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Development of a tool to determining the number of medium care beds required for a large surgical ICU


The minimal nurse to patient ratio for intensive care units (ICU) was recently set to 1:2. For medium care units (MCU) this minimal ratio is 1:4. The Therapeutic Intervention Scoring System (TISS-28) has been used to assess nurse workload. According to Reis-Miranda, one nurse can handle 46 TISS-28 points and a TISS-28 <20 has been suggested to qualify as medium care. In order to rationalize the use of intensive care resources in our 56-bed surgical ICU, which has a 1:2 nurse to patient ratio, we developed a tool for determining the required number of medium care beds. Comparison with a 11-bed MCU, which has a 1:3 ratio, was made.


A prospective observational study was designed in which the attending nurses scored TISS on a daily basis. In addition, ICU nurses and the attending physicians daily gave an opinion on whether or not the patient could have been taken care of in a MCU. Physicians were blinded for TISS scores. The label medium care was given when both nurses and physicians agreed on this issue. Daily TISS scores in the ICU were related to the subjective opinion of nurses and physicians. The ethical committee approved the study protocol.


All patients, except those with a burn injury, admitted to the ICU and to the MCU during an episode of 4 months were included, which provided 6077 patient-days in the ICU and 875 patient-days in the MCU for analysis. In the ICU the median (P25–P75) TISS was 34 (28–40), vs 27 (22–32) in the MCU (P < 0.0001). In the ICU, but not in the MCU, the median TISS was significantly higher during week days than during weekends (35 [29–41] vs 32 [28–38], respectively; P < 0.0001). Taking actual nurse staffing into account, ICU nurses on average handled 70 TISS points and MCU nurses 81 TISS points. In the ICU, 11% of patient-days were considered medium care by both physicians and nurses, which translated into up to five medium care beds within 56 ICU beds. Patient-day-labeled medium care scored 26 (23–29) for TISS, as compared with 35 (30–41) for intensive care (P < 0.0001). A receiver–operator characteristic curve revealed an area under the curve of 84.3% and identified a TISS of 29 as the best cutoff for medium care. Using this definition, 25% of all ICU and 57% of all MCU patient-days would be labeled medium care. However, this cutoff yields 19% false-positives. Using a cutoff of 20 TISS points, only 3% of ICU patient-days and 15% of MCU patient-days would qualify.


Our study provided a nurse–physician consensus-based definition of medium care, which equalled a median TISS of 26, a value approaching that of a MCU in our hospital setting. Using such a quantitative definition of medium care allows more rational allocation of nursing staff.

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Verhaeghe, L., Valcke, M., Wouters, P. et al. Development of a tool to determining the number of medium care beds required for a large surgical ICU. Crit Care 8 (Suppl 1), P324 (2004).

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