The association of partial pressures of oxygen and carbon dioxide with neurological outcome after out-of-hospital cardiac arrest: an explorative International Cardiac Arrest Registry 2.0 study

Pre-hospital care after return of spontaneous circulation: Are we achieving our targets?

Background

Early restoration of normal physiology when return of spontaneous circulation (ROSC) is obtained after an out-of-hospital cardiac arrest (OHCA) reduces the risk of developing post-cardiac arrest syndrome (PCAS). This study aims to investigate if (and to which extent) this can be achieved within the scope of practice of standard emergency medical services (EMS) crews.

Methods

A prospective mixed-methods quantitative and qualitative cohort study was performed including adult patients with a non-traumatic OHCA presented to a university hospital emergency department (ED) in the Netherlands after pre-hospital ROSC was obtained. Primary endpoint was the percentage of patients with deranged physiology post-ROSC in whom EMS crews were able to reach recommended treatment targets.

Results

During a 32-month period, 160 patients presenting with ROSC after OHCA were included. Median (IQR) pre-hospital treatment duration was 40 (34-51) minutes. When deranged physiology was present (n = 133), it could be restored by EMS crews in 29% of the patients. Although average etCO2 and SpO2 improved gradually over time during pre-hospital treatment, recommended treatment targets could not be achieved in respectively 55% (30/55) and 43% (20/46) of the patients. Similarly, airway problems (24/46, 52%), hypotension (20/23, 87%) and post-anoxic agitation (16/43, 37%) could often not be resolved by EMS crews. The ability to restore normal physiology by EMS could not be predicted based on patient characteristics or in-arrest variables.

Conclusion

Deranged physiology after an OHCA is commonly encountered, and often difficult to treat within the scope of practice of regular EMS crews. Involvement of advanced critical care teams with a wider scope of practice at an early stage may contribute to a better outcome for these patients.

Impact of lifeguard oxygen therapy on the resuscitation of drowning victims: Results from an Utstein Style for Drowning Study

INTRODUCTION

No published evidence was identified regarding the use of oxygen in the treatment of drowning in two recent systematic reviews. The aim of our study was to investigate the impact of on scene, pre-Emergency Medical Services (EMS) oxygen therapy by lifeguards in the resuscitation of drowning victims.

METHOD

We conducted a retrospective case match analysis of drowning patients presenting to the EDs of Sunshine Coast Hospital and Health Service. Patients were matched for age, sex and severity of drowning injury. The primary outcome was in-hospital mortality. Secondary outcomes included positive pressure ventilation (PPV) by EMS and the ED, as well as admission to the Intensive Care Unit.

RESULTS

There were 108 patients in each group. Median (IQR) age was 22 (15-43) in the oxygen group and 23 (15-44) years in the non-oxygen group. There were 45 females in the oxygen group and 41 females in the non-oxygen group. Sixteen patients had suffered cardiac arrest and three patients respiratory arrest in each group. There were five deaths in each group. Initial oxygen saturation on arrival of EMS was identical in both groups 89.2% (±19.9) in the oxygen group versus 89.3% (±21.1) (P = 0.294) in the non-oxygen group. The oxygen group required PPV more frequently with EMS (19 vs 11, P < 0.01) and in the ED (19 vs 15, P < 0.01).

CONCLUSION

On scene treatment with oxygen by lifeguards did not improve oxygenation or outcomes in drowning patients.

Association of Arterial Carbon Dioxide Tension Following In-Hospital Cardiac Arrest With Survival and Favorable Neurologic Outcome

BACKGROUND

In-hospital cardiac arrest (IHCA) continues to be associated with high morbidity and mortality. The objective of this study was to study the association of arterial carbon dioxide tension (PaCO2) on survival to discharge and favorable neurologic outcomes in adults with IHCA.

METHODS

The study population included 353 adults who underwent resuscitation from 2011 to 2019 for IHCA at an academic tertiary care medical center with arterial blood gas testing done within 24 hours of arrest. Outcomes of interest included survival to discharge and favorable neurologic outcome, defined as Glasgow outcome score of 4-5.

RESULTS

Of the 353 patients studied, PaCO2 classification included: hypocapnia (PaCO2 <35 mm Hg, n = 89), normocapnia (PaCO2 35-45 mm Hg, n = 151), and hypercapnia (PaCO2 >45 mm Hg, n = 113). Hypercapnic patients were further divided into mild (45 mm Hg < PaCO2 ≤55 mm Hg, n = 62) and moderate/severe hypercapnia (PaCO2 > 55 mm Hg, n = 51). Patients with normocapnia had the highest rates of survival to hospital discharge (52.3% vs. 32.6% vs. 30.1%, P < 0.001) and favorable neurologic outcome (35.8% vs. 25.8% vs. 17.9%, P = 0.005) compared those with hypocapnia and hypercapnia respectively. In multivariable analysis, compared to normocapnia, hypocapnia [odds ratio (OR), 2.06; 95% confidence interval (CI), 1.15-3.70] and hypercapnia (OR, 2.67; 95% CI, 1.53-4.66) were both found to be independently associated with higher rates of in-hospital mortality. Compared to normocapnia, while mild hypercapnia (OR, 2.53; 95% CI, 1.29-4.97) and moderate/severe hypercapnia (OR, 2.86; 95% CI, 1.35-6.06) were both independently associated with higher in-hospital mortality compared to normocapnia, moderate/severe hypercapnia was also independently associated with lower rates of favorable neurologic outcome (OR, 0.28; 95% CI, 0.11-0.73), while mild hypercapnia was not.

CONCLUSIONS

In this prospective registry of adults with IHCA, hypercapnia noted within 24 hours after arrest was independently associated with lower rates of survival to discharge and favorable neurologic outcome.

Association among blood pressure, end-tidal carbon dioxide, peripheral oxygen saturation and mortality in prehospital post-resuscitation care

Aim

Post-resuscitation care is described as the fourth link in a chain of survival in resuscitation guidelines. However, data on prehospital post-resuscitation care is scarce. We aimed to examine the association among systolic blood pressure (SBP), peripheral oxygen saturation (SpO2) and end-tidal carbon dioxide (EtCO2) after prehospital stabilisation and outcome among patients resuscitated from out-of-hospital cardiac arrest (OHCA).

Methods

In this retrospective study, we evaluated association of the last measured prehospital SBP, SpO2 and EtCO2 before patient handover with 30-day and one-year mortality in 2,611 patients receiving prehospital post-resuscitation care by helicopter emergency medical services in Finland. Statistical analyses were completed through locally estimated scatterplot smoothing (LOESS) and multivariable logistic regression. The regression analyses were adjusted by sex, age, initial rhythm, bystander CPR, and time interval from collapse to the return of spontaneous circulation (ROSC).

Results

Mortality related to SBP and EtCO2 values were U-shaped and lowest at 135 mmHg and 4.7 kPa, respectively, whereas higher SpO2 shifted towards lower mortality. In adjusted analyses, increased 30-day mortality and one year mortality was observed in patients with SBP < 100 mmHg (OR 1.9 [95% CI 1.4-2.4]) and SBP < 100 (OR 1.8 [1.2-2.6]) or EtCO2 < 4.0 kPa (OR 1.4 [1.1-1.5]), respectively. SpO2 was not significantly associated with either 30-day or one year mortality.

Conclusions

After prehospital post-resuscitation stabilization, SBP < 100 mmHg and EtCO2 < 4.0 kPa were observed to be independently associated with higher mortality. The optimal targets for prehospital post-resuscitation care need to be established in the prospective studies.

Restrictive versus high-dose oxygenation strategy in post-arrest management following adult non-traumatic cardiac arrest: a meta-analysis

PURPOSE

Neurological damage is the main cause of death or withdrawal of care in comatose survivors of cardiac arrest (CA). Hypoxemia and hyperoxemia following CA were described as potentially harmful, but reports were inconsistent. Current guidelines lack specific oxygen targets after return of spontaneous circulation (ROSC).

OBJECTIVES

The current meta-analysis assessed the effects of restrictive compared to high-dose oxygenation strategy in survivors of CA.

METHODS

A structured literature search was performed. Randomized controlled trials (RCTs) comparing two competing oxygenation strategies in post-ROSC management after CA were eligible. The primary end point was short-term survival (≤ 90 days). The meta-analysis was prospectively registered in PROSPERO database (CRD42023444513).

RESULTS

Eight RCTs enrolling 1941 patients were eligible. Restrictive oxygenation was applied to 964 patients, high-dose regimens were used in 977 participants. Short-term survival rate was 55.7% in restrictive and 56% in high-dose oxygenation group (8 trials, RR 0.99, 95% CI 0.90 to 1.10, P = 0.90, I2 = 18%, no difference). No evidence for a difference was detected in survival to hospital discharge (5 trials, RR 0.98, 95% CI 0.79 to 1.21, P = 0.84, I2 = 32%). Episodes of hypoxemia more frequently occurred in restrictive oxygenation group (4 trials, RR 2.06, 95% CI 1.47 to 2.89, P = 0.004, I2 = 13%).

CONCLUSION

Restrictive and high-dose oxygenation strategy following CA did not result in differences in short-term or in-hospital survival. Restrictive oxygenation strategy may increase episodes of hypoxemia, even with restrictive oxygenation targets exceeding intended saturation levels, but the clinical relevance is unknown. There is still a wide gap in the evidence of optimized oxygenation in post-ROSC management and specific targets cannot be concluded from the current evidence.

Ten rules for optimizing ventilatory settings and targets in post-cardiac arrest patients

Cardiac arrest (CA) is a major cause of morbidity and mortality frequently associated with neurological and systemic involvement. Supportive therapeutic strategies such as mechanical ventilation, hemodynamic settings, and temperature management have been implemented in the last decade in post-CA patients, aiming at protecting both the brain and the lungs and preventing systemic complications. A lung-protective ventilator strategy is currently the standard of care among critically ill patients since it demonstrated beneficial effects on mortality, ventilator-free days, and other clinical outcomes. The role of protective and personalized mechanical ventilation setting in patients without acute respiratory distress syndrome and after CA is becoming more evident. The individual effect of different parameters of lung-protective ventilation, including mechanical power as well as the optimal oxygen and carbon dioxide targets, on clinical outcomes is a matter of debate in post-CA patients. The management of hemodynamics and temperature in post-CA patients represents critical steps for obtaining clinical improvement. The aim of this review is to summarize and discuss current evidence on how to optimize mechanical ventilation in post-CA patients. We will provide ten tips and key insights to apply a lung-protective ventilator strategy in post-CA patients, considering the interplay between the lungs and other systems and organs, including the brain.

Oxygen targets and 6-month outcome after out of hospital cardiac arrest: a pre-planned sub-analysis of the targeted hypothermia versus targeted normothermia after Out-of-Hospital Cardiac Arrest (TTM2) trial

BACKGROUND

Optimal oxygen targets in patients resuscitated after cardiac arrest are uncertain. The primary aim of this study was to describe the values of partial pressure of oxygen values (PaO₂) and the episodes of hypoxemia and hyperoxemia occurring within the first 72 h of mechanical ventilation in out of hospital cardiac arrest (OHCA) patients. The secondary aim was to evaluate the association of PaO₂ with patients' outcome.

METHODS

Preplanned secondary analysis of the targeted hypothermia versus targeted normothermia after OHCA (TTM2) trial. Arterial blood gases values were collected from randomization every 4 h for the first 32 h, and then, every 8 h until day 3. Hypoxemia was defined as PaO₂ < 60 mmHg and severe hyperoxemia as PaO₂ > 300 mmHg. Mortality and poor neurological outcome (defined according to modified Rankin scale) were collected at 6 months.

RESULTS

1418 patients were included in the analysis. The mean age was 64 ± 14 years, and 292 patients (20.6%) were female. 24.9% of patients had at least one episode of hypoxemia, and 7.6% of patients had at least one episode of severe hyperoxemia. Both hypoxemia and hyperoxemia were independently associated with 6-month mortality, but not with poor neurological outcome. The best cutoff point associated with 6-month mortality for hypoxemia was 69 mmHg (Risk Ratio, RR = 1.009, 95% CI 0.93-1.09), and for hyperoxemia was 195 mmHg (RR = 1.006, 95% CI 0.95-1.06). The time exposure, i.e., the area under the curve (PaO₂-AUC), for hyperoxemia was significantly associated with mortality (p = 0.003).

CONCLUSIONS

In OHCA patients, both hypoxemia and hyperoxemia are associated with 6-months mortality, with an effect mediated by the timing exposure to high values of oxygen. Precise titration of oxygen levels should be considered in this group of patients.

TRIAL REGISTRATION

clinicaltrials.gov NCT02908308 , Registered September 20, 2016.

Non-linear association between arterial oxygen tension and survival after out-of-hospital cardiac arrest: A multicentre observational study

BACKGROUND

Studies to identify safe oxygenation targets after out-of-hospital cardiac arrest (OHCA) have often assumed a linear relationship between arterial oxygen tension (PaO₂) and survival, or have dichotomised PaO₂ at a supra-physiological level. We hypothesised that abnormalities in mean PaO₂ (both high and low) would be associated with decreased survival after OHCA.

METHODS

We conducted a retrospective multicentre cohort study of adult OHCA patients who received mechanical ventilation on admission to the intensive care unit (ICU). The potential non-linear relationship between the mean PaO₂ within the first 24 -hs of ICU admission and survival to hospital discharge (STHD) was assessed by a four-knot restricted cubic spline function with adjustment for potential confounders.

RESULTS

3764 arterial blood gas results were available for 491 patients in the first 24-hs of ICU admission. The relationship between mean PaO₂ over the first 24-hs and STHD was an inverted U-shape, with highest survival for those with a mean PaO₂ between 100 and 180 mmHg (reference category) compared to a mean PaO₂ of <100 mmHg (adjusted odds ratio [aOR] 0.50 95% confidence interval [CI] 0.30, 0.84), or >180 mmHg (aOR 0.41, 95% CI 0.18, 0.92). Mean PaO₂ within 24 -hs was the third most important predictor and explained 9.1% of the variability in STHD.

CONCLUSION

The mean PaO₂ within the first 24-hs after admission for OHCA has a non-linear association with the highest STHD seen between 100 and 180 mmHg. Randomised controlled trials are now needed to validate the optimal oxygenation targets in mechanically ventilated OHCA patients.