Drug Error: Another Defence Barrier

Drug error in Medicine could be potentially harmful to patient. Many mechanisms have been put in place to prevent or minimise its occurrence. We discuss the extent of the problem nationally and worldwide. We describe a new system which was introduced into our workplace with the intention to add another layer of defence against drug error.

Drugs Errors, Overview

The incidence of medication error during Medicine is uncertain. A prospective study of 55,426 procedures reported that drug errors occurred in 63 cases (0.11%). Another study of 7,794 patients reported that the incidence of a drug administration error was 0.75%.

Factors that have been identified as contributing to drug error relate to labels and to appearance and location of ampoules and syringes, and to inattention, poor communication, carelessness, haste, and fatigue on the part of the Practitioners.

Many drug administration errors are slips or lapses precipitated by episodes of momentary distraction that inevitably occur during the multitasking required of a practitioner. Such errors are inherent in any human activity and cannot be avoided simply by resolve—indeed, the person will often not even realise that an error has been made. Their reduction depends on improving the design of the system. Such design is described by Reason as Swiss cheese model: Defences, barriers, and safeguards occupy a key position in the system approach. High technology systems have many defensive layers: some are engineered (alarms, physical barriers), others rely on people (surgeons, anaesthetists, theatre staff), and yet others depend on procedures and guidelines.


Reason described Swiss cheese model: Defences, barriers, and safeguards occupy a key position in the system approach.

Their function is to protect potential victims and assets from local hazards. Mostly they do this very effectively, but there are always weaknesses. Reason states that in an ideal world each defensive layer would be intact. In reality, however, they are more like slices of Swiss cheese, having many holes. These holes, unlike the cheese, are continually opening, shutting, and shifting their location. The presence of holes in any one "slice" does not normally cause a bad outcome. Usually, this can happen only when the holes in many layers momentarily line up to permit a trajectory of accident opportunity bringing hazards into damaging contact with victims.

Hiring Toyota Production Systems to Minimize Drug Errors

In general, Medical errors can lead to adverse events. An adverse event attributable to error is a “preventable adverse event”. The problem of medical errors is now receiving attention as an important topic in operations management research. Implementation of Toyota Production System in health (TPS) care settings improved patient safety dramatically. The TPS often referred to as Lean thinking, based on industrial engineering principles and operational innovations, and is used to achieve waste reduction and efficiency while increasing product quality. Several key tools and principles, adapted to health care, have proved effective in improving hospital operations. In a recent study, this process improved the cervical cancer test quality by reducing the frequency of error per correlating cytologic-histologic specimen pair from 9.52% to 7.84%. In a chemistry laboratory the median pre-analytic processing time was reduced from 29 to 19 minutes, and the laboratory met the goal of reporting 80% of chemistry results in less than 1 hour for 11 consecutive months.

Giving the importance of the process the Institute for Healthcare Innovation (2005) has produced a white paper entitled: Going Lean in Healthcare. It states: Although health care differs in many ways from manufacturing, there are also surprising similarities:

Whether building a car or providing health care for a patient, workers must rely on multiple, complex processes to accomplish their tasks and provide value to the customer or patient. Waste (of money, time, supplies, or good will) decreases value.

One of the approaches used in the lean thinking is the 5S standards:

  1. Sort: sorting or segregating through the contents of the workplace and removing all unnecessary items
  2. Straighten: putting or arranging the necessary items in their place and providing easy access by clear identification.
  3. Shine: cleaning everything, keeping it clean and using cleaning to inspect the workplace and equipment for defects
  4. Standardise: creating visual control and guidelines for keeping the workplace organised, orderly, and clean, in other words, maintaining the shine.
  5. Sustain: instituting training and discipline to ensure that everyone follows the 5S standards

Our Project

We chose the operating theatres, particularly the Anaesthetics rooms as the potential for serious drug errors in anaesthetics is greater than in other specialities, because of the number of different drugs and syringes in use at any one time. It is also a very dynamic environment where risks of haste, lapses and multitasking are common. Our project consisted of re-organising the drug cupboard by keeping only essential drugs at the right quantity and at the right place.

We first classed the drugs into useful drug classes such as Emergency, Anaesthetics and Antibiotics. Within each class, drugs were arranged alphabetically using only generic names. Each drug will occupy a place indicated by a label used in the International Colour Coding System for Syringe Labelling.  Drugs not routinely used will be kept at a theatre central cupboard (TCC). By introducing colours, drug classes and keeping only essential drugs, we enhanced the visual cues and therefore build up another defence barrier against drug error. We also hoped that the proposed system would enable:

- Easy spotting of needed drug, mainly emergency one. This is very important because of the fast-pace of the operating room and multi-tasking by anaesthetists.

- Easy spotting of missing drugs

- Saving time to restock the cupboard

- Saving resources (essential drugs get used before they expire, drugs not routinely needed are not stocked).


We are unsure about the extent of drug and medical errors in our workplace. We do know from literature that drug errors in anaesthetics are common and could be fatal. Our attempt create another defense barrier to minimise the risk. Other mechanisms would include improvement of a drug error reporting system from which lessons could be learned.