Why evidence-based medicine?

This chapter considers briefly what counts as ‘evidence’ and describes three historical strands, in medical science generally, in epidemiology and in clinical trials, that have converged to give rise to the concept of evidence-based medicine. It then returns to the randomized controlled trial as the fundamental building block of evidence-based practice. Finally, through considering whether all trials are equally useful, it demonstrates that discerning what is the best way to proceed in the clinical management of individual patients and problems is not necessarily a simple matter.     

Why don't fistulas mature?

Fistula maturation requires a compliant and responsive vasculature capable of dilating in response to the increased velocity of blood flowing into the newly created low-resistance circuit. Successful maturation to a high volume flow circuit capable of sustaining hemodialysis typically occurs within the first few weeks after creation. Failure to achieve maturation within 4-8 weeks should prompt a search for reversible etiologies; however, an accepted definition of maturation, particularly for patients not yet on dialysis remains elusive. The most commonly identified etiology is neointimal hyperplasia typically occurring in the juxta-anastomotic vein. However, failed maturation has also been reported secondary to impaired arterial and venous dilation and accessory veins. The exact frequency of each of these etiologies is unclear. Understanding the etiologies of impaired fistula maturation will focus future studies of targeted interventions to improve the rate of fistula maturation and increase the number of dialysis patients with a functioning autogenous fistula.