Using ECG to Tailor Anesthesia Protocols

In The Literature

Bustamante R, González-Pérez E, Caro-Vadillo A, Aguado D. Impact of preanaesthetic electrocardiogram on decision making and modification of anaesthetic protocols in dogs. Vet Rec. 2024;195(5):e4266. doi:10.1002/vetr.4266

The Research …

The impact of routine preanesthetic testing on anesthetic drug choice for patients with unremarkable history and physical examination findings is unclear. In one study, only 0.2% of dogs required protocol modifications due to an abnormal laboratory test result.¹

The goal of this study was to evaluate whether a preanesthetic ECG in clinically healthy dogs would prompt changes to a standard anesthetic protocol (ie, premedication with methadone and an alpha-2 receptor agonist and induction with propofol) or inotropic support or would result in delay or cancellation of the procedure. A 6-lead ECG was used. Abnormal findings included ventricular premature complexes, P wave disturbances, and impulse conduction issues; sinus arrhythmia was not considered an alteration.

Of 228 dogs, 72 (31.6%) had an abnormal ECG. The most prevalent abnormalities were T wave amplitude (31.9%) and ST segment (23.6%) alterations. Echocardiogram was recommended for 5 dogs; 1 dog did not undergo echocardiogram because the owner declined, and the remaining 4 dogs had echocardiogram abnormalities. The anesthetic plan was modified due to ECG changes in 11 dogs (4.8% of all dogs; 15.3% of dogs with ECG alterations).

… The Takeaways

Key pearls to put into practice:

• Although ≈5% of dogs in this study required protocol modifications based on ECG findings, this number may have been significantly smaller if an alpha-2 receptor agonist was not administered as premedication, as this drug class greatly impacts the cardiovascular system.

• Routine preanesthetic ECG in young, clinically healthy dogs may be ideal but is unlikely to yield a significant abnormality and is currently not encouraged; however, older dogs and breeds predisposed to arrhythmias (eg, Doberman pinschers, boxers, German shepherd dogs) would more likely benefit from preanesthetic ECG.²

• Based on the most common ECG abnormalities noted in this study, preanesthetic ECGs would likely need to be interpreted by a cardiologist, which may not be practical in daily practice. Nevertheless, ECG monitoring during induction is recommended to facilitate early detection of abnormalities (eg, severe bradycardia) and prompt treatment.