Understanding Shock: Types, Causes, and Management

Shock

A physiologic state characterized by systemic reduction in tissue perfusion, resulting in decreased tissue oxygen delivery.

Inadequate tissue perfusion

A condition in which circulation fails to meet the metabolic need of the tissue and fails to remove metabolic waste products.

Anaerobic metabolism

A metabolic process that occurs when there is insufficient oxygen delivery to tissues.

Effects on Heart during Shock

Decreased cardiac output (CO), hypotension, and presence of myocardial depressants.

Effects on Lung during Shock

Decreased gas exchange, tachypnoea, and pulmonary edema.

Effects on Endocrine during Shock

Increased reabsorption of water due to ADH release.

Effects on CNS during Shock

Decreased perfusion leading to drowsiness.

Effects on Blood during Shock

Coagulation abnormalities, including disseminated intravascular coagulation (DIC).

Effects on Renal during Shock

Decreased glomerular filtration rate (GFR) and decreased urine output.

Effects on GIT during Shock

Mucosal ischemia leading to bleeding and increased enzyme levels in the liver.

Hypovolaemic Etiology

Caused by blood loss, plasma/body water loss, electrolyte imbalance, vomiting, diarrhea, or dehydration.

Cardiogenic Etiology

Caused by valvular heart disease, myocardial infarction, cardiac arrhythmias, or cardiomyopathy.

Obstructive Etiology

Caused by cardiac tamponade, pulmonary embolism, tension pneumothorax, or air embolism.

Neurogenic Etiology

Caused by paraplegia, quadriplegia, trauma to the spinal cord, or spinal anesthesia.

Anaphylactic Etiology

Caused by injections (e.g., penicillin, anesthetics), stings, or shellfish.

Septic Etiology

Caused by Gram-positive, Gram-negative bacteria, fungi, viruses, or protozoa.

Endocrine Etiology

Caused by hypo- and hyperthyroidism or adrenal insufficiency.

Clinical Features of Shock

Depend on the degree of volume loss and duration of shock.

Types of Shock

Mild shock, moderate shock, and severe shock.

Mild Shock Features

Collapse of subcutaneous veins, pale and cool extremities, normal urine output, normal pulse rate, normal blood pressure, and patient feels thirsty and cold.

Moderate Shock Features

Mild shock features plus drowsiness and confusion, oliguria, pulse rate increased usually less than 100/min, and blood pressure normal initially then falls in later stage.

Severe Shock Features

Unconsciousness, gasping respiration, anuria, rapid pulse, and profound hypotension.

Stages of Shock

Initial stage: cells become leaky and switch to anaerobic metabolism; Non-progressive stage: attempt to correct metabolic upset; Progressive stage: compensation begins to fail; Refractory stage: organs fail and shock can no longer be reversed.

Monitoring

Blood pressure, Heart rate, Respiratory rate, Urine output, Blood CBC, Pulse-oximetry, ECG, U/S, CT, X-ray

Central venous pressure

Normal; 5-10cmH2O, If CVP<5cmH2O - Inadequacy of blood volume, CVP>12cmH2O - Cardiac dysfunction

Cardiac output

Measurement of the volume of blood the heart pumps per minute.

Pulmonary catheter

A catheter placed in the pulmonary artery to measure pressures.

Doppler ultrasound

A method used to assess blood flow and cardiac output.

Pulse waveform analysis

A technique to analyze the shape of the pulse wave to assess cardiovascular function.

Urine output & LOC

Clinical indicators of systemic and organ perfusion.

Sr. Lactate estimation & Base deficit

Tests used to evaluate metabolic status and perfusion.

Blood gas analysis

Measurement of PO2, PCO2, and pH levels in the blood.

Mixed venous O2 saturation

Normal range is 50-70% indicating the balance of oxygen delivery and consumption.

Dynamic Fluid Response

Infusing 250-500ml of Fluid rapidly in 5-10 minutes. Responders show improvement, transient responders revert back, non-responders do not improve.

Vasopressors

Medications like Phenylephrine and Norepinephrine used in distributive shock states.

Inotropic Drugs

Medications like Dobutamine used to increase cardiac output in cardiogenic shock.

Fluid Therapy in Shock

Includes Crystalloid Solutions (Normal saline, Ringers Lactate solution, Hartmann's solution) and Colloid Solutions (Blood transfusion).

Oxygen Carrying Capacity

Only RBC contribute to oxygen carrying capacity (hemoglobin); other solutions support volume but do not provide additional oxygen carrying capacity.

End Points of Resuscitation

Classic/Traditional: Restoration of blood pressure, normalization of heart rate and urine output, appropriate mental status. Improved/Global: All of the above plus normalization of serum lactate levels, resolution of base deficit, adequate mixed venous saturation.

Goal directed approach

Urine output > 0.5 mL/kg/hr, CVP 5-10 cm H2O, MAP 65 to 90 mmHg, Central venous oxygen concentration > 70%.

Obstructive shock

Causes include cardiac tamponade, air embolism, and pulmonary embolism; cardiac arrhythmias are primarily associated with cardiogenic shock.

Agent of choice in Severe septic shock

Norepinephrine is the first-line agent, but vasopressin is often used as an adjunct.

Type of shock from abdominal injury

The clinical picture suggests hemorrhage leading to hypovolemic shock.

Newer methods for monitoring tissue perfusion

Include muscle tissue O2 probes, infrared spectroscopy, and sublingual capnometry; Doppler ultrasound is not considered a newer method.

Last signs of shock

Profound hypotension is one of the last signs, indicating severe circulatory failure.