This study has shown that changing the organizational structure of an ICU from open to closed format is associated with a reduction of postoperative mortality in high risk surgical patients.
Before format change patients could be admitted to the ICU by any one of a patient's physicians. During the patients ICU stay the care for the patients' health status was continued by this physician. After format change, admittance to the ICU was only possible in consultation with an intensivist. Patient care transferred from the primary physician to the intensivist. This intensivist had no clinical responsibilities outside the ICU. Furthermore, daily rounds by the attending intensivist were introduced and the ICU became permanently staffed with an intensivist during off-hours.
High risk surgical patients admitted to the ICU after format change had a higher mean APACHE II score. This implies that patients in the closed format group had a more severe disease and a higher risk of death. Another possible explanation for the difference in mean APACHE II score is the difference in mean age between the groups. Despite of the difference in mean APACHE II score, mortality decreased. This is reflected by the decrease in SMR after format change. This strengthens the observation that closed format ICU treatment is associated with reduced postoperative mortality in high risk surgical patients. The differences in baseline disease severity may be explained by a difference in admittance threshold between intensivists and physicians without critical care training. It appears that physicians without training in critical care medicine tend to apply a lower admittance threshold. Because of this, changing the format of an ICU may lead to a reduction of inappropriate ICU admissions and its associated costs. Another possible explanation for the increase in mean APACHE II score is the gradual change in demographic characteristics. The proportion of adults and elderly in the population is gradually increasing [14
]. This phenomenon causes the number of elderly patients with serious co-morbid conditions in need for surgery to increase. Since age is associated with a rise in pre-morbid conditions, the proportion of high risk surgical patients increases.
Although the severity of disease was higher in the closed format group, we found that mortality decreased significantly after format change. This finding is in accordance with the results of similar observational studies performed in various populations [15
The decline in mortality was also observed in patients that developed cardiopulmonary complications. It appears that cardiopulmonary complications were better treated after format change. This may be explained by the immediate on-site availability of an intensivist. The introduction of having daily rounds by a physician trained in critical care medicine might allow for earlier diagnosis and prompt treatment of the specific set of complications seen in the critically ill patient. However the current study does not provide any evidence for this statement.
Most studies on ICU format change and physician staffing patterns observe a decrease in total and ICU LOS [12
]. In contrast to these studies we observed an increase in total and ICU LOS. This may partly be explained by the difference in baseline severity of disease between the open and closed format group. Also improved treatment of severe complications may have resulted in an improved survival at the cost of a longer ICU stay.
With advances in intensive care medicine, caring for the critically ill has become more complicated. This has led to the discussion; who should care for the ICU patient. Many, mainly observational studies, have been executed to evaluate the quality of care in ICUs. Staffing ICUs with Intensive Care physicians and directing all care to the Intensive Care physician is associated with reduced hospital and ICU mortality [12
]. Other ICU characteristics that may also be associated with improved patient outcome are; increased nurse patient ratios [15
], having daily rounds by an intensivist [12
] and the use of computerized warning and monitoring systems [20
The retrospective analysis is a shortcoming of the present study. However, since a prospective database was used, specifically designed to document complications and criteria to score complications were protocolized and did not change over time, the quality of outcome data seems robust.
The present study compares outcome data that were obtained in different time periods. Medicine has developed, in particular, intensive care medicine and surgical procedures/care/technology. Extensive surgery has become possible at increasing age. Advanced insight of the perioperative care like fluid management, temperature, stress reduction, perioperative beta blockers, postoperative pain reduction have progressed over the study period. Furthermore, new antimicrobials/antifungals, improved glycemic control and transfusion practices became available during the study period. Advances in surgical technique, perioperative care, general and intensive care medicine may reduce postoperative mortality over time. This temporal trend in mortality reduction has biased the study results. We attempted to address the magnitude of this bias by looking at nationwide trends of mortality reduction for the general Dutch ICU population. The Dutch National Intensive Care Evaluation was founded in 1996. Over the years that followed an increasing number of ICUs started exporting data concerning severity of disease and outcome to a national database. When looking at nationwide trends a gradual decrease in SMR is observed for the general Dutch ICU population. In the year 1999 the SMR was 1.03 on a national level which decreased to 0.87 in the year 2004 [2
]. Although the study demonstrated a much larger decrease in SMR (1.4 to 0.7), it was not designed to distinguish between the general temporal trend and mortality reduction due to format change. However, since format change was a major change in this period and a proportionally large reduction in mortality was observed, format change is likely to have played a major role in mortality reduction.