This study was conducted by the research group on quality improvement of the European Society of Intensive Care Medicine (ESICM). Participating units chose one of two available study days (either 17 January or 24 January 2007) with a 24 hour observation period. Ultimately, 113 units from 27 countries on five continents participated. Thirty five of these units had participated in the first study in January 2004.
Definition, assessment, and description of medication errors at the administration stage
A medication error at the administration stage was defined as an error of omission or commission in the context of parenteral drug administration that harmed or could have harmed a patient. We exclusively addressed medication errors that were attributable to five types of error during the stage of administration: wrong dose, wrong drug, wrong route, wrong time, missed medication. Errors were further classified by type of drug administration (intravenous bolus, intravenous continuous, subcutaneous) and class of drug (sedation/analgesia, vasopressors/catecholamines, antimicrobial, coagulation related, electrolytes, insulin, others).
All nurses and physicians on duty in the participating units during the 24 hour study period were asked to fill in a single questionnaire available at the bedside of each patient. The questionnaire for each patient could therefore contain consecutive entries from several staff members. Every contributor to the questionnaire could see which medication errors, if any, were already reported, making duplicate reporting highly unlikely. The structured questionnaire asked if, and at what time, an error in parenteral medication had occurred. The questionnaire also asked for a formalised and coded description of every medication error so that we could assess contributing factors (communication-written, communication-oral, handover, workload/stress/fatigue, experience/knowledge/supervision, violation of protocol/standard, recently changed brand name of drugs, equipment failure, others); situational factors (admission/discharge, routine, emergency, movement with the hospital, intervention, urgent crisis of another patient, others); and grading of the impact of the error (a change registered or not, intervention necessary or not, no harm, temporary harm, permanent harm, death). For each error, we asked three questions: Were formal requirements for secure drug prescription fulfilled?6 7
Were trainees involved? and Did the same person both prepare and administer the drug?
A coordinator in each participating unit was responsible for briefing the team and transmitting the data. The coordinator’s obligations included the provision of information regarding characteristics of the unit, the actual staffing and patient flow during the study period, and the classification of the severity of illness and medical personnel workload for every patient. In addition, the coordinator assessed and reported the vital status of every patient at discharge from the unit, or on day 28 after the study period ended if the patient was still in the unit. Data acquisition and reporting were anonymous for both patients and medical personnel. As a consequence, reported errors were not attributable to the type of medical professional involved, whether nurse or physician.
The study included all patients staying in the participating units, including those admitted or discharged during the study period.
Patient related factors
For each patient, staff recorded basic demographic characteristics, as well as occurrence and descriptive factors of each parenteral medication error. To assess the range of opportunities for error (denominator), each single dose of parenteral medication given to each patient was counted. In medications with a continuous intravenous administration, each syringe for perfusion pumps or each infusion bottle was considered as a single dose.
To determine the severity of illness in each patient, the items necessary for calculating the sequential organ failure assessment (SOFA) score8
were collected to quantify the presence and degree of organ dysfunction or failure and consequently provide a surrogate for severity of illness. The score takes into account the function of six organ systems (respiratory, renal, hepatic, cardiovascular, haematology, and central nervous system) as well as the weight of some therapeutic interventions (such as use of catecholamines). The items for the nine equivalents of nursing manpower use score (NEMS)9
were recorded as a surrogate marker for the amount of nursing workload and consequently the level of care provided to each patient. The NEMS items are related to specific organ support and nursing and diagnostic or therapeutic interventions inside or outside the unit. Both scores were assessed for each patient on the day of the study.
The duration of each patient’s stay in the unit was assessed from the time of admission to discharge and was reported as length of stay (days) before and after the observation period. In addition, the actual time (hours) a patient stayed in the unit during the observation period was reported. For the objective of measuring outcome, the vital status (alive or dead) was assessed at discharge or on day 28 after the study period ended if the patient was still in the unit.
Intensive care unit related factors
Characteristics of hospital size (beds), type and size (beds) of intensive care unit, shift schedule for nurses and physicians (start and end as time of day), number of nurses and physicians appointed to each shift, number of occupied and free beds in each shift, maximum number of patients in each shift, and number of admitted and discharged patients in each shift were recorded for every unit. These data allowed us to calculate occupancy rate (maximum number of occupied beds divided by allocated beds), relative turnover (number of admitted and discharged patients divided by the number of unit beds), and the ratios of patients to nurses and patients to physicians for each shift in each unit. Information about any existing system for formal critical incident reporting as well as any computerised medication prescribing system was also recorded. With respect to the process of parenteral medication administration, further information was obtained about the use of infusions previously prepared by a pharmacist, use of perfusors with a fixed standard preparation, existence of a dedicated area for preparation of medications, number of different types (different model or different manufacturer) of perfusors and infusion pumps, routine check of perfusor or infusion pumps at every shift change, and labelling of all syringes prepared with drugs before use.
Database and data collection
Patients’ data were recorded on a dedicated project website (www.hsro-esicm.org
) with online data collection software. The website contained all documentation, including detailed definitions of all data fields and events; data collection sheets available for download; and access to the study database with data entry forms. To ensure consistent quality of the data in units from different participating countries, the questionnaires and the descriptive list of items were available in six languages: English, German, Italian, French, Portuguese, and Spanish.
The appointed unit coordinator entered data collected from each unit on the study database. During data entry, the software automatically performed plausibility and completeness checks. Each variable was defined in detail before the start of data collection, and the definitions were available in both paper and electronic form. To facilitate plausibility checking, each variable was assigned a range of probable values and a range of possible values (storage range).
Data collection started at the beginning of the nurses’ day shift. The study period was designed to overlap a second day (but not to exceed 24 hours) to ensure that data acquisition in each unit included at least one day shift and one night shift.
We used SAS, version 9.1 (SAS Institute, Cary, NC), for statistical analyses and considered P<0.05 (two sided) as significant. Unless otherwise specified, descriptive results are expressed as medians and interquartile ranges.
Denominators were the number of all patients in the final study sample, the number of patients exposed to a specific item, the number of all units contributing patients to the final study sample, the number of patient days (calculated as total hours of observation for all patients, divided by 24), or the total number of doses of parenteral medication. The numerator was the number of patients experiencing a medication error or the number of medication errors in total or in different categories.
Odds ratios were calculated with a dichotomous outcome variable—no medication error versus occurrence of at least one medication error during the observation period—with the patient as the unit of analysis. We chose this simple variable because ordering by counting the number of events (for example, when using an ordered outcome variable as 0 v 1, 2, 3, 4, or more medication errors) is questionable because of the different characteristics and severity of events. Moreover, this simple analysis is unaffected by possible duplicate reports for the same event.
For the analysis according to the criteria of completeness of documentation and relevance for the practice of intensive care we chose patients’ characteristics and characteristics of the intensive care unit (as listed above). We used univariate logistic regression to evaluate univariate associations between these and the outcome. We included variables that reached univariate significance (P<0.05 two sided) in a stepwise multivariate logistic regression analysis (SAS option stepwise). Clustering on the patient level or unit level was accounted for by including various patient and unit related variables to explain differences between patients and units, respectively. To differentiate between errors, we performed the calculations separately for all types of errors, errors of commission (wrong drug, wrong dose, wrong route), and errors requiring an intervention. In all regression analyses P<0.05 was considered significant.