Nursing Field Notes / Cardio · Pathophysiology Course

Shock 📉

The master page — all 5 types, all 4 stages

NG-050 Cardio · Shock ADHD-friendly visual edition

Shock is not a blood pressure number — it is a body-wide failure to deliver oxygen to tissue. Cells starve, switch to anaerobic metabolism, dump lactic acid, and organs begin to die. Every single type of shock is one of three broken things: the PUMP, the TANK, or the PIPES.

📄 Simple Nursing original — opens in Drive →

🫀 Pump · Tank · PipesEvery type of shock is one of those three broken. Name the broken part, you know the treatment.

🪜 4 stages, alwaysInitial → Compensatory → Progressive → Refractory. Catch it in COMPENSATORY — BP is still normal there.

🥶 Cold vs 🔥 WarmCold & clammy = hypovolemic, cardiogenic, late septic. Warm & flushed = early septic, neurogenic, anaphylactic.

🚨 MAP <65 = no perfusionAnd urine <30 mL/hr is the kidney telling you first.

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WHAT IT IS

STEP 1 · THE MACHINE

Blood is a delivery truck for oxygen. Shock is what happens when the deliveries stop — no matter which part of the delivery system broke.

🔧 The whole subject in one picture: PUMP · TANK · PIPES

Perfusion needs three intact parts — a pump that squeezes, enough fluid to squeeze, and pipes with enough tone to hold pressure. Break any one and blood pressure falls, tissue starves, and you have shock.

🧠 “Pump, Tank, Pipes.” Picture a fire truck. Pump broken = cardiogenic. Tank empty = hypovolemic. Hose split wide open = distributive (septic / neurogenic / anaphylactic). A hose kinked shut is the 6th kind — obstructive (tamponade, tension pneumothorax, massive PE).

🔬 Mechanism: no oxygen → acid

🩸 Perfusion drops — oxygen doesn't reach the cell

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⚙️ Cell switches to ANAEROBIC metabolism (metabolism without oxygen)

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🧪 Lactic acid piles up · blood glucose rises

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🫧 Metabolic acidosis — pH ↓, HCO₃⁻ ↓

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💀 Cell death → organ failure → MODS

The number that tracks it: LACTATE. Typical adult reference 0.5–2.2 mmol/L (lab-dependent); >2 = tissue is starving, >4 = severe.

🧠 “No O₂ = acid + sugar.” Anaerobic metabolism burns fuel dirty — it leaves lactic acid behind and pushes blood glucose up. Both appear before the blood pressure ever moves.

🧪 The number that defines perfusion: MAP

MAP = mean arterial pressure — the average pressure actually pushing blood into organs.

MAP = (SBP + 2 × DBP) ÷ 3

Goal in shock: MAP ≥ 65 mmHg. Below that, kidneys and brain stop being perfused.

🧠 “65 keeps you alive.” Diastole gets counted twice in the formula because the heart spends most of its time in diastole — that's why a narrowing pulse pressure is such an early shock clue.

📖 Four words you must be able to define

Word	Plain English	Where it shows up
Preload	How full the heart is before it squeezes — the volume coming back in.	Measured as CVP (typical 2–6 mmHg) or PAWP (typical 6–12 mmHg)
Afterload	How hard the heart must push to open the aortic valve — the resistance out front.	Reflected by SVR (typical 800–1200 dynes·sec/cm⁻⁵)
Cardiac output	HR × stroke volume — liters pumped per minute.	Typical adult 4–8 L/min
SVR	Systemic vascular resistance = pipe tone. Squeeze = high, dilate = low.	Low SVR is the whole problem in distributive shock

Ranges are standard adult values and vary slightly by textbook and monitoring system.

🧠 Preload = the LOAD going IN. Afterload = what comes AFTER the squeeze. Preload is a fullness problem; afterload is a tightness problem.

🗂️

5 TYPES OF SHOCK

STEP 2 · NAME IT

Each type has a fingerprint: what the preload does, what the output does, what the pipes do — and whether the skin is hot or cold.

⭐ The 5 types & what causes each

Type	Classic cause	Broken part
1. Septic 🦠	Widespread bloodborne infection — pneumonia, UTI/pyelonephritis, wound, line infection. Sepsis → septic shock.	PIPES
2. Neurogenic 🦴	Spinal cord injury at T6 or higher — sympathetic outflow is cut, so vessels lose all tone. Also spinal anesthesia.	PIPES
3. Hypovolemic 🩸 (hemorrhagic)	Blood or fluid loss — trauma, gunshot wound, surgery, GI bleed, burns, severe vomiting/diarrhea, DKA.	TANK
4. Cardiogenic 🫀	The heart fails to pump — MI (heart muscle dies), heart failure exacerbation, lethal dysrhythmia, valve or papillary muscle rupture.	PUMP
5. Anaphylactic 🐝	Severe allergic reaction — bee sting, peanut, shellfish, latex, penicillin, contrast dye.	PIPES
(6.) Obstructive ⛓️	Not on every list, but tested: cardiac tamponade, tension pneumothorax, massive PE — the pump is fine but something blocks filling or outflow.	KINKED HOSE

🧠 “SNAP-C” — Septic · Neurogenic · Anaphylactic · Plasma/blood loss (hypovolemic) · Cardiogenic. The first three (S-N-A) are all distributive — all three are pipe problems.

⭐ The hemodynamic fingerprint — memorize this grid

Type	Preload (CVP/PAWP)	CO	SVR	Skin
Hypovolemic	↓↓	↓	↑	Cold, clammy, pale
Cardiogenic	↑↑	↓↓	↑	Cold, clammy, mottled
Septic — warm / early	↓	↑	↓↓	WARM, flushed, dry
Septic — cold / late	↓	↓	↑	Cold, clammy, mottled
Neurogenic	↓	↓	↓↓	WARM, dry, pink + BRADYcardia
Anaphylactic	↓	↓	↓↓	WARM, flushed + hives / swelling

Only ONE type has a HIGH preload: cardiogenic. Only one type has a slow heart rate: neurogenic. Those two facts answer a huge number of questions.

🧠 “Cardiogenic is the full one. Neurogenic is the slow one.” Everything else is empty-and-fast.

🥶 Cold shock vs 🔥 warm shock — the skin tells you the type

Why septic shock changes sides: early, cytokines dilate every vessel and the heart speeds up to compensate → high output, warm skin. Later, capillaries leak the volume away and the heart tires → output falls, catecholamines and acidosis clamp the periphery → the same patient turns cold and mottled. Warm turning cold = septic shock is getting worse, not better.

🧠 “Sepsis starts a party, then turns off the lights.” Warm, flushed, bounding = the party (compensatory). Cold, mottled, thready = the lights went out (progressive).

🚨 Signs & symptoms common to ALL shock

📉 Severely low blood pressure — but this comes late
💓 Tachycardia — earliest vital sign change (except neurogenic)
🌬️ Tachypnea — blowing off CO₂ to fight acidosis
🧠 Mental status change — restless/anxious → confused → lethargic → unresponsive
🚽 Urine output < 30 mL/hr
🫱 Delayed capillary refill > 3 sec, weak thready peripheral pulses
🧪 Rising lactate, metabolic acidosis, rising BUN/creatinine

🧠 The brain and the bladder complain first. A newly restless, anxious patient whose urine bag has stopped filling is in shock until proven otherwise — no matter what the cuff says.

⚠️ Neurogenic is the odd one out

Spinal cord injury at T6 or higher severs sympathetic outflow. Nothing tells the vessels to squeeze and nothing tells the heart to speed up.

🐢 BRADYcardia — the only shock with a SLOW heart rate
🌡️ Warm, dry, pink skin below the injury
🥶 Poikilothermia — can't regulate temperature
📉 Hypotension with a wide pulse pressure

🧠 “Neuro = No signal = slow & warm.” If the stem says hypotension + bradycardia + warm dry skin after a cervical or high-thoracic injury, stop looking — it's neurogenic.

🪜

THE 4 STAGES

STEP 3 · STAGE IT

Same four stages for every type of shock. The one that matters is stage II — because the blood pressure is still normal there.

🪜 The 4 stages of shock — identical on every shock page

Stage	What's happening	What you see
I · INITIAL	Cardiac output falls just enough that cells switch to anaerobic metabolism → lactic acid builds, blood glucose rises.	Nothing. Signs & symptoms are ABSENT in this stage — only a rising lactate gives it away.
II · COMPENSATORY	The sympathetic nervous system and renin–angiotensin–aldosterone rescue the pressure: catecholamines, vasoconstriction, ADH and aldosterone hold on to salt and water.	Tachycardia · tachypnea · restless & anxious · cold clammy skin · narrowing pulse pressure · urine < 30 mL/hr. BP is still near normal.
III · PROGRESSIVE	Compensation fails. Capillaries leak, acidosis deepens, organs begin to die.	BP drops (MAP < 65) · confusion → lethargy · cold mottled skin · weak thready pulse · crackles · oliguria → anuria · rising BUN/creatinine.
IV · REFRACTORY (also called irreversible)	MODS — multiple organ dysfunction syndrome. The body no longer responds to fluids or vasopressors.	Unresponsive · profound hypotension · anuria · DIC · death is imminent.

🧠 “I Can't Perfuse Right” — Initial · Compensatory · Progressive · Refractory. The stage you must catch is COMPENSATORY: the cuff still looks fine, so your clues are heart rate, respiratory rate, mental status and urine output.

📈 Stage progression — general shock

🧠 Stage II is the whole exam. Test writers put a normal blood pressure in the stem on purpose. If HR and RR are up and the patient is suddenly anxious — that's compensatory shock, and it's the answer.

📈 What the vital signs do across the stages

🧠 The two lines cross. HR climbs long before BP falls — and in refractory shock the HR finally collapses too. A falling heart rate in late shock is not improvement.

✅ Nursing catches shock with 4 free assessments

🧠 Mental status — new restlessness or anxiety is the earliest sign of hypoxia

💓 HR & RR — both climb before the BP moves

🚽 Urine output — < 30 mL/hr for 2 hours = report it

🫱 Skin & cap refill — cool, clammy, mottled, > 3 sec

🧠 “BRUS” — Brain (mental status) · Rate (HR/RR) · Urine · Skin. Four things you can check at the bedside with no equipment, and all four turn abnormal before the blood pressure does.

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CARE

STEP 4 · FIX THE BROKEN PART

Oxygen and fluid for almost everyone — then a treatment aimed at whichever part is broken.

✅ Priority order that works for every shock

Airway & oxygen — high-flow O₂; intubate if the patient can't protect the airway

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Position — supine with legs elevated ~20–30° (modified Trendelenburg). Full Trendelenburg is NOT recommended — it crowds the diaphragm and raises ICP.

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Large-bore IV access ×2 — 18-gauge or larger; isotonic crystalloid (0.9% NS or LR), warmed

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Vasopressors — only after the tank is filled (see NG-053)

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Treat the cause — blood, antibiotics, epinephrine, revascularization, chest tube

Fluid comes before pressors because squeezing an empty tank raises the number on the monitor while making tissue perfusion worse. The exception is cardiogenic shock — that tank is already too full.

🧠 “Fill before you squeeze.” Toothpaste tube with nothing in it: squeezing harder doesn't get you toothpaste, it just splits the tube.

💊 Which treatment goes with which type

Type	First move	Key drug
Hypovolemic	STOP the loss + isotonic crystalloid, then blood products if hemorrhagic	Volume — not a pressor
Cardiogenic	Help the pump: inotrope + reduce workload; revascularize the MI (PCI)	Dobutamine (inotrope); norepinephrine if hypotensive
Septic	Cultures → broad-spectrum antibiotics within 1 hour + 30 mL/kg crystalloid	Norepinephrine — first-line pressor
Anaphylactic	Epinephrine IM immediately — anterolateral thigh; remove the trigger; airway	Epinephrine, then antihistamines & corticosteroids
Neurogenic	Immobilize the spine, fluids, and treat the bradycardia	Atropine for bradycardia; vasopressor for tone

🧠 Match the fix to the broken part. Empty tank → fill it. Broken pump → don't flood it. Wide pipes → squeeze them and kill what widened them.

🧪 Labs & monitoring that track shock

🧪 Lactate — the single best marker; recheck to prove your treatment worked
🫧 ABG — metabolic acidosis: pH ↓, HCO₃⁻ < 22 mEq/L
🩸 CBC — Hgb/Hct, WBC (high or low in sepsis)
🧫 Blood cultures ×2 — draw BEFORE the first antibiotic dose
🫘 BUN / creatinine — rising = the kidney is being starved
❤️ Troponin, 12-lead ECG, BNP if cardiogenic suspected
📟 Continuous — arterial line BP, ECG, SpO₂, hourly urine, CVP

🧠 “Cultures before drugs.” Once the antibiotic is in, the culture may never grow the organism — and then nobody can narrow the therapy.

❌ Never in shock

Never give hypotonic fluid (½ NS, D5W) to resuscitate — it leaves the vessels
Never flood the cardiogenic patient with fluid boluses — the pump is already overloaded
Never start a vasopressor into an empty tank — fill first, unless the tank is the problem's opposite
Never trust a normal BP to rule out shock — stage II hides behind it
Never delay antibiotics in septic shock waiting on results

🧠 The four “nevers” are four exam distractors. Each one sounds reasonable on the surface — that's exactly why they're wrong answers.

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QUICK RECALL

SAY IT OUT LOUD

🫀 Pump · Tank · PipesCardiogenic · Hypovolemic · Septic/Neurogenic/Anaphylactic

🪜 I·C·P·RInitial → Compensatory → Progressive → Refractory

📈 Only cardiogenichas a HIGH preload. Only neurogenic is BRADYcardic.

💧 Fill before you squeezeFluids first, vasopressors second — except cardiogenic.

🎯 Cover & check — 6 rapid-fire questions

Q1: Name the 4 stages in order.

Initial → Compensatory → Progressive → Refractory (irreversible). Signs are ABSENT in initial; BP is still normal in compensatory.

Q2: Which type of shock has an INCREASED preload?

Cardiogenic — the pump can't move the blood forward, so it backs up (high CVP/PAWP, JVD, crackles). Every other type has a LOW preload.

Q3: The patient is hypotensive with warm, dry, pink skin and a heart rate of 48 after a T4 spinal injury. Type?

Neurogenic shock — the only shock with bradycardia. Sympathetic outflow at T6 or higher is lost, so vessels dilate and the heart never speeds up.

Q4: Why is early septic shock warm and late septic shock cold?

Early: cytokines cause massive vasodilation (SVR ↓) and the heart compensates with a HIGH cardiac output → warm, flushed, bounding pulses, wide pulse pressure. Late: capillary leak drains the intravascular volume and myocardial depression drops the output, while catecholamines and acidosis clamp the periphery → cold, clammy, mottled, narrow pulse pressure. Warm turning cold means it is getting WORSE.

Q5: BP 118/76, HR 122, RR 28, restless, urine 20 mL/hr. Stage?

Compensatory (stage II). The normal BP is the trap — SNS and RAAS are still holding it up. Act now.

Q6: Why must fluids come before vasopressors?

A vasopressor squeezes the vessels. Squeezing an empty circulation raises the displayed blood pressure while shunting blood away from tissue — perfusion gets worse and extremities/gut become ischemic. Fill the tank, then add tone. (Cardiogenic shock is the exception: that tank is already overfull.)