Designing clinical trials in acute lung injury/acute respiratory distress syndrome

Influence of mild therapeutic hypothermia after cardiac arrest on hospital mortality

OBJECTIVE

Following two randomized controlled trials that demonstrated reduced mortality and better neurological outcome in cardiac arrest patients, mild therapeutic hypothermia was implemented in many intensive care units. Up to now, no large observational studies have confirmed the beneficial effects of mild therapeutic hypothermia.

DESIGN

Internet-based survey combined with a retrospective, observational study.

PATIENTS

All patients admitted to an intensive care unit in The Netherlands after cardiac arrest from January 1, 1999 until January 1, 2009.

DATA SOURCE

Dutch National Intensive Care Evaluation database.

METHODS

The moment of implementation of mild therapeutic hypothermia for each hospital participating in the Dutch National Intensive Care Evaluation database was determined with an Internet survey. To compare mortality before and after implementation of mild therapeutic hypothermia, the odds ratio adjusted for Simplified Acute Physiology Score II score, age, gender, propensity score, and in- or out-of-hospital cardiac arrest was calculated. Patients were excluded if 1) they were admitted to an intensive care unit that did not respond to the survey, 2) they were admitted within 3 months after implementation of mild therapeutic hypothermia, 3) they had a Glasgow Coma Scale score of >8, or 4) they did not satisfy the Simplified Acute Physiology Score II inclusion criteria.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 13,962 patients were admitted to an intensive care unit following cardiac arrest. In total 8,645 patients were excluded, 5,544 because of a Glasgow Coma Scale score of >8. Of the resultant 5,317 patients, 1,547 patients were treated before and 3,770 patients after implementation of mild therapeutic hypothermia. Patients admitted after implementation of mild therapeutic hypothermia had lower minimal and maximal temperatures (p < .0001) during the first 24 hrs on the intensive care unit compared to patients admitted before implementation of mild therapeutic hypothermia. The adjusted odds ratio of the hospital mortality of patients treated after implementation of mild therapeutic hypothermia was 0.80 (95% confidence interval of 0.65-0.98, p = .029).

CONCLUSION

The results of this retrospective, observational survey suggest that implementation of mild therapeutic hypothermia in Dutch intensive care units is associated with a 20% relative reduction of hospital mortality in cardiac arrest patients.

Toward early identification of acute lung injury in the emergency department

BACKGROUND

There are no studies evaluating the epidemiology of pediatric acute lung injury (ALI) in the emergency department (ED), where early identification and interventions are most likely to be helpful. The purpose of this study was to describe the epidemiology of the ALI precursor acute hypoxemic respiratory failure (AHRF) in the ED.

METHODS

We analyzed 11,664 pediatric patient records from 16 EDs. Records were selected if oxygen saturation (SpO(2)) was recorded during the visit. Virtual partial pressure of oxygen (pO(2)) was calculated from SpO(2), thus allowing calculation of ratios of pO(2) to fraction of inspired oxygen (FiO(2)) (PFRs). Patients with a PFR < 300 were classified as having AHRF. Univariate analyses and logistic regression were used to test the association of clinical factors with the presence of AHRF and intubation.

RESULTS

AHRF criteria (ie, PFR < 300) were met in 121 (2.9%) of the 4,184 patients with an oxygenation measurement. The following variables were independently associated with ALI: higher Pediatric Risk of Admission II score (adjusted odds ratio [95% confidence interval (CI)] = 1.12 [1.08-1.16]; p < .001), higher heart rate (1.02 [1.01-1.03]; p = .009), a positive chest radiograph (2.35 [1.02-5.43]; p = .045), and lower temperature (0.49 [0.36-0.68]; p < .001).The final model had an R(2) = .20.

CONCLUSION

We found nonintubated AHRF to be prevalent in the ED. The low R(2) for the regression model for AHRF underscores the lack of criteria for early identification of patients with respiratory compromise. Our findings represent an important first step toward establishing the true incidence of ALI in the pediatric ED.

Better conduct of clinical trials: the control group in critical care trials

OBJECTIVE

To review trial design issues related to control groups.

DESIGN

Review of the literature with specific reference to critical care trials.

MAIN RESULTS AND CONCLUSIONS

Performing randomized controlled trials in the critical care setting presents specific problems: studies include patients with rapidly lethal conditions, the majority of intensive care patients suffer from syndromes rather than from well-definable diseases, the severity of such syndromes cannot be precisely assessed, and the treatment consists of interacting therapies. Interactions between physiology, pathophysiology, and therapies are at best marginally understood and may have a major impact on study design and interpretation of results. Selection of the right control group is crucial for the interpretation and clinical implementation of results. Studies comparing new interventions with current ones or different levels of current treatments have the problem of the necessity of defining "usual care." Usual care controls without any constraints typically include substantial heterogeneity. Constraints in the usual therapy may help to reduce some variation. Inclusion of unrestricted usual care groups may help to enhance safety. Practice misalignment is a novel problem in which patients receive a treatment that is the direct opposite of usual care, and occurs when fixed-dose interventions are used in situations where care is normally titrated. Practice misalignment should be considered in the design and interpretation of studies on titrated therapies.

Inter-observer variability in chest radiograph reading for diagnosing acute lung injury in children

Acute lung injury (ALI), including its most serious form called acute respiratory distress syndrome (ARDS), is a devastating disease that can occur at any age. ALI/ARDS accounts for only 5-8% of admissions to pediatric intensive care units (PICUs) but is fatal in 30-60% of cases. International multicenter prospective studies are needed to better understand pediatric ALI/ARDS. However, a reproducible definition of ALI/ARDS is crucial to ensure that study populations are homogeneous. We designed a retrospective review to test the inter-observer variability of chest radiograph interpretation for presence of the American-European Consensus Conference (AECC) radiographic criterion for ALI/ARDS. The medical files of 24 children ventilated for ALI/ARDS in our PICU between January 1993 and December 2002 were reviewed. Five pediatric radiologists and five pediatric intensivists interpreted one frontal chest radiograph (FCR) per patient taken on the day of ALI/ARDS diagnosis. Each reader indicated whether the radiograph showed the AECC radiographic criterion for ALI/ARDS. Data analysis involved comparing each reader to all the others based on the raw agreement and Kappa coefficient (kappa). Features in the 24 patients were consistent with earlier studies. Global inter-observer agreement beyond chance was fair (kappa = 0.29 +/- 0.02) among the five radiologists (kappa = 0.26 +/- 0.05) and among the five intensivists (kappa = 0.29 +/- 0.05). Thus, considerable inter-observer variability occurred in assessing the radiographic criterion for ALI/ARDS, as previously shown in adults. Given the low incidence of ALI/ARDS in children, this variability may have a large impact in studies of pediatric ALI/ARDS.

Health technology assessment in critical care

BACKGROUND

Heath technology assessments (HTAs) evaluate the benefits and costs of devices for monitoring and therapy (and their associated requirements for human resources) which contribute to the high expense associated with ICU admission.

DISCUSSION

Given the limited resources available for health care and increasing demands, funds spent inefficiently or unnecessarily on technologies in the ICU may threaten the sustainability of the health care system or prevent other potentially cost-effective devices from being introduced into clinical care. We discuss the factors impeding the conducting of HTAs in the ICU and suggest strategies for change.

CONCLUSIONS

Despite the need for HTAs of ICU devices only few have been conducted. They should be undertaken more frequently, and their results used to influence clinical practice and hospital and regional-level policy decisions.

Inhaled nitric oxide for acute respiratory distress syndrome

Theoretical promise of benefit does not translate to improvements in morbidity and mortality

Rapid implementation of therapeutic hypothermia in comatose out-of-hospital cardiac arrest survivors

BACKGROUND

The implementation of therapeutic hypothermia (TH) into daily clinical practice appears to be slow. We present our experiences with rapid implementation of a simple protocol for TH in comatose out-of-hospital cardiac arrest (OHCA) survivors.

METHODS

From June 2002, we started cooling pre-hospitally with sport ice packs in the groin and over the neck. In the intensive care unit (ICU), we used ice-water soaked towels over the torso. All patients were endotracheally intubated, on mechanical ventilation and sedated and paralysed. The target temperature was 33 +/- 1 degrees C to be maintained for 12-24 h. We used simple inclusion criteria: (i) no response to verbal command during the ambulance transport independent of initial rhythm and cause of CA; (ii) age 18-80 years; and (iii) absence of cardiogenic shock (SBP < 90 mmHg despite vasopressors). We compared the first 27 comatose survivors with a presumed cardiac origin of their OHCA with 34 historic controls treated just before implementation.

RESULTS

TH was initiated in all 27 eligible patients. The target temperature was reached in 24 patients (89% success rate). ICU- and hospital- length of stay did not differ significantly before and after implementation of TH. Hypokalemia (P= 0.001) and insulin resistance (P= 0.025) were more common and seizures (P= 0.01) less frequently reported with the use of TH. The implementation of TH was associated with a higher hospital survival rate (16/27; 59% vs. 11/34; 32%, respectively; P< or = 0.05). Our results indicate a population-based need of approximately seven cooling patients per 100,000 person-years served.

CONCLUSION

Our simple, external cooling protocol can be implemented overnight in any system already treating post-resuscitation patients. It was well accepted, feasible and safe, but not optimal in terms of cooling rate. Neither safety concerns nor costs should be a barrier for implementation of TH.