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Chapter 38. "Closed" Intensive Care Units and Other Models of Care for Critically Ill Patients
Jeffrey M. Rothschild, M.D., M.P.H.
Harvard Medical School
Patients in the intensive care unit (ICU) require complex care
relating to a broad range of acute illnesses and pre-existing conditions. The
innate complexity of the ICU makes organizational structuring of care an
attractive quality measure and a target for performance improvement strategies.
In other words, organizational features relating to medical and nursing
leadership, communication and collaboration among providers, and approaches to
problem-solving1 may capture the quality of ICU care more
comprehensively than do practices related to specific processes of
Most features of ICU organization do not exert a demonstrable
impact on clinical outcomes such as morbidity and mortality.3 While
hard clinical outcomes may not represent the most appropriate measure of success
for many organizational features, the role of "intensivists" (specialists in
critical care medicine) in managing ICU patients has shown a beneficial impact
on patient outcomes in a number of studies. For this reason, the Leapfrog Group,
representing Fortune 500 corporations and other large healthcare purchasers, has
identified staffing ICUs with intensivists as one of three recommended hospital
safety initiatives for its 2000 purchasing principles (see also Chapter
In this chapter, we review the benefits of full-time
intensivists and the impact of "closed ICUs" (defined below) on patient
outcomes. Much of this literature makes no distinction between improved outcomes
in general and decreased harm in particular. However, given the high
mortality5 and complication rates6-8 observed in ICUs, it
seems reasonable to consider global interventions such as organizational changes
as patient safety practices.
The following practice definitions are synthesized from studies
reviewed for this chapter. For all of these models, the term "intensivist"
refers to a physician with primary training in medicine, surgery, anesthesiology
or pediatrics followed by 2-3 years of critical care medicine (CCM)
Open ICU model—An ICU in which patients are admitted under
the care of an internist, family physician, surgeon or other primary attending
of record, with intensivists available providing expertise via elective
consultation. Intensivists may play a de facto primary role in the
management of some patients, but only within the discretion of the
Intensivist Co-management—An open ICU model in which all
patients receive mandatory consultation from an intensivist. The internist,
family physician, or surgeon remains a co-attending-of-record with intensivists
collaborating in the management of all ICU patients.
Closed ICU model—An ICU in which patients admitted to the
ICU are transferred to the care of an intensivist assigned to the ICU on a
full-time basis. Generally, patients are accepted to the ICU only after
approval/evaluation by the intensivist. For periods typically ranging from one
week to one month at a time, the intensivist's clinical duties predominantly
consist of caring for patients in the ICU, with no concurrent outpatient
Mixed ICU models—In practice, the above models overlap to a
considerable extent. Thus, some studies avoid attempting to characterize ICUs in
terms of these models and focus instead on the level of involvement of
intensivists in patient care regardless of the organizational model. This
involvement may consist of daily ICU rounds by an intensivist (thus including
"closed model ICUs" and "intensivist comanagement"), ICU directorship by an
intensivist (possibly including examples of all 3 models above), or simply the
presence of a full-time intensivist in the ICU (also including examples of all 3
Intensivist models—ICU management may include all of these
models. These models are contrasted with the open ICU model, in which an
intensivist generally does not participate in the direct care of a significant
proportion of the ICU patients.
Prevalence and Severity of the Target Safety Problem
ICUs comprise approximately 10% of acute care hospital
beds.9 The number of annual ICU admissions in the United State
is estimated to be 4.4 million patients.10 Due to an aging population
and the increasing acuity of illness of hospitalized patients, both the total
number of ICU patients and their proportional share of hospital admissions
overall are expected to grow.11
ICU patients have, on average, mortality rates between 12 and
17%.25 Overall, approximately 500,000 ICU patients die annually in
the United States. A recent review estimated that this mortality could be
reduced by 15 to 60% using an intensivist model of ICU management.12
Young and Birkmeyer have provided estimates of the relative
reduction in annual ICU mortalities resulting from conversion of all urban ICUs
to an intensivist model of management model.10 Using conservative
estimates for current ICU mortality rates of 12%, and estimating that 85% of
urban ICUs are not currently intensivist-managed, the authors calculated that
approximately 360,000 patients die annually in urban ICUs without intensivists.
A conservative projection of a 15% relative reduction in mortality resulting
from intensivist-managed ICUs yields a predicted annual saving of nearly 54,000
By only measuring ICU mortality rates, this analysis may
underestimate the importance of intensivist-managed ICUs. In addition to
mortality, other quality of care outcome measures that might be improved by
intensivists include rates of ICU complications, inappropriate ICU utilization,
patient suffering, appropriate end-of-life palliative care, and futile
Opportunities for Impact
Currently, a minority of ICUs in the United States utilizes the
intensivist model of ICU management.13 Intensivists are even less
frequently found in non-teaching and rural hospitals. The potential impact of
the intensivist model is far-reaching.
Among 14 studies abstracted for this chapter, 2 were systematic
reviews and 12 were original studies. One systematic review is an abstract that
has not yet appeared in journal form and does not provide cited
references.12 The other systematic review evaluated 8 references, all
of which are included in this chapter.10 An additional 4 studies
absent from the systematic review are included here. These 4 studies include 2
abstracts that were published after the 1999 systematic review,14,15
and 2 studies of pediatric ICUs with intensivists.16,17
Among the original studies, 6 incorporated historical controls
and 5 used a cross-sectional approach. One study18 had both
historical and cross-sectional components. The original studies include 4
studies of adult medical ICUs, 6 studies of adult surgical ICUs and 2 studies of
pediatric multidisciplinary ICUs. Intensivist models used by the studies cited
for this review include 4 closed ICUs, 4 mixed ICUs, 3 ICUs with intensivist
comanagement and one open ICU.
Several studies were excluded, including abstracts with
insufficient data,19-25 unclear distinctions in patient management
between control groups and intervention (intensivist managed)
groups,26,27 intensivist models that may have important roles in
future practice (e.g., telemedicine consultation with remote management) but are
not yet widely available28,29 and considerably older
Required outcomes of interest in studies chosen for this
chapter were ICU mortality, overall in-hospital mortality, or both. Some studies
also included morbidity outcomes, adverse events and resource utilization (e.g.,
length of ICU and hospital stay), levels of patient acuity or severity of
illness (ICU utilization) and levels of high-intensity intervention usage.
Studies addressing the impact of intensivist ICU management on resource
utilization without mortality or outcome data were excluded. There are no data
regarding the impact of intensivists.
Evidence for Effectiveness of the Practice
As shown in Table 38.1, most of the studies report a decrease
in unadjusted in-hospital mortality and/or ICU mortality, although this decrease
did not reach statistical significance in 3 of the 14
studies.16,18,31 One study found a statistically insignificant
increase in the unadjusted mortality rates associated with the intensivist model
ICU.32 This study also found that the ratio of expected-to-actual
mortality was reduced in the intensivist-model ICUs. This finding was associated
with a higher severity of illness scores in the intensivist-model ICU
population. A similar finding of significantly improved outcomes after adjusting
for severity of illness and comparing expected-to-actual mortality rates was
demonstrated in one pediatric study.16 Overall, the relative risk
reduction for ICU mortality ranges from 29% to 58%. The relative risk reduction
for overall hospital mortality is 23% to 50%. These results are consistent with
those of a previous systematic review that found a 15% to 65% reduction in
mortality rates in intensivist-managed ICUs.10
Data concerning long-term survival (6 and 12 months) for
patients cared for in ICUs with and without intensivist management is not
available. Differences in outcomes between closed ICUs, mixed ICU models and
co-managed ICUs are difficult to assess. Studies that have addressed conversion
from an open to a closed model did not utilize full-time intensivists in the
open model study phases.18,32-34 Therefore it is not clear to what
extent improved patient outcomes resulted only from changes in intensivists'
direct patient care and supervision.
The observational studies evaluating these practices suffer
from 2 major limitations. Half of the studies retrospectively compared
post-implementation outcomes with those during an historical control period.
Because none of these studies included a similar comparison for a control unit
that remained open in both time periods, we lack information on secular trends
in ICU outcomes during the time periods evaluated. The other major limitation
associated with comparing mortality rates for ICU patients relates to
differences in ICU admission and discharge criteria under different
organizational models. Under the intensivist model, patients are generally
accepted to the ICU only after approval/evaluation by the intensivist. Thus,
conversion to an intensivist model ICU may bring about changes in the ICU
patient population that are incompletely captured by risk-adjustment models and
confound comparisons of mortality rates. Moreover, these changes in ICU
admitting practice may exert contradictory effects. For example, an intensivist
model ICU may result in fewer ICU admissions for patients with dismal prognoses,
and less futile care for patients already in the ICU. On the other hand,
intensivist-managed ICUs with stricter admission and discharge criteria may
result in a greater overall acuity of illness for the ICU patients and therefore
higher mortality rates.
Potential for Harm
The potential for harm resulting from intensivist management is
unclear. Concerns raised in the literature about intensivist-managed ICUs
include the loss of continuity of care by primary care physicians, insufficient
patient-specific knowledge by the intensivist,35 reduced use of
necessary sub-specialist consultations, and inadequate CCM training of residents
who formerly managed their own ICU patients.
Perhaps more worrisome is the impact that adoption of this
practice would have on physician staffing and workforce requirements. Without a
substantial increase in the numbers of physicians trained in CCM, projected
increases in the ICU patient population over the next 30 years will result in a
significant shortfall in the intensivist workforce.11
Costs and Implementation
These studies did not address the incremental costs associated
with implementation of full-time intensivists. Several studies have analyzed
resource utilization and length of stay associated with intensivist-managed
ICUs.13,16,18,19,29,31,32,36 The results of these studies are
variable with respect to costs. Some demonstrate a decrease in ICU expenses.
Others found increased costs, likely due to the increased use of expensive
technologies. Still others show little overall cost differential. The
cost-effectiveness and cost-benefit of an intensivist-model ICU requires further
Outcomes research in critical care is particularly challenging
for several reasons. It typically relies on observational outcomes studies, and
must account for the diversity and complexity of variables measured and
controlled for, such as patient-based, disease-based, provider-based and
therapy-based variables. Despite these challenges and limitations, the
literature fairly clearly shows that intensivists favorably impact ICU patient
outcomes. What remains unclear is which intensivist model to
recommend—intensivist consultation versus intensivist co-management versus
closed ICUs. Also, we do not know the degree to which the choice among these
models depends on intensivist background—i.e., medicine, anesthesiology or
surgery. Finally, because the mechanism of the benefit of intensivist models is
unknown, the degree to which this benefit can be captured by other changes in
practice (e.g., adoption of certain evidence-based processes of ICU care) remains
The major incentive for clarifying these issues concerns the
implications for staffing ICUs in the future. While the evidence supports the
beneficial role of full-time intensivists, the current number of trainees is
insufficient to keep pace with the expected increase in the number of ICU
patients.11 Until we are able to sufficiently increase the size and
number of CCM training programs for physician specialists, complementary
solutions for meeting critical care management demands should be considered.
These might include incorporating physician-extenders such as nurse
practitioners and physician assistants with specialized critical care training,
increased participation by hospitalists in care of ICU patients,37
regionalization of critical care services,38 or providing innovative
methods to extend intensivists' expertise to remote sites through telemedicine
consultations.28 The latter practice seems particularly promising—a
recent time series cohort study found an approximately 33% decrease in
severity-adjusted hospital mortality and a nearly 50% decrease in ICU
complications when a technology-enabled remote ICU management program was
instituted in a community-based ICU.28
Table 38.1. Intensivist management in the care of critically ill
||Study Design, Outcomes
||Mortality Relative Risk Reduction (%) |
|Closed ICU Model
||Tertiary care, urban, teaching hospital; patients with septic shock;
|Teaching hospitals (n=2); two study designs using historical and
||Retrospective: 19 (p=NS)|
Prospective: 26 (p=NS)
|Tertiary care, urban, teaching hospital; historical
|Tertiary care, urban, teaching hospital; historical
|Mixed ICU models
||ICUs (n=16) with different characteristics;
||Pediatric MICU SICU
|ICUs (n=39) with different characteristics; cross-sectional. Patients
with abdominal aortic surgery38
|ICUs (n=31) with different characteristics; cross-sectional. Patients
with esophageal resection14
|ICUs (n=39) with different characteristics; cross-sectional. Patients
with hepatic resection15
|Community teaching hospital; historical
||Tertiary care ICU in a teaching children's
||Pediatric MICU SICU
|Tertiary care, Canadian teaching hospital; historical
|Tertiary care, urban, teaching hospital; cross-sectional comparison
* ICU indicates intensive care unit; MICU, medical intensive care unit; Mixed,
mixed intensivist model (including daily ICU rounds by an intensivist, the
presence of a full-time intensivist, open units with co-management and closed
units with mandatory consultations or only intensivist management); NA, not
available as outcome (was not evaluated); NS, not statistically significant; and
SICU, surgical intensive care unit.
a Negative value indicates an increase in relative risk
b O/E is observed to expected mortality ratio based risk
c Hospital mortality measured 30-days after discharge
d RRR is the unadjusted mortality relative risk reduction
** OR is the adjusted odds ratio of increased mortality associated without an
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