Initial arterial carbon dioxide tension is associated with neurological outcome after resuscitation from cardiac arrest

Association of point-of-care blood variables obtained from dogs and cats during cardiopulmonary resuscitation and following return of spontaneous circulation with patient outcomes

OBJECTIVE

To investigate the association of point-of-care biochemical variables obtained during CPR or within 24 hours of return of spontaneous circulation (ROSC) with patient outcomes.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

Ninety-four dogs and 27 cats undergoing CPR according to the Reassessment Campaign on Veterinary Resuscitation guidelines.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Blood gas, acid-base, electrolyte, glucose, and plasma lactate values obtained during CPR or within 24 hours of ROSC were retrospectively evaluated and are described. The blood sample type and collection time with respect to CPR initiation and ROSC were recorded. Measured variables, collection times, and species were included in a multivariable logistic regression model to estimate the odds ratio (OR) and 95% confidence interval of ROSC, sustained ROSC (≥20 min), and survival to hospital discharge. Significance was set at P < 0.05. Seventy-two venous blood samples obtained during CPR and 45 first venous and arterial blood samples obtained after ROSC were included in logistic regression analysis. During CPR, PvO₂ (1.09 [1.036-1.148], P = 0.001) and venous standard base excess (SBE) (1.207 [1.094-1.331], P < 0.001) were associated with ROSC. PvO₂ (1.075 [1.028-1.124], P = 0.002), SBE (1.171 [1.013-1.353], P = 0.032), and potassium concentration (0.635 [0.426-0.946], P = 0.026) were associated with sustained ROSC. Potassium concentration (0.235 [0.083-0.667], P = 0.007) was associated with survival to hospital discharge. Following ROSC, pH (69.110 [4.393-1087], P = 0.003), potassium concentration (0.222 [0.071-0.700], P = 0.010), and chloride concentration (0.805 [0.694-0.933], P = 0.004) were associated with survival to hospital discharge.

CONCLUSIONS

Biochemical variables such as PvO₂ , SBE, and potassium concentration during CPR and pH, potassium, and chloride concentration in the postarrest period may help identify dogs and cats with lower odds for ROSC or survival to hospital discharge following CPR.

The association between arterial-end-tidal carbon dioxide difference and outcomes after out-of-hospital cardiac arrest

AIM

We sought to determine if the difference between P_aCO₂ and E_TCO₂ is associated with hospital mortality and neurologic outcome following out-of-hospital cardiac arrest (OHCA).

METHODS

This was a retrospective cohort study of adult patients who achieved return of spontaneous circulation (ROSC) after OHCA over 3 years. The primary exposure was the P_aCO₂-E_TCO₂ difference on hospital arrival. The primary outcome was survival to hospital discharge. The secondary outcome was favorable neurologic status at discharge. We used receiver operating characteristic (ROC) curves to determine discrimination threshold and multivariate logistic regression to examine the association between the P_aCO₂-E_TCO₂ difference and outcome.

RESULTS

Of 698 OHCA patients transported to the hospitals, 381 had sustained ROSC and qualifying E_TCO₂ and P_aCO₂ values. Of these, 160 (42%) survived to hospital discharge. Mean E_TCO₂ was 39 mmHg among survivors and 43 mmHg among non-survivors. Mean P_aCO₂-E_TCO₂ was 6.8 mmHg and 9.0 mmHg (p < 0.05) for survivors and non-survivors. After adjustment for Utstein characteristics, a higher P_aCO₂-E_TCO₂ difference on hospital arrival was not associated with hospital mortality (OR 0.99, 95% CI: 0.97-1.0) or neurological outcome. Area under the ROC curve or P_aCO₂-E_TCO₂ difference was 0.56 (95% CI 0.51-0.62) compared with 0.58 (95% CI 0.52-0.64) for E_TCO₂.

CONCLUSION

Neither P_aCO₂-E_TCO₂ nor E_TCO₂ were strong predictors of survival or neurologic status at hospital discharge. While they may be useful to guide ventilation and resuscitation, these measures should not be used for prognostication after OHCA.

Oxygenation and ventilation targets after cardiac arrest: A systematic review and meta-analysis

AIM

To perform a systematic review and meta-analysis of the literature on oxygenation and ventilation targets after successful resuscitation from cardiac arrest in order to inform an update of international guidelines.

METHODS

The review was performed according to PRISMA and registered on PROSPERO (ID: X). Medline, EMBASE, and the Cochrane Library were searched on August 22, 2019. The population included both adult and pediatric patients with cardiac arrest. Two investigators reviewed abstracts, extracted data, and assessed the risk of bias. Meta-analyses were performed for studies without excessive bias. Certainty of evidence was evaluated using GRADE.

RESULTS

We included 7 trials and 36 observational studies comparing oxygenation or ventilation targets. Most of the trials and observational studies included adults with out-of-hospital cardiac arrest. There were 6 observational studies in children. Bias for trials ranged from low to high risk, with group imbalances and blinding being primary concerns. Bias for observational studies was rated as serious or critical risk with confounding and exposure classification being primary sources of bias. Meta-analyses including two trials comparing low vs high oxygen therapy and two trials comparing hypercapnia vs no hypercapnia were inconclusive. Point estimates of individual studies generally favored normoxemia and normocapnia over hyper- or hypoxemia and hyper- or hypocapnia.

CONCLUSIONS

We identified a large number of studies related to oxygenation and ventilation targets in cardiac arrest. The majority of studies did not reach statistical significance and were limited by excessive risk of bias. Point estimates of individual studies generally favored normoxemia and normocapnia.

Non-pulsatile blood flow is associated with enhanced cerebrovascular carbon dioxide reactivity and an attenuated relationship between cerebral blood flow and regional brain oxygenation

BACKGROUND

Systemic blood flow in patients on extracorporeal assist devices is frequently not or only minimally pulsatile. Loss of pulsatile brain perfusion, however, has been implicated in neurological complications. Furthermore, the adverse effects of absent pulsatility on the cerebral microcirculation are modulated similarly as CO₂ vasoreactivity in resistance vessels. During support with an extracorporeal assist device swings in arterial carbon dioxide partial pressures (PaCO₂) that determine cerebral oxygen delivery are not uncommon-especially when CO₂ is eliminated by the respirator as well as via the gas exchanger of an extracorporeal membrane oxygenation machine. We, therefore, investigated whether non-pulsatile flow affects cerebrovascular CO₂ reactivity (CVR) and regional brain oxygenation (rSO₂).

METHODS

In this prospective, single-centre case-control trial, we studied 32 patients undergoing elective cardiac surgery. Blood flow velocity in the middle cerebral artery (MCAv) as well as rSO₂ was determined during step changes of PaCO₂ between 30, 40, and 50 mmHg. Measurements were conducted on cardiopulmonary bypass during non-pulsatile and postoperatively under pulsatile blood flow at comparable test conditions. Corresponding changes of CVR and concomitant rSO₂ alterations were determined for each flow mode. Each patient served as her own control.

RESULTS

MCAv was generally lower during hypocapnia than during normocapnia and hypercapnia (p < 0.0001). However, the MCAv/PaCO₂ slope during non-pulsatile flow was 14.4 cm/s/mmHg [CI 11.8-16.9] and 10.4 cm/s/mmHg [CI 7.9-13.0] after return of pulsatility (p = 0.03). During hypocapnia, non-pulsatile CVR (4.3 ± 1.7%/mmHg) was higher than pulsatile CVR (3.1 ± 1.3%/mmHg, p = 0.01). Independent of the flow mode, we observed a decline in rSO2 during hypocapnia and a corresponding rise during hypercapnia (p < 0.0001). However, the relationship between ΔrSO₂ and ΔMCAv was less pronounced during non-pulsatile flow.

CONCLUSIONS

Non-pulsatile perfusion is associated with enhanced cerebrovascular CVR resulting in greater relative decreases of cerebral blood flow during hypocapnia. Heterogenic microvascular perfusion may account for the attenuated ΔrSO₂/ΔMCAv slope. Potential hazards related to this altered regulation of cerebral perfusion still need to be assessed.

TRIAL REGISTRATION

The study was retrospectively registered on October 30, 2018, with Clinical Trial.gov (NCT03732651).

Targeted Temperature Management and Postcardiac arrest Care

Despite recent advances, care of the post-cardiac arrest patient remains a challenge. In this article, the authors discuss an approach to the initial care of post-cardiac arrest patients with particular focus on targeted temperature management (TTM). The article starts with history, physiologic rationale, and the major randomized controlled trials that have shaped guidelines for post-cardiac arrest care. It also reviews controversial topics, including TTM for nonshockable rhythms, TTM dose, and surface versus endovascular cooling. The article concludes with a brief review of other key aspects of post-arrest care: coronary angiography, hemodynamic optimization, ventilator management, and prognostication.

The acute respiratory distress syndrome after out-of-hospital cardiac arrest: Incidence, risk factors, and outcomes

OBJECTIVE

To define the incidence of the acute respiratory distress syndrome (ARDS) following out-of-hospital cardiac arrest (OHCA) and characterize its impact on outcome.

METHODS

This was a retrospective cohort study conducted at two urban, tertiary, academic hospitals from 2007 to 2014. We included adults with non-traumatic OHCA and survived for ≥48 h. Patients who received mechanical ventilation for ≥24 h, had 2 consecutive arterial blood gases with a ratio of the partial pressure of oxygen to the fraction of inspired oxygen ≤300, and bilateral radiographic opacities within 48 h of hospital admission were defined as having ARDS. We examined the associations between ARDS and outcome using multivariable analyses and performed sensitivity analyses excluding patients with evidence of cardiac dysfunction.

RESULTS

Of 978 OHCA patients transported to the study hospitals, 600 were mechanically ventilated and survived ≥48 h. A total of 287 (48%, 95% CI 44-52%) met criteria for ARDS within 48 h of admission. There were no differences in demographics, OHCA etiology, or cardiac rhythm according to ARDS status. Patients with ARDS had higher hospital mortality, longer ICU stays, more ventilator days, and were less likely to survive with full neurologic recovery. Upon excluding patients with cardiac dysfunction, the incidence of ARDS was unchanged.

CONCLUSION

Nearly half of initial OHCA survivors develop ARDS within 48 h of hospital admission. ARDS was associated with poor outcome and increased resource utilization. OHCA should be considered among the traditional ARDS risk factors.

Critical Care of the Post-Cardiac Arrest Patient

The post-cardiac arrest syndrome is a highly inflammatory state characterized by organ dysfunction, systemic ischemia and reperfusion injury, and persistent precipitating pathology. Early critical care should focus on identifying and treating arrest etiology and minimizing further injury to the brain and other organs by optimizing perfusion, oxygenation, ventilation, and temperature. Patients should be treated with targeted temperature management, although the exact temperature goal is not clear. No earlier than 72 hours after rewarming, prognostication using a multimodal approach should inform discussions with families regarding likely neurologic outcome.

Ventilator Management and Respiratory Care After Cardiac Arrest: Oxygenation, Ventilation, Infection, and Injury

Return of spontaneous circulation after cardiac arrest results in a systemic inflammatory state called the post-cardiac arrest syndrome, which is characterized by oxidative stress, coagulopathy, neuronal injury, and organ dysfunction. Perturbations in oxygenation and ventilation may exacerbate secondary injury after cardiac arrest and have been shown to be associated with poor outcome. Further, patients who experience cardiac arrest are at risk for a number of other pulmonary complications. Up to 70% of patients experience early infection after cardiac arrest, and the respiratory tract is the most common source. Vigilance for early-onset pneumonia, as well as aggressive diagnosis and early antimicrobial agent administration are important components of critical care in this population. Patients who experience cardiac arrest are at risk for the development of ARDS. Risk factors include aspiration, pulmonary contusions (from chest compressions), systemic inflammation, and reperfusion injury. Early evidence suggests that they may benefit from ventilation with low tidal volumes. Meticulous attention to mechanical ventilation, early assessment and optimization of respiratory gas exchange, and therapies targeted at potential pulmonary complications may improve outcomes after cardiac arrest.