Resus: Septic Shock and Sepsis

Distributive Shock (Reduced SVR vasodilated)

💡 Distributive shock is characterised by a loss of systemic vascular resistance (SVR) despite normal or increased cardiac output. It results in relative hypovolaemia due to peripheral vasodilation and abnormal blood flow distribution - seen in sepsis, anaphylaxis, and neurogenic shock.

🧠 About

• Definition: Acute circulatory failure due to inappropriate vasodilation and maldistribution of blood flow, leading to end-organ hypoperfusion.
• Typically presents with warm peripheries, bounding pulse, and low diastolic BP - unlike the cool, clammy appearance of hypovolaemic or cardiogenic shock.

🔬 Pathophysiology

• Systemic vasodilation → ↓ systemic vascular resistance (SVR) → ↓ effective circulating volume.
• Compensatory ↑ cardiac output (hyperdynamic phase) → followed by myocardial depression if untreated.
• Microcirculatory dysfunction and capillary leak → tissue oedema and hypoxia.
• Ultimately causes lactic acidosis and cellular energy failure.

🧩 Major Causes

• 1. Septic Shock: Bacterial infection, pancreatitis, burns, or toxic shock syndrome.
• 2. Anaphylactic Shock: Hypersensitivity reaction causing mast-cell-mediated vasodilation and bronchospasm.
• 3. Neurogenic Shock: Loss of sympathetic tone after spinal cord injury or brainstem damage.

📈 Base deficit > 5 mmol/L and rising lactate indicate tissue hypoperfusion. Serial lactate trends are the best markers of response to resuscitation.

🩺 Clinical Features

• Hypotension, tachycardia (may be absent in neurogenic shock).
• Bounding pulse, wide pulse pressure, warm, flushed peripheries.
• Altered mental status: confusion → obtundation → coma.
• Oliguria or anuria.
• Features of underlying cause:
  • Sepsis: Fever, rigors, cellulitis, pneumonia, peritonitis, gangrene.
  • Anaphylaxis: Urticaria, angioedema, bronchospasm, hypotension.
  • Neurogenic: Bradycardia, warm dry skin below lesion, absent reflexes.

🔎 Investigations

• FBC (anaemia, leucocytosis), U&E (AKI), LFTs, coagulation screen.
• Arterial blood gas and lactate – assess acidosis and perfusion.
• Blood cultures prior to antibiotics.
• ECG and troponin – exclude cardiogenic element.
• Chest X-ray, abdominal imaging (CT/US) to locate infection or bleeding source.
• Consider cortisol/thyroid studies if adrenal or endocrine cause suspected.

💊 Management Principles

• 1️⃣ Resuscitation: ABCs with high-flow oxygen; fluid resuscitation (crystalloids 30 mL/kg bolus if septic).
• 2️⃣ Identify and treat the cause:
  • Sepsis: “Sepsis Six” – oxygen, cultures, IV antibiotics, IV fluids, lactate, urine output monitoring.
  • Anaphylaxis: IM adrenaline 500 micrograms (repeat every 5 min if needed), IV fluids, hydrocortisone 200 mg, chlorphenamine 10 mg IV.
  • Neurogenic: Elevate legs, maintain MAP > 85 mmHg, give IV fluids, and use vasopressors (noradrenaline/phenylephrine); atropine for bradycardia.
• 3️⃣ Vasopressors and Inotropes:
  • Noradrenaline = first-line for septic or neurogenic shock once volume replete.
  • Adrenaline (low-dose infusion) if anaphylaxis refractory to IM therapy.
  • Consider vasopressin as adjunct if noradrenaline requirement high.
• 4️⃣ Monitoring:
  • Continuous ECG, arterial line, and urinary catheter.
  • Serial lactate and base deficit to track perfusion improvement.
  • Target MAP ≥ 65 mmHg and urine output ≥ 0.5 mL/kg/h.
• 5️⃣ Escalation: Seek early critical care input for persistent hypotension or multiorgan failure.

🧠 Clinical Pearls

• Warm peripheries and low diastolic BP are classic of distributive (vs cold, clammy in hypovolaemic).
• In sepsis, vasoplegia is driven by nitric oxide and inflammatory cytokines - volume alone is never enough.
• In neurogenic shock, HR may be low despite hypotension - don’t miss the absence of tachycardia.
• Always reassess: response = best diagnostic test in any form of shock.

📚 References

• NICE NG51 (2024): Sepsis: recognition, diagnosis, and early management.
• Resuscitation Council UK. Anaphylaxis Algorithm 2023.
• ATLS 10th Ed. Neurogenic and Distributive Shock Management.
• Marik PE. Vasopressors in distributive shock. Crit Care Med 2019.

Assessing a Patient who is Shocked

🚨 Assessing a patient in shock requires immediate action. 👉 Radial pulse ≈ SBP ≥ 80 mmHg. 👉 Femoral pulse ≈ SBP ≥ 70 mmHg. 👉 Carotid pulse ≈ SBP ≥ 60 mmHg. ⚠️ Hypotension is a late finding - don’t wait for it.

🫀 Shock = inadequate tissue perfusion. 💡 Remember: Shock can exist without hypotension → look for tachycardia, tachypnoea, confusion, oliguria.

🔎 Introduction

• Defined as acute circulatory collapse with poor organ perfusion.
• Caused by ↓ cardiac output, ↓ systemic vascular resistance, or both.
• Rapid recognition + intervention = survival.

⚠️ Clinical Features of Shock

• 🫁 Tachypnoea
• ❤️ Tachycardia >100 bpm (children: may be >160 bpm)
• ⬇️ SBP <100 mmHg (late; <70 + 2×age in children = hypotension)
• 🧠 Altered mental state
• 🚽 Oliguria <0.5 mL/kg/hr
• Multi-organ failure if severe
• Vasodilatory: Warm peripheries, low diastolic BP
• Hypovolaemic: Cold, clammy, poor refill

📊 Classification of Shock

• 🫀 Cardiogenic: MI, myocarditis, endocarditis
• 🫁 Obstructive: PE, tamponade, tension PTX
• 🦠 Septic: Infections (urine, chest, abdo, meningitis in children)
• 🤧 Anaphylactic: Allergic reactions
• 🩸 Hypovolaemic: Trauma, GI bleed, obstetric haemorrhage
• 🧠 Neurogenic: Spinal cord injury

🔍 Clinical Indicators of Aetiology

• ❤️ Chest pain → MI, dissection, PE
• 🫁 Breathlessness + cyanosis → LVF, PTX, tamponade
• 🩸 Haematemesis/melaena → GI bleed
• 🦴 Pelvic/femur fracture → haemorrhage or fat embolism
• 🦠 Fever/cough → Sepsis
• 🫀 Severe SOB + ketotic breath → DKA
• ♀️ Pregnancy + abdo pain → ectopic, abruption
• 👶 Child with non-blanching rash → meningococcal sepsis
• 🟤 Pigmentation + hypotension → Addisonian crisis

🧪 Investigations

• FBC → WCC (infection), Hb (bleed)
• U&E → AKI
• Glucose → DKA/HHS
• Lactate → tissue hypoxia
• Troponin → MI
• D-dimer → PE/DIC
• CXR → consolidation, widened mediastinum, LVF
• Cortisol → Addison’s
• hCG → rule out pregnancy-related causes

🛠️ Management

• ABC → airway, O₂, IV access, circulation
• Identify and treat underlying cause
• Early escalation to senior/critical care
• Special considerations:
  • Pregnancy → left lateral tilt, rapid obstetric involvement
  • Children → weight-based fluids & drugs, beware rapid deterioration

💡 Pearls

• Radial pulse = SBP ~80, femoral = 70, carotid = 60.
• Shock without hypotension is common early (look for tachycardia + confusion).
• Never delay treating sepsis - antibiotics within 1 hour save lives.
• In trauma, assume hypovolaemia from bleeding until proven otherwise.
• Persistent hypotension after 2L NS → consider blood, sepsis, or cardiogenic/obstructive cause.
• Pregnancy and children mask shock until late - act early.