Nursing Field Notes / Cardio · Pathophysiology Course

Hypovolemic Shock 🩸

The TANK is empty — hemorrhagic & non-hemorrhagic

NG-184 Cardio · Shock ADHD-friendly visual edition

Volume is gone. Blood loss from trauma, a gunshot wound, surgery — or fluid loss from burns, vomiting, diarrhea, or DKA. Less volume in → less preload → less cardiac output → tissue starves. The fix is not a drug. The fix is volume, and stopping the leak.

📄 Simple Nursing original — opens in Drive →

🪣 Empty tankPreload ↓↓ · CO ↓ · SVR ↑ · skin COLD, clammy, pale.

💓 Fast & narrowTachycardia + narrowing pulse pressure is the earliest measurable change.

🩸 Hgb can look NORMALIn acute hemorrhage you lose whole blood. H&H falls later, after fluids dilute it.

🚰 Stop the leak, fill the tankTwo large-bore IVs ≥18 g · warmed isotonic fluid · then blood.

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CAUSE

STEP 1 · WHERE IT WENT

Volume either left the body, or left the bloodstream and stayed inside the body. Both empty the tank.

🪣 The tank, and the two ways it empties

A swollen, edematous patient can still be in hypovolemic shock. The edema is the missing volume — it's just in the wrong compartment.

🧠 “Out of the body, or out of the vessel.” Bleeding puts the volume on the floor. Burns and third spacing put it in the tissue. Either way the pump has nothing to pump.

🩸 Hemorrhagic — the classic cause

🚗 Trauma — MVC, crush, long-bone or pelvic fracture
🔫 Gunshot / stab wound
🔪 Surgery — intra-op and post-op bleeding
🫃 GI bleed — varices, ulcer (watch for melena, hematemesis)
💥 Ruptured AAA or ruptured ectopic pregnancy
🤱 Postpartum hemorrhage — boggy uterus

Hidden bleeds you can't see: chest, abdomen, retroperitoneum, pelvis, thigh. A femur fracture can hide over a liter.

🧠 “Blood on the floor + four more.” The four hidden places blood goes: chest, abdomen, pelvis/retroperitoneum, long-bone thigh. Don't rule out hemorrhage just because the dressing is dry.

🔥 Burns — the biggest non-bleeding cause

Burned capillaries leak plasma into tissue for the first 24–48 hours. The patient swells while the circulation empties.

Parkland (consensus) formula: 4 mL × kg × %TBSA of lactated Ringer's in the first 24 hours — half in the first 8 hours from the TIME OF THE BURN, the rest over the next 16.

Titrate to urine output, the real endpoint: ≈ 0.5 mL/kg/hr in adults (higher in children and electrical burns).

🧠 “4 · kg · TBSA — half in 8.” The clock starts when the burn happened, not when the patient arrived. If they got there 2 hours late, that first half must go in over the remaining 6.

🔎

CLUES

STEP 2 · SPOT IT EARLY

Cold, fast, dry, and not making urine — with a blood pressure that lies to you until it's late.

⭐ How much blood is gone? The 4 classes of hemorrhage

Class	Loss	HR	BP	Urine	Mental status
I	<15% (<750 mL)	<100	Normal	>30 mL/hr	Slightly anxious
II	15–30% (750–1500 mL)	100–120	Normal — but pulse pressure NARROWS	20–30 mL/hr	Mildly anxious
III	30–40% (1500–2000 mL)	120–140	FALLS	5–15 mL/hr	Confused
IV	>40% (>2000 mL)	>140	Profoundly low	Negligible	Lethargic → unresponsive

Adult circulating volume is roughly 5 L (≈70 mL/kg). The blood pressure does not fall until Class III — about 1.5 liters gone.

🧠 “Tennis, football, both.” Class II ≈ 15–30 %, Class III ≈ 30–40 %, Class IV > 40 %. Anchor on the one that matters: a normal BP still allows a 1500 mL loss.

🚨 Signs & symptoms — cold shock

💓 Tachycardia — first, and often the only early change
🤏 Narrowing pulse pressure (diastolic rises as vessels clamp)
🥶 Cold, clammy, pale/mottled skin; cap refill >3 sec
🫱 Weak, thready peripheral pulses
🫁 Tachypnea, then air hunger
😰 Restless, anxious → confused → lethargic
👅 Thirst, dry mucous membranes, poor skin turgor
🚽 Urine <30 mL/hr, dark and concentrated
🫗 Flat neck veins, low CVP
🧍 Orthostatic hypotension — SBP drop ≥20 mmHg or DBP drop ≥10 mmHg on standing

🧠 “FLAT and FAST.” Flat neck veins, flat CVP, flat urine bag — with a fast, thready pulse. That combination is only hypovolemia. (Cardiogenic shock gives you the opposite neck: distended.)

🧪 Labs — and the trap inside them

🩸 Hgb & Hct — may be NORMAL in the first hours of acute hemorrhage
🧪 Lactate >2 mmol/L = tissue starving; >4 = severe
🫧 ABG — metabolic acidosis, base deficit
🫘 BUN:creatinine >20:1 = prerenal (dehydration) pattern
💧 Urine specific gravity >1.030 (normal 1.005–1.030), urine sodium low
🧂 Serum osmolality & sodium ↑ in pure water/fluid loss

🧠 “You can bleed to death with a normal H&H.” Treat the patient's vital signs and skin, not the hemoglobin. The number catches up hours later.

📊 Where hypovolemic sits among the shocks

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

🧠 Hypovolemic and cardiogenic look identical at the skin — both cold, clammy, thready. The neck veins separate them: flat = empty tank, distended = broken pump.

🪜

THE 4 STAGES

STEP 3 · STAGE IT

Same four stages as every shock — here they are with the bleeding patient's own findings written in.

🪜 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 — hypovolemic findings on each stage

🧠 “15 · 30 · 40.” Under 15 % nothing shows. At 30 % the heart is racing but the cuff still lies. Past 30 % the pressure finally drops — and you are already behind.

🩺

CARE

STEP 4 · PLUG IT & FILL IT

Two jobs, in this order: stop the loss, then replace the loss. Everything else is support.

✅ Priority order

Stop the loss — direct pressure, tourniquet, uterine massage, endoscopy, OR. You cannot out-transfuse an open artery.

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Oxygen — high-flow; the remaining red cells must carry more

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Two large-bore IVs ≥18 gauge (or an intraosseous line) — short and fat beats long and thin

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Warmed isotonic crystalloid — 0.9% NS or lactated Ringer's

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Blood products for hemorrhage — PRBCs; massive transfusion protocol gives PRBC : FFP : platelets ≈ 1:1:1

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Position & warm — supine, legs elevated ~20–30°, blankets and fluid warmer

Vasopressors are NOT the treatment for hypovolemic shock. Squeezing an empty tank raises the monitor number and starves the tissue further. Use them only as a short bridge while volume is running.

🧠 “Plug it, fill it, warm it.” Three verbs in order. The exam almost always wants control the bleeding or start the fluids before any drug.

💧 Which fluid — and why not the others

Use	Why
0.9% Normal Saline ✅	Isotonic — stays in the vessel. Large volumes can cause hyperchloremic metabolic acidosis.
Lactated Ringer's ✅	Isotonic, more physiologic. Contains potassium and lactate — caution in renal failure and liver failure.
PRBCs / whole blood ✅	The only fluid that also carries oxygen. Required for real hemorrhage.
D5W, 0.45% NS ❌	Hypotonic — leaves the vessel and swells cells. Never a resuscitation fluid.

🧠 “Isotonic stays.” If the tank is empty you need fluid that stays in the pipes. Anything hypotonic wanders off into the cells and makes things worse.

🚨 Transfusion & the lethal triad

🌡️ Warm every fluid and blood unit — cold blood causes hypothermia and arrhythmia
🧊 The lethal triad: hypothermia + acidosis + coagulopathy — each one worsens the other two
🧪 Massive transfusion watch: low calcium (citrate binds it), high potassium, low platelets, dilutional coagulopathy
💉 Tranexamic acid (TXA) in trauma is given within 3 hours of injury
👀 Stay with the patient for the first 15 minutes of a blood transfusion — reactions happen early

🧠 “Cold, sour, leaky.” Hypothermia (cold) + acidosis (sour) + coagulopathy (leaky) = the triad that kills trauma patients even after the bleeding stops.

📈 How you know it's working

🚽Urine ≥ 30 mL/hrthe best bedside endpoint

🎯MAP ≥ 65perfusion restored

💓HR fallingless SNS drive needed

🫱Warm, dry skincap refill < 3 sec

🧠Alert & orientedbrain is perfused

🧪Lactate clearingrecheck it

Over-resuscitation is real: new crackles, JVD, rising CVP, dropping SpO₂ and frothy sputum mean you've pushed past the target into fluid volume overload. Slow the rate and tell the provider.

🧠 The urine bag is the cheapest hemodynamic monitor in the room. Kidneys are the first organ sacrificed and the first to recover — watch that bag hourly.

❌ Never

Never give hypotonic fluid to resuscitate
Never lead with a vasopressor before volume
Never use full Trendelenburg — legs up ~20–30° only
Never wait on a hemoglobin to decide someone is bleeding
Never infuse cold blood fast without a warmer

🧠 Each “never” here is a classic distractor. If an option delays volume or delays stopping the bleed, it's wrong.

⚡

QUICK RECALL

SAY IT OUT LOUD

🪣 Empty tankPreload ↓↓ · CO ↓ · SVR ↑ · cold, clammy, pale · flat neck veins

🤏 Narrow pulse pressureThe earliest BP change — long before the systolic drops

🩸 30% before BP fallsClass III (1500 mL) is when the systolic finally moves

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

🎯 Cover & check — 6 rapid-fire questions

Q1: Trauma patient, BP 116/92, HR 118, RR 26, cool clammy skin, urine 20 mL/hr. What stage and what class?

Compensatory (stage II), roughly Class II hemorrhage (15–30 %, 750–1500 mL). Note the narrowed pulse pressure — the diastolic climbed because the vessels are clamped down. Act now; do not wait for the systolic to fall.

Q2: Why can the hemoglobin be normal in an actively hemorrhaging patient?

Whole blood loss removes red cells and plasma in the same proportion, so the concentration (the ratio) is unchanged. Hgb/Hct fall later, once crystalloid or the body's own fluid shift dilutes what's left.

Q3: Flat neck veins vs distended neck veins — which shock is which?

Flat = hypovolemic (empty tank, low preload/CVP). Distended = cardiogenic or obstructive (blood backing up behind a failing or blocked pump).

Q4: What size IV, how many, and what fluid?

Two IVs, 18-gauge or larger (short and wide-bore), warmed isotonic crystalloid — 0.9 % NS or lactated Ringer's — then blood products for hemorrhage.

Q5: Burn patient — what formula and what's the timing catch?

Parkland/consensus: 4 mL × kg × %TBSA of lactated Ringer's over 24 hours, with half given in the first 8 hours measured from the TIME OF THE BURN — not from arrival. Titrate to urine output (about 0.5 mL/kg/hr in adults).

Q6: Why not just start norepinephrine?

Because the problem is missing volume, not missing vessel tone. Vasoconstricting an empty circulation raises the displayed BP while worsening tissue perfusion and risking limb and gut ischemia. Fill the tank; pressors are only a short bridge.