Cardiopulmonary arrest (CPA) is characterized by sudden cessation of spontaneous and effective circulation and ventilation. CPCR provides artificial ventilation and circulation until advanced life support can be provided and there is return of spontaneous circulation (ROSC). Unified veterinary CPCR guidelines do not yet exist but the ACVECC is currently conducting a Reassessment Campaign on Veterinary Resuscitation (RECOVER) to create consensus guidelines; these findings will be released in March 2012.

Preparedness

Major reasons for unsuccessful resuscitation include delayed diagnosis of CPA and delayed initiation of CPCR. Common signs of an impending CPA include alterations in respiratory rate and/or character, hypotension, bradycardia, hypothermia, and cyanosis.

All hospitals should have well-trained personnel and a fully-stocked "crash cart" minimally including supplies for venous access, airway establishment & management, and pharmacologic support.

Every patient should have an advanced directive ("code status") upon admission to the hospital. Each patient's "code status" should be clearly identifiable to all medical staff, and should adhere to the classic 3-color system (Table 1).

Table 1. Advanced Directive Classification System.

Basic Life Support (BLS)

The C-A-B (Chest compression, Airway, Breathing) approach to CPCR is advocated as it provides simultaneous treatment of circulatory and ventilatory failure.

Animals should be placed in right lateral recumbency with the compressor standing above the patient. For dogs < 7 kg and cats, the hand should be placed on one side of the thorax and the thumb on the other. Animals between 7–10 kg should have compressions performed over the 4th–6th intercostal space at the costochondral junction. Dogs > 10 kg should have compressions performed over the widest diameter of the thoracic cage just dorsal to the costochondral junction.

Rescuers should aim for ~30% compression of the chest wall at a rate of 80–120 per minute with allowance of complete recoil following each compression (Class IIb). This recommended compression rate has been associated with higher mean aortic and coronary perfusion pressures, improved ROSC and 24-hour survival. Incomplete recoil is associated with higher intrathoracic pressures that may cause decreased coronary perfusion and decreased cerebral perfusion. Chest compressions should be performed for ~2 minutes following administration of drugs before checking the ECG.

Rescue fatigue may lead to inadequate compression technique. When possible, rotate the compressor every few minutes taking care to avoid a delay greater than 5 seconds when making this switch (Class IIb). Interruption of chest compressions will cause decreased coronary perfusion pressure and blood flow, as well as lower survival rates. Internal cardiac massage should be performed in patients with penetrating chest wounds, chest wall trauma including fractured ribs, pleural space disease, pericardial effusion and lack of ROSC following 5 minutes of external compressions.

Orotracheal intubation is the most common method for establishing an airway. Provide 100% F_iO₂. The respiratory rate should be 8–10 breathes per minute; each breath should be given over 1 second (Class IIa) with sufficient tidal volume to produce visible chest rise. Airway pressure should not exceed 20 cm H₂O. Capnography is recommended for monitoring CPCR efficacy (Class IIa), as an increase in ETCO₂ to 18–24 mm Hg is associated with ROSC.

Interposed abdominal compressions should be initiated if there is an assistant available to perform this intervention. Abdominal compressions are delivered in counterpoint to the rhythm of chest compressions, so abdominal pressure is maintained whenever the chest is not being compressed. Compressions are applied just cranial to the umbilicus and hand position, depth, rhythm and rate of abdominal compression are similar to those for chest compressions.

Advanced Life Support (ALS)

A central IV catheter is often ideal for administration of emergency drugs. The next best route is via a peripheral IV or IO catheter. IT administration is an acceptable route for epinephrine, atropine, naloxone, lidocaine and vasopressin. The drugs are diluted with sterile water to 2–2.5x IV doses for all drugs (exception: epinephrine must be given at 3–10x IV dose) and administered to the lower airways via a red rubber catheter followed by several large volume breaths to hasten drug absorption. IT administration of sodium bicarbonate and amiodarone is contraindicated.

Upon initiation of BLS, advanced measures such as drug administration and defibrillation may commence. ECG rhythm will dictate the necessity for drug therapy or defibrillation (Table 2). Reversal agents should be administered when indicated (Table 3).

Table 2. Common Medications and Interventions for ALS.

Table 3. Common Reversal Agents.

Fluid therapy is an essential component of ALS for patients with poor venous return. However IV fluids should not be administered at "full shock" doses unless the patient was hypovolemic before the CPA (Table 4). While CPA is associated with vasodilation and poor cardiac output, caution must be taken to avoid overly aggressive fluid therapy as increased right atrial pressure in relation to aortic pressure will lead to lower coronary perfusion pressure.

Table 4. Fluid Therapy Guidelines.

Impedance Threshold Device (ITD)

Intrathoracic pressure decreases during thoracic decompression promoting venous return. However, air being drawn into the lungs during this phase partially impairs venous return. The ITD prevents air movement into the lungs during the decompression phase of CPCR. Intrathoracic pressure is more negative, thus improving venous return, stroke volume, cardiac output and oxygen delivery to the tissues.

Hypothermia

Hypothermia commonly develops in patients undergoing CPCR. Experimental animal and human trial evidence suggests permissive hypothermia, or active induction of mild-to-moderate hypothermia, may have some degree of protective benefit on neurological outcome in patients experiencing CPA.

Prognosis

Despite efforts, prognosis for animals that undergo CPA is grave. A recent review of 265 non-anesthetized critical care unit patients receiving CPCR documented 4.1% of cats and 9.6% of dogs survived to hospital discharge.

References

References are available upon request.