Veterinary Emergency and Critical Care

Shock is a critical pathophysiological state characterized by inadequate cellular energy production stemming from impaired tissue perfusion or oxygen utilization. Although clinical manifestations vary by etiology, the unifying principle is insufficient delivery of oxygen and nutrients to meet metabolic demands, resulting in widespread organ dysfunction if uncorrected.

Cardiac emergencies constitute a significant portion of critical presentations in small animal practice, requiring rapid recognition and decisive intervention. Arrhythmias, acute congestive heart failure (CHF), and cardiopulmonary arrest each pose life-threatening challenges.

Cardiopulmonary Resuscitation (CPR) in dogs and cats aims to restore spontaneous circulation (ROSC) when cardiac arrest occurs. Effective CPR integrates both compression techniques (thoracic or cardiac pump theory), appropriate ventilation, fluid therapy considerations, and timely drug administration.

Pulmonary edema refers to the abnormal accumulation of fluid in the lung parenchyma—specifically in the interstitial and/or alveolar spaces—resulting in impaired gas exchange and respiratory compromise.

Vasopressors and inotropes are pivotal agents in critical care, employed when standard fluid therapy and supportive measures fail to maintain adequate blood pressure or cardiac output.

Acute Respiratory Distress Syndrome (ARDS) is a severe, life-threatening condition characterized by diffuse injury to the alveolar-capillary barrier, leading to non-cardiogenic pulmonary edema and profound hypoxemia.

Smoke inhalation injury occurs when toxic gases, particulate matter, and thermal damage combine to cause significant respiratory and systemic effects in animals exposed to fire, combustion, or other smoke-generating scenarios.

Hypoxaemia (reduced arterial oxygen tension, PaO₂) and hypercapnia (elevated arterial carbon dioxide tension, PaCO₂) are two fundamental abnormalities in respiratory physiology that commonly prompt emergencies in veterinary critical care.

In critically ill small animal patients, ensuring adequate oxygenation and ventilation is paramount for survival. Oxygen supplementation and mechanical ventilation can be lifesaving, but each strategy carries inherent risks that demand careful titration and monitoring.

Certain toxins can precipitate life-threatening respiratory compromise in small animals. Snake envenomation, particularly from neurotoxic species, can impair respiratory muscles leading to acute failure, whereas pyrethrin or pyrethroid toxicity may cause airway irritation or systemic neurotoxic effects that impact breathing.

Traumatic brain injury (TBI) results from external mechanical forces causing cerebral tissue damage and subsequent neurological dysfunction. In small animal emergency and critical care, prompt recognition and management of TBI is paramount to minimizing secondary injury and optimizing outcomes.

Seizures are a frequent neurological emergency in small animal practice, resulting from sudden, abnormal electrical discharges in the brain. They can range from brief focal episodes to life-threatening status epilepticus (SE).

Tetanus and botulism are two notable neuromuscular disorders caused by potent bacterial toxins—tetanospasmin (from Clostridium tetani) and botulinum toxin (from Clostridium botulinum). While both pathogens disrupt normal nerve-muscle function, their effects on the nervous system diverge significantly, resulting in distinct clinical presentations and management approaches.

Intracranial hypertension (ICH) is a life-threatening elevation in intracranial pressure (ICP) that poses a major risk to neurological function. It can develop secondary to traumatic brain injury, intracranial masses, inflammatory processes, or severe systemic derangements that affect intracranial dynamics.

Disseminated Intravascular Coagulation (DIC) is a serious, complex hemostatic disorder in which widespread activation of the coagulation pathways leads to microthrombi and consumption of platelets and clotting factors.

Coagulopathies present frequently in small animal emergency care, potentially resulting in severe hemorrhage and life-threatening complications. Two common categories of coagulopathies encountered in dogs and cats include rodenticide toxicity—particularly anticoagulant rodenticides—and thrombocytopenia from various etiologies.

Blood transfusions are often life-saving in veterinary emergency and critical care, whether addressing acute blood loss, severe anemia, or coagulopathies. However, the administration of blood products requires a thorough understanding of blood typing, cross-matching, and potential transfusion-related complications.

Thrombosis—an abnormal formation of a blood clot within the vasculature—can compromise organ perfusion and precipitate life-threatening conditions such as saddle thrombus in cats, pulmonary thromboembolism in dogs, or venous thromboses in critical patients.

Septic shock represents a severe and life-threatening complication of infection where profound systemic inflammation, microvascular dysfunction, and circulatory collapse converge, leading to multiple organ failure if not rapidly treated. In small animals, sepsis can stem from various primary infections (e.g., pyometra, pneumonia, gastrointestinal perforation), but once it evolves into septic shock, mortality rates rise significantly.

Systemic Inflammatory Response Syndrome (SIRS) is a clinical syndrome characterized by a dysregulated inflammatory response that can occur in response to infectious or non-infectious insults. Although SIRS is not synonymous with sepsis, it serves as an early indicator of significant systemic inflammation which, if unaddressed, may escalate to severe sepsis, septic shock, or multiple organ dysfunction.

Nosocomial infections—also referred to as hospital-acquired or healthcare-associated infections—are infections acquired during a patient’s stay in a veterinary clinic or hospital setting. They can be especially problematic in critically ill dogs and cats, whose immune status may already be compromised.

Prostatic abscesses in dogs (and rarely in cats) arise when bacterial infection within the prostate gland leads to localized accumulations of pus. Risk factors include underlying prostatic hyperplasia, prostatitis, or compromised immune function.

Diabetic ketoacidosis (DKA) is a serious complication of diabetes mellitus in dogs and cats, characterized by severe insulin deficiency and subsequent hyperglycemia, ketonemia, and metabolic acidosis. Patients often present in crisis with dehydration and electrolyte derangements that can rapidly progress to life-threatening complications if not treated promptly.

Hypoglycemia refers to an abnormally low blood glucose concentration that can result in neurologic and systemic manifestations, posing an acute, life-threatening condition if not corrected promptly. In small animals, hypoglycemia stems from various causes—ranging from neonatal or toy breed hypoglycemia to hyperinsulinism (e.g., insulinoma) or severe sepsis.

An Addisonian crisis refers to an acute, life-threatening exacerbation of hypoadrenocorticism—characterized by severe cortisol ± aldosterone deficiency. In small animals (particularly dogs), this results in profound electrolyte imbalances (notably hyperkalemia and hyponatremia), circulatory collapse, and potentially fatal shock if not rapidly identified and treated.

Disorders of calcium metabolism—particularly hypercalcemia and hypocalcemia—are frequent considerations in small animal emergency and critical care. These imbalances can lead to life-threatening neurologic, cardiovascular, and muscular complications if unrecognized or unmanaged.

In small animal emergency and critical care, toxic exposures remain frequent and potentially life-threatening presentations. Three particularly common toxins—non-steroidal anti-inflammatory drugs (NSAIDs), anticoagulant rodenticides, and ethylene glycol—cause significant morbidity and require prompt identification and intervention.

Snake and insect envenomation represent significant acute emergencies in veterinary practice, particularly in regions where venomous snakes or stinging insects (e.g., bees, wasps, ants, scorpions) are prevalent. Toxins can induce neurotoxicity, hemotoxicity, and systemic inflammatory or allergic responses, posing severe risks to patients.

Chocolate toxicity is a common and potentially serious emergency in dogs (and less frequently in cats) due to ingestion of methylxanthines—mainly theobromine and caffeine—found in cocoa products. The clinical presentation can range from mild gastrointestinal upset to severe cardiovascular and neurological disturbances.

Intravenous lipid emulsion (ILE) therapy has emerged as a valuable adjunct in veterinary emergency and critical care, particularly for lipophilic toxin exposures (e.g., local anesthetic overdose, certain rodenticides, avermectins). By creating a “lipid sink,” ILE can reduce circulating toxin levels, thereby mitigating clinical signs.

Acute kidney injury (AKI) encompasses a spectrum of acute renal function decline—from mild, transient azotemia to severe oliguria or anuria with multi-organ implications. In small animal emergency and critical care, AKI often arises from ischemic or toxic insults, though sepsis and other systemic disorders frequently contribute.

Urethral obstruction is a frequent and often emergent presentation in small animal practice. In particular, male cats are prone to obstructive feline lower urinary tract disease (FLUTD), while male dogs may encounter obstruction from uroliths or prostatic enlargement.

Post-obstructive diuresis is a phenomenon observed once a urinary obstruction (commonly involving the urethra) is relieved, resulting in an excessive or rapid production of urine. This diuresis can be profound in dogs and cats that have experienced prolonged obstruction, carrying significant risks of hypovolemia, electrolyte imbalances, and other metabolic disturbances.

Chronic Kidney Disease (CKD) refers to a persistent reduction in renal function over weeks to months (or longer), leading to progressive azotemia and potential for electrolyte and acid-base disturbances.

Trauma resuscitation represents a cornerstone of emergency and critical care, where rapid, systematic intervention within the so-called “Golden Hour” can substantially reduce morbidity and mortality. This “Golden Hour” concept refers to the early period following traumatic injury—traditionally the first 60 minutes—when prompt diagnosis and treatment of life-threatening injuries most significantly influence outcomes

Wound healing is a complex physiological process, crucial for restoring tissue integrity after traumatic or surgical injury. In small animal veterinary medicine, managing wounds effectively is essential to prevent infection, minimize pain, and promote functional recovery.

Fractures and open wounds are frequent presentations in small animal emergency practice, necessitating rapid assessment, stabilization, and appropriate initial wound management. In the acute phase, controlling hemorrhage, preventing further contamination, and providing analgesia are critical steps to preserve limb function and promote healing.

Burn injuries in small animal patients result in complex local and systemic effects that can be life-threatening if not managed appropriately. The severity of thermal injury depends on burn depth, percentage of total body surface area (TBSA) involved, and inhalation component.

Blood gas analysis is integral to evaluating and managing critically ill dogs and cats, providing real-time assessment of acid-base balance, oxygenation, and ventilation. Understanding how to interpret arterial (or venous) blood gases (ABGs/VBGs) and identify primary and compensatory acid-base disturbances is essential in small animal emergency and critical care

Electrocardiography (ECG) is a cornerstone diagnostic in emergency and critical care, offering a real-time look at cardiac electrical activity. Identifying arrhythmias and conduction abnormalities in dogs and cats can guide urgent interventions—whether for life-threatening tachyarrhythmias (ventricular tachycardia) or conduction blocks requiring pacemaker placement.

Point-of-care ultrasound (POCUS) describes the use of portable ultrasound devices by clinicians at the patient’s side, enabling real-time, goal-directed imaging to support immediate clinical decisions. In veterinary emergency and critical care, POCUS provides rapid assessment of body cavities (thoracic, abdominal), cardiac function, and vascular structures.

Laboratory diagnostics constitute a cornerstone of emergency and critical care, offering rapid insights into a patient’s hemodynamic status, organ function, and metabolic balance. A complete blood count (CBC), serum biochemistry profile, and urinalysis are fundamental tests that guide immediate decision-making regarding fluid therapy, oxygen support, transfusions, and more.

Fluid therapy is a cornerstone of veterinary emergency and critical care, pivotal in stabilizing hemodynamically compromised patients. Two major categories—crystalloids and colloids—offer distinct physiologic effects, indications, and potential side effects.

Electrolyte imbalances are commonly encountered in emergency and critical care settings, often signaling serious underlying pathologies or complications of intensive treatment. Among these, hyperkalemia and hyponatremia are two critical derangements that demand immediate recognition and management to prevent life-threatening complications such as arrhythmias or severe neurologic changes.

Free water deficit refers to a state of reduced total body water relative to sodium content, often manifesting clinically as hypernatremia. In small animal emergency and critical care, recognizing and managing free water deficits are vital for preventing neurological complications associated with rapid or inadequate correction.

Pericardiocentesis—the procedure of aspirating fluid from the pericardial sac—is a life-saving intervention in small animals experiencing pericardial effusion. In emergency and critical care settings, rapid identification of tamponade physiology and prompt decompression can be crucial. Appropriate patient selection, understanding the technical approach, and awareness of potential complications are essential for safe and effective pericardiocentesis.

Nasogastric (NG) and esophagostomy (E-tube) tubes are commonly used in veterinary emergency and critical care to provide enteral nutrition when oral intake is not feasible or safe. These tubes help maintain caloric intake, prevent malnutrition, and support recovery in anorectic or critically ill patients.

Emergency cesarean sections (C-sections) are critical procedures in veterinary emergency and critical care, often performed to save the lives of both the dam and her offspring in situations where natural delivery is compromised.

Diagnostic workflows are fundamental to effective veterinary emergency and critical care, providing a structured approach to rapidly assess, diagnose, and manage acutely ill or injured animals. From the initial presentation to the formulation and implementation of a management plan, a systematic diagnostic process ensures timely and accurate identification of life-threatening conditions.

Effective client communication is paramount in veterinary emergency and critical care, where decisions often need to be made swiftly under stressful circumstances. Discussing prognosis, costs, and expectations with pet owners requires a blend of empathy, clarity, and professionalism to ensure informed decision-making and maintain trust.

Ethical considerations are integral to veterinary emergency and critical care, where rapid decision-making often impacts the lives and well-being of both animals and their owners. Among these ethical dilemmas, euthanasia decisions and do-not-resuscitate (DNR) orders are particularly significant.

Passing the Membership Examination of the Australian and New Zealand College of Veterinary Scientists (ANZCVS) in Small Animal Medicine is a significant milestone in your veterinary career. Here are practical tips and strategies to help you succeed in both the written and oral components of the exam.