Top 7 Updates for Veterinary Cardiopulmonary Resuscitation

In 2024, the Reassessment Campaign on Veterinary Resuscitation (RECOVER) guidelines were revised for the first time since 2012. These updated guidelines for cardiopulmonary resuscitation (CPR) in veterinary medicine include modifications for basic life support, advanced life support, and monitoring during CPR. Awareness of these modifications is important for optimizing outcomes for dogs and cats undergoing CPR.

Following are the top updates for veterinary CPR.

1. Compression Depth Depends On Patient Recumbency

Previous guidelines included a broad recommendation for compression one-third to one-half of the width of the chest during CPR in dogs and cats.¹ The new guidelines confine this recommendation to dogs and cats in lateral recumbency. For dogs in dorsal recumbency, a compression depth of one-quarter the width of the chest is recommended to help avoid complications (ie, rib fractures, pulmonary contusions) associated with deeper compressions for dogs with chest conformations resembling that of humans.^2,3

2. Use of a Tight-Fitting Face Mask (Rather Than Mouth-to-Snout Ventilation) When Endotracheal Tube Intubation Is Not Possible

Endotracheal tube (ETT) intubation is recommended for ventilation in dogs and cats. If ETT intubation is not possible, a tight-fitting face mask should be used for oxygenation and ventilation.² Although oxygenation and ventilation are improved with a tight-fitting mask or mouth-to-snout technique compared with compression-only CPR, a tight-fitting mask removes risks (eg, zoonotic disease, opioid inhalation) to the rescuer and provides targeted oxygen delivery and is therefore preferable.^2,4

3. End-Tidal Carbon Dioxide To Guide Intubation & Chest Compressions

End-tidal carbon dioxide (ETCO₂) should be monitored in all dogs and cats undergoing CPR. ETCO₂ ≥12 mm Hg is likely indicative of appropriate ETT intubation. ETCO₂ <12 mm Hg indicates immediate measures are needed to confirm proper intubation.⁵ Although studies in humans have shown that high ETCO₂ is consistent with appropriate ETT intubation, low ETCO₂ is poorly predictive of inappropriate intubation (eg, esophageal intubation), as low values may have other causes besides inappropriate intubation (eg, poor cardiac output).⁶ In these situations, lung auscultation or direct visualization of the larynx is recommended.⁵

During CPR, chest compressions should target ETCO₂ ≥18 mm Hg, as numerous studies in dogs, cats, and humans have indicated that higher ETCO₂ values are predictive of positive neurologic outcomes, survival to discharge, and return of spontaneous circulation.^5,7,8 Options to optimize ETCO₂ may include performing deeper compressions, changing the individual performing compressions, altering the compression point, and modifying the form of the individuals performing compressions.

4. Single Administration of Atropine During Cardiopulmonary Resuscitation

In the new guidelines, a single dose of atropine (0.04 mg/kg IV or intraosseous) is suggested for dogs and cats with nonshockable rhythms (eg, asystole, pulseless electrical activity).⁹ In the previous guidelines, atropine administration could be considered every other cycle (every 3-5 minutes) for nonshockable rhythms.¹⁰ The new guidelines recommend against repeated doses of atropine due to the drug’s long half-life (4 hours in humans) and association of higher doses with poor outcomes in dogs.^9,11,12

5. Epinephrine Administration Only at a Standard Dose

High-dose epinephrine (0.1 mg/kg) is no longer recommended at any point during CPR. High-dose epinephrine has not been associated with improved outcomes, and some evidence suggests association with poor neurologic outcomes and survival in humans.^9,13 Standard epinephrine is now recommended at a dose of 0.01 mg/kg (previously termed low dose) administered IV or intraosseous every other cycle (ie, 2 minutes of compressions) for nonshockable rhythms during CPR in dogs and cats.⁹

6. Doubled Dose for Second Defibrillation Attempt

Use of a biphasic defibrillator over a monophasic defibrillator is recommended in dogs and cats with shockable rhythms (eg, ventricular fibrillation, pulseless ventricular tachycardia). The new guidelines recommend a single defibrillation attempt at a dose of 2 J/kg for the first attempt.^14,15 If a dog or cat maintains a shockable rhythm, the dose should be doubled (4 J/kg) and maintained for all subsequent defibrillation attempts.⁹

The initial dose was based on human studies that showed no difference in outcomes between high and low doses for the first defibrillation attempt. A lower dose is less likely to cause myocardial injury; however, higher subsequent doses have been associated with a higher likelihood of rhythm conversion.^14,15

7. Consideration of Esmolol For Refractory Shockable Rhythms

The optimal treatment for refractory shockable rhythms (ie, >2 shocks administered) is unknown. Administration of lidocaine in dogs, amiodarone in cats, and vasopressin in cats and dogs (or epinephrine if vasopressin is unavailable) have been suggested.¹⁰ The new guidelines also suggest that esmolol (0.5 mg/kg IV or intraosseous over 3-5 minutes, followed by 50 micrograms/kg/minute IV CRI) may be considered for refractory shockable rhythms in dogs and cats.⁹

Beta-blocker administration may be associated with higher rates of return of spontaneous circulation.^16,17 Epinephrine administration during initial treatment was significantly associated with conversion to subsequent shockable rhythms after initial treatment for nonshockable rhythms.¹⁸ Beta-1 stimulation from epinephrine during CPR may lead to development of a shockable rhythm; therefore, esmolol administration may be reasonable in dogs and cats initially treated for a nonshockable rhythm.⁹

Conclusion

Regular re-evaluation of human and veterinary literature has led to significant guideline revisions for providing CPR in dogs and cats. In addition to these changes, the CPR algorithm and the rhythm diagnosis algorithm developed by RECOVER have also been updated. Knowledge of these revisions may help improve outcomes for CPR in veterinary species, and use and posting of the algorithms may aid anyone performing CPR. Further studies are needed to tailor evidence-based recommendations for CPR.