Crit Care Med 2010;38:283-287

Severity scores such as Acute Physiology and Chronic Health Evaluation II have been advocated as entry criteria for clinical trials and in clinical decision-making. We present ten reasons why we believe this approach is not appropriate and may even be detrimental.

Data sources
Available relevant literature from authors’ personal databases and personal knowledge of past and future clinical trial development.

Data synthesis
Severity scores were not designed for use in individual patients or for therapeutic decision-making for specific interventions. Difficulties with the time window needed to calculate these scores and the need to administer therapies early further limit their use in this context. The complex nature of the scores makes it difficult to use them at the bedside and there is considerable interobserver variability in score calculation. Inclusion of chronic health and age points in severity scores may prevent younger, previously healthy patients, with similar acute physiological dysfunction and therefore total lower severity scores, from trial inclusion or from receiving therapies that may be beneficial.

Conclusions
We believe severity of illness scores are poor surrogates for risk stratification and should not be used as a criterion for patient enrollment into clinical trials or as the basis for individual treatment decisions.

Critical Care Medicine 2009;37:1545-1557

Although intensive care units (ICUs) with higher overall patient volume may achieve better outcomes than lower volume ICUs, there are few data on the effects of increasing patient loads on patients within the ICU.

Objectives
To examine the association of ICU occupancy with the patient outcomes within the same ICU.

Methods
We examined 200,499 patients in 108 ICUs using the Acute Physiology and Chronic Health Evaluation IV database in 2002-2005. Daily census on the day of admission was determined for each patient and defined in relation to the mean census. We used conditional logistic regression to compare inpatient outcomes of patients admitted on high census days to those admitted in the same ICU on low census days. We controlled for severity of illness at the patient level using data on clinical, demographic, and physiologic variables on admission to the ICU.

Measurements and main results
Patients admitted on high census days had the same odds of inpatient mortality or transfer to another hospital as patients admitted on average or on low census days. These findings were robust to multiple alternative definitions of day of admission census and were confirmed in several subgroup analyses.

Conclusions
The ICUs in this data are able to function as high reliability organizations. They are able to scale up their operations to meet the needs of a wide range of operating conditions while maintaining consistent patient mortality outcomes.

Critical Care 2009, 13:R84

Caring for the critically ill is a 24-hour-a-day responsibility, but not all resources and staff are available during off hours. We evaluated whether intensive care unit (ICU) admission during off hours affects hospital mortality.

Methods
This retrospective multicentre cohort study was carried out in three non-academic teaching hospitals in the Netherlands. All consecutive patients admitted to the three ICU’s between 2004 and 2007 were included in the study, except for patients who did not fulfil APACHE II criteria (readmissions, burns, cardiac surgery, younger than 16 years, length of stay less than 8 hours). Data were collected prospectively in the ICU databases. Hospital mortality was the primary endpoint of the study. Off hours was defined as the interval between 10 pm and 8 am during weekdays and between 6 pm and 9 am during weekends. Intensivists, with no responsibilities outside the ICU, were present in the ICU during daytime and available for either consultation or assistance on site during off hours. Residents were available 24 hours a day 7 days a week in two and fellows in one of the ICUs.

Results
A total of 6725 patients were included in the study, 4553 (67.7%) admitted during daytime and 2172 (32.3%) admitted during off hours. Baseline characteristics of patients admitted during daytime were significantly different from those of patients admitted during off hours. Hospital mortality was 767 (16.8%) in patients admitted during daytime and 469 (21.6%) in patients admitted during off hours (P<0.001, unadjusted odds ratio 1.36, 95%CI 1.20-1.55). Standardized mortality ratios were similar for patients admitted during off hours and patients admitted during daytime. In a logistic regression model APACHE II expected mortality, age and admission type were all significant confounders but off hours admission was not significantly associated with a higher mortality (P=0.121, adjusted odds ratio 1.125, 95%CI 0.969-1.306).

Conclusions
The increased mortality after ICU admission during off hours is explained by a higher illness severity in patients admitted during off hours.

Ann Int Med 2008;148:801-809

Critically ill patients admitted to intensive care units (ICUs) are thought to gain an added survival benefit from management by critical care physicians, but evidence of this benefit is scant.

Objective
To examine the association between hospital mortality in critically ill patients and management by critical care physicians.

Design
Retrospective analysis of a large, prospectively collected database of critically ill patients.

Setting
123 ICUs in 100 U.S. hospitals.

Patients
101 832 critically ill adults.

Measurements
Through use of a random-effects logistic regression, investigators compared hospital mortality between patients cared for entirely by critical care physicians and patients cared for entirely by non–critical care physicians. An expanded Simplified Acute Physiology Score was used to adjust for severity of illness, and a propensity score was used to adjust for differences in the probability of selective referral of patients to critical care physicians.

Results
Patients who received critical care management (CCM) were generally sicker, received more procedures, and had higher hospital mortality rates than those who did not receive CCM. After adjustment for severity of illness and propensity score, hospital mortality rates were higher for patients who received CCM than for those who did not. The difference in adjusted hospital mortality rates was less for patients who were sicker and who were predicted by propensity score to receive CCM.

Limitation
Residual confounders for illness severity and selection biases for CCM might exist that were inadequately assessed or recognized.

Conclusion
In a large sample of ICU patients in the United States, the odds of hospital mortality were higher for patients managed by critical care physicians than those who were not. Additional studies are needed to further evaluate these results and clarify the mechanisms by which they might occur.

Critical Care 2008, 12:R33

Low mixed or central venous saturation (S(c)vO₂) can reveal global tissue hypoxia and therefore can predict poor prognosis in critically ill patients. Early goal directed therapy (EGDT), aiming at an ScvO₂ ≥ 70%, has been shown to be a valuable strategy in patients with sepsis or septic shock and is incorporated in the Surviving Sepsis Campaign guidelines.

Methods
In this prospective observational multi-center study, we determined central venous pressure (CVP), hematocrit, pH, lactate and ScvO₂ or SvO₂ in a heterogeneous group of critically ill patients early after admission to the intensive care units (ICUs) in three Dutch hospitals.

Results
Data of 340 acutely admitted critically ill patients were collected. The mean SvO₂ value was > 65% and the mean ScvO₂ value was > 70%. With mean CVP of 10.3 ± 5.5 mmHg, lactate plasma levels of 3.6 ± 3.6 and acute physiology, age and chronic health evaluation (APACHE II) scores of 21.5 ± 8.3, the in-hospital mortality of the total heterogeneous population was 32.0%. A subgroup of septic patients (n = 125) showed a CVP of 9.8 ± 5.4 mmHg, mean ScvO₂ values of 74.0 ± 10.2%, where only 1% in this subgroup revealed a ScvO₂ value < 50%, and lactate plasma levels of 2.7 ± 2.2 mmol/l with APACHE II scores 20.9 ± 7.3. Hospital mortality of this subgroup was 26%.

Conclusion
The incidence of low ScvO₂ values for acutely admitted critically ill patients is low in Dutch ICUs. This is especially true for patients with sepsis/septic shock.

BMJ 2007;335:xxx-xxx

To determine whether clinicians’ prognoses in patients with severe acute exacerbations of obstructive lung disease admitted to intensive care match observed outcomes in terms of survival.

Design
Prospective cohort study.

Setting
92 intensive care units and three respiratory high dependency units in the United Kingdom.

Participants
832 patients aged 45 years and older with breathlessness, respiratory failure, or change in mental status because of an exacerbation of COPD, asthma, or a combination of the two.

Main outcome measures
Outcome predicted by clinicians. Observed survival at 180 days.

Results
517 patients (62%) survived to 180 days. Clinicians’ prognoses were pessimistic, with a mean predicted survival of 49% at 180 days. For the fifth of patients with the poorest prognosis according to the clinician, the predicted survival rate was 10% and the actual rate was 40%. Information from a database covering 74% of intensive care units in the UK suggested no material difference between units that participated and those that did not. Patients recruited were similar to those not recruited in the same units.

Conclusions
Because decisions on whether to admit patients with COPD or asthma to intensive care for intubation depend on clinicians’ prognoses, some patients who might otherwise survive are probably being denied admission because of unwarranted prognostic pessimism.

Critical Care Medicine 2006;34:2929-2939

Evaluate the effect of intensive care (ICU) admission body mass index (BMI) on 30-day and 12-month survival in critically ill patients and determine the impact of obesity on outcome.

Design
Prospective, observational cohort study.

Setting
Fourteen-bed medical and surgical ICU of a university-affiliated hospital.

Patients
Four hundred and ninety-three adult patients.

Interventions
None.

Measurements and Main Results
BMI (kg/m²) was calculated from height (m) and measured weight (kg) within 4 hrs of ICU admission, using the PROMED weighing device, or premorbid weight (documented in the previous month) (BMI_measured). Follow-up was for =12 months post-ICU admission. Time to mortality outcome, censored at 30 and 365 days (12-months), was analyzed using a log-normal accelerated failure time regression model. Predictor variables were parameterized as time ratios (TR), where TR <1 is associated with decreased survival time and TR >1 is associated with prolonged survival time. Mean (sd) age and Acute Physiology and Chronic Health Evaluation II score were 62.3 (17.5) years and 20.7(8.4), respectively; 56.0% (285 of 493) of patients were male and 60.6% (299 of 493) medical. ICU admission weight and BMI_measured (available in 433 patients) were 79.1 (22.1) kg and 27.8 (7.0) kg/m², respectively. In 16.9% (73 of 433) of patients, weight was =100 kg, and in 29.8% (129 of 433), BMI_measured was =30 kg/m². Raw intensive care, 30-day, and 12-month mortality rates were 15.2% (66 of 433), 22.3% (95 of 433), and 37.3% (159 of 433), respectively. BMI_measured was a significant determinant of mortality at 30 days (TR 1.853, 95% confidence interval 1.053-3.260, p = .032) and 12 months (TR 1.034, 95% confidence interval 1.005-1.063, p = .019). The effect of BMI on 12-month mortality was linear, such that increasing BMI was associated with decreasing mortality.

Conclusions
ICU admission BMI was a determinant of short- to medium-term survival. Obesity was not associated with adverse outcomes and may be protective.

Critical Care Medicine 2005;33:750-755

To identify factors associated with granting or refusing intensive care unit (ICU) admission, to analyze ICU characteristics and triage decisions, and to describe mortality in admitted and refused patients.

Design
Observational, prospective, multiple-center study.

Setting
Four university hospitals and seven primary-care hospitals in France.

Interventions
None.

Measurements and Main Results
Age, underlying diseases (McCabe score and Knaus class), dependency, hospital mortality, and ICU characteristics were recorded. The crude ICU refusal rate was 23.8% (137/574), with variations from 7.1% to 63.1%. The reasons for refusal were too well to benefit (76/137, 55.4%), too sick to benefit (51/137, 37.2%), unit too busy (9/137, 6.5%), and refusal by the family (1/137). In logistic regression analyses, two patient-related factors were associated with ICU refusal: dependency (odds ratio [OR], 14.20; 95% confidence interval [CI], 5.27-38.25; p < .0001) and metastatic cancer (OR, 5.82; 95% CI, 2.22-15.28). Other risk factors were organizational, namely, full unit (OR, 3.16; 95% CI, 1.88-5.31), center (OR, 3.81; 95% CI, 2.27-6.39), phone admission (OR, 0.23; 95% CI, 0.14-0.40), and daytime admission (OR, 0.52; 95% CI, 0.32-0.84). The Standardized Mortality Ratio was 1.41 (95% CI, 1.19-1.69) for immediately admitted patients, 1.75 (95% CI, 1.60-1.84) for refused patients, and 1.03 (95% CI, 0.28-1.75) for later-admitted patients.

Conclusions
ICU refusal rates varied greatly across ICUs and were dependent on both patient and organizational factors. Efforts to define ethically optimal ICU admission policies might lead to greater homogeneity in refusal rates, although case-mix variations would be expected to leave an irreducible amount of variation across ICUs.