Just 3 weeks after the initial WHO checklist study was published in 2009, the United Kingdom implemented it on a national scale. In 2011, Nevada in the USA was the first state to mandate the use of a surgical checklist in its hospitals. To date, a total of 26 countries have implemented the WHO checklist on a national scale, whilst others are using locally adapted versions.

The WHO checklist underwent an international pilot at 8 hospitals in 8 cities across all continents between 2007 and 2008. Its use demonstrated a 36 % improvement in the rate of overall complications and decrease in death rates by 47 % [13]. Furthermore, the WHO checklist has been associated with significantly improved rates of mortality and complications following implementation in rural and resource-poor settings, which was a documented criticism of the original study [14]. Additional studies exploring surgical checklists have also reported significantly improved mortality though with a smaller overall effect [15, 16].

However, these positive effects have not been universal. In 2014, the statewide mandatory implementation of a surgical safety checklist in Ontario, Canada, was not associated with any improvement in mortality or complication rates [17]. Whilst there have not been any reported direct harms of surgical safety checklists, there are concerns that poor implementation strategies, low rates of compliance and decreased staff vigilance may adversely affect their efficacy [18]. Furthermore, several of the studies have been questioned regarding their pre-post intervention methodology as the inference of causation is not necessarily possible using this study design.

There are multiple theories as to how surgical safety checklists may improve surgical care. As the checklist involves changes in both the system of working and the behaviour of people working within the system, the underlying mechanism of improvement is likely to be multi-factorial. Common theories include the following:

In addition to the outcomes reported above, surgical safety checklists have been reported to improve communication within operating theatre teams, through improved teamwork and the use of debriefing [19]. Significantly positive changes in safety culture have been identified after the implementation of surgical safety checklists in Europe [20, 21].

One of the main controversies over surgical safety checklists is the uncertainty regarding whether the observed improvements in patient outcomes are directly attributable to the content of the checklist or the behaviour changes it may cause. The improved communication and vigilance of surgical staff may play a crucial role in the ongoing success of checklists as they complete their transition from novelty to longstanding tradition in surgery. The signs are encouraging though: checklists have been in use in the aviation since the 1930s and their effectiveness is still enormously valued [22].

A further important issue regarding the efficacy of checklists is compliance. One of the principal criticisms of the Ontario checklist study is that its implementation was mandatory [17, 23]. The method with which a checklist is implemented is thought to be crucial to its future effectiveness. Visible senior leadership and an institutional commitment to quality improvement have been cited as vital factors in ensuring compliance with, and the overall success or failure of, a surgical checklist [24].

Following this, the checklist has been adapted into various forms including wrong-site surgery checklists and anaesthetic equipment checklists. These checklists were implemented in multiple institutions throughout 2009 and 2010.

A “comprehensive surgical safety system” dubbed the SURPASS checklist was also developed to address the other half of adverse events that occur outside the operating room and thus covers the whole patient journey [25]. The SURPASS checklist was also associated with improved outcomes in a controlled pre-post intervention study with its introduction to six hospitals in the Netherlands halving in-hospital mortality [26]. Similarly, when adopted as part of a wider team-training program, checklists have been associated with improved morbidity and mortality [19, 27].

Outside of surgery, checklists have been developed for other interventions that may be prone to adverse events such as endoscopy [28] and regional nerve block administration [29].