Oxygen saturation levels and retinopathy of prematurity in extremely preterm infants - a case control study

PURPOSE

To investigate the association of risk factors, including oxygen exposure, for developing retinopathy of prematurity (ROP) in preterm infants at increased risk of ROP.

METHODS

A case-control study was conducted where each infant born at < 28 weeks gestation with ROP was matched with another without ROP over five years (July 2015 - June 2020). Clinical information about the infants was collected from electronic medical records, including method of oxygen delivery, oxygen saturation (SpO2), fraction of inspired oxygen (FiO2) and mean airway pressure (MAP) measurements. MATLAB was used for a time-averaged analysis. Stata/SE 16.0 was used for statistical analysis.

RESULTS

123 ROP/non-ROP pairs were included in this study. The time-averaged SpO2 analysis showed non-ROP group spent more time in hyperoxia than the ROP group (p < 0.001). The non-ROP group had lower respiratory severity scores and analysis when FiO2 > 21% showed that were was no difference in SpO2 between the two groups when the infants were receiving oxygen support. Conditional logistic regressions showed neonatal surgery significantly increased the risk of ROP (OR = 1.4347, p = 0.010), while the influence of birthweight (odds ratio of 0.9965, p = 0.001) and oxygen exposure (OR = 0.9983, p = 0.012) on ROP outcome was found to be negligible as their odds ratios indicated no influence.

CONCLUSIONS

At times when infants were receiving respiratory support (FiO2 > 21%) the SpO2 data indicated no difference in SpO2 between the ROP and non-ROP groups. Analysis of clinical variables found that neonatal surgery increased the odds of developing ROP.

Time-varying intensity of oxygen exposure is associated with mortality in critically ill patients with mechanical ventilation

BACKGROUND

There is no consensus exists regarding the association between oxygen exposure (arterial oxygen tension or fraction of inspired oxygen) and outcomes for patients with mechanical ventilation. Additionally, whether the association remains persistent over time is unknown. We aimed to explore the association between exposure to different intensities of oxygen exposure over time and 28-day mortality in patients with mechanical ventilation.

METHODS

We obtained data from the Medical Information Mart for Intensive Care IV (MIMIC-IV), which included adult (≥ 18 years) patients who received invasive mechanical ventilation for at least 48 h. We excluded patients who received extracorporeal membrane oxygenation (ECMO) or who initiated ventilation more than 24 h after ICU admission. The primary outcome was 28-day mortality. Piece-wise exponential additive mixed models were employed to estimate the strength of associations over time.

RESULTS

A total of 7784 patients were included in the final analysis. Patients had a median duration of invasive mechanical ventilation of 8.1 days (IQR: 3.8-28 days), and the overall 28-day mortality rate was 26.3%. After adjustment for baseline and time-dependent confounders, both daily time-weighted average (TWA) arterial oxygen tension (PaO₂) and fraction of inspired oxygen (FiO₂) were associated with increased 28-day mortality, and the strength of the association manifested predominantly in the early-middle course of illness. A significant increase in the hazard of death was found to be associated with daily exposure to TWA-PaO₂ ≥ 120 mmHg (Hazard ratio 1.166, 95% CI 1.059-1.284) or TWA-FiO₂ ≥ 0.5 (Hazard ratio 1.496, 95% CI 1.363-1.641) during the entire course. A cumulative effect of harmful exposure (TWA-PaO₂ ≥ 120 mmHg or TWA-FiO₂ ≥ 0.5) was also observed.

CONCLUSION

PaO₂ and FiO₂ should be carefully monitored in patients with mechanical ventilation, especially during the early-middle course after ICU admission. Cumulative exposure to higher intensities of oxygen exposure was associated with an increased risk of death.

Early Hyperoxia in Patients with Traumatic Brain Injury Admitted to Intensive Care in Australia and New Zealand: A Retrospective Multicenter Cohort Study

BACKGROUND

Early hyperoxia may be an independent risk factor for mortality in critically ill traumatic brain injury (TBI) patients, although current data are inconclusive. Accordingly, we conducted a retrospective cohort study to determine the association between systemic oxygenation and in-hospital mortality, in critically ill mechanically ventilated TBI patients.

METHODS

Data were extracted from the Australian and New Zealand Intensive Care Society Centre for Outcome and Resource Evaluation Adult Patient Database. All adult TBI patients receiving mechanical ventilation in 129 intensive care units between 2000 and 2016 were included in analysis. The following data were extracted: demographics, illness severity scores, physiological and laboratory measurements, institutional characteristics, and vital status at discharge. In-hospital mortality was used as the primary study outcome. The primary exposure variable was the 'worst' partial arterial pressure of oxygen (PaO2) recorded during the first 24 h in ICU; hyperoxia was defined as > 299 mmHg. Adjustment for illness severity utilized multivariable logistic regression, the results of which are reported as the odds ratio (OR) 95% CI.

RESULTS

Data concerning 24,148 ventilated TBI patients were extracted. By category of worst PaO2, crude in-hospital mortality ranged from 27.1% (PaO2 40-49 mmHg) to 13.3% (PaO2 140-159 mmHg). When adjusted for patient and institutional characteristics, the only PaO2 category associated with a significantly greater risk of death was < 40 mmHg [OR 1.52, 1.03-2.25]. A total of 3117 (12.9%) patients were hyperoxic during the first 24 h in ICU, with a crude in-hospital mortality rate of 17.8%. No association was evident in between hyperoxia and mortality in adjusted analysis [OR 0.97 (0.86-1.11)].

CONCLUSIONS

In this large multicenter cohort of TBI patients, hyperoxia in the first 24 h after ICU admission was not independently associated with greater in-hospital mortality. Hypoxia remains associated with greater in-hospital mortality risk and should be avoided where possible.