Pre-Anesthesia ECG

February 2, 2018

In the medical practice, anesthesia is commonly utilized for many surgical procedures which patients require to be immobile and unaware, or when pain may be endured. The application of anesthesia is also intended to minimize the surgical stress response. In veterinary, anesthesia is performed for a wider range of circumstances than in human due to animals’ inability to cooperate to certain clinical or therapeutic procedures. Specifically for small animals such as dogs and cats, general anesthesia is typically placed due to the small size of the patient, types of procedures and the degree of control. However, a study conducted in 1999 shows that 1 in 9 dogs and cats are likely to experience anesthetic complications with a 1 in 233 risk of death. The risk of death is even higher for sick animals with 1 in 75 for dogs and 1 in 71 for cats. A very high risk induced by anesthesia may put veterinarians and pet owners in an awry position of wanting to cure the animals or putting them in additional danger.


In many cases, anesthetic complications arise due to unsuitable anesthetic protocols to the background health of the animals. To address this issue, many studies suggested the necessity of the ECG conduction prior to anesthetic procedure as a standard procedure to help the clinician making a reliable decision, especially for dogs and cats over certain age (> 5 years) or specific type of breed that are more prone to cardiomyopathy (thinning of heart muscles) such as Doberman, Boxer or Great Dane. Besides, a recent study performed in 700 dogs in 2016 shows that there is no significant ECG alterations found with different weight, gender and age of the animals, which indicates the consistency of ECG for routine application in determining a safe anesthetic protocol.




How significant ECG can influence the following anesthesia procedure?


Considering ECG data with respect to the normal ranges for the species can be very critical in addressing problems before anesthesia is occupied. For instance, if the ECG tracings on a patient show prominent vagal influence such as slow heart rate or sinus arrhythmia (irregular heartbeat) meanwhile the focus of surgery will be on tissues with high degree of vagal influence like respiratory system or gastrointestinal, anesthetic protocol should employ anticholinergic agent that can block or reduce vagal influence or at least are not the one that tends to cause bradycardia (abnormally slow heart rhythm). On the other hand, if ECG tracings detect faster heart rates, it is better not to employ any anesthetic that will block the vagal influence or induce even faster heart rates. Another possibility is the presence of abnormal ECG tracings. In this case, prior treatment to address the problem needs to be done before anesthetic is administered. By doing pre-anesthetic ECG, anesthesia protocols can be adjusted for suitability of each patient.


Pre-anesthetic ECG also can provide an indication of possible problems that may occur during the anesthetic period. As an example, 40 to 50% of dogs that have been hit by car have heart and lung trauma which can potentially lead the development of cardiac arrhythmias and ventilation / perfusion problems during anesthesia in the early post traumatic period. Another case that the clinician should be aware of is the post gastric dilation volvulus (GDV) patient as they have a high chance of developing cardiomyopathy as well that can lead to the development of ventricular arrhythmias during the post surgical period, only within 72 hours after corrective surgery. By the help of prior ECG screening, the clinician can set a proper planning for the preventive purpose.




Botelho, A. F., Oliveira, M. S., Soto-Blanco, B., & Melo, M. M. (2016). Computerized electrocardiography in healthy conscious guinea pigs (Cavia porcellus). Pesquisa Veterinária Brasileira, 36(12), 1203-1208. doi:10.1590/s0100-736×2016001200011

Gaynor, J. S.; Dunlop, C. I.; Wagner, A.E.; et al. (January 1999). “Complications and mortality associated with anesthesia in dogs and cats”. Journal of the American Animal Hospital Association. 35 (1): 13–17. doi:10.5326/15473317-35-1-13. PMID 9934922.

Lee, L., PhD, DACVA. (2011). Preanesthetic Evaluations in Small Animals – Which Values to Look For? – WSAVA2011 – VIN. Retrieved February 19, 2018, from

Sawyer, D. C. (2008). The practice of veterinary anesthesia: small animals, birds, fish and reptiles. Jackson, WY: Tenton New Media.

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