6.1 Acute Anaphylaxis, Sepsis & Cardiopulmonary Resuscitation

Acute Anaphylaxis, Sepsis & Cardiopulmonary Resuscitation

Emergency medicine forms a major pillar of the UPSC Combined Medical Services (CMS) General Medicine paper. A thorough understanding of immediate resuscitation protocols, drug dosages, diagnostic scoring systems, and life-support algorithms is essential for scoring high in clinical emergency questions.

---

1. Acute Anaphylaxis: Emergency Recognition & Management

Anaphylaxis is a severe, life-threatening, systemic IgE-mediated (Type 1) hypersensitivity reaction characterized by rapid onset of airway, breathing, or circulatory compromise. It results from mass degranulation of tissue mast cells and circulating basophils, releasing vasoactive mediators including histamine, tryptase, leukotrienes (LTC4, LTD4, LTE4), and platelet-activating factor (PAF).

Clinical Manifestations

Anaphylaxis involves multiple organ systems simultaneously:

• Cutaneous (90%): Urticaria (hives), angioedema (swelling of lips, tongue, uvula), flushing, and intense pruritus.
• Respiratory (70%): Laryngeal edema (stridor, hoarseness, sensation of throat tightness), bronchospasm (wheezing, dyspnea), intercostal retractions, and asphyxia.
• Cardiovascular (45%): Vasodilation and endothelial leak leading to distributive shock, profound hypotension, tachycardia, syncopal episodes, and cardiac arrest.
• Gastrointestinal (30%): Severe abdominal cramps, nausea, vomiting, and diarrhea.

Immediate Emergency Management Protocol

1. Remove / Discontinue Trigger: Stop IV medications, blood products, or allergen infusions immediately.
2. First-Line Drug of Choice — Intramuscular Adrenaline (Epinephrine):
   • Adult Dose: 0.5 mg (0.5 mL of 1:1,000 or 1 mg/mL solution) administered Intramuscularly (IM) into the anterolateral aspect of the mid-thigh (vastus lateralis muscle).
   • Pharmacodynamics: Alpha-1 agonist activity causes vasoconstriction (reversing hypotension and mucosal edema); Beta-1 agonist increases inotropy/chronotropy; Beta-2 agonist causes bronchodilation and inhibits further mast cell degranulation.
   • Repeat Dosing: If clinical response is inadequate, repeat the 0.5 mg IM dose every 5 to 15 minutes.
   • Pediatric Dose: 0.01 mg/kg IM (maximum 0.3 mg per dose).
3. Airway & Oxygenation: Administer 100% high-flow oxygen (10–15 L/min via non-rebreather mask). Perform early endotracheal intubation if signs of laryngeal edema or stridor progress; maintain low threshold for emergency cricothyroidotomy.
4. Fluid Resuscitation: Establish two large-bore (14G or 16G) peripheral IV lines. Administer rapid IV boluses of 1 to 2 Liters of isotonic crystalloids (0.9% Normal Saline or Ringer's Lactate) for persistent hypotension due to capillary leak.
5. Second-Line Adjunctive Therapies (administered ONLY after Adrenaline):
   • H1-Receptor Antagonists: Cetirizine 10 mg IV or Diphenhydramine 25–50 mg IV (alleviates cutaneous symptoms).
   • H2-Receptor Antagonists: Ranitidine 50 mg IV or Famotidine 20 mg IV.
   • Corticosteroids: Hydrocortisone 200 mg IV or Dexamethasone 8 mg IV (onset 4–6 hours; primary role is preventing biphasic anaphylactic reactions occurring 8–72 hours later).
   • Inhaled Beta-2 Agonists: Nebulized Salbutamol (2.5–5 mg) for persistent bronchospasm.

---

2. Sepsis & Septic Shock (Sepsis-3 International Guidelines)

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection.

Bedside Screening: quick SOFA (qSOFA) Score

The Sepsis-3 consensus established qSOFA as a rapid bedside tool to identify adult patients outside the ICU with suspected infection who are at high risk of poor outcomes. A score of ≥ 2 points indicates significant risk:

1. Respiratory Rate ≥ 22 breaths per minute (1 point)
2. Altered Mental Status (Glasgow Coma Scale score < 15) (1 point)
3. Systolic Blood Pressure ≤ 100 mmHg (1 point)

Sequential Organ Failure Assessment (SOFA) Score

Organ dysfunction is formally defined as an acute increase in the total SOFA score of ≥ 2 points attributable to the infection, evaluating six organ systems: PaO2/FiO2 ratio (respiratory), Platelets (hematologic), Bilirubin (hepatic), Mean Arterial Pressure / Vasopressors (cardiovascular), Glasgow Coma Scale (neurologic), and Creatinine / Urine Output (renal).

Septic Shock Definition

Septic shock is a subset of sepsis in which underlying circulatory and cellular/metabolic abnormalities are profound enough to substantially increase mortality. It is diagnosed clinically by:

• Persistent hypotension requiring vasopressors to maintain a Mean Arterial Pressure (MAP) ≥ 65 mmHg, AND
• Serum Lactate level > 2 mmol/L (18 mg/dL) despite adequate volume resuscitation.

Surviving Sepsis Campaign: Hour-1 Bundle

Upon identification of sepsis or septic shock, initiate all 5 components of the Hour-1 Bundle immediately:

1. Measure Lactate Level: Re-measure within 2–4 hours if initial lactate is elevated (> 2 mmol/L).
2. Obtain Blood Cultures: Take at least two sets of blood cultures (aerobic and anaerobic) prior to initiating antimicrobial therapy.
3. Administer Broad-Spectrum Antibiotics: Empirical IV therapy (e.g., Piperacillin-Tazobactam 4.5g IV or Meropenem 1g IV + Vancomycin 15–20 mg/kg IV) within 1 hour.
4. Rapid Fluid Resuscitation: Administer 30 mL/kg of IV crystalloid within the first 3 hours for hypotension or serum lactate ≥ 4 mmol/L. Ringer's Lactate is preferred over Normal Saline to avoid hyperchloremic metabolic acidosis.
5. Vasopressor Therapy: Apply vasopressors if MAP remains < 65 mmHg during or after fluid loading.
   • First-Choice Vasopressor: Norepinephrine (titrated from 0.02–0.5 mcg/kg/min to maintain MAP ≥ 65 mmHg).
   • Second-Line / Adjunct Vasopressor: Vasopressin (0.03 units/min fixed dose) or Epinephrine (0.05–0.5 mcg/kg/min).
   • Inotrope: Add Dobutamine if persistent hypoperfusion continues despite adequate MAP and volume (cardiomyopathy of sepsis).

3. Cardiopulmonary Resuscitation (CPR) & Advanced Cardiovascular Life Support (ACLS)

Cardiopulmonary arrest requires rapid, coordinated execution of Basic Life Support (BLS) and Advanced Cardiovascular Life Support (ACLS) based on updated AHA/ERC resuscitation standards.

High-Quality Chest Compression Parameters

High-quality BLS forms the cornerstone of survival in sudden cardiac arrest:

• Compression Rate: 100 to 120 compressions per minute.
• Compression Depth: 5 to 6 cm (2 to 2.4 inches) in adults (avoiding excessive depth > 6 cm).
• Chest Recoil: Allow complete chest wall recoil after each compression; do not lean on the patient's chest.
• Minimize Interruptions: Keep pauses in compressions to less than 10 seconds (Chest Compression Fraction > 80%).
• Compression-to-Ventilation Ratio: 30:2 for single and dual rescuers in adults without an advanced airway.
• Advanced Airway Ventilation: Once an endotracheal tube or supraglottic airway is placed, give 1 breath every 6 seconds (10 breaths/min) while continuous chest compressions proceed without pauses.

Reversible Causes of Cardiac Arrest: The 5 H's and 5 T's

During CPR, active search for and treatment of underlying treatable causes is critical:

---

Rhythm-Specific ACLS Management Algorithms

A. Shockable Rhythms: Ventricular Fibrillation (VF) & Pulseless Ventricular Tachycardia (pVT)

1. Immediate Unsynchronized Defibrillation: Deliver 1 shock (Biphasic: 120–200 J; Monophasic: 360 J).
2. Resume CPR Immediately: Continue high-quality CPR for 2 minutes without stopping to re-check pulse. Establish IV or Intraosseous (IO) access.
3. Rhythm Check (after 2 mins): If VF/pVT persists, deliver Shock #2 and resume CPR.
4. First Vasopressor Dose: Give Adrenaline 1 mg IV/IO (10 mL of 1:10,000 solution) after the second shock. Repeat every 3 to 5 minutes throughout resuscitation.
5. Antiarrhythmic Administration:
   • If refractory VF/pVT persists after the third shock, give Amiodarone 300 mg IV/IO bolus. A second dose of 150 mg IV can be given after 5 minutes.
   • Alternative Antiarrhythmic: Lidocaine (First dose: 1 to 1.5 mg/kg IV/IO; Second dose: 0.5 to 0.75 mg/kg IV/IO).

B. Non-Shockable Rhythms: Asystole & Pulseless Electrical Activity (PEA)

1. Resume CPR Immediately: Continue CPR for 2-minute cycles. Do NOT shock.
2. Early Vasopressor Therapy: Administer Adrenaline 1 mg IV/IO as early as possible after recognizing asystole or PEA. Repeat every 3 to 5 minutes.
3. Identify & Treat Reversible Causes: Focus heavily on searching for the 5 H's and 5 T's (e.g., fluid bolus for hypovolemia, needle decompression for tension pneumothorax).
4. Re-evaluate Rhythm: Check rhythm after every 2 minutes of CPR. If rhythm changes to VF/pVT, transition immediately to the shockable algorithm.