Canadian Journal of Anesthesia

, Volume 50, Issue 8, pp 767–774 | Cite as

Statistical process control methods allow the analysis and improvement of anesthesia care

General Anesthesia



Quality aspects of the anesthetic process are reflected in the rate of intraoperative adverse events. The purpose of this report is to illustrate how the quality of the anesthesia process can be analyzed using statistical process control methods, and exemplify how this analysis can be used for quality improvement.


We prospectively recorded anesthesia-related data from all anesthetics for five years. The data included intraoperative adverse events, which were graded into four levels, according to severity. We selected four adverse events, representing important quality and safety aspects, for statistical process control analysis. These were: inadequate regional anesthesia, difficult emergence from general anesthesia, intubation difficulties and drug errors. We analyzed the underlying process using ‘p-charts’ for statistical process control.


In 65,170 anesthetics we recorded adverse events in 18.3%; mostly of lesser severity. Control charts were used to define statistically the predictable normal variation in problem rate, and then used as a basis for analysis of the selected problems with the following results:
  • - Inadequate plexus anesthesia: stable process, but unacceptably high failure rate;

  • - Difficult emergence: unstable process, because of quality improvement efforts;

  • - Intubation difficulties: stable process, rate acceptable;

  • - Medication errors: methodology not suited because of low rate of errors.


By applying statistical process control methods to the analysis of adverse events, we have exemplified how this allows us to determine if a process is stable, whether an intervention is required, and if quality improvement efforts have the desired effect.

Les méthodes de contrôle statistique du processus permettent d’analyser et d’améliorer les soins anesthésiques



La qualité du processus anesthésique se vérifie par le taux d’événements peropératoires indésirables. Nous avons voulu illustrer comment analyser la qualité de l’anesthésie en utilisant les méthodes de contrôle statistique du processus et comment cette analyse peut améliorer la qualité.


Nous avons prospectivement recueilli des données anesthésiques sur cinq ans. Elles comprenaient des événements indésirables, classés selon quatre niveaux de sévérité. Nous avons sélectionné quatre événements indésirables qui représentent des aspects importants de la qualité et de la sécurité pour l’analyse du contrôle statistique du processus. Il s’agissait : de l’anesthésie régionale inadéquate, du retour à la conscience difficile après une anesthésie générale, des difficultés d’intubation et des erreurs de médicaments. Nous avons analysé le processus d’origine à l’aide des “graphiques-p” pour le contrôle statistique du processus.


Pour 65 170 anesthésies réalisées, nous avons noté des événements indésirables dans 18,3 % des cas, la plupart bénins. Nous avons utilisé les graphiques de contrôle pour définir statistiquement la variation prévisible normale du taux de problème et, ensuite, l’utiliser comme base de l’analyse des problèmes sélectionnés. Les résultats sont les suivants :
  • - Anesthésie régionale inadéquate : processus stable, mais taux d’échec élevé inacceptable.

  • - Réveil difficile : processus instable à cause des efforts d’amélioration de la qualité.

  • - Difficultés d’intubation : processus stable, taux acceptable.

  • - Erreurs de médicaments : méthodologie inappropriée à cause du faible taux d’erreurs.


En appliquant le contrôle statistique du processus à l’analyse d’événements indésirables, nous avons montré comment il permet de déterminer si un processus est stable, si une intervention est nécessaire et si les efforts d’amélioration de la qualité ont produit les effets recherchés.


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Copyright information

© Canadian Anesthesiologists 2003

Authors and Affiliations

  1. 1.Department of Anesthesia and Intensive CareSt. Olav’s Hospital, University Hospital of TrondheimTrondheimNorway

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