The Swiss Cheese Model

Patients are typically not injured by a single event resulting from a single act of a careless individual. More often an underlying systems problem made the error possible, and numerous individual actions “fall through the cracks” of a system that does not catch them, resulting in error and harm. James Reason described the “Swiss cheese” model of error ( Fig. 11.1 ), in which he explained how numerous contributing factors are responsible for the ultimate harm. Reason developed this model to illustrate how analyses of major accidents and catastrophic systems failures tend to reveal multiple, smaller failures that led up to the actual adverse event. In the model, each slice of cheese represents a safety barrier or precaution relevant to a particular hazard. For example, if the hazard were wrong-site surgery, slices of the cheese might include processes for identifying the right or left side on radiology tests, a protocol for signing the correct site when the surgeon and patient first meet, and a second protocol for reviewing the medical record and checking the previously marked site in the operating room. Each barrier has “holes”; hence, the term Swiss cheese. For some serious events (e.g., operating on the wrong person) the holes will rarely align; however, even rare cases of harm are unacceptable. Reason’s model highlights the need to think of safety as a system—a set of organizational and cultural layers that influence and shape one another. Reason has eloquently summarized the process, stating “rather than being the main instigators of an accident, operators tend to be the inheritors of system defects created by poor design, incorrect installation, faulty maintenance, and bad management decisions. Their part is usually that of adding the final garnish to a lethal brew whose ingredients have already been long in the cooking.”

Swiss cheese model of organizational accidents.

(From Reason JT. Human Error . Cambridge, UK: Cambridge University Press; 1990.)

Fig. 11.2 illustrates the use of the Swiss cheese model to evaluate a real near-miss case involving the misidentification of an obstetric patient who nearly underwent the wrong procedure (an unwanted tubal ligation). It describes how the combination of numerous system errors came very close to allowing the wrong procedure to be performed. The events unfolded as follows:

• 1.
  

  A nulliparous woman in active labor at term arrived on the labor and delivery unit in severe pain. She spoke a foreign language and was poorly understood by the labor and delivery staff. No translator was called because her husband was helping with the translation.

  
  
• 2.
  

  Because the patient was in such severe pain, she rushed to answer all the questions and answered several incorrectly. As per hospital policy (due to HIPAA [Health Insurance Portability and Accountability Act of 1996] regulations), the husband was asked to leave the room while the history was being taken and was therefore not present to assist in the translation.

  
  
• 3.
  

  There was another patient on the labor and delivery unit with the same last name and a similar sounding first name. The hospital protocol for this occurrence was not followed. Patient initials, not last names, were listed on the labor and delivery “board,” so that other staff were unaware of the identical patient names.

  
  
• 4.
  

  The patient developed a nonreassuring fetal heart rate (FHR) tracing and was scheduled for urgent cesarean delivery. The obstetric resident physician informed the anesthesiologist of this decision and, mistaking the two patients with identical names, booked the case for a cesarean delivery plus bilateral tubal ligation. Unlike the other patient with the same name, the patient going to the operating room did not want or expect a tubal ligation.

  
  
• 5.
  

  The case was delayed because of a shift change, and the obstetricians urged the nurses to hurry. This caused friction between the nurses and obstetricians, and they did not work as a team. There was no “huddle,” and communication between labor and delivery staff and operating room staff was suboptimal.

  
  
• 6.
  

  The patient arrived in the operating room and was very anxious and crying. The anesthesiologist administered fentanyl 50 µg to calm the patient, and she became very sedated.

  
  
• 7.
  

  A “time-out” was performed, but it was not taken seriously. The patient was asleep and did not participate. The attending obstetrician was not present. Conversations continued during the time-out.

  
  
• 8.
  

  Following the flawed time-out, it was agreed that this patient was to undergo a primary cesarean delivery and tubal ligation. Her husband was not present during the time-out but was brought to the room immediately after this activity. The surgical procedure began.

  
  
• 9.
  

  The attending obstetrician arrived after the start of the procedure and questioned the planned tubal ligation, not because he knew about the second patient but because he was informed that this patient was nulliparous. Immediate investigation revealed that the patient was not supposed to receive a tubal ligation. A major error was narrowly averted.

“Swiss cheese” diagram of near-miss event illustrating how numerous layers/barriers to harm were breached and how these events almost resulted in permanent harm (permanent sterility) to the patient.

As in many such situations, a conglomeration of many missteps resulted in the potential for patient harm.

Medical Errors

Today there is widespread interest in changing the health care culture to build safer systems, including ensuring the appropriate physical work environment, developing redundancies in safety procedures and use of safety bundles, allowing health care workers to report their mistakes (including near misses) without fear of punishment, and providing mechanisms to learn from the experiences. None of these steps will achieve the ultimate goal of complete patient safety without the support of physicians as well as hospital administrators and other key stakeholders. In addition, although vital to improving the current condition, these steps do not obviate the need for well-trained and well-rested physicians and nurses. The American College of Obstetricians and Gynecologists (ACOG) Committee Opinion on Patient Safety in Obstetrics and Gynecology highlights the following seven objectives for patient safety:

• 1.
  

  Develop a commitment to encourage a culture of patient safety.

  
  
• 2.
  

  Implement recommended safe medication practices.

  
  
• 3.
  

  Reduce the likelihood of surgical errors.

  
  
• 4.
  

  Improve communication with health care providers.

  
  
• 5.
  

  Improve communication with patients.

  
  
• 6.
  

  Establish a partnership with patients to improve safety.

  
  
• 7.
  

  Make safety a priority in every aspect of practice.

In a different committee opinion, the ACOG also states that there is increasing awareness within the patient safety movement that fatigue and even partial sleep deprivation impairs performance. These goals and opinions relate to the anesthesia provider as well. Although the Accreditation Council on Graduate Medical Education (ACGME) has enacted restrictions on resident physician work hours to prevent sleep deprivation, there are no such limits on attending physician work hours. Rothschild et al. found that the risk for surgical complications was increased if attending physicians had slept less than 6 hours the night before the procedure.

Medical error has been defined as a “failure of a planned action to be completed as intended, or the use of a wrong plan to achieve an aim.” Communication problems are consistently identified as a leading cause of medical errors in obstetrics, and perceptions are often misaligned. The Joint Commission has found that although the majority of these events have multiple root causes, lack of effective communication along with leadership and human factors are often the primary causes of sentinel events. Several of the 2017 Joint Commission National Patient Safety Goals relate to error reduction on the labor and delivery unit ( Box 11.1 ). Departments of anesthesiology and obstetrics and gynecology should regularly review the national patient safety goals established by the Joint Commission. Hospitals are regularly surveyed to verify their compliance with these goals.

Although those working in health care have made great efforts to reduce preventable patient harm, the progress has not been as dramatic as necessary. Leape and Berwick, two “fathers” of the field of patient safety, suggested that the lack of progress following the release of the initial IOM report is a result of the “culture of medicine.” They, and others, believe that this culture is deeply rooted, both by custom and training, in autonomous individual performance. A recently published systematic review found evidence that interventions to improve teamwork, communication, and safety culture demonstrated improvements in patient outcomes. It is probable that systematic and appropriate use of medical simulation for improved training, along with other important changes to our systems, will facilitate the necessary cultural changes and lead to improved patient safety. Labor and delivery units are no different than other medical care environments, and most still have many opportunities to change culture and practice to optimize patient safety. Nabhan and Ahmed-Tawfik have suggested that the concept of patient safety in obstetrics is “not as strong as desirable for the provision of reliable health care.” In some units, a punitive culture still exists and results in suppression of error reporting, lack of proper communication, and failure of appropriate feedback. Obviously, this culture needs to change before we can significantly improve patient safety. Kacmar has opined that achieving the ideal of a culture of safety for all obstetric units requires multidisciplinary collaboration, frequent reassessment for areas of improvement, and a culture of openness to change when improvement opportunities arise.

Pronovost and Freischlag eloquently described the operating room environment when they stated that “operating rooms are among the most complex political, social, and cultural structures that exist, full of ritual, drama, hierarchy, and too often conflict.” These authors concluded that poor teamwork contributes prominently to most adverse events, including those in the operating room.