This Month in AJKD

Article Outline

• In the Literature: Vasopressin V2 Receptor Antagonists in Hyponatremia
• Acute Kidney Injury After Cardiovascular Surgery
• Cognitive Function in Hemodialysis Patients
• Rethinking Urea as an Adequacy Marker

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In the Literature: Vasopressin V₂ Receptor Antagonists in Hyponatremia 

See Madias, pages 184-187.

In this issue, Dr Madias discusses the recent study by Schrier et al in the New England Journal of Medicine, which examines Tolvaptan, an oral vasopressin V₂ receptor antagonist, and its effectiveness in raising serum sodium concentration in patients with euvolemic or hypervolemic hyponatremia. Madias stresses that while recent studies suggest that aquaresis via nonpeptide vasopressin V₂ receptor antagonists will emerge as the main treatment option of euvolemic and hypervolemic hyponatremia, additional research is needed on the following: the safety and efficacy of vasopressin V₂ receptor antagonists in patients with syndrome of inappropriate antidiuretic hormone (SIADH), congestive heart failure, or cirrhosis; the potential consequences of chronic activation of the unblocked vasopressin V_1α receptor on blood vessels and the heart; and why hyponatremia fails to respond to these agents in a substantial number of patients.

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• Reproduced with permission from Schrier R, et al: Tolvaptan, a selective oral vasopressin V₂ receptor antagonist, for hyponatremia. N Engl J Med 355:2099-2112, 2006. ©2006 Massachusetts Medical Society.

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Acute Kidney Injury After Cardiovascular Surgery 

See Welten et al, pages 219-228 and Onorati et al, pages 229-238.

Decreased kidney function is a well-known complication of cardiothoracic surgery and is associated with increased long-term mortality. However, little is known about the effects of kidney injury during surgery, where kidney function transiently deteriorates but returns to baseline values within 3 days. In this issue, Welten et al evaluated kidney function in 1,324 patients undergoing cardiac surgery. They found that 30-day mortality was highest in those patients with persistent worsening of kidney function (HR 7.3, 95% CI 2.7 to 19.8), but there was also an increased risk of mortality in patients with temporary worsening (HR 3.7, 95% CI 1.4 to 9.9). Also in this issue, Onorati et al describe a method to prevent temporary acute kidney injury during cardiothoracic surgery. They randomized 100 patients undergoing cardiopulmonary bypass surgery with an intra-aortic balloon pump (IABP) either to pulsatile or nonpulsatile perfusion during surgery. Those patients assigned to pulsatile perfusion had significantly lower daily diuretic use, lower lactate levels, and higher estimated glomerular filtration rate after surgery as compared to those assigned to nonpulsatile perfusion.

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Cognitive Function in Hemodialysis Patients 

See Murray et al, pages 270-278.

Hemodialysis patients are at risk for acute confusion during dialysis due to hemodynamic changes and large solute and fluid shifts, yet the extent to which global cognitive function varies over the dialysis cycle is unclear. In this issue, Murray et al measured cognitive function in 28 hemodialysis patients at 4 time points (1 hr before dialysis, 1 hr into dialysis, 1 hr after, and the next day). The composite score of the different cognitive tests was significantly lower during dialysis as compared to shortly before the session or on the next day (P<0.001 for both comparisons). The authors note the importance of this finding, particularly since many clinical assessments and care recommendations occur during the dialysis session, which may be the time when the patient is most confused and has the greatest difficulty comprehending or remembering important information.

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Rethinking Urea as an Adequacy Marker 

See Eloot et al, pages 279-288 and Lowrie, pages 181-183.

Adequacy of hemodialysis is determined by the reduction in concentrations of uremic retention solutes during the dialysis treatment. Although urea is the current standard marker for small-molecule removal, few studies compare the kinetics of urea with those of other small water-soluble uremic compounds. In this issue, Eloot et al compared plasma and erythrocyte reduction ratios of several guanidino compounds and urea. They found that the plasma and erythrocyte reduction ratios varied widely, thus suggesting that urea is not necessarily representative of kinetic behavior of other uremic retention compounds. An accompanying editorial by Dr Lowrie defends the use of urea as a marker for dialysis dose. He re-examines the concept of solute kinetics to quantify dialysis dose, reviews clinical trials of dialysis dose to clinical outcomes, and suggests a new method to quantify and prescribe dialysis dose.

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