Early hyperoxemia is associated with lower adjusted mortality after severe trauma: results from a French registry

Evaluation of a portable, lightweight modular system to deliver high inspired oxygen to trauma casualties without the use of pressurised cylinders

INTRODUCTION

Administering supplemental oxygen is a standard of care for trauma casualties to minimise the deleterious effects of hypoxaemia. Forward deployment of oxygen using pressurised cylinders is challenging, for example, logistics (weight and finite resource) and environmental risk (fire and explosion). Oxygen concentrators may overcome these challenges. Although previous studies successfully demonstrated fractional inspired oxygen (FiO2) >0.8 using oxygen concentrators and ventilators, the systems did not fulfil the size, weight and power requirements of agile military medical units. This study evaluated whether a modular system of commercially available clinical devices could supply high FiO2 to either ventilated or spontaneously breathing casualties.

METHODS

As a proof of principle, we configured an Inogen One G5 oxygen concentrator, Ventway Sparrow ventilator and Wenoll rebreather system to ventilate a simulated lung (tidal volume 500 mL). Casualty oxygen consumption (gas withdrawal inspiratory limb) and carbon dioxide (CO2) production (CO2 added expiratory limb) were simulated (respiratory quotient of 0.7-0.8). Three circuit configurations were evaluated: open (supplementary oxygen introduced into air inlet of ventilator); semiclosed (ventilator replaces rebreather bag of Wenoll, oxygen connected to either ventilator or Wenoll); and semiclosed with reservoir tubing (addition of 'deadspace' tube between ventilator patient circuit and Wenoll). Data presented as mean and 95% reference range.

RESULTS

There were modest increases in FiO2 with increasing Inogen settings in 'open' configuration 0.23 (0.23-0.24) and 0.30 (0.28-0.32) (Inogen output 420 and 1260 mL/min, respectively). With the 'semiclosed' configuration and oxygen added directly into rebreather circuit, FiO2 increased to 0.36 (0.36-0.37). The addition of the 'reservoir tubing' elevated FiO2 to 0.78 (0.71-0.85). FiO2 remained stable over a 4-hour evaluation period. Fractional inspired carbon dioxide CO2 increased over time, reaching 0.005 after 170 (157-182) min.

CONCLUSION

Combining existing lightweight devices can deliver high (>0.8) FiO2 and offers a potential solution for the forward deployment of oxygen without needing pressurised cylinders.

Provider Perceptions of Oxygenation Strategies for Critically Ill Trauma Patients With and Without Moderate-to-Severe Traumatic Brain Injury

BACKGROUND

Hypoxia and hyperoxia (pulse oximetry [SpO2] > 96%) are associated with increased mortality in critically ill patients. However, provider practices regarding oxygenation in traumatic brain injury (TBI) patients are unknown. This study assesses views on oxygenation of critically ill trauma patients with and without TBI and how this varies between Neurological ICU (NeuroICU) and Surgical-Trauma ICU (STICU) providers.

METHODS

This is a cross-sectional survey of Level I trauma center's NeuroICU and STICU providers. We used Likert scales, yes-no questions, and multiple-choice case-based scenarios to characterize provider views on oxygenation with descriptive statistics to characterize responses. Significant differences regarding TBI and non-TBI patients or NeuroICU and STICU providers were determined using Fisher's exact test and a P-value of .05.

RESULTS

A total of 83 providers initiated the survey, and 53 providers completed it. Most providers identified a threshold SpO2 < 92% for the administration of supplemental oxygen in critically ill TBI patients. A total of 9% of providers "somewhat or completely agreed" that they were more likely to give supplemental oxygen to a critically ill trauma patient with TBI than one without TBI and the same SpO2. A total of 48% of providers selected an SpO2 < 90% as the point at which supplemental oxygen should be initiated in patients without TBI, compared to 27% of providers in patients with TBI (P < .01). This threshold for supplemental oxygen use varied by provider type for non-TBI patients, but not for TBI patients (30% NeuroICU and 69% STICU providers selected SpO2 < 90% in non-TBI, P < .05; 30% NeuroICU and 35% STICU providers selected SpO2 < 90% in TBI, P = .85).

CONCLUSIONS

Critical care providers at UCHealth University of Colorado Hospital approach the oxygenation of critically ill trauma patients with and without TBI differently. Specifically, critical care respondents accepted a different lower oxygen saturation threshold for TBI and non-TBI patients. NeuroICU and STICU respondents differed in their threshold for the down-titration of supplemental oxygen. Targeted education for critical care providers may reduce these discrepancies and optimize oxygen use.

An exploratory study investigating the effect of targeted hyperoxemia in a randomized controlled trial in a long-term resuscitated model of combined acute subdural hematoma and hemorrhagic shock in cardiovascular healthy pigs

Severe physical injuries and associated traumatic brain injury and/or hemorrhagic shock (HS) remain leading causes of death worldwide, aggravated by accompanying extensive inflammation. Retrospective clinical data indicated an association between mild hyperoxemia and improved survival and outcome. However, corresponding prospective clinical data, including long-term resuscutation, are scarce. Therefore, the present study explored the effect of mild hyperoxemia for 24 hours in a prospective randomized controlled trial in a long-term resuscitated model of combined acute subdural hematoma (ASDH) and HS. ASDH was induced by injecting 0.1 ml × kg-1 autologous blood into the subdural space and HS was triggered by passive removal of blood. After 2 hours, the animals received full resuscitation, including retransfusion of the shed blood and vasopressor support. During the first 24 hours, the animals underwent targeted hyperoxemia (PaO2 = 200 - 250 mmHg) or normoxemia (PaO2 = 80 - 120 mmHg) with a total observation period of 55 hours after the initiation of ASDH and HS. Survival, cardiocirculatory stability, and demand for vasopressor support were comparable between both groups. Likewise, humoral markers of brain injury and systemic inflammation were similar. Multimodal brain monitoring, including microdialysis and partial pressure of O2 in brain tissue, did not show significant differences either, despite a significantly better outcome regarding the modified Glasgow Coma Scale 24 hours after shock that favors hyperoxemia. In summary, the present study reports no deleterious and few beneficial effects of mild targeted hyperoxemia in a clinically relevant model of ASDH and HS with long-term resuscitation in otherwise healthy pigs. Further beneficial effects on neurological function were probably missed due to the high mortality in both experimental groups. The present study remains exploratory due to the unavailability of an a priori power calculation resulting from the lack of necessary data.

Hyperoxia is associated with a greater risk for mortality in critically ill traumatic brain injury patients than in critically ill trauma patients without brain injury

OBJECTIVE

The role of hyperoxia in patients with traumatic brain injury (TBI) remains controversial. The objective of this study was to determine the association between hyperoxia and mortality in critically ill TBI patients compared to critically ill trauma patients without TBI.

DESIGN

Secondary analysis of a multicenter retrospective cohort study.

SETTING

Three regional trauma centers in Colorado, USA, between October 1, 2015, and June 30, 2018.

PATIENTS

We included 3464 critically injured adults who were admitted to an intensive care unit (ICU) within 24 h of arrival and qualified for inclusion into the state trauma registry. We analyzed all available SpO2 values during the first seven ICU days. The primary outcome was in-hospital mortality. Secondary outcomes included the proportion of time spent in hyperoxia (defined as SpO2 > 96%) and ventilator-free days.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

In-hospital mortality occurred in 163 patients (10.7%) in the TBI group and 101 patients (5.2%) in the non-TBI group. After adjusting for ICU length of stay, TBI patients spent a significantly greater amount of time in hyperoxia versus non-TBI patients (p = 0.024). TBI status significantly modified the effect of hyperoxia on mortality. At each specific SpO2 level, the risk of mortality increases with increasing FiO2 for both patients with and without TBI. This trend was more pronounced at lower FiO2 and higher SpO2 values, where a greater number of patient observations were obtained. Among patients who required invasive mechanical ventilation, TBI patients required significantly more days of ventilation to day 28 than non-TBI patients.

CONCLUSIONS

Critically ill trauma patients with a TBI spend a greater proportion of time in hyperoxia compared to those without a TBI. TBI status significantly modified the effect of hyperoxia on mortality. Prospective clinical trials are needed to better assess a possible causal relationship.

High arterial oxygen levels and supplemental oxygen administration in traumatic brain injury: insights from CENTER-TBI and OzENTER-TBI

PURPOSE

The effect of high arterial oxygen levels and supplemental oxygen administration on outcomes in traumatic brain injury (TBI) is debated, and data from large cohorts of TBI patients are limited. We investigated whether exposure to high blood oxygen levels and high oxygen supplementation is independently associated with outcomes in TBI patients admitted to the intensive care unit (ICU) and undergoing mechanical ventilation.

METHODS

This is a secondary analysis of two multicenter, prospective, observational, cohort studies performed in Europe and Australia. In TBI patients admitted to ICU, we describe the arterial partial pressure of oxygen (PaO₂) and the oxygen inspired fraction (FiO₂). We explored the association between high PaO₂ and FiO₂ levels within the first week with clinical outcomes. Furthermore, in the CENTER-TBI cohort, we investigate whether PaO₂ and FiO₂ levels may have differential relationships with outcome in the presence of varying levels of brain injury severity (as quantified by levels of glial fibrillary acidic protein (GFAP) in blood samples obtained within 24 h of injury).

RESULTS

The analysis included 1084 patients (11,577 measurements) in the CENTER-TBI cohort, of whom 55% had an unfavorable outcome, and 26% died at a 6-month follow-up. Median PaO₂ ranged from 93 to 166 mmHg. Exposure to higher PaO₂ and FiO₂ in the first seven days after ICU admission was independently associated with a higher mortality rate. A trend of a higher mortality rate was partially confirmed in the OzENTER-TBI cohort (n = 159). GFAP was independently associated with mortality and functional neurologic outcome at follow-up, but it did not modulate the outcome impact of high PaO₂ levels, which remained independently associated with 6-month mortality.

CONCLUSIONS

In two large prospective multicenter cohorts of critically ill patients with TBI, levels of PaO₂ and FiO₂ varied widely across centers during the first seven days after ICU admission. Exposure to high arterial blood oxygen or high supplemental oxygen was independently associated with 6-month mortality in the CENTER-TBI cohort, and the severity of brain injury did not modulate this relationship. Due to the limited sample size, the findings were not wholly validated in the external OzENTER-TBI cohort. We cannot exclude the possibility that the worse outcomes associated with higher PaO₂ were due to use of higher FiO₂ in patients with more severe injury or physiological compromise. Further, these findings may not apply to patients in whom FiO₂ and PaO₂ are titrated to brain tissue oxygen monitoring (PbtO₂) levels. However, at minimum, these findings support the need for caution with oxygen therapy in TBI, particularly since titration of supplemental oxygen is immediately applicable at the bedside.

Effect of sex on the association between arterial partial pressure of oxygen and in-hospital mortality in ICU patients with cardiogenic shock: a retrospective cohort study

Background

Maintaining tissue perfusion and oxygen supply are essential for cardiogenic shock (CS) treatment. Sex has been reported to be associated with mortality and oxygen use in patients with CS. Males and females respond differently to hypoxia. We designed this cohort study to evaluate the effects of sex on the association between the arterial partial pressure of oxygen (PaO₂) and in-hospital mortality.

Methods

We used the Medical Information Mart for Intensive Care (MIMIC) IV database for this cohort study. The outcome was in-hospital mortality. The relationship between the PaO₂ and in-hospital mortality was compared with sex (via an interaction test) using multivariable Cox regression models. Presence of interaction between PaO₂ and sex was tested by using inter interaction terms.

Results

A total of 1,772 patients with CS were enrolled in this study. The association between PaO₂ and in-hospital mortality appeared to differ between males and females [hazard ratio (HR): 0.997, 95% confidence interval (CI): 0.995-0.999 vs. HR: 1.002, 95% CI: 0.999-1.003, P for interaction =0.002]. We repeated the analyses, based on different PaO₂ category (PaO₂ <60 mmHg; PaO₂ 60-100 mmHg; PaO₂ >100 mmHg) and the results remained stable, P for interaction =0.008.

Conclusions

Sex affects the relationship between PaO₂ and in-hospital mortality in CS patients. Our findings may lead to the development of individualized therapies that focus on the use of different target oxygen partial pressures in different sexes to treat patients with CS.

The effect of targeted hyperoxemia in a randomized controlled trial employing a long-term resuscitated, model of combined acute subdural hematoma and hemorrhagic shock in swine with coronary artery disease: An exploratory, hypothesis-generating study

Controversial evidence is available regarding suitable targets for the arterial O₂ tension (P_aO₂) after traumatic brain injury and/or hemorrhagic shock (HS). We previously demonstrated that hyperoxia during resuscitation from hemorrhagic shock attenuated cardiac injury and renal dysfunction in swine with coronary artery disease. Therefore, this study investigated the impact of targeted hyperoxemia in a long-term, resuscitated model of combined acute subdural hematoma (ASDH)-induced brain injury and HS. The prospective randomized, controlled, resuscitated animal investigation consisted of 15 adult pigs. Combined ASDH plus HS was induced by injection of 0.1 ml/kg autologous blood into the subdural space followed by controlled passive removal of blood. Two hours later, resuscitation was initiated comprising re-transfusion of shed blood, fluids, continuous i.v. noradrenaline, and either hyperoxemia (target P_aO₂ 200 – 250 mmHg) or normoxemia (target P_aO₂ 80 – 120 mmHg) during the first 24 h of the total of 54 h of intensive care. Systemic hemodynamics, intracranial and cerebral perfusion pressures, parameters of brain microdialysis and blood biomarkers of brain injury did not significantly differ between the two groups. According to the experimental protocol, P_aO₂ was significantly higher in the hyperoxemia group at the end of the intervention period, i.e., at 24 h of resuscitation, which coincided with a higher brain tissue PO₂. The latter persisted until the end of observation period. While neurological function as assessed using the veterinary Modified Glasgow Coma Score progressively deteriorated in the control group, it remained unaffected in the hyperoxemia animals, however, without significant intergroup difference. Survival times did not significantly differ in the hyperoxemia and control groups either. Despite being associated with higher brain tissue PO₂ levels, which were sustained beyond the intervention period, targeted hyperoxemia exerted neither significantly beneficial nor deleterious effects after combined ASDH and HS in swine with pre-existing coronary artery disease. The unavailability of a power calculation and, thus, the limited number of animals included, are the limitations of the study.

ICONIC study—conservative versus conventional oxygenation targets in intensive care patients: study protocol for a randomized clinical trial

Background

Oxygen therapy is a widely used intervention in acutely ill patients in the intensive care unit (ICU). It is established that not only hypoxia, but also prolonged hyperoxia is associated with poor patient-centered outcomes. Nevertheless, a fundamental knowledge gap remains regarding optimal oxygenation for critically ill patients. In this randomized clinical trial, we aim to compare ventilation that uses conservative oxygenation targets with ventilation that uses conventional oxygen targets with respect to mortality in ICU patients.

Methods

The “ConservatIve versus CONventional oxygenation targets in Intensive Care patients” trial (ICONIC) is an investigator-initiated, international, multicenter, randomized clinical two-arm trial in ventilated adult ICU patients. The ICONIC trial will run in multiple ICUs in The Netherlands and Italy to enroll 1512 ventilated patients. ICU patients with an expected mechanical ventilation time of more than 24 h are randomized to a ventilation strategy that uses conservative (PaO₂ 55–80 mmHg (7.3–10.7 kPa)) or conventional (PaO₂ 110–150 mmHg (14.7–20 kPa)) oxygenation targets. The primary endpoint is 28-day mortality. Secondary endpoints are ventilator-free days at day 28, ICU mortality, in-hospital mortality, 90-day mortality, ICU- and hospital length of stay, ischemic events, quality of life, and patient opinion of research and consent in the emergency setting.

Discussion

The ICONIC trial is expected to provide evidence on the effects of conservative versus conventional oxygenation targets in the ICU population. This study may guide targeted oxygen therapy in the future.

Trial registration

Trialregister.nl NTR7376. Registered on 20 July, 2018.

Perioperative Management of Polytrauma Patients with Severe Traumatic Brain Injury Undergoing Emergency Extracranial Surgery: A Narrative Review

Managing the acute phase after a severe traumatic brain injury (TBI) with polytrauma represents a challenging situation for every trauma team member. A worldwide variability in the management of these complex patients has been reported in recent studies. Moreover, limited evidence regarding this topic is available, mainly due to the lack of well-designed studies. Anesthesiologists, as trauma team members, should be familiar with all the issues related to the management of these patients. In this narrative review, we summarize the available evidence in this setting, focusing on perioperative brain protection, cardiorespiratory optimization, and preservation of the coagulative function. An overview on simultaneous multisystem surgery (SMS) is also presented.

Dangers of hyperoxia

Oxygen (O2) toxicity remains a concern, particularly to the lung. This is mainly related to excessive production of reactive oxygen species (ROS). Supplemental O2, i.e. inspiratory O2 concentrations (FIO2) > 0.21 may cause hyperoxaemia (i.e. arterial (a) PO2 > 100 mmHg) and, subsequently, hyperoxia (increased tissue O2 concentration), thereby enhancing ROS formation. Here, we review the pathophysiology of O2 toxicity and the potential harms of supplemental O2 in various ICU conditions. The current evidence base suggests that PaO2 > 300 mmHg (40 kPa) should be avoided, but it remains uncertain whether there is an "optimal level" which may vary for given clinical conditions. Since even moderately supra-physiological PaO2 may be associated with deleterious side effects, it seems advisable at present to titrate O2 to maintain PaO2 within the normal range, avoiding both hypoxaemia and excess hyperoxaemia.

Target arterial PO2 according to the underlying pathology: a mini-review of the available data in mechanically ventilated patients

There is an ongoing discussion whether hyperoxia, i.e. ventilation with high inspiratory O2 concentrations (FIO2), and the consecutive hyperoxaemia, i.e. supraphysiological arterial O2 tensions (PaO2), have a place during the acute management of circulatory shock. This concept is based on experimental evidence that hyperoxaemia may contribute to the compensation of the imbalance between O2 supply and requirements. However, despite still being common practice, its use is limited due to possible oxygen toxicity resulting from the increased formation of reactive oxygen species (ROS) limits, especially under conditions of ischaemia/reperfusion. Several studies have reported that there is a U-shaped relation between PaO2 and mortality/morbidity in ICU patients. Interestingly, these mostly retrospective studies found that the lowest mortality coincided with PaO2 ~ 150 mmHg during the first 24 h of ICU stay, i.e. supraphysiological PaO2 levels. Most of the recent large-scale retrospective analyses studied general ICU populations, but there are major differences according to the underlying pathology studied as well as whether medical or surgical patients are concerned. Therefore, as far as possible from the data reported, we focus on the need of mechanical ventilation as well as the distinction between the absence or presence of circulatory shock. There seems to be no ideal target PaO2 except for avoiding prolonged exposure (> 24 h) to either hypoxaemia (PaO2 < 55-60 mmHg) or supraphysiological (PaO2 > 100 mmHg). Moreover, the need for mechanical ventilation, absence or presence of circulatory shock and/or the aetiology of tissue dysoxia, i.e. whether it is mainly due to impaired macro- and/or microcirculatory O2 transport and/or disturbed cellular O2 utilization, may determine whether any degree of hyperoxaemia causes deleterious side effects.

Hyperoxemia during resuscitation of trauma patients and increased intensive care unit length of stay: inverse probability of treatment weighting analysis

Background

Information on hyperoxemia among patients with trauma has been limited, other than traumatic brain injuries. This study aimed to elucidate whether hyperoxemia during resuscitation of patients with trauma was associated with unfavorable outcomes.

Methods

A post hoc analysis of a prospective observational study was carried out at 39 tertiary hospitals in 2016–2018 in adult patients with trauma and injury severity score (ISS) of > 15. Hyperoxemia during resuscitation was defined as PaO₂ of ≥ 300 mmHg on hospital arrival and/or 3 h after arrival. Intensive care unit (ICU)-free days were compared between patients with and without hyperoxemia. An inverse probability of treatment weighting (IPW) analysis was conducted to adjust patient characteristics including age, injury mechanism, comorbidities, vital signs on presentation, chest injury severity, and ISS. Analyses were stratified with intubation status at the emergency department (ED). The association between biomarkers and ICU length of stay were then analyzed with multivariate models.

Results

Among 295 severely injured trauma patients registered, 240 were eligible for analysis. Patients in the hyperoxemia group (n = 58) had shorter ICU-free days than those in the non-hyperoxemia group [17 (10–21) vs 23 (16–26), p < 0.001]. IPW analysis revealed the association between hyperoxemia and prolonged ICU stay among patients not intubated at the ED [ICU-free days = 16 (12–22) vs 23 (19–26), p = 0.004], but not among those intubated at the ED [18 (9–20) vs 15 (8–23), p = 0.777]. In the hyperoxemia group, high inflammatory markers such as soluble RAGE and HMGB-1, as well as low lung-protective proteins such as surfactant protein D and Clara cell secretory protein, were associated with prolonged ICU stay.

Conclusions

Hyperoxemia until 3 h after hospital arrival was associated with prolonged ICU stay among severely injured trauma patients not intubated at the ED.

Trial registration

UMIN-CTR, UMIN000019588. Registered on November 15, 2015.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13017-021-00363-2.