Deaths by horse kick...

A couple of years ago, I came across an editorial in the journal Anaesthesia that caught my attention - "Deaths by horsekick in the Prussian army - and other 'Never Events' in large organisations".  The editoral was written by Jaideep Pandit, who at the time was a Consultant Anaesthetist and Professor in the Nuffield Department of Anaesthetics at Oxford University Hospitals NHS Trust in England.  Dr. Pandit stated, "It was arguably the Prussian military that first recognised the notion of a 'never event' when it became concerned (in peacetime) about the number of its officers killed by horsekick in the cavalry."

The term Never Event was first introduced in 2001 by Ken Kizer, MD, former CEO of the National Quality Forum (NQF) to describe "particularly shocking" cases of medical error that should never occur in hospitals today.  Examples include, but are not limited to, surgeries performed on the wrong patient, surgeries performed on the wrong site (e.g. left versus right), an unintended retained foreign object in a patient after surgery, or the wrong procedure performed on a patient.  These medical errors should be largely preventable if a hospital follows existing national guidance and/or national safety recommendations on how an event can be prevented.  

The accidental death of a cavalry officer in the army from getting kicked by a horse was clearly a serious incident that could lower morale or adversely impact operational readiness.  Army cavalry officers required a lot of training, and experienced officers were not easy to replace.  Rather than blaming the victim for being too careless or the horse for being too vicious, the Polish mathematician Ladislaus Bortkiewicz conducted his own analysis, studying the death rates over a 20-year period (1875-1894).  In his book, Das Gesetz der kleinen Zahlen (in English: The Law of Small Numbers), Bortkiewicz noted that the data followed a Poisson distribution:

Classically, a Poisson distribution is a discrete probability distribution (similar, but different than the well-known Gaussian or normal distribution) that expresses the probability of a given number of events occurring in a fixed interval of time if these events occur with a known constant mean rate and independently of the time since the last event.  The Poisson distribution describes rare and more or less random events.  Bortkiewicz concluded that because deaths by horsekicks in the Prussian army cavalry followed a Poisson distribution, they could be assumed to have arisen completely by chance and not as a result of specific intent or design.  In other words, because they occurred purely by chance, they were largely not preventable.

Dr. Pandit's editorial was written in response to an article that appeared in that same issue of the journal Anaesthesia by I.K. Moppett and S.H. Moppett, "Surgical caseload and the risk of Never Events in England".  Moppett and Moppett surveyed all of the English acute hospitals in the National Health Service to determine the number of surgical Never Events and surgical caseload volumes for 2011-2014.  They noted that the number of Never Events followed a Poisson distribution.  

Moppett and Moppett also reviewed other hospital-wide safety metrics, such as the standardized mortality ratio (SMR).  The SMR is a ratio between observed deaths and expected deaths (based on patient acuity), so the SMR should ideally always be below zero (observed deaths less than expected deaths) and never above zero (observed deaths greater than expected deaths).  There was no association between the number of Never Events and the hospital-wide standardized mortality ratio.

Moppett and Moppett concluded, "The data support the hypothesis that Never Events should be viewed as rare, random events...The risk of serious harm from surgical Never Events in England is very low but not zero...Never Events are important, but as they are rare, apparently random events they are the wrong metric to gauge safety within the operating theatre."

By their very definition, Never Events are rare (thankfully).  Even if they do follow a Poisson distribution, that doesn't mean that they occur purely by chance.  Moppett and Moppett also wrote that "in some respects, our findings are no surprise - other things being equal, larger organisations should have more Never Events."  I don't think that is necessarily a true statement.  

So, what do we know?  First, at an individual patient level, a Never Event is likely to have a significantly adverse impact on both outcome and experience.  Second, at the hospital level, a Never Event may not negatively impact the standardized mortality ratio (which is an imperfect and arguably suspect marker of hospital quality in and of itself), but that doesn't mean that it should not be taken seriously.  Third, based on my own personal experience, these kinds of events are exceedingly rare.  However, when they do occur, it's usually because some best practice was not followed.

I've often stated that so-called High Reliability Organizations implement best practices in order to (1) decrease the chance that an error occurs and (2) minimize the impact of an error if it does occur.  What has worked for HROs can also work for hospitals.  Never Events should occur exactly as often as the name states - NEVER.