Shocks

Sepsis Wrap Up

Overview of Circulatory Shock

  • Definition: Circulatory shock is an umbrella term for all forms of shock causing hypoperfusion of organs and tissues.

    • Leads to insufficient nutrient and oxygen supply to meet metabolic demands.

    • Resultant processes include ischemia, anaerobic metabolism, and tissue necrosis.

  • Types of Circulatory Shock:

    1. Distributive Shock: Three categories:

    • Septic Shock

    • Anaphylactic Shock

    • Neurogenic Shock (e.g., due to spinal cord injury or severe head injury leading to systemic vasodilation)

    1. Hypovolemic Shock: Due to significant blood or plasma volume loss.

    2. Cardiogenic Shock: Resulting from heart dysfunction.

    3. Obstructive Shock: Caused by external obstruction to the heart's pumping ability.

Histamine's Role in Allergic Reactions

  • Function: Histamine is the main mediator of allergic inflammation.

    • Mechanism:

    • Binds to H1 receptors on endothelial and smooth muscle cells, increasing vascular permeability and leading to edema.

    • Causes leakage of white blood cells and plasma (exudate) into surrounding tissues.

    • Results in changes in osmotic pressure, promoting fluid movement out of circulation.

    • Causes stagnation of blood flow due to low-pressure systems from vasodilation and activates platelets, increasing clotting risks.

  • Effects:

    • Blood stasis and endothelial injury leading to intrinsic coagulation cascades.

    • Release of Platelet Activating Factor (PAF) from mast cells, leading to bronchoconstriction.

    • Prostaglandins are also involved in the inflammatory response.

Allergens and Their Reactions

  • Definition: An allergen (also referred to as an antigen) is a substance that triggers an allergic response.

  • Common Allergens:

    • Drugs:

    • Penicillins, Sulfa antibiotics, blood products, morphine (whole blood is the highest risk, albumin is the lowest).

    • Foods:

    • Nuts, shellfish, and others.

    • Venoms:

    • From wasps, ants, etc.

    • Latex:

    • First exposure leads to specific IgE synthesis; second exposure induces an IgE-mediated immune response usually within 15 minutes.

Allergy to Anaphylaxis Continuum

  • Symptoms of Allergy:

    • Pruritus (itchiness)

    • Urticaria (hives)

    • Lacrimation (watery eyes)

    • Rhinitis (runny nose)

    • Angioedema

  • Pathophysiology of Anaphylaxis:

    • Allergen binds to IgE, causing mast cell degranulation and the release of histamine and various cytokines, complements, leukotrienes, bradykinins, and nitric oxide.

    • Examples include:

    • Localized Allergy:

      • Wasp sting causes localized swelling and urticaria without compromising airway, breathing, circulation (ABCs).

    • Inhaled Allergens:

      • Dander exposure results in rhinitis and watery eyes without compromising ABCs.

Symptoms of Allergic Reactions

  • Common Symptoms Include:

    • Rash

    • Lacrimation

    • Runny nose

    • Sneezing

    • Red eyes

    • Itching

Clinical Considerations in Allergic Reactions

  • Questions to Consider:

    • Which drug class is applicable to allergy-mediated inflammation?

    • In cases of localized allergy, what would be the treatment approach?

    • If the allergy progresses (generalized itching, slight concern, normal vital signs), how would you assess for worsening conditions?

Anaphylaxis

  • Definition: Anaphylaxis is a severe, potentially life-threatening systemic response characterized by significant vasodilation and bronchoconstriction.

    • Symptoms may include warmth and a flushed appearance as a result of vasodilation, hypotension, and respiratory compromise.

  • Treatment Protocol for Anaphylaxis:

    1. Epinephrine:

    • Administered intramuscularly as first-line treatment.

    • Causative agents must be stopped (e.g., transfusion reactions require stopping blood product administration).

    1. Glucocorticoids:

    • Dexamethasone IV is given for longer-term management (not life-saving).

    • Post-stabilization: consider prescribing oral prednisone for 3 days and an EpiPen.

    • 2nd generation antihistamines may be used as adjunctive therapy.

  • Phase of Anaphylaxis: It's critical to understand different stages, with hypoperfusion and fluid shifts leading to circulatory collapse potentially causing up to 35% volume loss within 10 minutes.

  • General Treatment Approach:

    • ABCs: Administer high-flow oxygen and consider intubation, if necessary.

    • Utilize beta-2 adrenergic agonists (e.g., Salbutamol) for bronchospasm management.

    • Administer Epinephrine via IV if needed following the initial IM dose, along with fluid resuscitation using Normal Saline (NS) boluses.

Hypovolemic Shock

  • Definition: Hypovolemic shock occurs due to a significant decrease in blood or plasma volume, leading to inadequate filling of vascular compartments and decreased cardiac output.

    • Defined by an acute loss of 20% or greater volume.

  • Causes:

    • Blood loss from trauma, surgery, burns, etc.

    • Low extracellular fluid resulting from severe dehydration due to low intake, vomiting, or diarrhea.

  • Physiology: Initial volume loss triggers sympathetic nervous system (SNS) compensation to maintain perfusion; continued losses lead to decompensation and shock.

Signs and Symptoms of Hypovolemic Shock

  • Initial Symptoms:

    • Consistent with compensatory mechanisms:

    • Tachycardia

    • Thirst

    • End-organ vasoconstriction (e.g., cool, pale integument)

    • Oliguria (urine output < 20ml/hour)

    • Drenching diaphoretic skin

    • Normal blood pressure maintained by SNS.

  • Progressive Symptoms:

    • Hypotension (SBP < 90 mmHg)

    • Thready pulse indicative of vasoconstriction and low blood pressure

    • Decreased respiratory rate

    • Central nervous system changes like irritability, restlessness, or altered levels of consciousness (confusion progressing to coma).

    • Signs of cellular dysfunction may manifest as electrolyte imbalances or hyperglycemia.

Shock Classification: Septic vs. Anaphylactic vs. Hypovolemic

  • Septic and Anaphylactic Shock:

    • General appearance on survey may be flushed and warm due to vasodilation.

  • Hypovolemic Shock Appearance:

    • Characterized as cool and pale/mottled due to vasoconstriction, causing accelerated ischemic events.

Treatments for Hypovolemic Shock

  • IV Fluids: Utilize crystalloid solutions (Normal Saline - NS, Lactated Ringer's - LR), colloids (Albumin 5% or 25%, Dextran), or blood products (PRBCs, whole blood, fresh frozen plasma - FFP).

    • Monitoring Parameters: Essential to monitor perfusion status, blood pressure, and pulse. Be cautious of potential circulatory overload due to excessive fluid administration.

    • Urine Output Tracking: Maintain clear records of input/output (I&O) to assess kidney function.

    • Clearance Calculation: Monitor renal function through appropriate calculations.

    • Cautions: There exists a risk for allergic reactions to colloids and blood products, and dilutional coagulopathy may arise from high crystalloid volumes.

Complications of Hypovolemic Shock

  • Main Complications:

    1. Hypoxia: leading to impaired cellular function.

    2. Metabolic Acidosis: Due to lactate accumulation leading to organ dysfunction/failure.

    3. Multi-Organ Dysfunction Syndrome (MODS): Affects multiple systems including renal failure and impacts brain function.

    4. Gastrointestinal Ischemia: Can arise as blood flow is redirected away from the gut.

    5. Lung Injury (ARDS): Results in pulmonary hypoperfusion, inflammation, pulmonary edema, and may lead to respiratory failure.

    6. Renal Impacts: Renal failure and electrolyte imbalances frequently require treatment, including possible renal dialysis to substitute for renal function.

Renal Function: Effects and Treatments

  • Erythropoietin (EPO) Production:

    • EPO is a hormone produced in the kidneys that stimulates RBC synthesis in the bone marrow. This is crucial for maintaining oxygen-carrying capacity. Low EPO production results in decreased RBC levels and potential hypoxemia.

  • Vitamin D Activation:

    • The kidneys activate Vitamin D, which in its active form, calcitriol, facilitates calcium absorption in the gastrointestinal tract and kidneys.

Cardiogenic Shock

  • Etiology: Commonly results from myocardial infarction (particularly STEMI), arrhythmias, cardiac insufficiency, or other shocks impacting cardiac function.

  • Operational Dynamics: This shock type indicates ineffective cardiac output to meet body demands despite appropriate total blood volume; it emphasizes that Left Ventricular Cardiac Output (LV CO) equals Right Ventricular Cardiac Output (RV CO).

Treatment Overview for Cardiogenic Shock

  • Goals: Primarily aims to optimize cardiac output through the following strategies:

    • Reduce both preload and afterload while enhancing contractility through various pharmacologic interventions and fluid management:

    • Diuretics:

    • Spironolactone, a potassium-sparing diuretic, decreases sodium retention through aldosterone antagonism.

    • Furosemide (Lasix) for rapid diuresis with caution in hypotension.

    • Vasodilators:

    • Direct-acting vasodilators like nitroglycerin and nitroprusside may improve coronary circulation but require monitoring for hypotension.

    • Synergistic strategies with ACE inhibitors, adrenergic antagonists, and calcium channel antagonists can improve hemodynamics.

    • Inotropic Agents:

    • Phosphodiesterase inhibitors (e.g., Milrinone) and catecholamines (e.g., Dobutamine) for contractility enhancement but with caution regarding vasoconstriction.

Temporary Management of Cardiogenic Shock

  • Advanced Treatment:

    • Intra-aortic balloon pump (IABP): A device that is 26 cm long, inserted into the descending aorta through a catheter.

    • Function: Inflates during diastole and deflates before systole, enhancing blood flow through a suction effect, particularly beneficial in acute ischemic events.

Obstructive Shock

  • Definition: Characterized by mechanical obstruction to blood flow in the central circulation.

  • Etiology Examples:

    • Large embolisms (e.g., pulmonary embolism - PE) and cardiac tamponade are primary causes.

  • Management Strategies:

    • Address the underlying issue:

    • For cardiac tamponade, perform pericardiocentesis.

    • For PE, employ anticoagulants, thrombolytics, and consider aspiration of the obstruction.

  • Invasive Procedures:

    • Aspiration thrombectomy via femoral venous access may be required to remove life-threatening pulmonary emboli.