Initiate ALS as soon as feasible, with ECG monitoring to guide management. Figure 312 and Table 10 direct specific actions based on the arrest rhythm present. In contrast to people, the most common arrest rhythm in MWDs is pulseless electrical activity (PEA; 24%), followed by asystole (23%), and then ventricular fibrillation (VF; 20%). Sinus bradycardia commonly precedes arrest in many situations in dogs.2,5
- 70% of MWDs that arrest will have PEA, asystole, or sinus bradycardia as the initial arrest rhythm.2,5 Epinephrine or vasopressin are best choices for these rhythms or for empiric use if ECG capability is not available. In the deployed setting, there is no role for transthoracic pacing in MWDs with PEA or asystole.
- Bradycardia due to a pronounced vagal response is very common in dogs, and use of atropine may prevent development of cardiopulmonary arrest.
- VF, while present initially in only 20% of MWDs with an arrest rhythm, often develops during resuscitation.2 Perform external defibrillation if possible and as rapidly as possible if VF is noted; biphasic defibrillation is ideal.5,7 Apply paddles to either side of the chest with the MWD in dorsal recumbency (on its back), or place a flat paddle under the MWD lying in lateral recumbency and a standard paddle on the upper chest wall. Defibrillate up to 3 times at each energy level if prior attempts are not successful, but perform aggressive chest compressions for at least 2 minutes before attempting each defibrillation.
- IV access is critical. Place multiple IV or IO catheters or perform venous cut-down (See CPG 6, Figure 33). Follow all drugs with a 10 mL saline push. Do not give large volumes of fluids to MWDs during CPR, unless severe hypovolemia is thought present. Give fluids initially to facilitate drug delivery only.