Shock

Shock: Inadequate Oxygen Delivery Leading to Acidosis & Organ Dysfunction

Key Concept:

(Preload + Contractility + Afterload) → Stroke Volume × HR = Cardiac Output × O₂ = Oxygen Delivery

Each type of shock disrupts different variables, but all result in impaired oxygen delivery at the cellular level.

Hemodynamic Variables Affected by Shock:

Preload (Volume in Ventricle):Hypovolemic Shock
- Roughly correlates with CVP but isn’t equal to total blood volume
- Venous dilation can cause inadequate return to the heart despite normal volume
Contractility (Pump Strength): Cardiogenic Shock
Afterload (Resistance to Ejection): Distributive Shock

Compensatory Mechanisms:

Pulmonary: Increased respiratory effort to eliminate CO₂
Adrenal: Epinephrine release (↑ heart rate & contractility)
Renal: RAAS activation → Sodium & water retention → ↓ urine output
ADH (“Add Hydration Hormone”): Water retention → ↓ urine output
Sympathetic Nervous System: Vasoconstriction to maintain perfusion
Intracellular Fluid Shift: Fluid moves from interstitial & intracellular spaces into the bloodstream to support circulation

Clinical Signs of Shock (Driven by Compensation):

Tachypnea (Increased Respiratory Rate)
Tachycardia (Increased Heart Rate)
Reduced Urine Output (Renal Compensation)
Vasoconstriction (Cool Extremities, Shunting Blood to Core Organs)

A subtly decreased pulse pressure is an early indicator, while a markedly reduced pulse pressure suggests a late-stage response. Alternatively, a widening pulse pressure may indicate low systemic vascular resistance (SVR) with the heart exerting greater effort to maintain circulation.

Types of Shock:

Hypovolemic: ↓ Preload → ↓ Stroke Volume → ↓ Cardiac Output
- Causes: Hemorrhage, plasma loss (burns, ascites, third-spacing)
Cardiogenic: ↓ Contractility
Distributive: ↓ Afterload
Obstructive: Physical barrier to circulation

Primary Interventions (ABCs):

A: Airway
B: Breathing
C: Circulation
D: Disability (Neurological Status)
E: Exposure (Identify & Treat Underlying Cause)

Hypovolemic Shock

Reduced preload → decreased stroke volume → lower cardiac output

Causes include hemorrhage or “relative” volume depletion from conditions like burns, ascites, and third-spacing.

Classification of Hypovolemic Shock:

Class I: Up to 750 mL loss (<15% of total blood volume)
Class II: 750-1500 mL loss (15-30% of total blood volume)
Class III: 1500-2000 mL loss (30-40% of total blood volume)
Class IV: >2000 mL loss (>40% of total blood volume)

Key Signs:

Airway (A): Maintained
Breathing (B): Rapid breathing with increased effort
Circulation (C):
- Tachycardia
- Systolic BP adequate initially, but pulse pressure narrows
- Weak peripheral pulses
- Delayed capillary refill
- Cool, pale, or mottled skin
- Oliguria (low urine output)
Disability (D): Altered mental status
Exposure (E): Extremities colder than the trunk

Treatment:

Fluid resuscitation with warm isotonic crystalloid (20 mg/kg), titrated to maintain perfusion.
Sodium bicarbonate (NaHCO₃) is NOT recommended to correct metabolic acidosis unless acidosis stems from renal or gastric losses.

Cardiogenic Shock

Underlying causes:

Heart failure (CHF)
Cardiomyopathy
Myocarditis
Blunt cardiac trauma
Myocardial infarction (MI)
Sepsis
Toxicity (poisoning/overdose)
Direct myocardial injury

Assessment:

Airway (A): Open and patent
Breathing (B): Rapid, shallow respirations
Circulation (C):
- MI signs: Chest pain, arrhythmias, elevated troponins
- Left-sided heart failure (fluid backup in lungs)
  - Pulmonary edema
  - Crackles
  - Weak peripheral pulses
  - Hypotension
- Right-sided heart failure (fluid backup in systemic circulation)
  - Jugular vein distension (JVD)
  - Peripheral edema
  - Hepatomegaly
Disability (D): Decreased LOC (ranging from anxiety to unconsciousness)
Exposure (E): Pale, cool, clammy skin

Treatment:

Optimize preload and afterload based on the patient’s condition
Nitroglycerin (NTG) for vasodilation
Inotropes to enhance contractility
Beta-blockers to increase ventricular filling time

Distributive Shock (Anaphylactic, Septic, Neurogenic)

Airway (A): Open and patent
Breathing (B): Rapid respirations with increased work of breathing
Circulation (C):
- Tachycardia
- Bounding pulses OR weak pulses
- Capillary refill brisk or delayed
- Skin variations:
  - Warm, flushed skin OR cool, pale skin
- Blood pressure variations:
  - Hypotension with wide pulse pressure
  - Hypotension with narrow pulse pressure
  - Normotension possible
- Oliguria (low urine output)
Disability (D): Altered mental status (restlessness, confusion, lethargy)
Exposure (E):
- Fever or hypothermia
- Extremities warm or cool
- Petechiae or purpuric rash may be present

Anaphylactic Shock (Severe allergic reaction, distributive type)

Epinephrine (1:1,000 concentration) – first-line treatment
Signs: Swelling, rash, hypotension
Additional treatment:
- Antihistamines (H1 & H2 blockers)
- Corticosteroids to prevent rebound symptoms

Septic Shock (Bacterial or fungal infection-driven shock)

Hyperdynamic Phase (Early “Warm Shock”)

Airway (A): Open
Breathing (B): Increased respiratory rate
Circulation (C):
- Tachycardia
- Systolic BP near normal, but diastolic BP low = widened pulse pressure
Disability (D): Altered mental status (agitation, anxiety, malaise)
Exposure (E): Fever, flushed skin, possible petechiae

Hypodynamic Phase (Late “Cold Shock”)

Airway (A): Open
Breathing (B): Shallow, rapid breaths
Circulation (C):
- Decreased cardiac output (CO)
- Severe hypotension, tachycardia
- Increased systemic vascular resistance (SVR)
Disability (D): Lethargy, coma
Exposure (E): Hypothermia, pale/mottled skin

Treatment:

Address the infection!
Oxygen support
Fluid resuscitation
Vasopressors as needed:
- Dopamine (for normotensive patients)
- Norepinephrine (for warm shock)
- Epinephrine (for cold shock)

Neurogenic Shock

Key Features:

Airway (A): Maintained and unobstructed
Breathing (B): Diaphragmatic (belly) breathing due to impaired chest wall movement
Circulation (C):
- Severe vasodilation from loss of vascular tone
- Profound hypotension
- Bradycardia with full, regular pulses
- Priapism (sustained erection) in males
Disability (D): Paralysis (paraplegia/quadriplegia) based on injury level
Exposure (E):
- Below injury level: Warm, dry skin due to inability to constrict blood vessels
- Above injury level: Cool, pale skin
- Poikilothermia: Body temperature fluctuates with the environment

Key Reminder:

“C3, 4, 5 keeps the diaphragm alive” → Injury at these levels can compromise respiratory function.

Management:

Supportive care: Vasopressors to maintain blood pressure
Fluids: Administer cautiously to avoid overload
Positioning: Keep bed flat—raising the head can worsen hypotension
Spinal immobilization: Prevent further injury
Acute injury (<8 hours): High-dose methylprednisolone (Solu-Medrol) for potential neuroprotection

Obstructive Shock (Physical obstruction impairing cardiac output)

Causes:

Pulmonary embolism (PE)
Coarctation of the aorta
Aortic stenosis
Cardiac tamponade
Tension pneumothorax

General Management:

Support ABCs
High-flow oxygen
Intubation if necessary

Pulmonary Embolism (PE) – A Major Cause of Obstructive Shock

Risk Factors:

Central venous catheters
Sickle cell disease
Malignancy
Connective tissue disorders
Coagulation abnormalities

Assessment:

Airway (A): Open
Breathing (B): Respiratory distress, increased work of breathing
Circulation (C):
- Tachycardia
- Cyanosis
- Hypotension
- Systemic venous congestion (right heart failure signs)
Disability (D): Anxiety
Exposure (E): Extremities cooler than the trunk

Treatment:

Anticoagulation: Heparin, t-PA, or streptokinase
Oxygen therapy (high-flow O₂)

Coarctation of the Aorta

Signs & Symptoms:

Elevated blood pressure in upper extremities
Low blood pressure in lower extremities

Treatment:

Prepare for imaging (aortogram, cardiac catheterization)
Provide supplemental oxygen

Aortic Stenosis

Key Features:

Airway (A): Maintained
Breathing (B): Dyspnea, persistent cough
Circulation (C):
- Chest pain
- Hypoxemia
Disability (D): Syncope, altered mental status
Exposure (E): Cyanosis

Treatment:

Cardiac catheterization for assessment
Valve replacement if indicated

Cardiac Tamponade

Pathophysiology:

Excess fluid or air accumulates in the pericardial space, impairing cardiac function
Common causes:
- Penetrating chest trauma
- Post-cardiac surgery
- Pericarditis

Classic Signs: Beck’s Triad (The 3 D’s)

Distant (muffled) heart sounds
Distended jugular veins (JVD)
Decreased blood pressure (hypotension)

Additional Symptoms:

Airway (A): Unobstructed
Breathing (B): Increased work of breathing (WOB), tachypnea
Circulation (C):
- Poor peripheral pulses
- Narrowed pulse pressure
- Pulsus paradoxus: SBP drops >10 mmHg during inspiration
- JVD
Disability (D): Altered mental status
Exposure (E): Cyanosis, extremities cooler than trunk

Management:

Emergency needle decompression
Definitive surgical intervention (pericardial window or cardiac repair)
Oxygen support

Tension Pneumothorax

Causes:

Chest trauma
Worsening condition during positive-pressure ventilation

Key Signs & Symptoms:

Hypotension
Hypoxia
Absent breath sounds

Assessment by System:

Airway (A):
- May remain open
- Tracheal deviation toward the unaffected side (late sign)
Breathing (B):
- Severe respiratory distress, increased work of breathing (WOB)
- Hyperresonance on the affected side
- Chest hyperexpansion on the affected side
- Diminished breath sounds bilaterally
Circulation (C):
- Jugular vein distension (JVD)
- Pulsus paradoxus (drop in SBP >10 mmHg during inspiration)
- Rapid decline in perfusion
Disability (D):
- Altered mental status
Exposure (E):
- Cool extremities

Treatment:

Immediate needle decompression (needle thoracostomy)
Chest tube placement for definitive management

Trauma Assessment Overview

Obtaining TNCC certification is strongly advised for emergency department (ED) personnel, even if not mandatory.

Initial Assessment	Evaluation Approach
Airway	Gather a full set of vital parameters
Breathing	Apply essential interventions: • Run lab diagnostics • Monitor continuously • Insert NG/OG tubes as needed • Provide oxygen and ventilation assistance • Manage discomfort effectively
Circulation	Perform a detailed body check and gather patient history
Neurological Status	Inspect back surfaces carefully: • Give special attention to potential pelvic trauma
Exposure & Environment	—

Triage Essentials

Neutropenia

Fever in a neutropenic patient is a medical emergency.
Neutropenic or oncology patients should never wait in the general waiting area.
Anyone undergoing chemotherapy should be assumed to be neutropenic.

Critical Conditions & Signs

Infant diarrhea can lead to metabolic acidosis.
Testicular torsion requires immediate intervention.
Altered level of consciousness (ALOC)? Always check blood glucose first to rule out hypoglycemia.
Kehr’s sign (splenic injury): LUQ pain, SOB, and referred pain to the left shoulder.
Hamman’s sign: A crunching sound in sync with heartbeats, indicating tracheobronchial trauma.
Handling evidence: Store clothing and belongings in paper bags, not plastic.
Tooth avulsion: Place in milk or Save-a-Tooth solution. Reimplantation success declines rapidly after 60 minutes.

FAST Exam (Focused Assessment with Sonography for Trauma)

Used for blunt abdominal trauma.
Positive FAST = >200 mL of blood detected.
False negatives can occur with hollow organ or retroperitoneal bleeds.

Facial Fractures – Le Fort Classification

Le Fort I: Horizontal fracture separating the upper teeth from the face (resembles a mustache).
Le Fort II: Triangular fracture along the nasofrontal suture (resembles a BVM mask).
Le Fort III: Complete separation of the midface from the skull (fracture behind the eyes).

Suture Removal Guidelines

Face: 3-5 days
Scalp: 7-10 days
Hands/Feet: 7-10 days
Joints: 14 days
Extremities: 10-14 days

Precaution Levels

Standard Precautions – Applied to all patients.
Contact Precautions – Required for:
- C. difficile, MRSA, wound infections
Bloodborne Precautions – Required for:
- Percutaneous injuries
- HIV, hepatitis B/C, malaria, measles, herpes, chickenpox
- Applies to blood, CSF, pleural, pericardial, and peritoneal fluids.
- NOT required for sputum, vomit, sweat, feces, or nasal secretions.
Droplet Precautions – Required for:
- Pertussis, influenza, adenovirus, rhinovirus, N. meningitidis, Group A Strep
Airborne Precautions – Required for:
- Anthrax, tuberculosis, SARS, measles, chickenpox, disseminated herpes zoster

Mass Casualty Incidents

Types of Mass Casualty Incidents (MCI)

Category of Disaster	Illustrative Incidents
Naturally Occurring Events	Avalanches, severe snowstorms, forest fires, extreme temperatures, earth movements, violent storms, volcanic activity
Man-Made Emergencies	Building collapses, chemical leaks, detonations, hostage situations, underground accidents, radioactive threats, structure fires, travel-related crashes (e.g., plane or car accidents)

Emergency Management Phases

Mitigation: Identifying risks and vulnerabilities to minimize potential MCI impact.
Preparedness: Establishing protocols, training, and resources for MCI response.
Response: Executing established plans and protocols during an MCI.
Recovery: Implementing strategies for restoring normal operations post-MCI.

Triage Systems

Adults: START (Simple Triage and Rapid Treatment) for rapid patient assessment.
Pediatrics:JumpSTART, which modifies START by:
- Replacing capillary refill assessment with a pulse check.
- Providing 5 rescue breaths before declaring an apneic child nonviable.

Medical Screening Exam (MSE) Components

Assessing for an Emergency Medical Condition (EMC)
- Triage alone does not fulfill MSE requirements.
Evaluation Based on Clinical Condition
- The provider must determine, with reasonable clinical confidence, whether an EMC is present.
- Cardiac symptoms require an immediate EKG.