Effects of hyperoxemia on aneurysmal subarachnoid hemorrhage outcomes: a systematic review and meta-analysis

Association between SpO2 and the risk of death in elderly T2DM patients with cerebral infarction: a retrospective cohort study

Objective

This study aimed to evaluate the SpO2 (transcutaneous oxygen saturation) -mortality link in elderly T2DM (diabetes mellitus type 2) patients with cerebral infarction and identify their optimal SpO2 range.

Methods

In this investigation, we employed a comprehensive approach. Initially, we screened the MIMIC-IV database, identifying elderly T2DM patients with cerebral infarction, utilizing specific ICD-9 and ICD-10 codes. We then harnessed the power of restricted cubic splines to craft a visual representation of the correlation between SpO2 and 1-year mortality. To enhance our analysis, we harnessed Cox multivariate regression, allowing us to compute adjusted hazard ratios (HR) accompanied by 95% confidence intervals (CIs). Additionally, we crafted Cumulative Mortality Curve analyses, augmenting our study by engaging in rigorous subgroup analyses, stratifying our observations based on pertinent covariates.

Results

In this study, 448 elderly T2DM patients with cerebral infarction were included. Within 1-year post-discharge, 161 patients (35.94%) succumbed. Employing Restricted Cubic Spline analysis, a statistically significant U-shaped non-linear relationship between admission ICU SpO2 levels and 1-year mortality was observed (P-value < 0.05). Further analysis indicated that both low and high SpO2 levels increased the mortality risk. Cox multivariate regression analysis, adjusting for potential confounding factors, confirmed the association of low (≤94.5%) and high SpO2 levels (96.5-98.5%) with elevated 1-year mortality risk, particularly notably high SpO2 levels (>98.5%) [HR = 2.06, 95% CI: 1.29-3.29, P-value = 0.002]. The cumulative mortality curves revealed the following SpO2 subgroups from high to low cumulative mortality at the 365th day: normal levels (94.5% < SpO2 ≤ 96.5%), low levels (SpO2 ≤ 94.5%), high levels (96.5% < SpO2 ≤ 98.5%), and notably high levels (>98.5%). Subgroup analysis demonstrated no significant interaction between SpO2 and grouping variables, including Sex, Age, Congestive heart failure, Temperature, and ICU length of stay (LOS-ICU; P-values for interaction were >0.05).

Conclusions

Striking an optimal balance is paramount, as fixating solely on lower SpO2 limits or neglecting high SpO2 levels may contribute to increased mortality rates. To mitigate mortality risk in elderly T2DM patients with cerebral infarction, we recommend maintaining SpO2 levels within the range of 94.5-96.5%.

Exposure to severe hyperoxemia worsens survival and neurological outcome in patients supported by veno-arterial extracorporeal membrane oxygenation: A meta-analysis

BACKGROUND

Veno-arterial Extracorporeal Membrane Oxygenation (VA-ECMO) is a rescue treatment in refractory cardiogenic shock (CS) or refractory cardiac arrest (CA). Exposure to hyperoxemia is common during VA-ECMO, and its impact on patient's outcome remains unclear.

METHODS

We conducted a systematic review (PubMed and Scopus) and meta-analysis investigating the effects of exposure to severe hyperoxemia on mortality and poor neurological outcome in patients supported by VA-ECMO. When both adjusted and unadjusted Odds Ratio (OR) were provided, we used the adjusted one. Results are reported as OR and 95% confidence interval (CI). Subgroup analyses were conducted according to VA-ECMO indication and hyperoxemia thresholds.

RESULTS

Data from 10 observational studies were included. Nine studies reported data on mortality (n = 5 refractory CA, n = 4 CS), and 4 on neurological outcome. As compared to normal oxygenation levels, exposure to severe hyperoxemia was associated with higher mortality (nine studies; OR: 1.80 [1.16-2.78]; p = 0.009; I2 = 83%; low certainty of evidence) and worse neurological outcome (four studies; OR: 1.97 [1.30-2.96]; p = 0.001; I2 = 0%; low certainty of evidence). Magnitude and effect of these findings remained valid in subgroup analyses conducted according to different hyperoxemia thresholds (>200 or >300 mmHg) and VA-ECMO indication, although the association with mortality remained uncertain in the refractory CA population (p = 0.13). Analysis restricted to studies providing adjusted OR data confirmed an increased likelihood of poorer neurological outcome (three studies; OR: 2.11 [1.32-3.38]; p = 0.002) in patients exposed to severe hyperoxemia but did not suggest higher mortality (five studies; OR: 1.68 [0.89-3.18]; p = 0.11).

CONCLUSIONS

Severe hyperoxemia exposure after initiation of VA-ECMO may be associated with an almost doubled increased probability of poor neurological outcome and mortality. Clinical efforts should be made to avoid severe hyperoxemia during VA-ECMO support.

Hyperoxia is Dose-Dependently Associated with an Increase of Unfavorable Outcomes in Ventilated Patients with Aneurysmal Subarachnoid Hemorrhage: A Retrospective Cohort Study

Background

Adequate oxygenation in patients with aneurysmal subarachnoid hemorrhage (SAH) is imperative. However, hyperoxia increases formation of reactive oxygen species and may be associated with a dose-dependent toxicity. We postulated a threshold for arterial partial pressure of oxygen (paO₂) above which toxicity effects precipitate and sought to study the effects on 30-day mortality, favorable outcome at discharge and at 3 months, and delayed cerebral ischemia.

Methods

In this retrospective single-center cohort study, patients with SAH and mechanical ventilation > 72 h were included. Oxygen integrals were calculated above the following thresholds: 80, 100, 120, and 150 mm Hg and time-weighted mean paO₂. All calculations were done from admission to end of day 1, day 3, and day 14. We conducted multivariable logistic regression analyses adjusted for age, sex, duration of ventilation, and Hunt and Hess grade. Time-weighted mean paO₂ was categorized by quartiles. Favorable outcome was defined as Glasgow Outcome Scale scores of 4 and 5.

Results

From November 2010 to February 2021, 282 of 549 patients fulfilled the inclusion criteria. Odds ratios for 30-day mortality increased dose dependently and were as follows: 1.07 (95% confidence interval [CI] 1.03–1.11; p = 0.001) for each 1 mm Hg per day above 80 mm Hg; 1.16 (95% CI 1.07–1.27), above 100 mm Hg; 1.36 (95% CI 1.15–1.61), above 120 mm Hg; and 1.59 (95% CI 1.22–2.08), above 150 mm Hg (all p < 0.001) at day 14. For favorable outcome at 3 months, odds ratios were 0.96 (95% CI 0.92–0.99) for each 1 mm Hg per day above 80 mm Hg; 0.90 (95% CI 0.84–0.98), above 100 mm Hg; 0.83 (95% CI 0.72–0.97), above 120 mm Hg; and 0.77 (95% CI 0.61–0.97), above 150 mm Hg (all p < 0.05). For time-weighted mean paO₂, lowest 30-day mortality and highest favorable outcome at 3 months were found in the second quartile (78–85 mm Hg). Thirty-day mortality increased above 93 mm Hg (fourth quartile), with an odds ratio of 3.4 (95% CI 1.4–8.4, p = 0.007). Odds ratios for favorable outcome at 3 months were 0.28 (95% CI 0.12–0.69), 0.27 (95% CI 0.11–0.67), and 0.24 (95% CI 0.10–0.59) for the first, third, and fourth quartiles, respectively (all p < 0.01). No significant association was found at day 1 and day 3, for favorable outcome at discharge, or for delayed cerebral ischemia.

Conclusions

Integrals above the defined paO₂ thresholds were dose-dependently associated with an increase in mortality in ventilated patients with SAH. When we considered time-weighted mean paO₂, unfavorable outcomes and 30-day mortality were more frequent both below and above a certain range. Unfavorable outcomes increased in paO₂ ranges usually defined as normoxia. This emphasizes the necessity to further characterize oxygenation thresholds in ventilated patients with SAH in prospective clinical studies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12028-022-01534-y.