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Am Fam Physician. 2001;63(5):847

Current thinking about threats to patient safety caused by medical errors is often focused on the immediate consequences of mistakes in the hospital setting that affect specific aspects of care, such as testing procedures or medications. Some mistakes, however, become apparent distant from where they were committed and only after a lapse in time. The model of a toxic cascade organizes an approach to making U.S. health care safer for patients by locating upstream sources and downstream consequences of errors within a comprehensive, multilevel scheme.

A Toxic Cascade conceptualizes four levels of threats to patient safety. This model's application is not limited to any particular health care setting. Each part of the cascade occurs in different ways in all parts of the health care system. The cascade can evolve entirely within a single health care location or across organizational boundaries.

  • I. Trickles: Trickles make virtually no noise, leave behind little trace of their existence and are mostly absorbed unseen. The health system analogy is with errors such as misfiled records; these types of errors are ones that clinicians in any setting recognize, that may or may not affect patients directly and that do not cause direct harm. Their immediate consequences are inconveniences, frustrations and irritations that are frequently addressed as they occur, with no expectation that this level of intervention will avert similar problems in the future. Downstream consequences are usually unknown.

  • II. Creeks: Creeks are more obvious than trickles because they are seen and heard and create barriers to passage. The health care analogy is with mistakes such as prescribing drugs to patients who have an allergy as a contraindication. These mistakes worry clinicians because of the potential seriousness of the harm they could cause patients. The immediate consequences of these threats to patient safety are often dealt with in the setting in which they are detected. Upstream sources are seldom explored, and downstream consequences are often unknown.

  • III. Rivers: Too big to ignore, rivers may be quiet, but they redefine the landscape. The health system analogy is with mistakes such as undiagnosed fractures that result in actual harm to patients. People who are responsible for making health care safer for patients often respond immediately by dealing with the specific type of problem in one specific part of the health system. Clinicians, patients and courts tend to place the blame for these events on individuals, who may be punished. These individuals are followed by others at risk of making the same mistakes in the same systems, leaving upstream sources unexplored.

  • IV. Torrents: So powerful that to stop them seems impossible, raging torrents make a noise that drowns out conversation and makes critical thinking difficult. The health system analogy is with errors that kill people. The Institute of Medicine reported that 44,000 to 98,000 patients die of adverse effects of health care in hospitals each year. We do not yet know about torrents in other parts of the health system or know enough about the upstream origins of lethal problems.

From trickles to torrents, toxic cascades most likely exist in every health care setting. The comprehensive safety effort that patients deserve will discover the consequence and source of errors, incorporating all locations of care.

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