Adverse outcomes are injuries arising from patients’ underlying diseases whereas adverse events (or harms) are injuries resulting from medical care. There are two types of adverse events (AE): preventable and non-preventable.

• Preventable AE are characterized by unintended physical injury resulting from the absence of indicated medical treatment or contributed by medical care. An example of a preventable AE would be an elder who develops herpes zoster and whose physician did not counsel the patient to be immunized.
• Non-preventable AE occur when patients experience harm from their medical care in the absence of any errors. An example of non-preventable AE would be explained complications of surgery.

Unsafe acts are known as violations and errors.

• Violations are purposeful deviations from an operating procedure, standard or rule.
• An error is non-purposeful and results from doing something wrong or failing to do the right thing, leading to undesirable patient outcomes. There are three types of errors: slips, lapses, and mistakes.
  • A slip is observable by others and an example is accidentally pushing the wrong button on the glucose meter resulting with units displayed in mmol/L instead of the standard mg/dL.
  • A lapse is not observable and is related to memory failures such as failing to chart an administered medication.
  • A mistake is an action that is intended but is the incorrect action, such as having a patient undergo an abdominal x-ray when an abdominal CT scan was the needed study (5).

A systems way of thinking acknowledges that even thoughtful humans make errors and concludes that safety depends on creating complex organizations (systems) that anticipate errors and either prevent or detect them before they cause harm. Human factors engineering is the study of the interrelationship between humans and their environment and all the factors that make it easier to do the work in the right way. This field uses anatomy, physiology, physics, and biomechanics to understand how people perform in their environment under different circumstances in order to improve quality of care (6). The “Swiss cheese model” (SCM) illustrates how analyses of major accidents and systems failures tend to reveal multiple, smaller failures leading up to the actual hazard (2). The analogy relates to holes lining up in consecutive pieces of Swiss cheese.

Root Cause Analysis (RCA) and cause and effect (fish bone) diagrams can assist in identifying main causes for the observed patient harm.

• RCA is a retrospective systematic approach to dissecting an error, investigating all the relevant facts to understand the “root” cause of an event and identify system flaws. By identifying these systems factors, one can identify and suggest solutions to prevent similar errors from causing harm. RCA works by first identifying what happened in the order it occurred using a flow chart. The group must then determine what should have happened and the safest, most efficient flow of events in ideal conditions.
• Cause & effect analysis involves organizing possible causes into general categories such as: people, equipment, environment and processes. For each category, it is helpful to ask why up to 5 times to get the underlying root cause of that subcause. Visual representations show a problem statement (the fish’s head in the fish bone diagram) centered on the right hand side of a page, with lines (cause categories) branching off a main trunk extending to the left edge of the page. Subcauses then branch off the main cause categories, hence giving the appearance of a fish skeleton and leading to the term fishbone diagram. Using the diagram, casual statements can be developed as well as a list of recommended actions to prevent the future recurrence of the event.