Veterinary anesthesia is considered safe for most patients when proper safety and training protocols are in place. However, complications can and commonly do occur, and veterinary team members should know how to identify and address them.
The most common veterinary anesthetic complications involve the central nervous, respiratory, and cardiovascular systems. A solid anesthesia protocol can prevent many complications, while vigilant monitoring and appropriate interventions allow most patients who develop minor complications to recover without incident.
Here are six of the most common veterinary anesthetic complications, and how your team can prevent or correct them for better patient outcomes.
Excessive anesthetic depth is the most common veterinary anesthetic complication and a major contributor to respiratory and cardiovascular depression. The absence of a palpebral reflex and a relaxed jaw tone are expected at a surgical plane, but patients who move beyond this level may become unstable.
Excessive depth can develop when inhalant vaporizer settings are too high or from additive medication effects. Depth is also impacted by hypothermia, hypotension, and individual drug sensitivities.
Signs of excessive depth include:
Management strategies include:
Close and continuous monitoring of anesthetic depth using physiologic signs (e.g., jaw tone, anal tone, eye position) and monitoring equipment is essential to maintain patients at an appropriate surgical plane.
Hypoventilation—taking too few or too shallow breaths—increases carbon dioxide (i.e., hypercapnia). Hypercapnia can cause a cascade of anesthetic complications, including respiratory acidosis, hypoxemia, and bradycardia.
Hypoventilation may occur secondary to excessive anesthetic depth, drug-induced respiratory depression, poor body positioning, airway obstruction, or mechanical issues with the breathing circuit. Brachycephalic breeds, obese patients, and those receiving high doses of opioids or alpha-2 agonists are at increased risk.
Signs of respiratory complications include:
Management strategies include:
Monitoring ETCO₂ throughout the procedure allows the team to detect hypoventilation before it progresses to hypoxemia or respiratory arrest.
Hypoxemia—a decrease in blood oxygen saturation—can rapidly become life-threatening. Most commonly, it develops secondary to hypoventilation or airway obstruction and can lead to tissue hypoxia, organ damage, and cardiac arrest. Hypoxemia is more likely in animals with pre-existing respiratory or cardiovascular disease.
Signs of hypoxemia include:
Management strategies include:
Pulse oximetry is a critical tool, but it can be finicky in cases of vasoconstriction and anemia, or in small patients. Always interpret SpO₂ values in the context of clinical signs and use capnography and other parameters to guide decision-making.
Hypotension—a mean arterial pressure (MAP) below 60 mmHg or systolic pressure below 90 mmHg—is a frequently encountered anesthetic complication. Low blood pressure translates to inadequate tissue perfusion, which can compromise vital organs such as the kidneys, brain, and heart. Persistent hypotension during anesthesia increases the risk of postoperative complications, including acute kidney injury and delayed recovery.
Causes often include a combination of vasodilation, bradycardia, decreased cardiac output, and hypovolemia. Inhalant anesthetics have a dose-dependent depressive effect on vascular tone and myocardial contractility, which can contribute to these effects.
Signs of hypotension include:
Management strategies include:
Continuous blood pressure monitoring using noninvasive or direct arterial techniques is essential during general anesthesia. Doppler equipment is preferred when available.
Cardiac arrhythmias are veterinary anesthetic complications that may be benign or may signal serious underlying issues that compromise hemodynamic stability. Identifying the arrhythmia and evaluating its impact on perfusion can help determine whether treatment is necessary.
Arrhythmias can occur in response to anesthetic drugs, hypoxia, hypercapnia, acid–base disturbances, or pain. They may also reflect underlying cardiac disease or electrolyte imbalances. Splenic, thoracic, and ophthalmic surgeries are associated with higher arrhythmia incidence due to increased vagal tone or direct myocardial irritation.
Common anesthetic-related arrhythmias include bradycardia, tachycardia, ventricular premature contractions (VPCs), and atrial fibrillation.
Management strategies include:
Continuous ECG monitoring allows arrhythmia identification, but interpretation should always be paired with assessment of the patient’s clinical status. Not all changes, such as isolated VPCs or mild sinus arrhythmias, require intervention; continued close monitoring may suffice in some cases.
Hypothermia—a core body temperature below 98 degrees—begins developing immediately after induction because of vasodilation, decreased metabolic rate, exposure of body cavities, and administration of room-temperature fluids and gases. Risk is increased for small patients, older patients, and those undergoing lengthy procedures or surgeries involving open body cavities.
Hypothermia increases anesthetic depth by slowing metabolism and drug clearance, depresses cardiovascular and respiratory function, impairs thermoregulation, delays recovery, and elevates post-operative oxygen demand due to shivering.
Signs of hypothermia include:
Management strategies include:
Hypothermia’s systemic effects can make other complications more challenging to manage. Treating temperature as a core anesthetic priority can significantly improve patient stability.
Most veterinary anesthetic complications are avoidable with careful planning, consistent monitoring, and prompt interventions. A thorough pre-anesthetic assessment, balanced drug protocol, and temperature and fluid support help reduce risks. During anesthesia, teams should remember to monitor the patient, not only the machines.
When in doubt, reassess anesthetic depth, patient parameters, and equipment to adjust as needed. Minor corrections made early can prevent larger problems. Anesthetic complications are manageable when teams prepare. With the right protocols, monitoring, and response strategies, you can improve anesthesia safety and outcomes for every patient.
Looking to learn more about veterinary anesthesia administration, safety, complications, and troubleshooting? Check out our Foundations of Anesthesia & Sedation certificate course that provides 10 RACE-approved CE hours while boosting confidence across your team.