The results of this study can be used as an initial step when constructing an instrument for measuring the nursing care intensity in perioperative settings. In the future, the instrument may provide objective evidence of nursing care intensity and thus facilitate resource allocation. A further significance of this study lies in its potential to make perioperative nursing visible, so the nursing outcomes may be evaluated and proved.

More testing is needed to achieve a valid tool for allocating nursing staff in operating departments. Reliable tools are needed to match patients' care needs with available nursing resources.

Patient classification systems generate information for staff allocation based on a patient's care needs. This study aims to test further the instrument for assessing nursing intensity (NI) in perioperative settings. Nine operating departments from five university hospitals were involved. The perioperative nurses gathered data from patients (N = 876) representing different fields of surgery. Reliability was tested by parallel classifications (n = 144). Also, the users' (n = 40) opinions were surveyed. The results support the predictive validity and interrater reliability of the instrument. The nurses considered the instrument feasible to use. The patients' low ASA class did not automatically signify low NI; however, high ASA class was more frequently associated with high intraoperative NI. Intraoperative NI indicated the length of the postanaesthesia care and the type of the follow-up unit. Parallel classifications ensured the homogenous use of the instrument. The use of the instrument is recommended.