Cardiology

Background

Shock is a life-threatening condition characterized by inadequate tissue perfusion and oxygen delivery to meet metabolic demands, leading to cellular dysfunction, organ failure, and potentially death if untreated. It represents a final common pathway of diverse pathologies resulting in circulatory collapse. 

II) Classification

By Mechanism: 

• Hypovolemic Shock: Decreased intravascular volume (e.g., hemorrhage, dehydration, burns). 

• Cardiogenic Shock: Pump failure (e.g., MI, cardiomyopathy, valvular disease). 

• Obstructive Shock: Physical obstruction to blood flow (e.g., cardiac tamponade, PE, tension pneumothorax). 

• Distributive Shock: Maldistribution of blood due to vasodilation (e.g., sepsis, anaphylaxis, neurogenic shock). 

By Onset: 

• Acute Shock: Sudden onset, often with rapid progression. 

• Chronic Shock: Less common; may occur in indolent conditions such as adrenal insufficiency or heart failure. 

III) Epidemiology 

• Sex: No significant sex predilection overall; type-dependent (e.g., septic shock may be more common in men). 

• Age: Elderly and infants are at higher risk due to limited compensatory mechanisms. 

• Geography: Sepsis-related shock more prevalent in resource-limited settings. 

• Comorbidities: Diabetes, heart disease, immunosuppression, trauma, recent surgery. 

Etiology

I) What Causes It 

• Hypovolemic: Hemorrhage, vomiting, diarrhea, third-spacing, burns. 

• Cardiogenic: Myocardial infarction, arrhythmias, myocarditis, end-stage cardiomyopathy. 

• Obstructive: Pulmonary embolism, cardiac tamponade, tension pneumothorax, aortic dissection. 

• Distributive: Sepsis, anaphylaxis, spinal cord injury (neurogenic), adrenal crisis. 

II) Risk Factors 

• Major trauma or surgery 

• GI bleeding 

• Acute coronary syndromes 

• Immunocompromise 

• Indwelling catheters 

• Allergies (for anaphylaxis) 

• Spinal cord injuries 

• Adrenal insufficiency 

Clinical Presentation

I) History (Symptoms) 

• Lightheadedness, syncope 

• Dyspnea 

• Confusion or altered mental status 

• Cold extremities 

• Decreased urine output 

• Chest pain (cardiogenic) 

• Fever or chills (septic) 

• Rash or urticaria (anaphylactic) 

II) Physical Exam (Signs) 

Vital Signs: 

• Hypotension (SBP <90 mmHg or MAP <65 mmHg) 

• Tachycardia (unless bradycardia in neurogenic or beta-blocker use) 

• Tachypnea 

• Hypothermia or fever (in sepsis) 

General Appearance: 

• Pale, diaphoretic, lethargic or agitated 

• Cool, clammy skin (except in early distributive shock—warm extremities) 

Cardiovascular: 

• Weak, thready pulses 

• JVD in cardiogenic or obstructive shock 

• Muffled heart sounds (tamponade) 

Respiratory: 

• Crackles in cardiogenic shock 

• Decreased breath sounds (pneumothorax) 

Abdomen: 

• Tenderness, distension (bleeding, sepsis) 

Differential Diagnosis (DDx)

• Acute heart failure 

• Pulmonary embolism 

• Severe sepsis without hypotension 

• Adrenal crisis 

• Arrhythmias 

• Upper GI bleeding 

• Drug overdose 

• Hypoglycemia 

Diagnostic Tests

Initial Tests: 

• Vitals + Pulse Oximetry: Detect hypoperfusion 

• EKG: MI, arrhythmias 

• CBC: Anemia, leukocytosis 

• CMP: Electrolytes, renal/liver function 

• Lactate: Marker of tissue hypoperfusion 

• Blood cultures + Procalcitonin: If sepsis suspected 

• Cardiac biomarkers: Troponin, BNP 

• Coagulation panel: DIC risk in septic shock 

• Arterial blood gas (ABG): Metabolic acidosis 

• CXR: Pulmonary causes (e.g., pneumonia, pneumothorax) 

• Point-of-care ultrasound (POCUS): Volume status, tamponade, PE, IVC collapsibility 

• CT Chest/Abdomen: For trauma, PE, or source of infection 

Treatment

I) Medical Management: 

Initial Stabilization: 

• ABC approach: Airway protection, oxygen, IV access 

• Fluids: 30 mL/kg isotonic crystalloids for suspected hypovolemia or sepsis 

• Vasopressors: Norepinephrine is first-line in septic/cardiogenic shock unresponsive to fluids 

• Inotropes: Dobutamine in cardiogenic shock with low CO 

Targeted Therapy: 

• Hypovolemic: Stop bleeding, volume replacement (PRBCs, crystalloids) 

• Cardiogenic: Revascularization (PCI), diuretics, vasopressors, mechanical support 

• Obstructive: Treat underlying cause (e.g., thrombolytics for PE, needle decompression for tension pneumothorax) 

• Distributive: Treat source of infection (early broad-spectrum antibiotics), antihistamines/steroids for anaphylaxis, vasopressors 

II) Interventional/Surgical: 

• Pericardiocentesis (tamponade) 

• Chest tube (tension pneumothorax) 

• Embolectomy or catheter-directed thrombolysis (massive PE) 

• PCI/CABG (MI-related cardiogenic shock) 

• Exploratory laparotomy (trauma or GI bleed) 

Patient Education, Screening, Vaccines

• Recognize early warning signs of infection or allergic reactions 

• Adherence to chronic disease management (e.g., heart failure, diabetes) 

• Medication compliance, especially anticoagulants or steroids 

• Medical alert bracelets for anaphylaxis or adrenal insufficiency 

• Vaccines: 

• Influenza annually 

• Pneumococcal vaccines (PPSV23, PCV15/20) 

• COVID-19 vaccination 

Consults

• Critical Care: All patients in shock should be monitored in ICU 

• Cardiology: For cardiogenic or obstructive causes 

• Pulmonology: Suspected PE or ARDS 

• Infectious Disease: Source control in sepsis 

• Surgery/Trauma: Source control in hemorrhagic or obstructive shock 

• Allergy/Immunology: For recurrent anaphylaxis 

• Endocrinology: Adrenal insufficiency, thyroid storm 

Follow-Up

• ICU Monitoring: Continuous BP, cardiac telemetry, urine output 

• Daily labs: Lactate clearance, organ function markers 

• Long-term: 

• Outpatient management of underlying condition 

• Cardiac rehabilitation if applicable 

• Patient education on signs of recurrence 

• Repeat Imaging: If obstructive cause or source control evaluation needed 

• Vaccination Review: Post-sepsis or splenectomy