Conservative Oxygen Research Articles

Conservative versus conventional oxygen therapy for cardiac surgical patients: A before-and-after study.

Avoiding hypoxaemia is considered crucial in cardiac surgery patients admitted to the intensive care unit (ICU). However, avoiding hyperoxaemia may also be important. A conservative approach to oxygen therapy may reduce exposure to hyperoxaemia without increasing the risk of hypoxaemia. Using a before-and-after design, we evaluated the introduction of conservative oxygen therapy (target SpO2 88%-92% using the lowest FiO2) for cardiac surgical patients admitted to the ICU. We studied 9041 arterial blood gas (ABG) datasets: 4298 ABGs from 245 'conventional' and 4743 ABGs from 298 'conservative' oxygen therapy patients. During mechanical ventilation (MV) and while in the ICU, compared to the conventional group, conservative group patients had significantly lower FiO2 exposure and PaO2 values ( P < 0.001 for each). Accordingly, using the mean PaO2 during MV, more conservative group patients were classified as normoxaemic (226 versus 62 patients, P < 0.01), fewer as hyperoxaemic (66 versus 178 patients, P < 0.01) and no patient in either group as hypoxaemic or severely hypoxaemic. Moreover, more ABG samples were hyperoxaemic or severely hyperoxaemic during conventional treatment ( P < 0.001). Finally, there was no difference in ICU or hospital length of stay, ICU or hospital mortality or 30-day mortality between the groups. Our findings support the feasibility and physiological safety of conservative oxygen therapy in patients admitted to ICU after cardiac surgery.

Extracorporeal membrane oxygenation for primary graft dysfunction after heart transplant

ObjectiveVenoarterial extracorporeal membrane oxygenation is a useful treatment for severe primary graft dysfunction after heart transplant. The ideal timing of initiation is unknown. MethodsWe retrospectively reviewed 362 adult heart transplant recipients at our center between January 2011 and December 2017. Thirty-eight patients (10.5%) experienced severe primary graft dysfunction treated with venoarterial extracorporeal membrane oxygenation. As our institution adopted a prompt venoarterial extracorporeal membrane oxygenation policy in 2015, patients were stratified into pre-2015 (conservative extracorporeal membrane oxygenation: n = 18) and post-2015 (prompt extracorporeal membrane oxygenation: n = 20) cohorts. Clinical outcomes were compared. ResultsBaseline characteristics were similar (conservative vs prompt) except for age (51.82 vs 59.96 years, P = .036), aspartate transaminase (32 vs 21.5 U/L, P = .038), male donor (44.4 vs 80%, P = .042), and donor ejection fraction (60 vs 65%, P = .047). Median ischemic time was significantly longer in the conservative extracorporeal membrane oxygenation cohort (210 vs 148 minutes, P = .005). Median time to initiation of extracorporeal membrane oxygenation was significantly shorter in the prompt extracorporeal membrane oxygenation cohort (7.26 vs 1.95 hours, P < .0001). There was no difference in intensive care unit stay or major complications. In-hospital mortality improved from 28% (conservative) to 5% (prompt, P = .083). Post-transplant survival at 1 year was 67% in the conservative extracorporeal membrane oxygenation cohort and 90% in the prompt extracorporeal membrane oxygenation cohort (P = .117). There was no difference in the Kaplan–Meier survival curves (P = .071), although Cox regression suggested, but certainly did not prove, a 74.6% lower risk of mortality in the prompt extracorporeal membrane oxygenation group (P = .094). ConclusionsPrompt venoarterial extracorporeal membrane oxygenation use for primary graft dysfunction after heart transplant results in excellent myocardial recovery and a possible decrease in mortality without increased risk of complications.

Effect of conservative and conventional oxygen therapy on the prognosis of critically ill patients: a Meta-analysis

To compare the efficacy and safety of conservative and conventional oxygen therapy in critically ill patients. Relevant literature and randomized controlled trials (RCTs) about the effect of conservative oxygen therapy and conventional oxygen therapy on the prognosis of intensive care unit (ICU) critically ill patients was searched from CNKI, VIP, Wanfang Data, Chinese Clinical Trial Registry, PubMed, Embase, the Cochrane Library, and ClinicalTrials.gov by using the keywords "critically ill patients, conservative oxygen therapy, liberal oxygen therapy, conventional oxygen therapy, mortality" until October 30th in 2018. The main outcome indicators were short-term mortality (28-day mortality or ICU mortality); secondary indicators were 90-day mortality, duration of mechanical ventilation, the length of ICU stay, total hospitalization time, new infection rate in ICU and incidence of new organ dysfunction in ICU. In the conservative oxygen therapy group, the aim of pulse oxygen saturation (SpO2) was 0.90-0.92 or the arterial partial oxygen pressure (PaO2) was 70-100 mmHg (1 mmHg = 0.133 kPa), while in conventional oxygen therapy group SpO2 > 0.96 or PaO2 > 150 mmHg. Literature search, quality evaluation and data extraction was conducted independently by the two authors. The quality of these study was evaluated using Cochrane risk deviation assessment tool, and the relevant data were analyzed using RevMan 5.3 software. Four studies were included in the analysis, these studies were assessed as moderate to high quality studies. A total of 1 076 patients were enrolled, with 539 in the conservative oxygen therapy group and 537 in the conventional oxygen therapy group. Compared with conventional oxygen therapy group, short-term mortality [odds ratio (OR) = 0.66, 95% confidence interval (95%CI) = 0.50-0.87, P = 0.003] and the incidence of new organ dysfunction in ICU (OR = 0.64, 95%CI = 0.41-0.99, P = 0.04) were significantly decreased in conservative oxygen therapy group, duration of mechanical ventilation was significantly prolonged [standardized mean difference (SMD) = 17.17, 95%CI = 7.14-27.21, P = 0.000 8]. But there was no significantly difference in 90-day mortality (OR = 0.83, 95%CI = 0.59-1.17, P = 0.28), new infection rate in ICU (OR = 0.90, 95%CI = 0.66-1.21, P = 0.47), the length of ICU stay (SMD = -0.22, 95%CI = -1.02-0.59, P = 0.60) and total hospitalization time (SMD = 1.44, 95%CI = -1.43-4.31, P = 0.32) between the two groups. Compared with conventional oxygen therapy, conservative oxygen therapy can reduce short-term mortality and the incidence of organ dysfunction in critically ill patients, but cannot decrease the length of ICU stay and total hospitalization time.

Is an IOTA of evidence enough?

Clinical questionDo patients with acute illness admitted to the hospital and treated with liberal oxygen therapy compared with those treated with conservative oxygen therapy have differences in mortality and morbidity?Article chosenChu DK, Kim LH, Young PJ, et al. Mortality and morbidity in acutely ill adults treated with liberal versus conservative oxygen therapy (IOTA): a systematic review and meta-analysis. Lancet 2018;391(10131):1693-705. OBJECTIVES: To analyse the existing literature to assess the potential benefits or harms of supplemental oxygen use in acutely ill patients.

Design and Conduct of The New Zealand Oxygen Therapy in Acute Coronary Syndromes Trial

The New Zealand oxygen trial was designed to determine whether supplemental oxygen influences 30-day mortality in patients presenting with suspected acute coronary syndrome (ACS). Methods: This trial evaluated two oxygen protocols administered as part of usual care by the ambulance, emergency department, coronary care unit (CCU), and cardiac catheter lab to patients presenting with proven or suspected ACS. The high oxygen strategy recommended: “give oxygen for ischaemic chest pain or ischaemic ECG changes and maintain SpO2 ≥95%”. The Conservative oxygen strategy recommended: “Do not give oxygen unless the measured oxygen saturation is consistently <90%. If oxygen is given, aim target SpO2 90 to 94%.” Randomisation was by regional cardiac clinical network (n = 4) and study period. The study population included patients attended by the ambulance service managed on the ACS pathway or with an ACS and included in the All New Zealand Acute Coronary Syndrome-Quality Improvement (ANZACS-QI) registry between 11 July 2016 and 11 July 2018, excluding two 2-week crossover periods. Data for the primary outcome of 30-day total mortality are currently awaited. Information on study conduct, audit of protocol adherence, and comparison with other reported trials will be presented. Conclusion: The New Zealand oxygen study demonstrates that simple pragmatic trials can be undertaken at modest cost in NZ as part of usual care. Results will inform whether oxygen administration has a neutral, favourable, or unfavourable effect on 30-day mortality in patients presenting with a suspected ACS.

Review: Liberal oxygen increases mortality in acutely ill adults compared with conservative oxygen therapy.

Source Citation Chu DK, Kim LH, Young PJ, et al. Mortality and morbidity in acutely ill adults treated with liberal versus conservative oxygen therapy (IOTA): a systematic review and meta-analysis....

Conservative versus liberal oxygenation targets in critically ill children: the randomised multiple-centre pilot Oxy-PICU trial.

Oxygen saturation monitoring for children receiving respiratory support is standard worldwide. No randomised clinical trials have compared peripheral oxygen saturation (SpO2) targets for critically ill children. The harm of interventions to raise SpO2 to > 94% may exceed their benefits. We undertook an open, parallel-group randomised trial of children > 38weeks completed gestation and < 16years of age receiving invasive or non-invasive respiratory support and supplemental oxygen who were admitted urgently to one of three paediatric intensive care units. A 'research without prior consent' approach was employed. Children were randomly assigned to a liberal oxygenation group (SpO2 targets > 94%) or a conservative oxygenation group (SpO2=88-92% inclusive). Outcomes were measures of feasibility: recruitment rate, protocol adherence and acceptability, between-group separation of SpO2 and safety. The Oxy-PICU trial was registered before recruitment: ClinicalTrials.gov identifier NCT03040570. A total of 159 children met the inclusion criteria, of whom 119 (75%) were randomised between April and July 2017, representing a rate of 10 patients per month per site. The mean time to randomisation from first contact with an intensive care team was 1.9 (SD 2.2)h. Consent to continue in the study was obtained in 107 cases (90%); the children's parents/legal representatives were supportive of the consent process. The median (interquartile range, IQR) of time-weighted individual mean SpO2 was 94.9% (92.6-97.1) in the conservative oxygenation group and 97.5% (96.2-98.4) in the liberal group [difference 2.7%, 95% confidence interval (95% CI) 1.3-4.0%, p < 0.001]. Median (IQR) time-weighted individual mean FiO2 was 0.28 (0.24-0.37) in the conservative group and 0.37 (0.30-0.42) in the liberal group (difference 0.08, 95% CI 0.03-0.13, p < 0.001). There were no significant between-group differences in length of stay, duration of organ support or mortality. Two prespecified serious adverse events (cardiac arrests) occurred, both in the liberal oxygenation group. A definitive clinical trial of peripheral oxygen saturation targets is feasible in critically ill children.

Mortality and morbidity in acutely ill adults treated with liberal versus conservative oxygen therapy (IOTA): a systematic review and meta-analysis

Supplemental oxygen is often administered liberally to acutely ill adults, but the credibility of the evidence for this practice is unclear. We systematically reviewed the efficacy and safety of liberal versus conservative oxygen therapy in acutely ill adults. In the Improving Oxygen Therapy in Acute-illness (IOTA) systematic review and meta-analysis, we searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, HealthSTAR, LILACS, PapersFirst, and the WHO International Clinical Trials Registry from inception to Oct 25, 2017, for randomised controlled trials comparing liberal and conservative oxygen therapy in acutely ill adults (aged ≥18 years). Studies limited to patients with chronic respiratory diseases or psychiatric disease, patients on extracorporeal life support, or patients treated with hyperbaric oxygen therapy or elective surgery were excluded. We screened studies and extracted summary estimates independently and in duplicate. We also extracted individual patient-level data from survival curves. The main outcomes were mortality (in-hospital, at 30 days, and at longest follow-up) and morbidity (disability at longest follow-up, risk of hospital-acquired pneumonia, any hospital-acquired infection, and length of hospital stay) assessed by random-effects meta-analyses. We assessed quality of evidence using the grading of recommendations assessment, development, and evaluation approach. This study is registered with PROSPERO, number CRD42017065697. 25 randomised controlled trials enrolled 16 037 patients with sepsis, critical illness, stroke, trauma, myocardial infarction, or cardiac arrest, and patients who had emergency surgery. Compared with a conservative oxygen strategy, a liberal oxygen strategy (median baseline saturation of peripheral oxygen [SpO2] across trials, 96% [range 94-99%, IQR 96-98]) increased mortality in-hospital (relative risk [RR] 1·21, 95% CI 1·03-1·43, I2=0%, high quality), at 30 days (RR 1·14, 95% CI 1·01-1·29, I2=0%, high quality), and at longest follow-up (RR 1·10, 95% CI 1·00-1·20, I2=0%, high quality). Morbidity outcomes were similar between groups. Findings were robust to trial sequential, subgroup, and sensitivity analyses. In acutely ill adults, high-quality evidence shows that liberal oxygen therapy increases mortality without improving other patient-important outcomes. Supplemental oxygen might become unfavourable above an SpO2 range of 94-96%. These results support the conservative administration of oxygen therapy. None.

Excess oxygen in acute illness: adding fuel to the fire

Oxygen is essential for life and is the third most abundant element in the universe. This abundance is evident in the treatment of acutely ill adults admitted to intensive and progressive care units around the world, in whom excess oxygen is frequently provided for inhalation. The typical motivation for liberal oxygen administration is the prevention of hypoxaemia. By contrast, few health-care providers are concerned about hyperoxaemia—ie, highly elevated arterial oxygen concentrations (arterial oxygen tension >100 mm Hg). As a cardiologist working in cardiac intensive care, I am familiar with the panic often incited by a patient with hypoxaemia. Bedside alarms ring, nurses justifiably fret, and pagers vibrate. However, I have never been called to treat a patient with hyperoxaemia. On the basis of accumulating observational evidence 1 Damiani E Adrario E Girardis M et al. Arterial hyperoxia and mortality in critically ill patients: a systematic review and meta-analysis. Crit Care. 2014; 18: 711 Crossref PubMed Scopus (210) Google Scholar , 2 Helmerhorst HJ Roos-Blom MJ van Westerloo DJ de Jonge E Association between arterial hyperoxia and outcome in subsets of critical illness: a systematic review, meta-analysis, and meta-regression of cohort studies. Crit Care Med. 2015; 43: 1508-1519 Crossref PubMed Scopus (198) Google Scholar , 3 Aggarwal NR Brower RG Hager DN et al. Oxygen exposure resulting in arterial oxygen tensions above the protocol goal was associated with worse clinical outcomes in acute respiratory distress syndrome. Crit Care Med. 2018; 46: 517-524 Crossref PubMed Scopus (55) Google Scholar and a compelling meta-analysis of randomised trials by Derek K Chu and colleagues in The Lancet, 4 Chu DK Kim LH-Y Young PJ et al. Mortality and morbidity in acutely ill adults treated with liberal versus conservative oxygen therapy (IOTA): a systematic review and meta-analysis. Lancet. 2018; 391: 1693-1705 Summary Full Text Full Text PDF PubMed Scopus (411) Google Scholar perhaps that is about to change. Mortality and morbidity in acutely ill adults treated with liberal versus conservative oxygen therapy (IOTA): a systematic review and meta-analysisIn acutely ill adults, high-quality evidence shows that liberal oxygen therapy increases mortality without improving other patient-important outcomes. Supplemental oxygen might become unfavourable above an SpO2 range of 94–96%. These results support the conservative administration of oxygen therapy. Full-Text PDF

Oxygen in the critically ill: friend or foe?

To examine the potential harmful effects of hyperoxia and summarize the results of most recent clinical studies evaluating oxygen therapy in critically ill patients. Excessive oxygen supplementation may have detrimental pulmonary and systemic effects because of enhanced oxidative stress and inflammation. Hyperoxia-induced lung injury includes altered surfactant protein composition, reduced mucociliary clearance and histological damage, resulting in atelectasis, reduced lung compliance and increased risk of infections. Hyperoxemia causes vasoconstriction, reduction in coronary blood flow and cardiac output and may alter microvascular perfusion. Observational studies showed a close relationship between hyperoxemia and increased mortality in several subsets of critically ill patients. In absence of hypoxemia, the routine use of oxygen therapy in patients with myocardial infarction, stroke, traumatic brain injury, cardiac arrest and sepsis, showed no benefit but rather it seems to be harmful. In patients admitted to intensive care unit, a conservative oxygen therapy aimed to maintain arterial oxygenation within physiological range has been proved to be well tolerated and may improve outcome. Liberal O2 use and unnecessary hyperoxia may be detrimental in critically ill patients. The current evidence supports the use of a conservative strategy in O2 therapy to avoid patient exposure to unnecessary hyperoxemia.

Protocol for a randomised pilot multiple centre trial of conservative versus liberal oxygenation targets in critically ill children (Oxy-PICU)

IntroductionOptimal targets for systemic oxygenation in paediatric critical illness are unknown. Observational data indicate that high levels of arterial oxygenation are associated with poor outcomes in resuscitation of the newborn...

Relationship between hyperoxemia and ventilator associated pneumonia.

Previous studies suggest a relationship between hyperoxemia and ventilator-associated pneumonia (VAP). Hyperoxemia is responsible for denitrogenation phenomena, and inhibition of surfactant production, promoting atelectasis in mechanically ventilated patients. Further, hyperoxemia impairs the efficacy of alveolar macrophages to migrate, phagocyte and kill bacteria. Oxygen can also cause pulmonary-specific toxic effect called hyperoxic acute lung injury leading to longer duration of mechanical ventilation. All these hyperoxic effects are well-known risk factors for VAP. A recent retrospective large single center study identified hyperoxemia as an independent risk factor for VAP. However, two recent randomized controlled trials evaluated the impact of conservative oxygen strategy versus a liberal strategy, but did not confirm the role of hyperoxemia in lower respiratory tract infection occurrence. In this review, we discuss animal and human studies suggesting a relationship between these two common conditions in mechanically ventilated patients and potential interventions that should be evaluated. Further large prospective studies in carefully selected groups of patients are required to confirm the potential role of hyperoxemia in VAP pathogenesis and to evaluate the impact of a conservative oxygen strategy vs. a conventional strategy on the incidence of VAP.

Conservative Oxygen Therapy Might be Beneficial to Patients in the Intensive Care Unit

Conservative Oxygen Therapy Might be Beneficial to Patients in the Intensive Care Unit

Soil water migration in the unsaturated zone of semiarid region in China from isotope evidence

Abstract. Soil water is an important driving force of the ecosystems, especially in the semiarid hill and gully region of the northwestern Loess Plateau in China. The mechanism of soil water migration in the reconstruction and restoration of Loess Plateau is a key scientific problem that must be solved. Isotopic tracers can provide valuable information associated with complex hydrological problems, difficult to obtain using other methods. In this study, the oxygen and hydrogen isotopes are used as tracers to investigate the migration processes of soil water in the unsaturated zone in an arid region of China's Loess Plateau. Samples of precipitation, soil water, plant xylems and plant roots are collected and analysed. The conservative elements deuterium (D) and oxygen (18O) are used as tracers to identify variable source and mixing processes. The mixing model is used to quantify the contribution of each end member and calculate mixing amounts. The results show that the isotopic composition of precipitation in the Anjiagou River basin is affected by isotopic fractionation due to evaporation. The isotopic compositions of soil waters are plotted between or near the local meteoric water lines, indicating that soil waters are recharged by precipitation. The soil water migration is dominated by piston-type flow in the study area and rarely preferential flow. Water migration exhibited a transformation pathway from precipitation to soil water to plant water. δ18O and δD are enriched in the shallow (&lt; 20 cm depth) soil water in most soil profiles due to evaporation. The isotopic composition of xylem water is close to that of soil water at the depth of 40–60 cm. These values reflect soil water signatures associated with Caragana korshinskii Kom. uptake at the depth of 40–60 cm. Soil water from the surface soil layer (20–40 cm) comprised 6–12 % of plant xylem water, while soil water at the depth of 40–60 cm is the largest component of plant xylem water (ranging from 60 to 66 %), soil water below 60 cm depth comprised 8–14 % of plant xylem water and only 5–8 % is derived directly from precipitation. This study investigates the migration process of soil water, identifies the source of plant water and finally provides a scientific basis for identification of model structures and parameters. It can provide a scientific basis for ecological water demand, ecological restoration, and management of water resources.

Effect of Conservative vs Conventional Oxygen Therapy on Mortality Among Patients in an Intensive Care Unit: The Oxygen-ICU Randomized Clinical Trial.

Despite suggestions of potential harm from unnecessary oxygen therapy, critically ill patients spend substantial periods in a hyperoxemic state. A strategy of controlled arterial oxygenation is thus rational but has not been validated in clinical practice. To assess whether a conservative protocol for oxygen supplementation could improve outcomes in patients admitted to intensive care units (ICUs). Oxygen-ICU was a single-center, open-label, randomized clinical trial conducted from March 2010 to October 2012 that included all adults admitted with an expected length of stay of 72 hours or longer to the medical-surgical ICU of Modena University Hospital, Italy. The originally planned sample size was 660 patients, but the study was stopped early due to difficulties in enrollment after inclusion of 480 patients. Patients were randomly assigned to receive oxygen therapy to maintain Pao2 between 70 and 100 mm Hg or arterial oxyhemoglobin saturation (Spo2) between 94% and 98% (conservative group) or, according to standard ICU practice, to allow Pao2 values up to 150 mm Hg or Spo2 values between 97% and 100% (conventional control group). The primary outcome was ICU mortality. Secondary outcomes included occurrence of new organ failure and infection 48 hours or more after ICU admission. A total of 434 patients (median age, 64 years; 188 [43.3%] women) received conventional (n = 218) or conservative (n = 216) oxygen therapy and were included in the modified intent-to-treat analysis. Daily time-weighted Pao2 averages during the ICU stay were significantly higher (P < .001) in the conventional group (median Pao2, 102 mm Hg [interquartile range, 88-116]) vs the conservative group (median Pao2, 87 mm Hg [interquartile range, 79-97]). Twenty-five patients in the conservative oxygen therapy group (11.6%) and 44 in the conventional oxygen therapy group (20.2%) died during their ICU stay (absolute risk reduction [ARR], 0.086 [95% CI, 0.017-0.150]; relative risk [RR], 0.57 [95% CI, 0.37-0.90]; P = .01). Occurrences were lower in the conservative oxygen therapy group for new shock episode (ARR, 0.068 [95% CI, 0.020-0.120]; RR, 0.35 [95% CI, 0.16-0.75]; P = .006) or liver failure (ARR, 0.046 [95% CI, 0.008-0.088]; RR, 0.29 [95% CI, 0.10-0.82]; P = .02) and new bloodstream infection (ARR, 0.05 [95% CI, 0.00-0.09]; RR, 0.50 [95% CI, 0.25-0.998; P = .049). Among critically ill patients with an ICU length of stay of 72 hours or longer, a conservative protocol for oxygen therapy vs conventional therapy resulted in lower ICU mortality. These preliminary findings were based on unplanned early termination of the trial, and a larger multicenter trial is needed to evaluate the potential benefit of this approach. clinicaltrials.gov Identifier: NCT01319643.

Should Oxygen Therapy Be Tightly Regulated to Minimize Hyperoxia in Critically Ill Patients?

Oxygen is both lifesaving and toxic. Appropriate use of oxygen aims to provide a balance between the two effects. Although local oxygen toxicity to the lung is well accepted, recent evidence has called into question the negative consequences of hyperoxemia in other organ beds. Hyperoxia following cardiac arrest, traumatic brain injury, and stroke has been shown to worsen outcomes. The role of hyperoxemia in mechanically ventilated patients, in the face of non-toxic inspired oxygen concentrations, is less clear. This paper will review the data for and against the use of conservative oxygen targets and the avoidance of hyperoxemia in mechanically ventilated patients.

Moderate hyperoxic versus near-physiological oxygen targets during and after coronary artery bypass surgery: a randomised controlled trial.

BackgroundThe safety of perioperative hyperoxia is currently unclear. Previous studies in patients undergoing coronary artery bypass surgery suggest reduced myocardial damage when avoiding extreme perioperative hyperoxia (>400 mmHg). In this study we investigated whether an oxygenation strategy from moderate hyperoxia to a near-physiological oxygen tension reduces myocardial damage and improves haemodynamics, organ dysfunction and oxidative stress.MethodsThis was a single-blind, single-centre, open-label, randomised controlled trial in patients undergoing elective coronary artery bypass surgery. Fifty patients were randomised to a partial pressure of oxygen in arterial blood (PaO2) target of 200–220 mmHg during cardiopulmonary bypass and 130–150 mmHg during intensive care unit (ICU) admission (control group) versus lower targets of 130–150 mmHg during cardiopulmonary bypass and 80–100 mmHg at the ICU (conservative group). Primary outcome was myocardial injury (CK-MB and Troponin-T) at ICU admission and 2, 6 and 12 hours thereafter.ResultsWeighted PaO2 during cardiopulmonary bypass was 220 mmHg (interquartile range (IQR) 211–233) vs. 157 (151–162) in the control and conservative group, respectively (P < 0.0001). During ICU admission, weighted PaO2 was 107 mmHg (86–141) vs. 90 (84–98) (P = 0.03), respectively. Area under the curve of CK-MB was median 23.5 μg/L/h (IQR 18.4–28.1) vs. 21.5 (15.8–26.6) (P = 0.35) and 0.30 μg/L/h (0.25–0.44) vs. 0.39 (0.24–0.43) (P = 0.81) for Troponin-T. Cardiac index, systemic vascular resistance index, creatinine, lactate and F2-isoprostane levels were not different between groups.ConclusionsCompared to moderate hyperoxia, a near-physiological oxygen strategy does not reduce myocardial damage in patients undergoing coronary artery bypass surgery. Conservative oxygen administration was not associated with increased lactate levels or hypoxic events.Trial registrationNetherlands Trial Registry NTR4375, registered on 30 January 2014Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1240-6) contains supplementary material, which is available to authorized users.

Effectiveness and Clinical Outcomes of a Two-Step Implementation of Conservative Oxygenation Targets in Critically Ill Patients: A Before and After Trial.

Conservative oxygen therapy is aimed at the prevention of harm by iatrogenic hyperoxia while preserving adequate tissue oxygenation. Our aim was to study the effectiveness and clinical outcomes of a two-step implementation of conservative oxygenation targets in the ICU. This was a before and after stepwise implementation study of conservative oxygenation targets, between July 2011 and July 2014. The primary endpoint was the proportion of PaO2 values within the target range. Secondary outcomes included ventilator-free days at day 28, length of stay, and mortality. Three closed-format ICUs in the Netherlands. We analyzed data on 15,045 eligible admissions. The first implementation phase consisted of providing training and feedback on new guidelines instructing for explicit targets for arterial oxygen tension (PaO2, 55-86 mm Hg) and oxyhemoglobin saturation (SpO2, 92-95%). In the second phase, bedside clinicians were additionally assisted in guideline adherence by a computerized decision-support system. The proportion of PaO2 in the target range increased from 47% at baseline to 63% in phase 1 and to 68% in phase 2 (p < 0.0001). Episodes of hyperoxia decreased (p < 0.0001), whereas hypoxic episodes remained unchanged (p = 0.06) during the study. Mechanical ventilation time was significantly lower (p < 0.01) during both study phases. After adjustment for potential confounders, ventilator-free days in phase 1 and phase 2 were higher than baseline: adjusted mean difference, 0.55 (95% CI, 0.25-0.84) and 0.48 (95% CI, 0.11-0.86), respectively. Adjusted ICU mortality and ICU-free days did not significantly differ between study phases. Hospital mortality decreased in reference to baseline: adjusted odds ratio, 0.84 (95% CI, 0.74-0.96) for phase 1 and 0.82 (95% CI, 0.69-0.96) for phase 2. Stepwise implementation of conservative oxygenation targets was feasible, effective, and seemed safe in critically ill patients. The implementation was associated with several changes in clinical outcomes, but the causal impact of conservative oxygenation is still to be determined.

Conservative versus liberal oxygenation targets for mechanically ventilated patients-a pilot multicenter randomized controlled trial.

Panwar and colleagues recently reported the results of a prospective multicenter international interventional trial comparing two oxygenation targets in all-comer patients receiving invasive mechanical ventilation in ICU, namely a conservative (SpO2 88–92%) versus a liberal target (≥96%), by accommodating FIO2 (1). The rationale behind this was that no previous trial was done to compare different oxygenation goals in mechanically ventilated patients. Even though oxygen therapy is frequently used in the critical care setting, its goals are not well defined. The primary outcome was the area under curve of transcutaneous oxygen saturation (SpO2). They included 104 patients in both groups and found that the primary end-point was significantly lower in the conservative than in the liberal group. From this result the authors concluded that reaching a conservative oxygenation target is feasible, which will serve for an upcoming large trial testing these two oxygenation levels. We would like to split the present editorial into three sections. The first is about the pathophysiological rationale of the study. The second deals with the methodology and the results of the trial. The third will discuss its strengths and limitations.

Conservative oxygen therapy in mechanically ventilated patients following cardiac arrest: A retrospective nested cohort study

BackgroundIn mechanically ventilated (MV) cardiac arrest (CA) survivors admitted to the intensive care unit (ICU) avoidance of hypoxia is considered crucial. However, avoidance of hyperoxia may also be important. A conservative approach to oxygen therapy may reduce exposure to both. MethodsWe evaluated the introduction of conservative oxygen therapy (target SpO2 88–92% using the lowest FiO2) during MV for resuscitated CA patients admitted to the ICU. ResultsWe studied 912 arterial blood gas (ABG) datasets: 448 ABGs from 50 ‘conventional’ and 464 ABGs from 50 ‘conservative’ oxygen therapy patients. Compared to the conventional group, conservative group patients had significantly lower PaO2 values and FiO2 exposure (p<0.001, respectively); more received MV in a spontaneous ventilation mode (18% vs 2%; p=0.001) and more were exposed to a FiO2 of 0.21 (19 vs 0 patients, p=0.001). Additionally, according to mean PaO2, more conservative group patients were classified as normoxaemic (36 vs 16 patients, p<0.01) and fewer as hyperoxaemic (14 vs 33 patients, p<0.01). Finally, ICU length of stay was significantly shorter for conservative group patients (p=0.04). There was no difference in the proportion of survivors discharged from hospital with good neurological outcome (14/23 vs 12/22 patients, p=0.67). ConclusionsOur findings provide preliminary support for the feasibility and physiological safety of conservative oxygen therapy in patients admitted to ICU for MV support after cardiac arrest (Trial registration, NCT01684124).