Electrocardiogram (ECG)- is the primary factor that determines the advanced life support decision. ECG leads should be attached as soon as possible after BLS is initiated. Anyone responding to a code should be familiar with ECG rhythm diagnosis. The equipment to perform an ECG should be always ready and available. Make sure your team is trained to know where to place the leads and how to operate the machine. A conductive gel should remain with the machine to improve contact with the leads and the patient. Never use alcohol as it is highly flammable and might ignite with electrical defibrillation.
A three lead ECG electrode monitoring is usually adequate. Leads are placed as white= right forelimb, black= left forelimb and red= left hind limb. If you don’t remember where the leads, go simply place the three leads on three different limbs and you will get an ECG tracing that is sufficient for CPR. Alligator clamp electrodes or pre-gelled adhesive electrodes can be used to obtain an ECG. Pre-gelled adhesive electrodes are preferred during CPR and can be placed on foot pads and taped in place. Pre-gelled pads taped in place are less likely to fall off during compressions. ECG should be monitored during the brief 2- 5 second pauses during 2-minute compression cycles.
Evaluating the ECG is important and will help guide treatment decisions. If chest compressions are being performed there will be too much motion artifact to interpret the ECG. There are three major types of rhythms that we are looking to interpret during the ECG in CPR; they are perfusing rhythms associated with pulses, non-shockable arrest rhythms that do not require electrical defibrillation (Asystole and PEA) and shockable arrest rhythms that require electrical defibrillation (VF and VT). Non- shockable rhythms are the most common rhythms in dogs and cats in cardiac arrest.
End Tidal Carbon Dioxide Monitor– Determines the amount of CO2 (EtCO2) in the exhaled air at the end of a breath. EtCO2 is determined by minute ventilation, which is the product of respiratory rate and tidal volume and the amount of blood returning from the tissue to the lungs. This can also help monitor the quality of chest compressions during CPR. The EtCO2 monitor should be placed immediately following intubation. ROSC, or return of spontaneous circulation, can also be identified using the EtCO2 monitor. Other devices such as blood pressure monitors and pulse oximeters are less useful during CPR as they rely on arterial pulse pressure and typically there is inadequate pulsatile flow for accurate readings.