Intensivist-to-Bed Ratio Impacts Length-of-Stay in the Medical ICU

Abstract & Commentary

By Leslie Hoffman, PhD, RN, Department of Acute/Tertiary Care, School of Nursing, University of Pittsburgh, is Associate Editor for Critical Care Alert.

Dr. Hoffman reports no financial relationship to this field of study.

Synopsis: Differences in intensivist-to-bed ratio ranging from 1:7.5 to 1:15 were associated with an increased ICU length-of-stay.

Source: Dara SI, et al. Intensivist-to-bed ratio: association with outcomes in the medical ICU. Chest. 2005;128:567-572.

This study examined the effect of variations in ICU staffing, defined in terms of intensivist-to-ICU bed ratio, on ICU length-of-stay (LOS) and ICU and hospital mortality. The study was conducted at the Mayo Clinic in Rochester, MN over a 9-month period when the medical ICU underwent a series of planned changes which resulted in its capacity increasing from 15 to 24 beds. As a consequence of these changes, the intensivist-to-bed ratio varied from 1:15 (initial ratio) to 1:7.5, 1:9.5, and 1:12 (final ratio), yielding 4 periods of comparison. Other than the change in bed ratio, the role of the intensivists did not undergo any major change. The intensivists were responsible for the delivery of all care in the ICU, made rounds at least twice daily, supervised all invasive procedures, wrote daily progress notes, and supervised educational activities of the critical care fellows and first and third year internal medicine residents who rotated through the unit. During the study period, there were no changes in the nurse-to-patient ratio (1:1 or 1:2) or frequency of house staff rotation (4-5 weeks).

A total of 2,492 patients were admitted to the medical ICU during the 9-month study interval. There were no statistically significant differences in severity of illness (APACHE III scores), predicted mortality rate after case-mix adjustment, or ICU readmission during the 4 periods of comparison. Also, there were no statistically significant differences in the ICU admission source (predominately the Emergency Department) during the 4 periods.

The ICU period with a 1:15 intensivist-to-bed ratio had a longer adjusted ICU LOS compared to the period with a 1:75 (P < .0001), 1:9.5 (P = .0003), and 1:12 ratio (P < .0001). The difference was not significant when comparisons were made between periods with a 1:75 bed ratio vs 1:9.5 (P = .20) or 1:12 (P = .51) ratio. Differences in bed ratio were not associated with significant differences in ICU or hospital mortality or hospital LOS.


In this study, there were no statistically significant differences in severity of illness during the 4 time periods, suggesting that changes in the number of available ICU beds did not influence the threshold for admission to the medical ICU. Also, there was no change in ICU or hospital mortality after case-mix adjustment, suggesting that variations in intensivist-to-bed ratio did not influence patient survival. However, there was an increase in ICU, but not hospital, LOS. This suggests that patients were stabilized and transferred from the medical ICU more quickly during periods when the intensivist-to-bed ratio was 1:7.5 compared to 1:15.

As noted by Alan Morris,1 humans are limited in their ability to simultaneously analyze large quantities of information, a concern given the thousands of pieces of information analyzed by ICU clinicians each day. By one estimate, an intensivist may be confronted with 1,000 pieces of information on each patient each day. In addition, as the number of patients managed increases, contact is more intermittent, increasing the likelihood that changes in the management plan will not occur as quickly.

In ICUs, the nurse-patient ratio is commonly varied from 1:1 to 1:2 dependent on patient needs. In contrast, the number of intensivists is usually determined by the size of the ICU and does not fluctuate dependent on changes in patient acuity or increased needs for teaching, supervision and consultation due to rotation of house staff. Findings of this study should be of interest to policy makers as they consider the projected increase in demand for critical care service. Although no differences were seen in mortality or hospital LOS, changes in ICU LOS can translate into substantial cost savings. The ability to focus on fewer patients has a number of additional advantages, including improved family and patient satisfaction, better end-of-life care, and improved interdisciplinary coordination.


  1. Morris AH. Developing and implementing computerized protocols for standardization of clinical decisions. Ann Intern Med. 2000;132:373-383.