SHOCK

SHOCK AND THE SYSTEMIC INFLAMMATORY RESPONSE SYNDROME

• Definition of Shock

  • A critical state where the body fails to maintain adequate tissue perfusion, leading to cellular dysfunction.

• Systemic Inflammatory Response Syndrome (SIRS)

  • A severe inflammatory state affecting the entire body, often accompanying various types of shock.

TREE OF LIFE OF SHOCK

• Formulae

  • $DO_2 = CaO_2 imes CO$

  • Where:

    • $CaO_2$ = Arterial Oxygen Content

    • $CO$ = Cardiac Output

  • Components of Cardiac Output (CO)

  • $CO = HR imes SV$

    • Where:

    • $HR$ = Heart Rate

    • $SV$ = Stroke Volume

  • Factors influence CO

  • Preload: Volume of blood in ventricles at the end of diastole.

  • Afterload: Resistance the heart must work against to eject blood.

  • Contractility: Strength of cardiac contraction.

PATHOPHYSIOLOGY OF SHOCK

• Stages of Shock

  • Early Stage: Compensating

  • Late Stage: Decompensating

  • Terminal Stage

Clinical Features at Each Stage

• Mentation

  • Early: Mild-mod depressed/anxious, Quiet, Alert, Responsive (QAR)

  • Late: Severe depression

• Cardiac

  • Early: Tachycardic with increased contractility, Capillary refill time (CRT) normal or prolonged

  • Late: Severe tachycardia or bradycardia, Pale or injected mucous membranes (MM), CRT prolonged or fast, Cardiac arrest

• Vasculature

  • Early: Vasoconstriction/hypertension

  • Late: Vasodilation/hypotension

  • Terminal: Profound vasodilation/hypotension

• Pulse

  • Fair to moderate pulse in early stage

  • Weak to absent pulse in late stage

• Respiratory

  • Early: Tachypneic

  • Late: Respiratory failure

• Other Signs

  • Early: Hyperglycemia

  • Late: Decreased renal function, hypoglycemia

TYPES OF SHOCK

• 1. Hypovolemic Shock

  • Cause: Decreased circulating blood volume due to fluid loss (causes include trauma, hemorrhage, severe vomiting, and diarrhea).

  • Treatment: Restore volume.

• 2. Distributive Shock

  • Cause: Irregular blood flow due to inappropriate vasodilation and pooling in capillaries.

  • Diseases Associated: Anaphylaxis, heat stroke, envenomation.

  • Treatment: Fluid therapy and vasopressors.

• 3. Obstructive Shock

  • Cause: Insufficient venous return to the heart (causes include Gastric Dilatation-Volvulus (GDV), pericardial tamponade).

  • Treatment: Treat underlying cause.

• 4. Cardiogenic Shock

  • Cause: Low cardiac output due to heart diseases.

  • Treatment: Improve heart function with antiarrhythmics, positive inotropes, vasopressors; manage pulmonary edema with diuretics.

• 5. Septic Shock

  • Cause: Severe systemic infections (e.g., pneumonia, parvovirus, intestinal perforation, severe tissue damage from heatstroke or pancreatitis).

  • Symptoms: Resulting inflammatory response causes various symptoms.

  • Treatment: Treat infection source (surgically/medically), administer antibiotics and fluid therapy.

CARDIAC OUTPUT IN TYPES OF SHOCK

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• Comparative Characteristics
  
  

  
  

  Type	MM Color	CRT	Pulses	HR	Temp	Mentation	Clinical Signs
  Hypovolemic	Pale	Prolonged	Weak	Tachycardia	Hypothermia	Depressed	Weakness
  Distributive	Early: Hyperemic	Early: <1 sec | Early: Bounding | Tachycardia | Hyperthermia | Depressed | Weakness | | | Late: Pale | Late: >2 sec	Late: Weak	Tachycardia	Hypothermia	Weakness	Collapse
  Obstructive	Pale	Prolonged	Weak	Increased	Hypothermia	Depressed	Collapse, cough
  Cardiogenic	Pale	Prolonged	Weak	Increased	Hypothermia	Depressed	Weakness, cough
  Septic	Pale	Prolonged	Weak	Increased	Hypothermia	Depressed	Cough
  FELINE SHOCK

  • Differences from Canine Shock

    • More difficult to recognize in cats compared to dogs.

  • Classic Signs for All Types in Cats

    • Bradycardia

    • Hypothermia

    • Hypotension

  DIAGNOSTICS AND MONITORING

  • Minimum Database for Diagnostic Assessment

    • Non-invasive Blood Pressure (NIBP)

    • Packed Cell Volume/Total Solids (PCV/TS)

    • Venous Blood Gas Analysis with Lactate

    • Point of Care Ultrasound (POCUS)

    • Electrocardiogram (ECG)

    • Importance of Reassessment: Regularly reassess to monitor progress.

  STABILIZATION

  • Goal: Rapid restoration of oxygen delivery (DO2).

  • Methods

    • Intravenous Catheter (IVC): Establish an access route.

    • Fluids:

    • Administer rapidly, except in cases of cardiogenic shock.

    • Cardiogenic Shock Treatment: May require positive inotropes, anti-arrhythmics, and diuretics.

  REPERFUSION INJURY AFTER SHOCK

  • Anaerobic Respiration

    • Occurs during shock, resulting in the production of waste products (e.g., lactate).

  • Flow Improvement

    • As perfusion improves, lactate and free radicals are picked up and released into the systemic circulation.

  • Systemic Inflammatory Response Syndrome (SIRS)

    • Inflammatory mediators are released leading to activated white blood cells (WBC) which can cause tissue damage.

    • Platelets consumed, resulting in impaired clotting.

  • Disseminated Intravascular Coagulation (DIC)

    • Can lead to spontaneous bleeding due to coagulopathy caused by shock.

  • Multiple Organ Dysfunction Syndrome (MODS)

    • Organ damage from tissue injury can lead to organ failure and death.

  FLUID THERAPY FOR SHOCK

  • Fluid Therapy Overview

    • Rapid administration is critical but should not be done in cardiogenic shock.

  • Administration Method

    • Isotonic crystalloids should be given rapidly; increments should be calculated based on body weight.

    • Dosage Guidelines

    • Dog: 80-90 ml/kg

    • Cat: 40-60 ml/kg

  • Additional Therapy

    • Blood products (e.g., colloids) may be indicated.

    • To Effect Dosage

    • Dog: 10-20 ml/kg

    • Cat: 5-10 ml/kg