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🌡 SIRS → Shock → MODS Study Guide

🔹 Systemic Inflammatory Response Syndrome (SIRS)

Definition

  • Exaggerated immune response to stressor (infection, trauma, etc.)

  • Goal: Localize and eradicate → but can become systemic

Criteria (Need 2 or more)

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

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

  • HR: >90 bpm

  • Breathing: RR >20 or PaCO₂ <32

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

Key Systems Activated

  • SAM (Sympathetic-Adreno-Medullary) → “Sprinter” = Fast

    • ↑ HR, ↑ contractility, ↑ BP

    • ↑ Glucose & fat breakdown

    • Vasodilation to skeletal muscles

  • HPA Axis (Hypothalamic-Pituitary-Adrenal) → “Hall Pass” = Slower

    • CRH → ACTH → Cortisol

    • Suppresses inflammation & healing

    • ↓ Insulin

  • RAAS (Renin-Angiotensin-Aldosterone-System) → “R-A-A-S”

    • Renin → Angiotensin squeezes vessels

    • Aldosterone holds salt & water

    • Sympathetic & ADH support

🔹 Shock

Definition

  • Inadequate O₂ delivery OR ↑ O₂ demand → cellular hypoxia

  • Can occur with high, normal, or low BP

Phases of Shock

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

  • Pre-shock/Compensated: Tachycardia, vasoconstriction, pressure adjustments

  • Shock/Decompensated: Organs lose perfusion

  • End-organ dysfunction: Irreversible, MODS, death

Bedside Diagnosis

  • MAP <65 → “65 to stay alive”

  • Shock Index (SI) = HR/SBP

    • Normal: 0.5–0.7

    • Danger: >0.8

  • Urine output <0.5 mL/kg/hr

  • Cool skin, delayed cap refill, altered LOC, ↑ lactate

⚡ Types of Shock (with visuals & mnemonics)

Type

Key Findings

Goal

Mnemonic

Hypovolemic

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

Fill tank (fluids, blood)

“Empty tank → Fill & Fix”

Cardiogenic

Cool, mottled, narrow pulse pressure, pulmonary edema

Support pump (O₂, inotropes)

“Bad Pump → Help Pump”

Distributive (Septic/Anaphylactic)

Early warm, bounding pulses, wide PP → later cool, poor perfusion

Fluids + vasopressors + cause control

“Pipes too wide → Fill & Squeeze”

Obstructive

Cool, weak pulses, signs of block (PE, tamponade, tension pneumo)

Remove obstruction

“Blocked Flow → Unblock to Go”

🔹 MODS (Multiple Organ Dysfunction Syndrome)

Definition

  • Failure of ≥2 organs from maladaptive inflammatory response

  • Body can’t maintain homeostasis without invasive support

  • High mortality

Prevention Checklist

  • 🫁 Respiratory: Avoid barotrauma, ARDS prevention

  • ❤ CV: Minimize transfusions, monitor flow

  • 🧪 Renal: Avoid nephrotoxins

  • 🍽 GI: Stress ulcer prophylaxis, early enteral feeds

  • 🩸 Heme: DVT prophylaxis

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

Organ-Specific MODS (Mnemonic-based)

Organ System

Key Patho

Mnemonic

Respiratory

ARDS, alveolar leak, ground glass X-ray, ↓ compliance

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

Cardiovascular

Cap leak, microthrombosis, AV shunts, RV depression

CAP = Capillary leak, AV shunt, Pump depressed

CNS

↓ GCS, cerebral edema, microabscesses, sedative effects

CALM = Consciousness ↓, Added edema, Little abscesses, Med effects

Renal

AKI, ischemia, nephrotoxins, ↑ intra-abd pressure

KID = Kidney injury, Ischemia/pressure, Drugs add risk

GI/Liver

Stress ulcers, translocation, cholestasis, poor clotting

GUT = Gut bleed, Unzipped barrier, Too sluggish liver

Hematologic

Bone marrow suppression, thrombocytopenia, DIC

LOW PLT = Look for platelets dropping

Immunologic

Infections (Staph, Enterococcus, Candida, Pseudomonas)

SEe CP

Endocrine

Hyperglycemia, insulin resistance, ADH ↑, adrenal insufficiency

SUGAR = Sugar ↑, ADH ↑, Glucocort gap

🔹 Quick Algorithms

SIRS? → Any 2 of THBW

  • Search source, labs, lactate, organ function

Suspected Shock?

  • Check SI >0.8

  • MAP <65?

  • Look: skin, urine, mental status, lactate

Type it:

  • Warm, bounding → Early distributive

  • Cool, clammy, narrow PP → Hypovolemic or Cardiogenic

  • Cool + blocked flow signs → Obstructive

Initial Actions (safe for all types):

  • Oxygen

  • IV access

  • Monitoring

  • Fluids (unless obstructive suspected)

  • Early antibiotics if sepsis

  • Vasopressors if hypotension persists

🔹 Mini Practice Prompts

  1. Temp 38.9, HR 110, RR 24, WBC 9k → Meets 2 SIRS criteria → Start sepsis workup

  2. BP 96/58, HR 120 → SI = 1.25 → Shock likely → Begin resuscitation

  3. Warm, flushed, wide PP → Early distributive → Fluids, vasopressors, antibiotics

  4. Cool, mottled, narrow PP, pulmonary edema → Cardiogenic → Cautious fluids, inotropes