Shock and Low Cardiac Output States Quiz

Types of Shock

• Shock is a serious medical condition characterized by circulatory system failure.
• Body organs and tissues don't receive enough oxygenated blood, leading to organ damage.
• Causes can include issues with the heart, blood vessels, or blood volume.
• Shock leads to reduced blood flow and cellular damage, potentially resulting in multiple organ failure and death.

Objectives

• Recognizing and understanding shock's definition, physiology, pathophysiology, types, causes, resuscitation methods, and the significance of the "golden hours."

Shock

• A serious medical condition.
• A circulatory system failure.
• Affects organs such as the brain, heart, and kidneys.
• Capable of causing severe tissue damage or even death.
• May result from various factors affecting the circulatory system.

Stroke volume (SV)

• Volume of blood pumped from the heart during each contraction (systole).
• Normal value is 70 mL for a 70 kg individual.

Cardiac Output (CO)

• Amount of blood pumped by the heart per minute.
• Calculated as stroke volume multiplied by heart rate (CO = SV x HR).
• Normal cardiac output is 5 liters/minute.

Pulse Pressure

• Difference between systolic and diastolic blood pressure.
• Normal range of 30-40 mmHg.
• Low pulse pressure (low/narrow) might signify reduced stroke volume. - High pulse pressure (high/wide), might signify increased stroke volume.

Systemic/Peripheral Vascular Resistance (SVR/PVR)

• Resistance within blood vessels that opposes blood flow.
• Systemic vasoconstriction increases vascular resistance.
• Systemic vasodilation decreases vascular resistance.

Preload and Afterload

• Preload: Volume of blood in ventricles at the end of diastole (filling pressure).
• Increased by hypervolemia, and regurgitation of cardiac valves.
• Afterload Resistance heart must overcome to pump blood.
• Increased by hypertension and vasoconstriction.

General Homeostasis

• A healthy balance between oxygen demand and supply.
• In shock, demand outweighs supply, leading to cellular damage and potentially death.

Pathophysiology

• Study of shock's underlying mechanisms.

Classification of Shock

• Low Cardiac Output States (Narrow Pulse Pressure/Cold Shock):
  • Heart's ineffective pumping.
  • Body’s insufficient oxygen supply.
  • Key characteristics include narrow pulse pressure and cold, clammy skin.
• Low Peripheral Resistance States (Widened Pulse Pressure/Warm Shock):
  • Excessive dilation of blood vessels.
  • Reduced blood pressure due to a lack of resistance.
  • Characterized by widened pulse pressure and warm, flushed skin.

Hypovolemic Shock

• Loss of blood volume due to hemorrhage, dehydration, burns, or diarrhea.
• Manifested by signs like decreased body fluids, poor skin turgor, and increased systemic vascular resistance.
• Diagnosed after significant intravascular volume loss.

Cardiogenic Shock

• Heart's inability to pump effectively due to conditions like ischemia, arrhythmias, or valvulopathies.
• Characterized by low cardiac output, fluid buildup in the pericardial sac constricting the heart muscles, and low blood pressure.

Obstructive Shock

• Mechanical obstruction prevents heart from filling/pumping blood efficiently.
• Causative factors include cardiac tamponade, tension pneumothorax, and massive pulmonary embolism.

Distributive Shock (Vascular):

• Systemic vasodilation (widening of blood vessels) without sufficient compensation.
• Related to sepsis, anaphylaxis, and neurogenic shock.

Septic Shock

• Bacteria, particularly gram-negative infections, cause it.
• Occurs after bacterial infections release endotoxins.
• Triggers a systemic inflammatory response, leading to hypovolemia and decreased cardiac output.

Anaphylactic Shock

• Allergic reaction causes vasodilation and loss of vascular tone due to histamine release.

Neurogenic Shock

• Injury to the spinal cord causing loss of sympathetic tone.
• Leads to widespread vasodilation and reduced blood pressure.

Hemodynamic Parameters

• Table showing estimated cardiac output, preload, afterload, and heart rate in various shock types.
• The table often presents typical values or expected trends during different shock types and stages.

Clinical Manifestations

• Specific symptoms vary depending on shock type but frequently include cold clammy skin, changes in heart rate, blood pressure, skin color.

Approach to a Shocked Patient

• Perform ABCDE assessment immediately.
• Establish vascular access (multiple large-bore IVs).
• Start hemodynamic monitoring (heart rate, blood pressure etc.).

Classify Shock Type

• Determine possible causes (etiology) and supportive data (X-rays, ECG and serum labs).
• Begin fluid resuscitation (fluids for volume restoration), based on hemodynamic response.

Specific Management for Shocks

• Tables and points to highlight treatment based on the type of shock.

References

• Bailey and Love's Short Practice of Surgery (26th Edition).