Interpretation and review of health-related quality of life data in CKD patients receiving treatment for anemia

Recent evidence suggests that targeting higher hemoglobin values with erythropoiesis stimulating agents (ESAs) may lack mortality benefits and may even result in adverse cardiovascular complications when used in chronic kidney disease patients. However, ESAs are frequently reported to result in improvements in health-related quality of life (HRQOL). The purpose of this review is to evaluate the magnitude and nature of ESA-associated improvements in HRQOL, as well as to understand how to interpret the clinical significance of HRQOL data. HRQOL findings should be analyzed not by statistical significance but rather by using a minimal clinically important difference approach, or, alternatively, a distribution-based approach (such as Cohen's effect size). HRQOL domains that are most improved with ESAs relate to physical symptoms, vitality, energy, and performance; domains of social functioning and mental health show modest improvement, whereas the domains of emotional functioning and pain show very little improvement. Additional domains not measured by commonly used instruments (such as the SF-36) that have been shown to improve with ESAs include sleep, cognitive functioning, and sexual functioning. The maximal increase in HRQOL per incremental increase in hemoglobin appears to occur in the range of 10-12 g/dl. Beyond this range, additional normalization of hemoglobin (to 12-14 g/dl) results in continued (albeit blunted) improvements in HRQOL.

Mechanisms of action of acetazolamide in the prophylaxis and treatment of acute mountain sickness

Acetazolamide, a potent carbonic anhydrase (CA) inhibitor, is the most commonly used and best-studied agent for the amelioration of acute mountain sickness (AMS). The actual mechanisms by which acetazolamide reduces symptoms of AMS, however, remain unclear. Traditionally, acetazolamide's efficacy has been attributed to inhibition of CA in the kidneys, resulting in bicarbonaturia and metabolic acidosis. The result is offsetting hyperventilation-induced respiratory alkalosis and allowance of chemoreceptors to respond more fully to hypoxic stimuli at altitude. Studies performed on both animals and humans, however, have shown that this explanation is unsatisfactory and that the efficacy of acetazolamide in the context of AMS is likely due to a multitude of effects. This review summarizes the known systemic effects of acetazolamide and incorporates them into a model encompassing several factors that are likely to play a key role in the drug's efficacy. Such factors include not only metabolic acidosis resulting from renal CA inhibition but also improvements in ventilation from tissue respiratory acidosis, improvements in sleep quality from carotid body CA inhibition, and effects of diuresis.