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🩺 SIRS → Shock → MODS Detailed Study Guide

🔹 Systemic Inflammatory Response Syndrome (SIRS)

Definition

  • Exaggerated host response to a stressor (infection, trauma, burns, pancreatitis, ischemia)

  • Not always sepsis, but most septic patients meet SIRS

  • Initiated by inflammatory mediators (cytokines, macrophages, platelets)

Diagnostic Criteria (Need ≥2)

👉 Mnemonic: “THBW” = Temperature, Heart, Breathing, White cells

  • Temperature: >38°C (100.4°F) or <36°C (96.8°F)

  • Heart rate: >90 bpm

  • Breathing: RR >20 OR PaCO₂ <32 mmHg

  • White count: WBC >12,000 or <4,000 or >10% bands

Underlying Control Systems Activated

  • Baroreceptors: Aortic arch, Carotid sinus, Low-pressure sensors
    Mnemonic: “ACL keeps you standing”

  • Sympathetic-Adreno-Medullary (SAM) system

    • FAST → Norepinephrine from nerves first

    • Then Epinephrine + Norepinephrine from adrenal medulla

    • ↑ HR, ↑ BP, ↑ contractility, ↑ skeletal muscle perfusion, ↑ glucose & fat breakdown
      Mnemonic: SAM = Sprinter → Strength, Speed, Sugar, Skeletal muscles

  • HPA Axis (Hypothalamic-Pituitary-Adrenal)

    • Slower response

    • CRH → ACTH → Cortisol

    • ↓ Inflammation, ↓ Insulin, Delayed wound healing
      Mnemonic: HPA = Hall Pass → “calms the hallway”

  • RAAS (Renin-Angiotensin-Aldosterone)

    • Renin → Angiotensin I → Angiotensin II → Aldosterone

    • Vasoconstriction, ↑ Na+ reabsorption, ↑ sympathetic tone, ADH release
      Mnemonic: R-A-A-S = Renin, Angiotensin squeezes, Aldosterone salt, Sympathetic/ADH support

Local Tissue Response

  • Vasodilation + endothelial leak → WBCs move into tissue

  • Platelets aggregate → microthrombosis → impaired perfusion

  • Capillary leak worsens

  • Leads to coagulopathy + multi-system dysfunction

🔹 Shock

Definition

  • Cellular hypoxia due to ↓ O₂ delivery or ↑ O₂ use

  • Progresses from SIRS → Shock → MODS if untreated

Phases

👉 Mnemonic: “CPF” = Compensated → Progressive → Final

  • Pre-shock (Compensated)

    • Tachycardia

    • Vasoconstriction (cool extremities)

    • MAP preserved (initially)

  • Shock (Decompensated)

    • Hypotension

    • End-organ hypoperfusion

    • Rising lactate

  • End-Organ Dysfunction (Irreversible)

    • Multi-system failure

    • Death if uncorrected

🧾 Bedside Assessment of Shoc

Hemodynamics

  • MAP <65 mmHg → red flag

  • Shock Index (SI) = HR / SBP

    • Normal: 0.5–0.7

    • 0.8 = shock suspicion

    • 1.0 = significant hypoperfusion

  • Severe bradycardia can also = shock

Renal

  • Urine output <0.5 mL/kg/hr

  • Dark urine → AKI

Skin

  • Cool, mottled, delayed cap refill (>3 sec)

Neuro

  • Altered LOC, anxiety, lethargy

Labs

  • ↑ Lactate = anaerobic metabolism

⚡ Types of Shock

Type

Pathophysiology

Key Findings

Nursing Priorities

Mnemonic

Hypovolemic

Low intravascular volume (bleed, DKA, burns)

Cool, weak pulses, ↓ CVP, oliguria, altered LOC

Fill tank (IV fluids, blood, cause control)

“Empty tank → Fill & Fix”

Cardiogenic

Pump failure (MI, arrhythmia, valve failure)

Cool mottled, narrow PP, oliguria, pulmonary edema

O₂, cautious fluids, inotropes, rhythm correction

“Bad Pump → Help Pump”

Distributive

Vasodilation (sepsis, anaphylaxis, neurogenic)

Early warm/flushed, bounding pulses, wide PP → late cool

Fluids + vasopressors + cause-specific (antibiotics/allergen removal)

“Pipes too wide → Fill & Squeeze”

Obstructive

Blocked flow (PE, tamponade, tension pneumo)

Cool, weak pulses, tachycardia, oliguria

Relieve obstruction (thrombolysis, chest tube, pericardiocentesis)

“Blocked flow → Unblock to go”

🔹 MODS (Multiple Organ Dysfunction Syndrome)

Definition

  • ≥2 organs fail after inflammatory cascade

  • Body can’t maintain balance without invasive support

  • Very high mortality

Prevention (Nursing Interventions)

  • 🫁 Respiratory: Avoid barotrauma, low tidal volume

  • ❤ Cardiovascular: Limit unnecessary PRBC transfusion

  • 🧪 Renal: Avoid nephrotoxins, monitor urine

  • 🍽 GI: Stress ulcer prophylaxis, early enteral feeds

  • 🩸 Heme: DVT prophylaxis

  • 🧬 Endocrine: Keep BG <180, steroids if adrenal insufficiency

MODS: Organ-Specific Breakdown

Organ

Pathophysiology

Mnemonic

Respiratory

ARDS: alveolar leak, ground-glass X-ray, barotrauma risk

LUNG = Leaks, V/Q mismatch, Nine rib sign, Ground glass

Cardio

↑ Cap leak, microthrombosis, AV shunting, RV depression

CAP = Capillary leak, AV shunt, Pump depressed

CNS

↓ GCS, cerebral edema, microabscesses, drug effects

CALM = Consciousness ↓, Added edema, Little abscesses, Meds matter

Renal

AKI (30% ICU pts), ischemia, nephrotoxic meds, ↑ abdominal pressure

KID = Kidney injury, Ischemia, Drugs

GI/Liver

Stress ulcers, bacterial translocation, cholestasis, ↓ clotting

GUT = Gut bleed, Unzipped barrier, Too sluggish liver

Heme

Thrombocytopenia, DIC, marrow suppression

LOW PLT

Immune

Opportunistic infections: Staph, Enterococcus, Candida, Pseudomonas

SEe CP

Endocrine

Hyperglycemia, insulin resistance, ADH ↑, adrenal insufficiency

SUGAR

🔹 Quick Algorithms

  1. SIRS?

    • Any 2 of THBW → search for infection/trauma → check lactate & organs

  2. Suspected Shock?

    • SI >0.8 or MAP <65 → assess perfusion

    • Check skin, urine, LOC, lactate

  3. Type Shock

    • Warm & bounding → early distributive

    • Cool & clammy → hypovolemic/cardiogenic

    • Cool + block signs → obstructive

  4. Immediate Nursing Moves

    • O₂

    • IV access

    • Monitor VS

    • Fluids (unless obstructive)

    • Early antibiotics if sepsis

    • Vasopressors if fluids fail