Effects of short-term hyperoxia on sytemic hemodynamics, oxygen transport, and microcirculation: An observational study in patients with septic shock and healthy volunteers

This research by Espinoza and others was published in Journal of Critical Care online in June 2019.
Purpose:  To characterize the microvascular effects of a brief period of hyperoxia, in patients with septic shock and in healthy volunteers.
Materials and methods:  In 20 patients with septic shock, we assessed systemic hemodynamics, sublingual microcirculation by SDF-videomicroscopy, and skin perfusion by capillary refill time (CRT), central-peripheral temperature (ΔT°), and perfusion index. Measurements were performed at baseline and after 5 min of inspired oxygen fraction of 1.00. Additionally, we studied 8 healthy volunteers, in whom hyperoxia was prolonged to 30 min.
Results:  In septic patients, hyperoxia increased mean arterial pressure and systemic vascular resistance, but cardiac output remained unchanged. The only significant change in sublingual microcirculation was a decreased heterogeneity flow index (1.03 [1.01–1.07] vs 1.01 [0.34–1.05], P = .002). Perfused vascular density (13.1 [12.0–15.0] vs 14.0 [12.2–14.8] mm/mm2, P = .21) and the other sublingual microvascular variables were unmodified. CRT and ΔT° did not change but perfusion index slightly decreased. In healthy volunteers, sublingual microcirculation and skin perfusion were stable.
Conclusions:  Short-term hyperoxia induced systemic cardiovascular changes but was not associated with noticeable derangement in sublingual microcirculation and skin perfusion. Nevertheless, longer exposures to hyperoxia might have produced different results.
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A mixed methods exploration of intensive care unit nurses’ perception of handling oxygen therapy to critically ill patients

This article was published on line in “Intensive and Critical Nursing” in January 2019 by Bunkenborg and Bundgaard.
Objectives:  Nurses handle supplementary oxygen to intensive care unit patients as part of their daily practise. To secure patients of optimal and safe care, knowledge of nurses’ perception of this practise, including influencing factors for adjusting oxygenation levels is essential. This study aimed to explore intensive care nurses’ perception of handling oxygenation and of factors that govern and influence this practise.
Research methodology/design:  A mixed methods approach was applied comprising six focus group interviews, conducted in February/March 2017, leading to construction of a questionnaire distributed to 535 ICU nurses in September 2017. Following a process of content analysis, the findings were discussed against Gittell’s framework for relational coordination.
Setting:  Intensive care units in rural, urban and university hospital settings.
Main outcome:  A deeper understanding of nurses’ perception of handling oxygenation to patients in the intensive care unit.
Findings and results:  Findings are presented through the categories Treatment Guidance, Nursing Practise, Knowledge and Competences and Inter-professional Collaboration.
Conclusion:  Nurses’ practise of handling supplementary oxygen therapy to the intensive care patient is influenced by day-by-day physician prescribed upper and lower limits for pO2 and pCO2, by nurses’ understanding of the individual clinical patient situation and by knowledge of pros and cons in relation to oxygen therapy including observational and clinical assessment expertise. Establishing working environments in the intensive care unit setting based on mutual inter- and intra-professional respect may contribute to enhance safe and high quality patient care.
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Intensive care doctors’ preferences for arterial oxygen tension levels in mechanically ventilated patients

This research by Schjørring and colleagues was published in Acta Anaesthesiologica Scandinavica in November 2018.
Background:  Oxygen is liberally administered in intensive care units (ICUs). Nevertheless, ICU doctors’ preferences for supplementing oxygen are inadequately described. The aim was to identify ICU doctors’ preferences for arterial oxygenation levels in mechanically ventilated adult ICU patients.
Methods:  In April to August 2016, an online multiple-choice 17-part-questionnaire was distributed to 1080 ICU doctors in seven Northern European countries. Repeated reminder e-mails were sent. The study ended in October 2016.
Results:  The response rate was 63%. When evaluating oxygenation 52% of respondents rated arterial oxygen tension (PaO2 ) the most important parameter; 24% a combination of PaO2 and arterial oxygen saturation (SaO2 ); and 23% preferred SaO2 . Increasing, decreasing or not changing a default fraction of inspired oxygen of 0.50 showed preferences for a PaO2 around 8 kPa in patients with chronic obstructive pulmonary disease, a PaO2 around 10 kPa in patients with healthy lungs, acute respiratory distress syndrome or sepsis, and a PaO2 around 12 kPa in patients with cardiac or cerebral ischaemia. Eighty per cent would accept a PaO2 of 8 kPa or lower and 77% would accept a PaO2 of 12 kPa or higher in a clinical trial of oxygenation targets.
Conclusion:  Intensive care unit doctors preferred PaO2 to SaO2 in monitoring oxygen treatment when peripheral oxygen saturation was not included in the question. The identification of PaO2 as the preferred target and the thorough clarification of preferences are important when ascertaining optimal oxygenation targets. In particular when designing future clinical trials of higher vs lower oxygenation targets in ICU patients.
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High-flow nasal cannula oxygen therapy alone or with non-invasive ventilation during the weaning period after extubation in ICU: the prospective randomised controlled HIGH-WEAN protocol

This article by Thille and colleagues as part of the REVA research network was published in BMJ Open in September 2018.
Introduction:  Recent practice guidelines suggest applying non-invasive ventilation (NIV) to prevent postextubation respiratory failure in patients at high risk of extubation failure in intensive care unit (ICU). However, such prophylactic NIV has been only a conditional recommendation given the low certainty of evidence. Likewise, high-flow nasal cannula (HFNC) oxygen therapy has been shown to reduce reintubation rates as compared with standard oxygen and to be as efficient as NIV in patients at high risk. Whereas HFNC may be considered as an optimal therapy during the postextubation period, HFNC associated with NIV could be an additional means of preventing postextubation respiratory failure. We are hypothesising that treatment associating NIV with HFNC between NIV sessions may be more effective than HFNC alone and may reduce the reintubation rate in patients at high risk.
Methods and Analysis:  This study is an investigator-initiated, multicentre randomised controlled trial comparing HFNC alone or with NIV sessions during the postextubation period in patients at high risk of extubation failure in the ICU. Six hundred patients will be randomised with a 1:1 ratio in two groups according to the strategy of oxygenation after extubation. The primary outcome is the reintubation rate within the 7 days following planned extubation. Secondary outcomes include the number of patients who meet the criteria for moderate/severe respiratory failure, ICU length of stay and mortality up to day 90.
Ethics and Dissemination: The study has been approved by the ethics committee and patients will be included after informed consent. The results will be submitted for publication in peer-reviewed journals.
The full text of this article is freely available via this link.

Intensive care doctors’ preferences for arterial oxygen tension levels in mechanically ventilated patients

This article by Schjorring and others was published in Acta Anaesthesioligica Scandinavica in June 2018.
Background:  Oxygen is liberally administered in intensive care units (ICUs). Nevertheless, ICU doctors’ preferences for supplementing oxygen are inadequately described. The aim was to identify ICU doctors’ preferences for arterial oxygenation levels in mechanically ventilated adult ICU patients.
Methods:  In April to August 2016, an online multiple-choice 17-part-questionnaire was distributed to 1080 ICU doctors in seven Northern European countries. Repeated reminder e-mails were sent. The study ended in October 2016.
Results:  The response rate was 63%. When evaluating oxygenation 52% of respondents rated arterial oxygen tension (PaO2 ) the most important parameter; 24% a combination of PaO2 and arterial oxygen saturation (SaO2 ); and 23% preferred SaO2 . Increasing, decreasing or not changing a default fraction of inspired oxygen of 0.50 showed preferences for a PaO2 around 8 kPa in patients with chronic obstructive pulmonary disease, a PaO2 around 10 kPa in patients with healthy lungs, acute respiratory distress syndrome or sepsis, and a PaO2 around 12 kPa in patients with cardiac or cerebral ischaemia. Eighty per cent would accept a PaO2 of 8 kPa or lower and 77% would accept a PaO2 of 12 kPa or higher in a clinical trial of oxygenation targets.
Conclusion:  Intensive care unit doctors preferred PaO2 to SaO2 in monitoring oxygen treatment when peripheral oxygen saturation was not included in the question. The identification of PaO2 as the preferred target and the thorough clarification of preferences are important when ascertaining optimal oxygenation targets. In particular when designing future clinical trials of higher vs lower oxygenation targets in ICU patients.
To access the full text of these articles via the journal’s homepage you require a personal subscription to the journal.  Some articles may be available freely without a password.  Library members can order individual articles via the Rotherham NHS Foundation Trust Library and Knowledge Service using the article requests online via this link.

Oxygen Requirements for Acutely and Critically Ill Patients

Oxygen administration is often assumed to be required for all patients who are acutely or critically ill. However, in many situations, this assumption is not based on evidence | Critical Care Nurse

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Injured body tissues and cells throughout the body respond both beneficially and adversely to delivery of supplemental oxygen. Available evidence indicates that oxygen administration is not warranted for patients who are not hypoxemic, and hyperoxia may contribute to increased tissue damage and mortality. Nurses must be aware of implications related to oxygen administration for all types of acutely and critically ill patients. These implications include having knowledge of oxygenation processes and pathophysiology; assessing global, tissue, and organ oxygenation status; avoiding either hypoxia or hyperoxia; and creating partnerships with respiratory therapists. Nurses can contribute to patients’ oxygen status well-being by being proficient in determining each patient’s specific oxygen needs and appropriate oxygen administration.

Full reference: Siela, D. & Kidd, M. (2017) Oxygen Requirements for Acutely and Critically Ill Patients. Critical Care Nurse. Vol. 37 (no. 4) pp.  58-70

High-flow nasal cannula oxygen therapy vs conventional oxygen therapy in cardiac surgical patients: A meta-analysis

This article is to be published in the Journal of Critical Care.  The full text of the article can be accessed via this link.

Introduction:  The use of high-flow nasal cannula (HFNC) for the treatment of many diseases has gained increasing popularity. In the present meta-analysis, we aimed to assess the efficacy and safety of HFNCs compared with conventional oxygen therapy (COT) in adult postextubation cardiac surgical patients.

Method:  We reviewed the Embase, PubMed, Cochrane Central Register of Controlled Trials, Wanfang databases, and the China National Knowledge Infrastructure. Two investigators independently collected the data and assessed the quality of each study. RevMan 5.3 was used for the present meta-analysis.

Results:  We included 495 adult postextubation cardiac surgical patients. There was no significant heterogeneity among the studies. Compared with COT, HFNCs were associated with a significant reduction in the escalation of respiratory support (risk ratio, 0.61; 95% confidence interval [CI], 0.46-0.82; z = 3.32, P < .001). There were no significant differences in the reintubation rate (risk ratio, 0.96; 95% CI, 0.04-24.84; z = 0.02, P = .98) or length of intensive care unit stay (weighted mean difference, 0.13; 95% CI, −0.88 to 7.92; z = 1.57, P = .12) between the 2 groups. No severe complications were reported in either group.

Conclusions:  The HFNC could reduce the need for escalation of respiratory support compared with COT, and it could be safely administered in adult postextubation cardiac surgical patients.