Evaluating the Influence of Preanaesthetic ECG on Anaesthetic Protocols in Dogs

(Original article published by Bustamante et al. "Impact of preanaesthetic electrocardiogram on decision making and modification of anaesthetic protocols in dogs" Vet Rec. 2024 Sep 7;195:e4266)

Preoperative assessment plays a crucial role in ensuring the safety and success of anaesthesia in veterinary medicine. Among various diagnostic tools, the electrocardiogram (ECG) is widely used to detect cardiac abnormalities before surgery. But how much does a preanaesthetic ECG actually influence decision-making and anaesthetic protocols in healthy dogs? A recent retrospective study conducted at the Complutense Veterinary Teaching Hospital sheds light on this question by examining the impact of ECG findings on further cardiac evaluation and anaesthetic management.

Understanding the Role of Preanaesthetic ECG

The ECG records the electrical activity of the heart and helps identify arrhythmias, conduction disturbances, and other abnormalities that may not be apparent during a physical exam. In human medicine, preoperative ECG screening is common practice, but its routine use in veterinary patients, especially healthy dogs, remains debated. This study focused on dogs without previously diagnosed heart disease to evaluate whether ECG findings could prompt additional cardiac tests or lead to changes in anaesthetic protocols.

Study Design and Methods

Researchers reviewed medical records of 228 healthy dogs that underwent general anaesthesia between December 2017 and June 2018. Each dog had a preanaesthetic ECG performed and assessed for abnormalities. The study documented:

• Types of ECG abnormalities detected

• Number of dogs referred for echocardiography based on ECG results

• Changes made to the standardised anaesthetic protocol due to ECG findings

• Anaesthesia-related decisions influenced by ECG data

  
  

This approach allowed the team to observe real-world clinical decisions influenced by ECG screening in a veterinary teaching hospital setting.

Key Findings from the Study

The study revealed several important points:

• ECG abnormalities appeared in 31.6% of dogs (72 out of 228), indicating that even apparently healthy dogs can have underlying electrical heart issues.

• Echocardiography was requested for only 2.2% of dogs (5 dogs), suggesting that most ECG abnormalities did not warrant further cardiac imaging.

• Anaesthetic protocols were modified in 15.3% of dogs with ECG abnormalities (11 dogs), showing that ECG findings influenced clinical decisions in a subset of cases.

  
  

The types of ECG abnormalities that most commonly led to echocardiography included:

• P wave disturbances

• Ventricular premature complexes

• Impulse conduction issues

  
  

Meanwhile, bradycardia and conduction abnormalities were the main reasons for adjusting anaesthetic protocols. These modifications aimed to reduce the risk of adverse cardiac events during anaesthesia.

Practical Implications for Veterinary Practice

This study highlights the value of preanaesthetic ECG screening in identifying dogs that may benefit from further cardiac evaluation or tailored anaesthetic plans. For veterinarians, this means:

• Incorporating ECG as a routine part of preoperative assessment can uncover hidden cardiac issues even in healthy dogs.

• Recognizing specific ECG abnormalities such as arrhythmias or conduction delays should prompt consideration of echocardiography to assess structural heart disease.

• Adjusting anaesthetic protocols based on ECG findings can improve patient safety by addressing risks like bradycardia or conduction blocks.

  
  

For example, a dog showing ventricular premature complexes on ECG might require closer monitoring or different drug choices during anaesthesia to prevent complications.

Limitations and Areas for Further Research

While the study provides valuable insights, it also has limitations:

• The sample size was relatively small, limiting the ability to explore relationships between dog demographics (age, breed, sex) and ECG abnormalities.

• The study was retrospective, relying on existing medical records, which may introduce bias or incomplete data.

• It did not assess long-term anaesthesia outcomes or postoperative complications related to ECG findings.

  
  

Future research could focus on larger, prospective studies that evaluate how routine preanaesthetic ECG screening affects surgical outcomes and overall patient safety. Additionally, exploring cost-benefit aspects of widespread ECG use in veterinary clinics would help guide clinical protocols.

Summary

Preanaesthetic ECG screening in healthy dogs reveals a significant number of electrical heart abnormalities that can influence clinical decisions. Although only a small percentage of dogs required further echocardiography, and fewer had anaesthetic protocols modified, the ECG helped identify patients at potential risk. This targeted approach supports safer anaesthesia by enabling tailored management strategies.