Hyperoxia and Hypocapnia During Pediatric ECMO: Associations With Complications, Mortality, and Functional Status Among Survivors. (Dalal)

Cashen K, et al. Hyperoxia and Hypocapnia During Pediatric Extracorporeal Membrane Oxygenation: Associations With Complications, Mortality, and Functional Status Among Survivors. Pediatr Crit Care Med. 2018 Mar;19(3):245-253.

OBJECTIVES: To determine the frequency of hyperoxia and hypocapnia during pediatric extracorporeal membrane oxygenation and their relationships to complications, mortality, and functional status among survivors.

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Metrics of Arterial Hyperoxia and Associated Outcomes in Critical Care. (Betters)

Helmerhorst HJ, Arts DL, Schultz MJ,et al. Metrics of Arterial Hyperoxia and Associated Outcomes in Critical Care. Crit Care Med. 2017 Feb;45(2):187-195.

OBJECTIVE: Emerging evidence has shown the potential risks of arterial hyperoxia, but the lack of a clinical definition and methodologic limitations hamper the interpretation and clinical relevance of previous studies. Our purpose was to evaluate previously used and newly constructed metrics of arterial hyperoxia and systematically assess their association with clinical outcomes in different subgroups in the ICU.

DESIGN: Observational cohort study.

SETTING: Three large tertiary care ICUs in the Netherlands.

PATIENTS: A total of 14,441 eligible ICU patients.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN RESULTS: In total, 295,079 arterial blood gas analyses, including the PaO2, between July 2011 and July 2014 were extracted from the patient data management system database. Data from all admissions with more than one PaO2 measurement were supplemented with anonymous demographic and admission and discharge data from the Dutch National Intensive Care Evaluation registry. Mild hyperoxia was defined as PaO2 between 120 and 200 mm Hg; severe hyperoxia as PaO2 greater than 200 mm Hg. Characteristics of existing and newly constructed metrics for arterial hyperoxia were examined, and the associations with hospital mortality (primary outcome), ICU mortality, and ventilator-free days and alive at day 28 were retrospectively analyzed using regression models in different subgroups of patients. Severe hyperoxia was associated with higher mortality rates and fewer ventilator-free days in comparison to both mild hyperoxia and normoxia for all metrics except for the worst PaO2. Adjusted effect estimates for conditional mortality were larger for severe hyperoxia than for mild hyperoxia. This association was found both within and beyond the first 24 hours of admission and was consistent for large subgroups. The largest point estimates were found for the exposure identified by the average PaO2, closely followed by the median PaO2, and these estimates differed substantially between subsets. Time spent in hyperoxia showed a linear and positive relationship with hospital mortality.

CONCLUSIONS: Our results suggest that we should limit the PaO2 levels of critically ill patients within a safe range, as we do with other physiologic variables. Analytical metrics of arterial hyperoxia should be judiciously considered when interpreting and comparing study results and future studies are needed to validate our findings in a randomized fashion design.

Early oxygenation and ventilation measurements after pediatric cardiac arrest: lack of association with outcome. (Dugan)

Crit Care Med. 2013 Jun;41(6):1534-1542. PMID: 23552509

OBJECTIVES: To explore oxygenation and ventilation status early after cardiac arrest in infants and children. We hypothesize that hyperoxia is common and associated with worse outcome after pediatric cardiac arrest.

DESIGN: Retrospective cohort study.

SETTING: Fifteen hospitals within the Pediatric Emergency Care Applied Research Network.

PATIENTS: Children who suffered a cardiac arrest event and survived for at least 6 hoursafter return of circulation.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN RESULTS: Analysis of 195 events revealed that abnormalities in oxygenation andventilation are common during the initial 6 hours after pediatric cardiac arrest. Hyperoxia was frequent, affecting 54% of patients. Normoxia was documented in 34% and hypoxia in 22% of patients. These percentages account for a 10% overlap of patients who had both hyperoxia and hypoxia. Ventilation status was more evenly distributed with hyperventilation observed in 38%, normoventilation in 29%, and hypoventilation in 46%, with a 13% overlap of patients who had both hyperventilation and hypoventilation. Derangements in bothoxygenation and ventilation were common early after cardiac arrest such that both normoxia and normocarbia were documented in only 25 patients (13%). Neitheroxygenation nor ventilation status was associated with outcome. After controlling for potential confounders, arrest location and rhythm were significantly associated with worse outcome; however, hyperoxia was not (odds ratio for good outcome, 1.02 [0.46, 2.84]; p = 0.96).

CONCLUSIONS: Despite recent resuscitation guidelines that advocate maintenance of normoxia and normoventilation after pediatric cardiac arrest, this is uncommonly achieved in practice. Although we did not demonstrate an associationbetween hyperoxia and worse outcome, the small proportion of patients kept within normal ranges limited our power. Preclinical data suggesting potential harm with hyperoxia remain compelling, and further investigation, including prospective, large studies involving robust recording of physiological derangements, is necessary to further advance our understanding of this important topic.

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