Cardiology

Background

Hypovolemic shock is an acute, life-threatening condition characterized by inadequate tissue perfusion due to a critical reduction in intravascular volume. This leads to decreased preload, stroke volume, and cardiac output, culminating in end-organ hypoxia and failure if not promptly addressed. 

II) Classification/Types

By Etiology: 

• Hemorrhagic Shock: Due to loss of whole blood (e.g., trauma, gastrointestinal bleeding, ruptured ectopic pregnancy). 

• Non-Hemorrhagic Shock: Loss of plasma or extracellular fluid (e.g., severe dehydration, burns, pancreatitis, third-spacing in peritonitis or bowel obstruction). 

By Severity (based on the American College of Surgeons Advanced Trauma Life Support classification): 

• Class I: <15% blood loss (compensated) 

• Class II: 15–30% blood loss (tachycardia, narrow pulse pressure) 

• Class III: 30–40% blood loss (hypotension, tachycardia, confusion) 

• Class IV: >40% blood loss (profound hypotension, lethargy, anuria) 

III) Epidemiology 

• Sex: Both sexes affected equally; hemorrhagic shock from trauma is more common in males. 

• Age: Extremes of age (infants, elderly) are more vulnerable due to limited compensatory mechanisms. 

• Geography: Higher incidence in regions with limited access to trauma care or safe water. 

• Settings: Common in trauma centers, ICUs, emergency departments, and surgical units. 

Etiology

I) What Causes It

Hemorrhagic: 

• Trauma (e.g., motor vehicle accidents, penetrating wounds) 

• Gastrointestinal bleeding (e.g., peptic ulcer, varices) 

• Obstetric hemorrhage (e.g., postpartum hemorrhage, ectopic rupture) 

• Vascular rupture (e.g., abdominal aortic aneurysm) 

Non-Hemorrhagic: 

• Severe dehydration (vomiting, diarrhea) 

• Burns (loss of plasma through damaged skin) 

• Pancreatitis (fluid sequestration) 

• Bowel obstruction with third-spacing 

II) Risk Factors

• Major trauma or surgery 

• Active gastrointestinal disease (ulcers, liver disease) 

• Coagulopathy or anticoagulant use 

• Diuretic use or poor fluid intake 

• Heat exposure or excessive sweating 

• Elderly age or comorbidities reducing reserve 

Clinical Presentation

I) History (Symptoms)

• Dizziness or lightheadedness 

• Weakness or fatigue 

• Thirst 

• Confusion or altered mental status (late) 

• Syncope 

• Abdominal or chest pain (if bleeding source present) 

• Vomiting, diarrhea (in non-hemorrhagic cases) 

II) Physical Exam (Signs)

Vital Signs: 

• Tachycardia (earliest sign) 

• Hypotension (especially orthostatic) 

• Tachypnea 

• Narrow pulse pressure 

Skin: 

• Cool, clammy, pale skin 

• Delayed capillary refill 

Neurologic: 

• Restlessness or agitation (early) 

• Lethargy or obtundation (late) 

Cardiovascular: 

• Weak peripheral pulses 

• Flat neck veins (unless tamponade or tension pneumothorax) 

Urinary: 

• Oliguria or anuria 

Differential Diagnosis (DDx)

• Cardiogenic shock (e.g., myocardial infarction, arrhythmia) 

• Distributive shock (e.g., septic, anaphylactic) 

• Obstructive shock (e.g., pulmonary embolism, cardiac tamponade) 

• Neurogenic shock (spinal cord injury) 

• Adrenal crisis 

Diagnostic Tests

Initial Tests: 

• CBC: Assess hemoglobin/hematocrit for bleeding; hemoconcentration in dehydration 

• Electrolytes, BUN/Creatinine: Elevated BUN:Cr ratio in dehydration 

• Lactate: Elevated due to tissue hypoperfusion 

• ABG: Metabolic acidosis (increased anion gap) 

• Type and Crossmatch: For anticipated transfusion 

• Coagulation Panel: Especially in trauma or liver disease 

• Urinalysis: Concentrated urine in dehydration 

• ECG: Rule out myocardial ischemia 

• Chest X-ray and FAST ultrasound: Evaluate trauma, hemothorax, hemoperitoneum 

• CT scan (contrast-enhanced): Identify source of bleeding (if stable) 

Treatment

I) Medical Management

Immediate Resuscitation: 

• Ensure airway and breathing 

• Place large-bore IVs or central access 

• Initiate fluid resuscitation (isotonic crystalloids – e.g., NS or LR) 

Fluid Management: 

• Hemorrhagic: Early balanced transfusion strategy (1:1:1 PRBCs:FFP:Platelets) 

• Non-Hemorrhagic: Crystalloids first, reassess with clinical and lab response 

Vasopressors: 

• Not first-line 

• May be needed temporarily after volume resuscitation in persistent hypotension 

Monitor: 

• Urine output (goal >0.5 mL/kg/hr) 

• Serial lactate clearance 

• Hemodynamic parameters (MAP, CVP if central line present) 

II) Surgical/Interventional

• Control of Bleeding Source: Surgery (e.g., trauma laparotomy), endoscopy, angiographic embolization 

• Endovascular Repair: For ruptured aneurysm or bleeding vessels 

Patient Education, Screening, Vaccines

• Educate on signs of dehydration and hypotension 

• Avoid NSAIDs in peptic ulcer disease 

• Importance of hydration, especially in hot weather or with vomiting/diarrhea 

• Adherence to anticoagulant monitoring 

• Vaccinations for underlying causes (e.g., hepatitis for cirrhotics) 

Consults

• Trauma Surgery: In all patients with hemorrhagic shock from trauma 

• Gastroenterology: For GI bleeding requiring endoscopy 

• Interventional Radiology: For embolization of bleeding sources 

• ICU/CCM: For unstable or rapidly deteriorating patients 

• Nephrology: If acute kidney injury from prolonged hypoperfusion 

• Obstetrics: In postpartum or gynecologic bleeding 

Follow-Up

• Monitor hemodynamics, urine output, and labs after stabilization 

• Identify and manage underlying cause (e.g., ulcer, ruptured aneurysm) 

• Prevent recurrence (e.g., PPI in GI bleed, optimize chronic disease) 

• Long-term monitoring for organ dysfunction from prolonged hypoperfusion 

• Reassess volume status and need for further intervention