Sodium nitroprusside enhanced cardiopulmonary resuscitation (SNPeCPR) improves vital organ perfusion pressures and carotid blood flow in a porcine model of cardiac arrest

A Narrative Review of Drug Therapy in Adult and Pediatric Cardiac Arrest

Drugs are used during cardiopulmonary resuscitation (CPR) in association with chest compressions and ventilation. The main purpose of drugs during resuscitation is either to improve coronary perfusion pressure and myocardial perfusion in order to achieve return of spontaneous circulation (ROSC). The aim of this up-to-date review is to provide an overview of the main drugs used during cardiac arrest (CA), highlighting their historical context, pharmacology, and the data to support them. Epinephrine remains the only recommended vasopressor. Regardless of the controversy about optimal dosage and interval between doses in recent papers, epinephrine should be administered as early as possible to be the most effective in non-shockable rhythms. Despite inconsistent survival outcomes, amiodarone and lidocaine are the only two recommended antiarrhythmics to treat shockable rhythms after defibrillation. Beta-blockers have also been recently evaluated as antiarrhythmic drugs and show promising results but further evaluation is needed. Calcium, sodium bicarbonate, and magnesium are still widely used during resuscitation but have shown no benefit. Available data may even suggest a harmful effect and they are no longer recommended during routine CPR. In experimental studies, sodium nitroprusside showed an increase in survival and favorable neurological outcome when combined with enhanced CPR, but as of today, no clinical data is available. Finally, we review drug administration in pediatric CA. Epinephrine is recommended in pediatric CA and, although they have not shown any improvement in survival or neurological outcome, antiarrhythmic drugs have a 2b recommendation in the current guidelines for shockable rhythms.

Closed-loop machine-controlled CPR system optimises haemodynamics during prolonged CPR

Objectives

We evaluated the feasibility of optimising coronary perfusion pressure (CPP) during cardiopulmonary resuscitation (CPR) with a closed-loop, machine-controlled CPR system (MC-CPR) that sends real-time haemodynamic feedback to a set of machine learning and control algorithms which determine compression/decompression characteristics over time.

Background

American Heart Association CPR guidelines (AHA-CPR) and standard mechanical devices employ a “one-size-fits-all” approach to CPR that fails to adjust compressions over time or individualise therapy, thus leading to deterioration of CPR effectiveness as duration exceeds 15–20 ​min.

Methods

CPR was administered for 30 ​min in a validated porcine model of cardiac arrest. Intubated anaesthetised pigs were randomly assigned to receive MC-CPR (6), mechanical CPR conducted according to AHA-CPR (6), or human-controlled CPR (HC-CPR) (10). MC-CPR directly controlled the CPR piston’s amplitude of compression and decompression to maximise CPP over time. In HC-CPR a physician controlled the piston amplitudes to maximise CPP without any algorithmic feedback, while AHA-CPR had one compression depth without adaptation.

Results

MC-CPR significantly improved CPP throughout the 30-min resuscitation period compared to both AHA-CPR and HC-CPR. CPP and carotid blood flow (CBF) remained stable or improved with MC-CPR but deteriorated with AHA-CPR. HC-CPR showed initial but transient improvement that dissipated over time.

Conclusion

Machine learning implemented in a closed-loop system successfully controlled CPR for 30 ​min in our preclinical model. MC-CPR significantly improved CPP and CBF compared to AHA-CPR and ameliorated the temporal haemodynamic deterioration that occurs with standard approaches.

Sodium Nitroprusside-Enhanced Cardiopulmonary Resuscitation Improves Blood Flow by Pulmonary Vasodilation Leading to Higher Oxygen Requirements

•

SNPeCPR improves coronary perfusion pressure, tissue perfusion, and carotid blood flow compared to epinephrine-based standard advanced cardiac life support.

•

In a porcine model of prolonged resuscitation, SNPeCPR was associated with decreased arterial oxygen saturation but improved tissue oxygen delivery due to improvement in blood flow.

•

Oxygen supplementation led to alleviation of hypoxemia and maintenance of the SNPeCPR hemodynamic benefits.

•

Arterial oxygen saturation must be a safety endpoint that will be prospectively assessed in the first SNPeCPR clinical trial in humans.

Sodium nitroprusside–enhanced cardiopulmonary resuscitation has shown superior resuscitation rates and neurologic outcomes in large animal models supporting the need for a randomized human clinical trial. This study is the first to show nonselective pulmonary vasodilation as a potential mechanism for the hemodynamic benefits. The pulmonary shunting that is created requires increased oxygen treatment, but the overall improvement in blood flow increases minute oxygen delivery to tissues. In this context, hypoxemia is an important safety endpoint and a 100% oxygen ventilation strategy may be necessary for the first human clinical trial.

Use of resuscitative balloon occlusion of the aorta in a swine model of prolonged cardiac arrest

AIM

We examined the use of a Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) catheter during cardiopulmonary resuscitation (CPR) after cardiac arrest (CA) to assess its effect on haemodynamics such as coronary perfusion pressure (CPP), common carotid artery blood flow (CCA-flow) and end-tidal CO₂ (PetCO₂) which are associated with increased return of spontaneous circulation (ROSC).

METHODS

Six male swine were instrumented to measure CPP, CCA-Flow, and PetCO₂. A 7Fr REBOA was advanced into zone-1 of the aorta through the femoral artery. Ventricular fibrillation was induced and untreated for 8 min. CPR (manual then mechanical) was initiated for 24 min. Continuous infusion of adrenaline (epinephrine) was started at minute-4 of CPR. The REBOA balloon was inflated at minute-16 for 3 min and then deflated/inflated every 3 min for 3 cycles. Animals were defibrillated up to 6 times after the final cycle. Animals achieving ROSC were monitored for 25 min.

RESULTS

Data showed significant differences between balloon deflation and inflation periods for CPP, CCA-Flow, and PetCO₂ (p < 0.0001) with an average difference (SD) of 13.7 (2.28) mmHg, 15.5 (14.12) mL min^-1 and -4 (2.76) mmHg respectively. Three animals achieved ROSC and had significantly higher mean CPP (54 vs. 18 mmHg), CCA-Flow (262 vs. 135 mL min^-1) and PetCO₂ (16 vs. 8 mmHg) (p < 0.0001) throughout inflation periods than No-ROSC animals. Aortic histology did not reveal any significant changes produced by balloon inflation.

CONCLUSION

REBOA significantly increased CPP and CCA-Flow in this model of prolonged CA. These increases may contribute to the ability to achieve ROSC.

The future is now: neuroprotection during cardiopulmonary resuscitation

PURPOSE OF REVIEW

Survival with favorable neurological function after cardiac arrest remains low. The purpose of this review is to identify recent advances that focus on neuroprotection during cardiopulmonary resuscitation (CPR).

RECENT FINDINGS

Multiple strategies have been shown to enhance neuroprotection during CPR. Brain perfusion during CPR is increased with therapies such as active compression decompression CPR and intrathoracic pressure regulation that improve cardiac preload and decrease intracranial pressure. Head Up CPR has been shown to decrease intracranial pressure thereby increasing cerebral perfusion pressure and cerebral blood flow. Sodium nitroprusside enhanced CPR increases cerebral perfusion, facilitates heat exchange, and improves neurologic survival in swine after cardiac arrest. Postconditioning has been administered during CPR in laboratory settings. Poloxamer 188, a membrane stabilizer, and ischemic postconditioning have been shown to improve cardiac and neural function after cardiac arrest in animal models. Postconditioning with inhaled gases protects the myocardium, with more evidence mounting for the potential for neural protection.

SUMMARY

Multiple promising neuroprotective therapies are being developed in animal models of cardiac arrest, and are in early stages of human trials. These therapies have the potential to be bundled together to improve rates of favorable neurological survival after cardiac arrest.

Correlation of end tidal carbon dioxide, amplitude spectrum area, and coronary perfusion pressure in a porcine model of cardiac arrest

Amplitude Spectrum Area (AMSA) values during ventricular fibrillation (VF) correlate with myocardial energy stores and predict defibrillation success. By contrast, end tidal CO₂ (ETCO2) values provide a noninvasive assessment of coronary perfusion pressure and myocardial perfusion during cardiopulmonary resuscitation (CPR). Given the importance of the timing of defibrillation shock delivery on clinical outcome, we tested the hypothesis that AMSA and ETCO2 correlate with each other and can be used interchangably to correlate with myocardial perfusion in an animal laboratory preclinical, randomized, prospective investigation. After 6 min of untreated VF, 12 female pigs (32 ± 1 Kg), isoflurane anesthetized pigs received sequentially 3 min periods of standard (S) CPR, S‐CPR+ an impedance threshold device (ITD), and then active compression decompression (ACD) + ITD CPR. Hemodynamic, AMSA, and ETCO2 measurements were made with each method of CPR. The Spearman correlation and Friedman tests were used to compare hemodynamic parameters. ETCO2, AMSA, coronary perfusion pressure, cerebral perfusion pressure were lowest with STD CPR, increased with STD CPR + ITD and highest with ACD CPR + ITD. Further analysis demonstrated a positive correlation between AMSA and ETCO2 (r = 0.37, P = 0.025) and between AMSA and key hemodynamic parameters (P < 0.05). This study established a moderate positive correlation between ETCO2 and AMSA. These findings provide the physiological basis for developing and testing a novel noninvasive method that utilizes either ETCO2 alone or the combination of ETCO2 and AMSA to predict when defibrillation might be successful.

Sodium nitroprusside enhanced cardiopulmonary resuscitation improves short term survival in a porcine model of ischemic refractory ventricular fibrillation

INTRODUCTION

Sodium nitroprusside (SNP) enhanced CPR (SNPeCPR) demonstrates increased vital organ blood flow and survival in multiple porcine models. We developed a new, coronary occlusion/ischemia model of prolonged resuscitation, mimicking the majority of out-of-hospital cardiac arrests presenting with shockable rhythms.

HYPOTHESIS

SNPeCPR will increase short term (4-h) survival compared to standard 2015 Advanced Cardiac Life Support (ACLS) guidelines in an ischemic refractory ventricular fibrillation (VF), prolonged CPR model.

METHODS

Sixteen anesthetized pigs had the ostial left anterior descending artery occluded leading to ischemic VF arrest. VF was untreated for 5min. Basic life support was performed for 10min. At minute 10 (EMS arrival), animals received either SNPeCPR (n=8) or standard ACLS (n=8). Defibrillation (200J) occurred every 3min. CPR continued for a total of 45min, then the balloon was deflated simulating revascularization. CPR continued until return of spontaneous circulation (ROSC) or a total of 60min, if unsuccessful. SNPeCPR animals received 2mg of SNP at minute 10 followed by 1mg every 5min until ROSC. Standard ACLS animals received 0.5mg epinephrine every 5min until ROSC. Primary endpoints were ROSC and 4-h survival.

RESULTS

All SNPeCPR animals (8/8) achieved sustained ROSC versus 2/8 standard ACLS animals within one hour of resuscitation (p=0.04). The 4-h survival was significantly improved with SNPeCPR compared to standard ACLS, 7/8 versus 1/8 respectively, p=0.0019.

CONCLUSION

SNPeCPR significantly improved ROSC and 4-h survival compared with standard ACLS CPR in a porcine model of prolonged ischemic, refractory VF cardiac arrest.

Sodium nitroprusside-enhanced cardiopulmonary resuscitation facilitates intra-arrest therapeutic hypothermia in a porcine model of prolonged ventricular fibrillation

OBJECTIVES

The aim of this study was to assess the effect of sodium nitroprusside-enhanced cardiopulmonary resuscitation on heat exchange during surface cooling. We hypothesized that sodium nitroprusside-enhanced cardiopulmonary resuscitation would decrease the time required to reach brain temperature less than 35°C compared to active compression-decompression plus impedance threshold device cardiopulmonary resuscitation alone, in the setting of intra-cardiopulmonary resuscitation cooling. We further hypothesized that the addition of epinephrine during sodium nitroprusside-enhanced cardiopulmonary resuscitation would mitigate heat exchange.

DESIGN

Prospective randomized animal investigation.

SETTING

Preclinical animal laboratory.

SUBJECTS

Female farm pigs (n=28).

INTERVENTIONS

After 10 minutes of untreated ventricular fibrillation, animals were randomized to three different protocols: sodium nitroprusside-enhanced cardiopulmonary resuscitation (n=8), sodium nitroprusside-enhanced cardiopulmonary resuscitation plus epinephrine (n=10), and active compression-decompression plus impedance threshold device alone (control, n=10). All animals received surface cooling at the initiation of cardiopulmonary resuscitation. Sodium nitroprusside-enhanced cardiopulmonary resuscitation included active compression-decompression plus impedance threshold device plus abdominal binding and 2 mg of sodium nitroprusside at 1, 4, and 8 minutes of cardiopulmonary resuscitation. No epinephrine was used during cardiopulmonary resuscitation in the sodium nitroprusside-enhanced cardiopulmonary resuscitation group. Control and sodium nitroprusside-enhanced cardiopulmonary resuscitation plus epinephrine groups received 0.5 mg of epinephrine at 4.5 and 9 minutes of cardiopulmonary resuscitation. Defibrillation occurred after 10 minutes of cardiopulmonary resuscitation. After return of spontaneous circulation, an Arctic Sun (Medivance, Louiseville, CO) was applied at maximum cooling on all animals. The primary endpoint was the time required to reach brain temperature less than 35°C beginning from the time of cardiopulmonary resuscitation initiation. Data are presented as mean±SEM.

MEASUREMENTS AND MAIN RESULTS

The time required to reach a brain temperature of 35°C was decreased with sodium nitroprusside-enhanced cardiopulmonary resuscitation versus control or sodium nitroprusside-enhanced cardiopulmonary resuscitation plus epinephrine (24±6 min, 63±8 min, and 50±9 min, respectively; p=0.005). Carotid blood flow was higher during cardiopulmonary resuscitation in the sodium nitroprusside-enhanced cardiopulmonary resuscitation group (83±15 mL/min vs 26±7 mL/min and 35±5 mL/min in the control and sodium nitroprusside-enhanced cardiopulmonary resuscitation plus epinephrine groups, respectively; p=0.001).

CONCLUSIONS

This study demonstrates that sodium nitroprusside-enhanced cardiopulmonary resuscitation facilitates intra-cardiopulmonary resuscitation hypothermia. The addition of epinephrine to sodium nitroprusside-enhanced cardiopulmonary resuscitation during cardiopulmonary resuscitation reduced its improvement in heat exchange.

A systematic review of neuroprotective strategies after cardiac arrest: from bench to bedside (Part I - Protection via specific pathways)

Neurocognitive deficits are a major source of morbidity in survivors of cardiac arrest. Treatment options that could be implemented either during cardiopulmonary resuscitation or after return of spontaneous circulation to improve these neurological deficits are limited. We conducted a literature review of treatment protocols designed to evaluate neurologic outcome and survival following cardiac arrest with associated global cerebral ischemia. The search was limited to investigational therapies that were utilized to treat global cerebral ischemia associated with cardiac arrest. In this review we discuss potential mechanisms of neurologic protection following cardiac arrest including actions of several medical gases such as xenon, argon, and nitric oxide. The 3 included mechanisms are: 1. Modulation of neuronal cell death; 2. Alteration of oxygen free radicals; and 3. Improving cerebral hemodynamics. Only a few approaches have been evaluated in limited fashion in cardiac arrest patients and results show inconclusive neuroprotective effects. Future research focusing on combined neuroprotective strategies that target multiple pathways are compelling in the setting of global brain ischemia resulting from cardiac arrest.

Novelties in pharmacological management of cardiopulmonary resuscitation

PURPOSE OF REVIEW

The ultimate goal of cardiopulmonary resuscitation is long-term neurologically intact survival. Despite numerous well-designed studies, the medications currently used in advanced cardiac life support have not demonstrated success in this regard. This review describes the novel therapeutics under investigation to improve functional recovery and survival.

RECENT FINDINGS

Whereas current medications focus on achieving return of spontaneous circulation and improved hemodynamics, novel therapies currently in development are focused on improving cellular survival and function by preventing metabolic derangement, protecting mitochondria, and preventing cell death caused by cardiac arrest. Improved cardiac and neurologic function and survival benefits have been observed using animal models of cardiopulmonary arrest.

SUMMARY

Although substantial data have shown benefits using robust animal models, further human studies are necessary to investigate the potential long-term benefits of these therapies.

Sodium nitroprusside enhanced cardiopulmonary resuscitation prevents post-resuscitation left ventricular dysfunction and improves 24-hour survival and neurological function in a porcine model of prolonged untreated ventricular fibrillation

AIM OF STUDY

Sodium nitroprusside-enhanced CPR, or SNPeCPR, consists of active compression-decompression CPR with an impedance threshold device, abdominal compression, and intravenous sodium nitroprusside (SNP). We hypothesize that SNPeCPR will improve post resuscitation left ventricular function and neurological function compared to standard (S) CPR after 15 min of untreated ventricular fibrillation in a porcine model of cardiac arrest.

METHODS

Pigs (n = 22) anesthetized with isoflurane underwent 15 min of untreated ventricular fibrillation, were then randomized to 6 min of S-CPR (n = 11) or SNPeCPR (n = 11) followed by defibrillation. The primary endpoints were neurologic function as measured by cerebral performance category (CPC) score and left ventricular ejection fraction.

RESULTS

SNPeCPR increased 24-hour survival rates compared to S-CPR (10/11 versus 5/11, p = 0.03) and improved neurological function (CPC score 2.5 ± 1, versus 3.8 ± 0.4, respectively, p = 0.004). Left ventricular ejection fractions at 1, 4 and 24 hours after defibrillation were 72 ± 11, 57 ± 11.4 and 64 ± 11 with SNPeCPR versus 29 ± 10, 30 ± 17 and 39 ± 6 with S-CPR, respectively (p < 0.01 for all).

CONCLUSIONS

In this pig model, after 15 min of untreated ventricular fibrillation, SNPeCPR significantly improved 24-hour survival rates, neurologic function and prevented post-resuscitation left ventricular dysfunction compared to S-CPR.