A medical error is a preventable adverse effect of medical care, whether or not it is evident or harmful to the patient.[1]  Among the problems that commonly occur during providing health care are adverse drug events and improper transfusions, misdiagnosis, under and over treatment, surgical injuries and wrong-site surgery, suicides, restraint-related injuries or death, falls, burns, pressure ulcers, and mistaken patient identities. High error rates with serious consequences are most likely to occur in intensive care units, operating rooms, and emergency departments. Medical errors are also associated with extremes of age, new procedures, urgency, and the severity of the medical condition being treated.

The Institute of Medicine’s (IOM) legendary report in 1999, "To Err is Human," estimated 98,000 iatrogenic deaths making it the sixth leading cause of death in the U.S. A later study in 2010 yielded almost twice that many deaths, at 180,000. The most recent study in 2013 suggested the numbers range from 210,000 to 440,000 deaths per year. The latter number would make it the third leading cause of death after heart disease and cancer.[2] However, these numbers can only be estimated because medical records are often inaccurate and providers might be reluctant to disclose mistakes.  

One of the 1999 IOM report’s main conclusions is that the majority of medical errors do not result from individual recklessness or the actions of a particular group. More commonly, errors are caused by faulty systems, processes, and conditions that lead people to make mistakes or fail to prevent them. For example, stocking patient-care units in hospitals with certain full-strength drugs, even though they are toxic unless diluted, has resulted in deadly mistakes. Thus, mistakes can best be prevented by designing the health system at all levels to make it safer--to make it harder for people to do something wrong and easier for them to do it right. Of course, individuals should be still held accountable when an error can be attributed to them.  As an example, anchoring bias (persistence with an initial diagnostic impression despite evidence of another diagnosis) is a major source of diagnostic error.  When an error occurs, however, blaming an individual does little to make the system safer and prevent someone else from committing the same error.[1]

The nine most common medical errors in the United States in 2014, by occurrence are: adverse drug events, catheter-associated urinary tract infection (CAUTI), central line-associated bloodstream infection (CLABSI), injury from falls and immobility, obstetrical adverse events, pressure ulcers, surgical site infections (SSI), venous thrombosis (blood clots), and ventilator-associated pneumonia (VAP).[3]

The November 2016 issue of Risk Management Monthly (Volume 10, Number 11) extracted highlights from The Emergency Medicine Closed Claims Study from The Doctors Company that analyzed 332 closed claims in emergency medicine in 2007-2013.  The major findings were:

1. Issues related to diagnosis constituted the majority of cases.  These included failure to diagnose, delayed diagnosis or an incorrect diagnosis.  This could involve one or more of the following:  failure to establish a differential diagnosis, failure to order diagnostic tests, failure to address abnormal findings, failure to consider available clinical information.  Other issues adversely influencing the diagnostic process were a failure to obtain a consult and a premature discharge from the ED.  The most frequently misdiagnosed conditions included acute cerebral vascular accident, myocardial infarction, spinal epidural abscess, pulmonary embolism, necrotizing fasciitis, meningitis, testicular torsion, subarachnoid hemorrhage, septicemia, lung cancer, fractures, and appendicitis. The study identified specific factors that contributed to the patient injury.[4]
2. Contributing factors in medical errors included failure to order appropriate tests and address abnormal results, and failure to use clinical information and establish the differential diagnosis were cited.  Patient characteristics such as obesity (led to skipping specific exam elements), non-adherence to treatment plans and follow-up appointments, and poor patient hygiene also contributed.  
3. Communication issues among providers led to medical errors, and these included:  failure to communicate, failure to review the medical record, poor professional rapport, and communication between providers and the patient/family including not using qualified interpreters when applicable.  
4. A summary of the study's tips for avoiding diagnostic error:  Avoid first impression or intuition-based diagnoses.  Complete and document a thorough differential diagnosis for each patient.  Ensure that all specialists who are called to evaluate patients in the ED receive a comprehensive summary of the clinical picture.  Practice effective handoffs.  The handoff discussion should include clear delegation of the individual who has responsibility for review and follow-up of all test results.[5]  

A study by Sklar, D.P., et al., addressing unanticipated deaths occurring within seven days after emergency department discharge made several observations.  There were 30 deaths per 100,000 discharges, half of which were unexpected but related to the ED visit and 60% of which involved a possible error.  There were four recurring themes:

1. Atypical presentations of unusual problems
2. Chronic diseases with decompensation.
3. For nearly all of the unexpected deaths, vital signs were abnormal at discharge (most often tachycardia).
4. Mental disability or psychiatric problems were frequent.  The study reported that such patients received fewer diagnostic tests and less pain relief and that follow-up was unclear in patients with chronic psychiatric diagnoses.  Another way to look at this is to remember that a psychiatric illness does not somehow "protect" a patient against developing a new medical condition.  It often is the case that those with underlying psychiatric conditions are more at risk to develop new, significant illnesses.  These may be even difficult to appreciate because of the bias often present when evaluating patients with psychiatric illnesses.[6]

The article Medical Malpractice Liability in the Age of Electronic Health Records cites three phases of malpractice risk associated with EHR systems:

1. Implementation phase.  During this, physicians are learning to use a new system.  Inadequate training, the biggest problem occurring during this phase, can create new error pathways.  Various intricacies of the different systems might defy standard logic, causing erroneous diversions by the user.
2. Transition phase.  During the transition from paper to a computerized system, records are frequently divided, and procedures to avoid errors are often not implemented.  User errors can create incorrect or missing data entries, and gaps in documentation and communication.
3. Mature phase.  Systemwide bugs and failures can occur during the mature phase (e.g., is tech support immediately available when the system goes down at 2 am), creating departmental chaos and significantly interfering with documentation.[7]