Association between short-term neurological outcomes and extreme hyperoxia in patients with out-of-hospital cardiac arrest who underwent extracorporeal cardiopulmonary resuscitation: a retrospective observational study from a multicenter registry

Association between sub-phenotypes identified using latent class analysis and neurological outcomes in patients with out-of-hospital cardiac arrest in Japan

BACKGROUND

In patients who experience out-of-hospital cardiac arrest (OHCA), it is important to assess the association of sub-phenotypes identified by latent class analysis (LCA) using pre-hospital prognostic factors and factors measurable immediately after hospital arrival with neurological outcomes at 30 days, which would aid in making treatment decisions.

METHODS

This study retrospectively analyzed data obtained from the Japanese OHCA registry between June 2014 and December 2019. The registry included a complete set of data on adult patients with OHCA, which was used in the LCA. The association between the sub-phenotypes and 30-day survival with favorable neurological outcomes was investigated. Furthermore, adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by multivariate logistic regression analysis using in-hospital data as covariates.

RESULTS

A total of, 22,261 adult patients who experienced OHCA were classified into three sub-phenotypes. The factor with the highest discriminative power upon patient's arrival was Glasgow Coma Scale followed by partial pressure of oxygen. Thirty-day survival with favorable neurological outcome as the primary outcome was evident in 66.0% participants in Group 1, 5.2% in Group 2, and 0.5% in Group 3. The 30-day survival rates were 80.6%, 11.8%, and 1.3% in groups 1, 2, and 3, respectively. Logistic regression analysis revealed that the ORs (95% CI) for 30-day survival with favorable neurological outcomes were 137.1 (99.4-192.2) for Group 1 and 4.59 (3.46-6.23) for Group 2 in comparison to Group 3. For 30-day survival, the ORs (95%CI) were 161.7 (124.2-212.1) for Group 1 and 5.78 (4.78-7.04) for Group 2, compared to Group 3.

CONCLUSIONS

This study identified three sub-phenotypes based on the prognostic factors available immediately after hospital arrival that could predict neurological outcomes and be useful in determining the treatment strategy of patients experiencing OHCA upon their arrival at the hospital.

Oxygenation management during veno-arterial ECMO support for cardiogenic shock: a multicentric retrospective cohort study

BACKGOUND

Hyperoxemia is common and associated with poor outcome during veno-arterial extracorporeal membrane oxygenation (VA ECMO) support for cardiogenic shock. However, little is known about practical daily management of oxygenation. Then, we aim to describe sweep gas oxygen fraction (FSO2), postoxygenator oxygen partial pressure (PPOSTO2), inspired oxygen fraction (FIO2), and right radial arterial oxygen partial pressure (PaO2) between day 1 and day 7 of peripheral VA ECMO support. We also aim to evaluate the association between oxygenation parameters and outcome. In this retrospective multicentric study, each participating center had to report data on the last 10 eligible patients for whom the ICU stay was terminated. Patients with extracorporeal cardiopulmonary resuscitation were excluded. Primary endpoint was individual mean FSO2 during the seven first days of ECMO support (FSO2 mean (day 1-7)).

RESULTS

Between August 2019 and March 2022, 139 patients were enrolled in 14 ECMO centers in France, and one in Switzerland. Among them, the median value for FSO2 mean (day 1-7) was 70 [57; 79] % but varied according to center case volume. Compared to high volume centers, centers with less than 30 VA-ECMO runs per year were more likely to maintain FSO2 ≥ 70% (OR 5.04, CI 95% [1.39; 20.4], p = 0.017). Median value for right radial PaO2 mean (day 1-7) was 114 [92; 145] mmHg, and decreased from 125 [86; 207] mmHg at day 1, to 97 [81; 133] mmHg at day 3 (p < 0.01). Severe hyperoxemia (i.e. right radial PaO2 ≥ 300 mmHg) occurred in 16 patients (12%). PPOSTO2, a surrogate of the lower body oxygenation, was measured in only 39 patients (28%) among four centers. The median value of PPOSTO2 mean (day 1-7) value was 198 [169; 231] mmHg. By multivariate analysis, age (OR 1.07, CI95% [1.03-1.11], p < 0.001), FSO2 mean (day 1-3)(OR 1.03 [1.00-1.06], p = 0.039), and right radial PaO2 mean (day 1-3) (OR 1.03, CI95% [1.00-1.02], p = 0.023) were associated with in-ICU mortality.

CONCLUSION

In a multicentric cohort of cardiogenic shock supported by VA ECMO, the median value for FSO2 mean (day 1-7) was 70 [57; 79] %. PPOSTO2 monitoring was infrequent and revealed significant hyperoxemia. Higher FSO2 mean (day 1-3) and right radial PaO2 mean (day 1-3) were independently associated with in-ICU mortality.

Oxygenation During Venoarterial Extracorporeal Membrane Oxygenation: Physiology, Current Evidence, and a Pragmatic Approach to Oxygen Titration

OBJECTIVES

This review aims to: 1) identify the key circuit and patient factors affecting systemic oxygenation, 2) summarize the literature reporting the association between hyperoxia and patient outcomes, and 3) provide a pragmatic approach to oxygen titration, in patients undergoing peripheral venoarterial extracorporeal membrane oxygenation (ECMO).

DATA SOURCES

Searches were performed using PubMed, SCOPUS, Medline, and Google Scholar.

STUDY SELECTION

All observational and interventional studies investigating the association between hyperoxia, and clinical outcomes were included, as well as guidelines from the Extracorporeal Life Support Organization.

DATA EXTRACTION

Data from relevant literature was extracted, summarized, and integrated into a concise narrative review. For ease of reference a summary of relevant studies was also produced.

DATA SYNTHESIS

The extracorporeal circuit and the native cardiorespiratory circuit both contribute to systemic oxygenation during venoarterial ECMO. The ECMO circuit's contribution to systemic oxygenation is, in practice, largely determined by the ECMO blood flow, whereas the native component of systemic oxygenation derives from native cardiac output and residual respiratory function. Interactions between ECMO outflow and native cardiac output (as in differential hypoxia), the presence of respiratory support, and physiologic parameters affecting blood oxygen carriage also modulate overall oxygen exposure during venoarterial ECMO. Physiologically those requiring venoarterial ECMO are prone to hyperoxia. Hyperoxia has a variety of definitions, most commonly Pa o2 greater than 150 mm Hg. Severe hypoxia (Pa o2 > 300 mm Hg) is common, seen in 20%. Early severe hyperoxia, as well as cumulative hyperoxia exposure was associated with in-hospital mortality, even after adjustment for disease severity in both venoarterial ECMO and extracorporeal cardiopulmonary resuscitation. A pragmatic approach to oxygenation during peripheral venoarterial ECMO involves targeting a right radial oxygen saturation target of 94-98%, and in selected patients, titration of the fraction of oxygen in the mixture via the air-oxygen blender to target postoxygenator Pa o2 of 150-300 mm Hg.

CONCLUSIONS

Hyperoxia results from a range of ECMO circuit and patient-related factors. It is common during peripheral venoarterial ECMO, and its presence is associated with poor outcome. A pragmatic approach that avoids hyperoxia, while also preventing hypoxia has been described for patients receiving peripheral venoarterial ECMO.

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.

Extracorporeal cardiopulmonary resuscitation in out-of-hospital cardiac arrest - current status

PURPOSE OF REVIEW

Extracorporeal cardiopulmonary resuscitation (ECPR) is an emerging treatment for refractory cardiac arrest. In recent years, several randomized controlled trials have been published that aimed to address the efficacy and effectiveness of ECPR for out-of-hospital cardiac arrest (OHCA). Despite the lack of high-quality evidence concerning clinical effectiveness and cost-effectiveness, ECPR is increasingly implemented throughout the world. In this review, we aim to provide an overview of the current status of ECPR for OHCA.

RECENT FINDINGS

Randomized controlled trials showed diverging results, largely due to differences in selection criteria and study design. Single-center studies, performed in centers with extraordinary expertise and dedication consistently achieve a low-flow time of around 60 min, but such achievements are rarely reproduced outside these centers. Strict patient selection can improve outcome but simultaneously limits the caseload. Preliminary data suggest that outcome may also be improved by avoiding hyperoxia postresuscitation.

SUMMARY

The potential of ECPR to increase survival in selected patients in highly dedicated systems seems to be proven, the question remains whether ECPR for OHCA can be widely implemented successfully and can develop into a sustainable, commonplace resource-effective treatment.

Exposure to Arterial Hyperoxia During Extracorporeal Membrane Oxygenator Support and Mortality in Patients With Cardiogenic Shock

BACKGROUND

Exposure to hyperoxia, a high arterial partial pressure of oxygen (PaO2), may be associated with worse outcomes in patients receiving extracorporeal membrane oxygenator (ECMO) support. We examined hyperoxia in the Extracorporeal Life Support Organization Registry among patients receiving venoarterial ECMO for cardiogenic shock.

METHODS

We included Extracorporeal Life Support Organization Registry patients from 2010 to 2020 who received venoarterial ECMO for cardiogenic shock, excluding extracorporeal CPR. Patients were grouped based on PaO2 after 24 hours of ECMO: normoxia (PaO2 60-150 mmHg), mild hyperoxia (PaO2 151-300 mmHg), and severe hyperoxia (PaO2 >300 mmHg). In-hospital mortality was evaluated using multivariable logistic regression.

RESULTS

Among 9959 patients, 3005 (30.2%) patients had mild hyperoxia and 1972 (19.8%) had severe hyperoxia. In-hospital mortality increased across groups: normoxia, 47.8%; mild hyperoxia, 55.6% (adjusted odds ratio, 1.37 [95% CI, 1.23-1.53]; P<0.001); severe hyperoxia, 65.4% (adjusted odds ratio, 2.20 [95% CI, 1.92-2.52]; P<0.001). A higher PaO2 was incrementally associated with increased in-hospital mortality (adjusted odds ratio, 1.14 per 50 mmHg higher [95% CI, 1.12-1.16]; P<0.001). Patients with a higher PaO2 had increased in-hospital mortality in each subgroup and when stratified by ventilator settings, airway pressures, acid-base status, and other clinical variables. In the random forest model, PaO2 was the second strongest predictor of in-hospital mortality, after older age.

CONCLUSIONS

Exposure to hyperoxia during venoarterial ECMO support for cardiogenic shock is strongly associated with increased in-hospital mortality, independent from hemodynamic and ventilatory status. Until clinical trial data are available, we suggest targeting a normal PaO2 and avoiding hyperoxia in CS patients receiving venoarterial ECMO.

Intra-aortic balloon pump use in out-of-hospital cardiac arrest patients who underwent extracorporeal cardiopulmonary resuscitation

AIM

To investigate the effect of intra-aortic balloon pump (IABP) use after extracorporeal membrane oxygenation-assisted cardiopulmonary resuscitation (ECPR) on short-term neurological outcomes and survival in patients with out-of-hospital cardiac arrest (OHCA).

METHODS

We retrospectively analysed data collected between June 2014 and December 2019 from the Japanese OHCA registry. Adult patients (aged ≥18 years) who underwent ECPR were included. We divided the patients into those who received IABP and those who did not receive IABP. The primary outcome was the 30-day favourable neurological outcomes in survived patients. The secondary outcome was the 30-day survival. We performed propensity score matching (PSM) to adjust for confounding factors after multiple imputations of missing data. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were estimated using logistic regression analysis after PSM to adjust for confounding factors after IABP initiation.

RESULTS

Among 2135 adult patients who underwent ECPR, 1173 received IABP. In 842 matched patients, IABP use was associated with survival (aOR, 1.98; 95% CI, 1.39-2.83; p < 0.001). However, IABP use was not significantly associated with the 30-day neurologically favourable outcome in 190 survived patients (aOR, 1.22; 95% CI, 0.79-1.89; p = 0.36).

CONCLUSION

The use of IABP in patients with OHCA who underwent ECPR was associated with 30-day survival. Among survived patients, there was no significant association between IABP use and 30-day neurological outcome. A further well-designed prospective study is needed.

Extracorporeal cardiopulmonary resuscitation in adults and children: A review of literature, published guidelines and pediatric single-center program building experience

Extracorporeal cardiopulmonary resuscitation (ECPR) is an adjunct supportive therapy to conventional cardiopulmonary resuscitation (CCPR) employing veno-arterial extracorporeal membrane oxygenation (VA-ECMO) in the setting of refractory cardiac arrest. Its use has seen a significant increase in the past decade, providing hope for good functional recovery to patients with cardiac arrest refractory to conventional resuscitation maneuvers. This review paper aims to summarize key findings from the ECPR literature available to date as well as the recommendations for ECPR set forth by leading national and international resuscitation societies. Additionally, we describe the successful pediatric ECPR program at Texas Children's Hospital, highlighting the logistical, technical and educational features of the program.

Optimizing PO2 during peripheral veno-arterial ECMO: a narrative review

During refractory cardiogenic shock and cardiac arrest, veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is used to restore a circulatory output. However, it also impacts significantly arterial oxygenation. Recent guidelines of the Extracorporeal Life Support Organization (ELSO) recommend targeting postoxygenator partial pressure of oxygen (P_POSTO₂) around 150 mmHg. In this narrative review, we intend to summarize the rationale and evidence for this P_POSTO₂ target recommendation. Because this is the most used configuration, we focus on peripheral VA-ECMO. To date, clinicians do not know how to set the sweep gas oxygen fraction (F_SO₂). Because of the oxygenator's performance, arterial hyperoxemia is common during VA-ECMO support. Interpretation of oxygenation is complex in this setting because of the dual circulation phenomenon, depending on both the native cardiac output and the VA-ECMO blood flow. Such dual circulation results in dual oxygenation, with heterogeneous oxygen partial pressure (PO₂) along the aorta, and heterogeneous oxygenation between organs, depending on the mixing zone location. Data regarding oxygenation during VA-ECMO are scarce, but several observational studies have reported an association between hyperoxemia and mortality, especially after refractory cardiac arrest. While hyperoxemia should be avoided, there are also more and more studies in non-ECMO patients suggesting the harm of a too restrictive oxygenation strategy. Finally, setting F_SO₂ to target strict normoxemia is challenging because continuous monitoring of postoxygenator oxygen saturation is not widely available. The threshold of P_POSTO₂ around 150 mmHg is supported by limited evidence but aims at respecting a safe margin, avoiding both hypoxemia and severe hyperoxemia.