved survival seen with VDRAs, especially paricalcitol.