**1. Introduction**

Chronic kidney disease (CKD) and its evolution to end-stage kidney disease (ESKD) are a rapidly increasing global health and healthcare burden [1]. In 2016, CKD ranked 13th leading cause of death and is projected to be the 5th leading cause of death globally in 2040 [2]. Worldwide, more than 850 million people suffer from CKD, acute kidney injury, and renal replacement therapy (RRT), a figure that is twice the estimated number of individuals with diabetes across the world [3]. Hemodialysis (HD) is the major mode of treatment for RRT worldwide. Advances in hemodialysis machine technology, dialyzers, and consumables have enabled hemodialysis to evolve from a treatment limited to a minority of patients with acute kidney failure in the 1950s to a life-sustaining routine outpatient treatment for multitudes of patients with CKD globally [4, 5].

Although the safety profile of hemodialysis has been satisfactory over the years, various errors such as dialysis machine errors, dialysate composition errors, and errors in dialysis techniques have been reported [6]. Hemodialysis has been associated with the highest mortality rates, followed by kidney transplantation and peritoneal dialysis [7, 8]. Given that hemodialysis patients are a high-risk population group, an error could have catastrophic consequences for such patients [9]. Patient safety during dialysis is thus a critical topic as it is the foundation of high-quality healthcare and minimal patient mortality. Dialysis facilities are complex as they involve providers from numerous disciplines and the use of advanced technology to care for patients with many serious illnesses. As organizations get more complex, the potential for error rises and possible risks need to be identified and prioritized [10].

Errors during dialysis care can result to harm and death. Numerous studies have detailed the increased risk of errors and their unintended consequences among patients undergoing life-sustaining dialysis [11–15]. Some risks are readily apparent in dialysis facilities, with membrane reuse, water quality, and infection control being key areas of safety risk. Other risks may not be as readily apparent, and data-driven efforts have helped to identify and establish safety measures [10]. According to Kliger, (2015), the most common sources of morbidity during dialysis are human factors at the machine interface and suboptimal communication among caregivers. Dialysis machines are seldom a major source of error and morbidity among patients undergoing dialysis. Other causes of possibly reversible adverse medical outcomes during dialysis include hyperkalemia, medication errors, access-related errors, infections, and patient falls [15]. A surveillance report from the United Kingdom over a period of 30 months indicated that there were 31 adverse incidents and five risks reported to UK authorities, of which 42% were from dialysis centers. About 36% of the incidents were due to failure of dialysis techniques or dialysis machine usage, 22% were due to failure of dialysis equipment or disposables, 19% were due to failure of dialysis machines, and 19% were attributed to medication errors [5].

Evidence suggests that attention to some of the highest-risk domains that patients are exposed to could offer insight into processes of care needed to reduce the risk of error and the effect of medical mistakes on patients. This chapter aimed at identifying and describing the type and frequency of medical errors and adverse events in hemodialysis units.
