Marga Hoogendoorn

55 I NTRODUCT I ON There are concerns regarding excessively high nursing workload, both in general and ICU wards 1 . An excessively high nursing workload can lead to burnout and job dissatisfaction among nurses 2 and have a deleterious effect on patients 3 . Workload has risen due to an increased turnover of patients, increased complexity of patients, together with nursing shortages 4 . All this makes planning of nursing capacity important. In the last 30 years different instruments have been developed to measure the nursing workload to give insight into the nursing staff needed per shift and provide much needed input for capacity planning 5 . To assess nursing workload in the ICU, Cullen et al. 6 created the Therapeutic Intervention Scoring System (TISS). The TISS was originally developed to classify nursing workload in relation to the severity of illness of ICU patients. The TISS consists of 76 therapeutic interventions that receive 1-4 points based on the severity of illness. It appeared that nursing workload is only partly related to severity of illness, since less severely ill patients could also generate a high nursing workload. For instance, a patient recovering from a serious illness with agitated delirium would not score high in severity of illness, but could demand very intensive nursing care, up to continuous bedside care throughout the day. This made the TISS less effective in assessing nursing workload. Therefore, the Nursing Activities Score (NAS) was developed by Miranda et al. in 2003 7 . The NAS describes activities that largely represent the work actually performed by nurses at the bedside in caring for patients and was developed to measure the nursing workload for each individual patient. The points assigned to nursing activities provide an average time consumption in caring for the patients instead of representing the severity of illness. The NAS was created by using the work-sampling approach: at random moments per shift the nurse was asked what he or she was doing at that specific moment. The researchers applied a weighting for each activity. The total NAS for an individual patient is the sum of NAS points for all activities, varying between 0 to 177 points (appendix 2). A score of 100 NAS points is equivalent to the amount of care that can be provided by one full-time equivalent nurse during either one shift or one day. A score above 100 points indicates that the care needed can only be provided by more than one nurse 7 . The NAS is considered a valuable tool and is widely used for workload measurement in ICUs 8, 9 . However, the performance of the NAS has not been comprehensively validated. One study showed that the NAS might either underestimate or overestimate the actual nursing time required by patients and therefore recommended revision of the original NAS because of inadequate