A pilot feasibility, safety and biological efficacy multicentre trial of therapeutic hypercapnia after cardiac arrest: study protocol for a randomized controlled trial

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.

Cerebral perfusion and metabolism with mild hypercapnia vs. normocapnia in a porcine post cardiac arrest model with and without targeted temperature management

Aim

To determine whether targeting mild hypercapnia (PaCO2 7 kPa) would yield improved cerebral blood flow and metabolism compared to normocapnia (PaCO2 5 kPa) with and without targeted temperature management to 33 °C (TTM33) in a porcine post-cardiac arrest model.

Methods

39 pigs were resuscitated after 10 minutes of cardiac arrest using cardiopulmonary bypass and randomised to TTM33 or no-TTM, and hypercapnia or normocapnia. TTM33 was managed with intravasal cooling. Animals were stabilized for 30 minutes followed by a two-hour intervention period. Hemodynamic parameters were measured continuously, and neuromonitoring included intracranial pressure (ICP), pressure reactivity index, cerebral blood flow, brain-tissue pCO2 and microdialysis. Measurements are reported as proportion of baseline, and areas under the curve during the 120 min intervention period were compared.

Results

Hypercapnia increased cerebral flow in both TTM33 and no-TTM groups, but also increased ICP (199% vs. 183% of baseline, p = 0.018) and reduced cerebral perfusion pressure (70% vs. 84% of baseline, p < 0.001) in no-TTM animals. Cerebral lactate (196% vs. 297% of baseline, p < 0.001), pyruvate (118% vs. 152% of baseline, p < 0.001), glycerol and lactate/pyruvate ratios were lower with hypercapnia in the TTM33 group, but only pyruvate (133% vs. 150% of baseline, p = 0.002) was lower with hypercapnia among no-TTM animals.

Conclusion

In this porcine post-arrest model, hypercapnia led to increased cerebral flow both with and without hypothermia, but also increased ICP and reduced cerebral perfusion pressure in no-TTM animals. The effects of hypercapnia were different with and without TTM.(Institutional protocol number: FOTS, id 14931).

Opioid-Associated Out-of-Hospital Cardiac Arrest: Distinctive Clinical Features and Implications for Health Care and Public Responses: A Scientific Statement From the American Heart Association

Opioid overdose is the leading cause of death for Americans 25 to 64 years of age, and opioid use disorder affects >2 million Americans. The epidemiology of opioid-associated out-of-hospital cardiac arrest in the United States is changing rapidly, with exponential increases in death resulting from synthetic opioids and linear increases in heroin deaths more than offsetting modest reductions in deaths from prescription opioids. The pathophysiology of polysubstance toxidromes involving opioids, asphyxial death, and prolonged hypoxemia leading to global ischemia (cardiac arrest) differs from that of sudden cardiac arrest. People who use opioids may also develop bacteremia, central nervous system vasculitis and leukoencephalopathy, torsades de pointes, pulmonary vasculopathy, and pulmonary edema. Emergency management of opioid poisoning requires recognition by the lay public or emergency dispatchers, prompt emergency response, and effective ventilation coupled to compressions in the setting of opioid-associated out-of-hospital cardiac arrest. Effective ventilation is challenging to teach, whereas naloxone, an opioid antagonist, can be administered by emergency medical personnel, trained laypeople, and the general public with dispatcher instruction to prevent cardiac arrest. Opioid education and naloxone distributions programs have been developed to teach people who are likely to encounter a person with opioid poisoning how to administer naloxone, deliver high-quality compressions, and perform rescue breathing. Current American Heart Association recommendations call for laypeople and others who cannot reliably establish the presence of a pulse to initiate cardiopulmonary resuscitation in any individual who is unconscious and not breathing normally; if opioid overdose is suspected, naloxone should also be administered. Secondary prevention, including counseling, opioid overdose education with take-home naloxone, and medication for opioid use disorder, is important to prevent recurrent opioid overdose.

Pediatric acute respiratory distress syndrome - current views

Acute respiratory distress syndrome (ARDS) mainly involves acute respiratory failure. In addition to this affected patients feel progressive arterial hypoxemia, dyspnea, and a marked increase in the work of breathing. The only clinical solution for the above pathological state is ventilation. Mechanical ventilation is necessary to support life in ARDs but it itself worsen lung injury and the term is known clinically as ‘ventilation induced lung injury’ (VILI). At the cellular level, respiratory epithelial cells are subjected to cyclic stretch, i.e. repeated cycles of positive and negative strain, during normal tidal ventilation. In aerated areas of diseased lungs, or even normal lungs subjected to injurious positive pressure mechanical ventilation, the cells are at risk of being over distended, and worsening injury by disrupting the alveolar epithelial barrier. Further, hypercapnic acidosis (HCA) in itself confers protection from stretch injury, potentially via a mechanisms involving inhibition of nuclear factor κB (NF-κB), a transcription factor central to inflammation, injury and repair. Mesenchymal stem cells are the latest in the field and are being investigated as a possible therapy for ARDS.

Neuroprotective Effects of the Glucagon-Like Peptide-1 Analog Exenatide After Out-of-Hospital Cardiac Arrest

Background:

In-hospital mortality in comatose patients resuscitated from out-of-hospital cardiac arrest (OHCA) is ≈50%. In OHCA patients, the leading cause of death is neurological injury secondary to ischemia and reperfusion. Glucagon-like peptide-1 analogs are approved for type 2 diabetes mellitus; preclinical and clinical data have suggested their organ-protective effects in patients with ischemia and reperfusion injury. The aim of this trial was to investigate the neuroprotective effects of the glucagon-like peptide-1 analog exenatide in resuscitated OHCA patients.

Methods:

We randomly assigned 120 consecutive comatose patients resuscitated from OHCA in a double-blind, 2-center trial. They were administered 17.4 μg exenatide (Byetta) or placebo over a 6-hour and 15-minute infusion, in addition to standardized intensive care including targeted temperature management. The coprimary end points were feasibility, defined as initiation of the study drug in >90% patients within 240 minutes of return of spontaneous circulation, and efficacy, defined as the geometric area under the neuron-specific enolase curve from 24 to 72 hours after admission. The main secondary end points included a composite end point of death and poor neurological function, defined as a Cerebral Performance Category score of 3 to 5 assessed at 30 and 180 days.

Results:

The study drug was initiated within 240 minutes of return of spontaneous circulation in 96% patients. The median blood glucose 8 hours after admission in patients receiving exenatide was lower than that in patients receiving placebo (5.8 [5.2–6.7] mmol/L versus 7.3 [6.2–8.7] mmol/L, P <0.0001). However, there were no significant differences in the area under the neuron-specific enolase curve, or a composite end point of death and poor neurological function between groups. Adverse events were rare with no significant difference between groups.

Conclusions:

Acute administration of exenatide to comatose patients in the intensive care unit after OHCA is feasible and safe. Exenatide did not reduce neuron-specific enolase levels and did not significantly improve a composite end point of death and poor neurological function after 180 days.

Clinical Trial Registration:

URL: http://www.clinicaltrials.gov . Unique identifier: NCT02442791.

Early Moderate Hyperoxemia Does Not Predict Outcome After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Targeting hyperoxemia is common practice in neurocritical care settings, but the safety of hyperoxemia has been questioned.

OBJECTIVE

To investigate the independent effect of hyperoxemia on outcome in patients with aneurysmal subarachnoid hemorrhage (SAH).

METHODS

We included 432 patients with aneurysmal SAH on mechanical ventilation for at least 24 hours after intensive care unit (ICU) admission. Arterial blood gas levels were calculated as time-weighted averages (TWAs) of all blood gas measurements during the first 24 hours in the ICU. Patients were categorized into 3 TWA-PaO2 bands (low, <97.5 mm Hg; intermediate, 97.5-150 mm Hg; high, ≥150 mm Hg). Outcome measures were unfavorable outcome at 3 months (Glasgow Outcome Scale score 1-3) and mortality. Multivariate logistic regression analysis was used to assess the independent effect of oxygen on outcome.

RESULTS

Overall, 28% of patients died, and a total of 53% had an unfavorable outcome at 3 months. Patients with an unfavorable outcome had significantly higher TWA-PaO2 levels compared with patients with a favorable outcome (137 mm Hg vs 118 mm Hg, P < .001). Multivariate analysis demonstrated no significant association between TWA-PaO2 bands and unfavorable outcome (with intermediate PaO2 as a reference, odds ratio [OR] for low PaO2 1.05, 95% confidence interval [CI]: 0.52-2.12, P = .89; OR for high PaO2: 1.09, 95% CI: 0.61-1.97, P = .77) or mortality (with intermediate PaO2 as reference, the OR for low PaO2 was 0.67 (95% CI: 0.30-1.46, P = .31), and the OR for high PaO2 was 0.73 (95% CI: 0.38-1.40, P = .34).

CONCLUSION

Early moderate hyperoxemia may not increase or decrease the risk of a poor outcome in mechanically ventilated aneurysmal SAH patients.

A systematic review and meta-analysis of the association between arterial carbon dioxide tension and outcomes after cardiac arrest

INTRODUCTION

Arterial carbon dioxide tension (PaCO₂) abnormalities are common after cardiac arrest (CA). Maintaining a normal PaCO₂ makes physiological sense and is recommended as a therapeutic target after CA, but few studies have examined the association between PaCO₂ and patient outcomes. This systematic review and meta-analysis aimed to assess the effect of a low or high PaCO₂ on patient outcomes after CA.

METHODS

We searched MEDLINE, EMBASE, CINAHL and Cochrane CENTRAL, for studies that evaluated the association between PaCO₂ and outcomes after CA. The primary outcome was hospital survival. Secondary outcomes included neurological status at the end of each study's follow up period, hospital discharge destination and 30-day survival. Meta-analysis was conducted if statistical heterogeneity was low.

RESULTS

The systematic review included nine studies; eight provided sufficient quantitative data for meta-analysis. Using PaCO₂ cut-points of <35mmHg and >45mmHg to define hypo- and hypercarbia, normocarbia was associated with increased hospital survival (odds ratio [OR] 1.30, 95% confidence interval [CI] 1.23, 1.38). Normocarbia was also associated with a good neurological outcome (cerebral performance category score 1 or 2) compared to hypercarbia (OR 1.69, 95% CI 1.13, 2.51) when the analysis also included an additional study with a slightly different definition for normocarbia (PaCO₂ 30-50mmHg).

CONCLUSIONS

From the limited data it appears PaCO₂ has an important U-shape association with survival and outcomes after CA, consistent with international resuscitation guidelines' recommendation that normocarbia be targeted during post-resuscitation care.

Targeted therapeutic mild hypercapnia after cardiac arrest: A phase II multi-centre randomised controlled trial (the CCC trial)

BACKGROUND

In intensive care observational studies, hypercapnia after cardiac arrest (CA) is independently associated with improved neurological outcome. However, the safety and feasibility of delivering targeted therapeutic mild hypercapnia (TTMH) for such patients is untested.

METHODS

In a phase II safety and feasibility multi-centre, randomised controlled trial, we allocated ICU patients after CA to 24h of targeted normocapnia (TN) (PaCO2 35-45mmHg) or TTMH (PaCO2 50-55mmHg). The primary outcome was serum neuron specific enolase (NSE) and S100b protein concentrations over the first 72h assessed in the first 50 patients surviving to day three. Secondary end-points included global measure of function assessment at six months and mortality for all patients.

RESULTS

We enrolled 86 patients. Their median age was 61 years (58, 64 years) and 66 (79%) were male. Of these, 50 patients (58%) survived to day three for full biomarker assessment. NSE concentrations increased in the TTMH group (p=0.02) and TN group (p=0.005) over time, with the increase being significantly more pronounced in the TN group (p(interaction)=0.04). S100b concentrations decreased over time in the TTMH group (p<0.001) but not in the TN group (p=0.68). However, the S100b change over time did not differ between the groups (p(interaction)=0.23). At six months, 23 (59%) TTMH patients had good functional recovery compared with 18 (46%) TN patients. Hospital mortality occurred in 11 (26%) TTMH patients and 15 (37%) TN patients (p=0.31).

CONCLUSIONS

In CA patients admitted to the ICU, TTMH was feasible, appeared safe and attenuated the release of NSE compared with TN. These findings justify further investigation of this novel treatment.