Incidence in ICU populations: how to measure and report it? (Stockwell)

Beyersmann J, Gastmeier P, Schumacher M. Incidence in ICU populations: how to
measure and report it? Intensive Care Med. 2014 Jun;40(6):871-6.

Incidence of ICU events is mostly measured in one of two ways which differ by the denominator only. Either the number of incident events divided by the number of ICU patients is reported or the number of incident events per 1,000 ICU days is calculated. The difference is relevant, but a connection is rarely made. We give an example where pneumonia diagnosis on admission has no effect on one measure of mortality incidence, but increases the other. We demonstrate how to connect the two measures of incidence. The conclusion is that so-called ‘competing incidences’ should also be reported.

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Use of tracheostomy in the PICU among patients requiring prolonged mechanical ventilation. (Stockwell)

Wakeham MK, Kuhn EM, Lee KJ, McCrory MC, Scanlon MC. Use of tracheostomy in the PICU among patients requiring prolonged mechanical ventilation. Intensive Care Med. 2014 Jun;40(6):863-70.

PURPOSE: The purpose of the present study is to describe the use of tracheostomy, specifically frequency, timing (in relation to initiation of mechanical ventilation), and associated factors, in a large cohort of children admitted to North American pediatric intensive care units (PICUs) and requiring prolonged mechanical ventilation.

METHODS: This was a retrospective cohort study. De-identified data were obtained from the VPS(LLC) database, a multi-site, clinical PICU database. Admissions between 1 July 2009 and 30 June 2011 were enrolled in the study if the patient required mechanical ventilation for at least 72 h and did not have a tracheostomy tube at initiation of mechanical ventilation.

RESULTS: A total of 13,232 PICU admissions from 82 PICUs were analyzed in the study; of these, 872 (6.6 %) had a tracheostomy tube inserted after initiation of mechanical ventilation. The rate varied significantly (0-13.4 %, p < 0.001) among the 45 PICUs that had 100 or more admissions included in the study. The median time to insertion of a tracheostomy tube was 14.4 days (IQR 7.4-25.7), and it also varied significantly by unit (4.3-30.4 days, p < 0.001) among those that performed at least ten tracheostomies included in the study.

CONCLUSIONS: There is significant variation in both the frequency and time to tracheostomy between the studied PICUs for patients requiring prolonged mechanical ventilation; among those who received a tracheostomy, the majority did so after two or more weeks of mechanical ventilation. Future studies examining tracheostomy benefits, disadvantages, outcomes, and resource utilization of this patient subgroup are indicated.

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Body position changes redistribute lung computed-tomographic density in patients with acute respiratory failure: impact and clinical fallout through the following 20 years. (Stockwell)

Gattinoni L, Pesenti A, Carlesso E. Body position changes redistribute lung computed-tomographic density in patients with acute respiratory failure: impact and clinical fallout through the following 20 years. Intensive Care Med. 2013 Nov;39(11):1909-1915.

ABSTRACT: In patients with acute respiratory distress syndrome (ARDS), in supine position, there is a decrease of inflation along the sternum vertebral axis, up to lung collapse. In 1991 we published a report showing that, in ARDS patients, shifting from supine to prone position led immediately to the inversion of the inflation gradient and to a redistribution of densities from dorsal to ventral lung regions. This led to a “sponge model” as a wet sponge, similar to a heavy edematous lung, squeezes out the gas in the most dependent regions, due to the weight-related increase of the compressive forces. The sponge model accounts for density distribution in prone position, for which the unloaded dorsal regions are recruited, while the loaded ventral region, collapses. In addition, the sponge model accounts for the mechanism through which the positive end-expiratory pressure acts as counterforce to oppose the collapsing, compressing forces. The final result of proning was that the inversion of gravitational forces, together with other factors such as lung-chest wall shape-matching and the heart weight led to a more homogeneous distribution of inflation throughout the lung parenchyma. This is associated with oxygenation improvement as the dorsal recruitment, for anatomical reasons, prevails on the ventral de-recruitment. The more homogeneous distribution of inflation (i.e. of stress and strain) decreases/prevents the ventilator-induced lung injury, as consistently shown in animal experiments. Finally, and a series of clinical trials led to the conclusion that in patients with severe ARDS, the prone position provides a significant survival advantage.

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Early blood lactate area as a prognostic marker in pediatric septic shock. (Kamat)

Kim YA, Ha EJ, Jhang WK, Park SJ. Early blood lactate area as a prognostic marker in pediatric septic shock. Intensive Care Med. 2013 Oct;39(10):1818-23.

PURPOSE: We attempted to evaluate whether the early lactate area is useful as an early prognostic marker of mortality in pediatric septic shock patients.

METHODS: We performed a retrospective study of pediatric patients with septic shock who were admitted to the pediatric intensive care unit of Asan Medical Center, Seoul, Korea. Serial arterial lactate levels were obtained immediately and then every 6 h after admission for a total of 24 h. The lactate area (mmol/lh) was defined as the sum of the area under the curve (AUC) of serial lactate levels measured during the 24 h following admission. We compared the lactate-associated parameters as a predictor of mortality.

RESULTS: A total of 65 patients were included in this study, and the overall 28-day mortality of these patients was 26.2 %. Survivors compared with non-survivors had an initial lactate level of 3.13 ± 2.79 vs. 6.16 ± 4.87 mmol/l, a lactate clearance of 32.8 ± 63.4 vs. -30.8 ± 75.6 %, and a lactate area of 59.7 ± 56.0 vs. 168.0 ± 107.0 mmol/lh (p < 0.05 for all variables). Receiver operating characteristic curves indicated a strong predictive power for the lactate area (AUC = 0.828), which demonstrated the largest AUC in comparison with the AUCs of the initial lactate level (0.699) or the 24-h lactate clearance (0.719). Using multivariate logistic regression analysis, the lactate area was a significant prognostic factor.

CONCLUSION: The early lactate area is a potentially feasible and clinically useful predictor of mortality in pediatric septic shock patients.

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