Veterinary-specific multiparameter patient monitoring systems can play an invaluable role in diagnostics for companion animals during each phase of a surgical procedure, namely peri-operative, operative, and post-operative. Many times, the trauma of surgery or the use of anaesthetic agents can frequently induce heart issues in patients, expose undetected conditions, or activate other complications. Multiparameter monitoring allows veterinarians to make treatment decisions based on the entire surgical picture.

Evaluating a patient’s vital signs with multiparameter monitors significantly increases a veterinarian’s ability to address the gamut of issues that can arise in a surgical scenario. Multiparameter monitors can detect irregular heart rates, arrhythmias, hypoventilation, systemic vasodilation, respiratory acidosis, and hypoxemia. Monitoring makes the veterinarian aware of the issue, but also helps them decide a course of action to either correct a problem or strategize the next steps for treatment.

Despite their accuracy, it is important to note multiparameter monitors do not preclude regular hands-on evaluation of surgical patients, particularly depth of anaesthesia, including eye position and palpebral responses, jaw and muscle tone, and response to stimuli. There are a few scenarios where monitors do not detect abnormalities, and reliance on electrocardiogram (ECG) alone can be particularly misleading.

Undetected conditions

When a very thorough history is taken and a complete physical examination is performed, it is rare for something to be unmasked by anaesthesia and surgery. Occasionally, undetected conditions can be diagnosed by chance when monitoring a patient during the surgical period.

“Often, when something is unmasked at surgery, one can go back and get a better history or recognize that something, on initial or previous physical examination—such as an irregular heart rate—was a true issue. To be sure, monitoring during the peri-anaesthetic period is yet another way to catch items missed on history or physical examination. While this re-emphasizes the importance of monitoring, it does not preclude the need for being very thorough in taking history and performing a physical examination,” Dr. Kruse-Elliott says.

Monitoring should help the decision-making process in determining whether to continue with the surgery. Once stabilized, further evaluation, testing, and prescription of a treatment plan for managing the newly discovered condition should be implemented, after full recovery and healing from surgery is attained.

Complications

A broad range of conditions may be recognized during anaesthesia and surgery. Some examples include:

• atrioventricular block that is not atropine responsive.
• obstructive airway patterns demonstrated by capnography.
• previously undiagnosed hypertension;
• hypotension associated with unrecognized surgical blood loss;
• electrolyte abnormalities such as hyperkalemia impacting the ECG; and adverse reactions to anesthesia.

One relatively common type of problem is the patient who has been endobronchial intubated inadvertently. When this occurs, mucous membrane colour will certainly be an indicator—pale, bluish, or brick-red membranes are all signs of a problem. However, an abnormally low pulse oximeter oxygen saturation value also should be an alert to check the endotracheal tube length and placement in the patient.

Troubleshooting problems and decision-making

Perhaps the most common surgical complication that both monitoring and physical examination detects is blood loss with associated hypotension. Gradual loss of a significant amount of blood volume can be missed by all staff involved in a surgery, particularly in small patients. Careful and close patient observation for increasing heart rate in the face of unchanged or worsening pulse quality is recommended, along with monitoring for increasing heart rate in the face of gradual development of hypotension suddenly escalating to severe hypotension. If caught in progress with monitoring, appropriate treatment—including fluids and blood components—can be started before the patient becomes critical.

There are other areas patient monitors can be useful for troubleshooting. A drop in EtCO2 is often the first indicator to cardiopulmonary arrest. Pleth variability index (PVI) is a great tool in determining the patient’s hydration status. An increase in PVI could be an indication of hypovolemia.

When problems are detected in a patient during surgical monitoring, decisions should involve directly checking the patient’s depth of anaesthesia, pulse, and ventilation quality via the monitor, as well as noting mucous membrane colour. Then, to determine the likely cause of the problem, a review of the patient history; physical status prior to anaesthesia and surgery; any major problems; and the type of surgery and reason for it should all be seriously considered. Some questions to ask relative to history include:

• Is bradycardia a pre-existing condition?
• Could the problem be drug-induced?
• Is it related to hypoxemia?
• Could it be a vagally mediated response?
• Is there hypothermia?

When the likely cause is determined, treatment can be initiated that relates directly to the problem and patient at hand.

Monitoring is vital for better outcomes

Most of the subjective determination of patient status is taken out of the equation with multiparameter monitoring systems, allowing for more objective determination of patient status, as many of the parameters are continuous, real-time reports of cardiopulmonary function. This is particularly important when training new, less experienced staff and when caring for patients with multiple complex disease conditions.

Overall, veterinarians who utilize multiparameter patient monitoring of vital signs in their patients before, during, and after surgical procedures will attain full awareness of patient conditions. This approach will help them be prepared for emergency situations, avert crises, and minimize lasting damage to save lives and obtain better patient outcomes.