Much has been written about human error in the setting of medication safety; much less has been written about violations, which may be equally important and even more common. Violations may vary from and individual's failure to label a syringe to an organization's failure to invest in medication safety. Perhaps the most compelling challenge in this regard is lack of engagement by practitioners in the safety initiatives that exist within their organizations. This chapter includes a discussion of the 4 main reasons for violations: 1) rules must be violated in order for the work to be done; 2) a sense of powerfulness, that one can skillfully complete the job without needing rules; 3) violations represent short-cuts that allow the work to be done better or faster; 4) poor work planning, which results in having to invent the work process as one goes and solve problems as they arise. Reducing violations requires understanding why, and then fixing, the reasons for the violations. An understanding of violation in all its shades and a greater willingness to name this problem and to expect accountability for it within the context of a just culture may well be the key to improving medication safety in the future.

The process of medication management in anesthesia is both complicated (numerous steps) and complex, in that it requires continual adaptation to a continually changing environment. In addition, medication safety depends on systemic factors, some of which involve processes far from the clinical interface. The system in which medications are managed is complex, if only because humans are a key part of this system. The processes of human cognition are particularly complex, and include knowledge, evidence, information, wisdom and expertise. These processes are explored in some detail, including a discussion of short term and long-term memory. Each practitioner responds to an internally developed mental model of the current situation, which may differ considerable from that of other team members. An understanding of complexity and human cognition may often provide an explanation for failure in healthcare: such an understanding provides a foundation for our overall pursuit of medication safety.