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Shock Classification

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In one line

·Shock means blood flow is too weak to feed the body's organs, so waste builds up (lactate rises), the kidneys slow down (less pee), thinking gets fuzzy, skin looks blotchy, and blood pressure drops.

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Normal physiology

·Normal blood flow delivers oxygen and fuel to every organ at exactly the rate each organ needs, and carries away waste. The heart pumps blood forward, blood vessels squeeze or relax to steer flow where it's needed, and there is enough blood volume to fill the system. This balance—blood flow (perfusion) meeting metabolic demand—keeps every organ fed and happy.

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What goes wrong

·Shock happens when one of four things breaks the delivery system: the tank runs dry (not enough blood), the pump fails (heart can't squeeze), the pipes spring open too wide (blood vessels dilate and leak), or a blockage clogs the line. Each break has a different fix, so naming which one matters.

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Hallmark signs

·Fast heart rate (tachycardia)
·Low blood pressure (hypotension)
·Fast breathing (tachypnea)
·Confusion or altered mental status
·Cool, pale, clammy skin or mottled (blotchy) skin
·Slow capillary refill (when you press the skin, color comes back slowly)
·Low urine output (oliguria)
·Weak or thready pulse

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Red flags · escalate now

·Blood pressure stays low (systolic under 90) even after giving fluids
·Confusion, no response, or cannot wake the patient up
·Urine output drops to almost nothing (under 0.5 mL per kg per hour)
·Skin turns mottled (blotchy purple) or stays cold and pale
·Heart rate stays very fast (over 120) or becomes very slow and irregular

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Workup

·Serum lactate
·Arterial or venous blood gas (ABG or VBG)
·Complete blood count (CBC)
·Basic metabolic panel (BMP) or comprehensive metabolic panel (CMP)
·Troponin (high-sensitivity troponin I or T)
·B-type natriuretic peptide (BNP) or N-terminal pro-BNP (NT-proBNP)
·Blood cultures (two sets from different sites)
·12-lead electrocardiogram (ECG)

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Treatment

·Identify the shock type using history, exam, POCUS, and labs
·For bleeding shock: stop the bleeding (surgery, endoscopy, angiography with embolization), give blood products in balanced 1:1:1 ratio (packed red cells : fresh frozen plasma : platelets), and give IV crystalloid (normal saline or lactated Ringer's) cautiously
·For heart-pump-failure shock (cardiogenic): emergency catheterization and stenting (PCI) if it is a heart attack, inotropes (dobutamine at 2.5–20 mcg/kg/min or milrinone), vasopressors (norepinephrine) if pressure is very low, and mechanical support (intra-aortic balloon pump, Impella, VA-ECMO) if drugs are not enough
·For infection shock (septic): give broad-spectrum IV antibiotics within 1 hour of recognizing septic shock (current Surviving Sepsis Campaign guideline), give 30 mL/kg IV crystalloid fluid bolus in the first 3 hours, and start norepinephrine (first-choice vasopressor) to keep mean arterial pressure ≥ 65 mmHg if fluids alone do not work
·For blockage shock (obstructive): drain fluid around the heart (pericardiocentesis with needle and catheter) for cardiac tamponade (the heart squeezed by fluid around it), give clot-busting drugs or suction out clots (catheter-directed thrombolysis or embolectomy) for massive pulmonary embolism (a clot lodging in a lung artery), or place a large-bore needle and chest tube for tension pneumothorax
·Monitor and treat to these targets: lactate dropping toward normal (below 2 mmol/L), mean arterial pressure ≥ 65 mmHg, urine output ≥ 0.5 mL/kg/hr, skin warm with capillary refill under 3 seconds, and mental status clearing

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NCLEX trap

·Fluids help hypovolemic shock (from bleeding or losing too much water) and distributive shock (from infection spreading through the blood, like sepsis). But fluids HURT cardiogenic shock (when the heart is too weak to pump) because you flood a pump that's already failing—like trying to pour more water into an overflowing bathtub. Always figure out the TYPE of shock first using bedside heart ultrasound (POCUS—a quick ultrasound at the bedside that shows how the heart is pumping), listen to the lungs, and check the neck veins. THEN choose fluids, pressors (drugs that squeeze blood vessels to raise pressure), or other fixes. The wrong choice kills fast.
·Low pressure is the RESULT of something broken upstream—an empty tank (bleeding), a broken pump (the heart can't squeeze), blocked pipes (a blood clot in the lungs or fluid squeezing the heart), or wide-open pipes (sepsis makes blood vessels relax too much). Pushing pressure up with drugs BEFORE you fix the real break is like flooring the gas pedal when your engine has no oil—you wreck what's left. Fix the upstream problem FIRST: stop bleeding, support the pump with drugs like dobutamine (helps the heart squeeze harder), drain fluid squeezing the heart, or give antibiotics for sepsis. Add pressors only if pressure stays low AFTER you start the real fix.
·Cold, clammy skin means the body is shunting blood away from the skin to protect the brain and heart—it's an emergency alarm. It happens in hypovolemic shock (give fluids), cardiogenic shock (do NOT give fluids—help the pump instead with an inotrope like dobutamine), and obstructive shock (fix the blockage, like draining fluid around the heart or treating a blood clot in the lungs). Warm skin with low pressure usually means distributive shock like sepsis (give fluids AND antibiotics). Use the whole picture—neck veins (are they flat or full?), lung sounds (wet crackles or clear?), and ultrasound of the heart—to tell them apart before you treat.
·High lactate (above 2 mmol/L) is the body's SOS signal that cells aren't getting enough oxygen because blood flow is broken. Cells switch to backup energy (anaerobic metabolism—making energy without oxygen) and produce lactic acid as waste. The real fix is restore blood flow and oxygen delivery: stop bleeding, support the failing pump with inotropes, treat sepsis with antibiotics and fluids, or relieve a blockage like a pulmonary embolism (a clot lodging in a lung artery) (blood clot in the lung) or cardiac tamponade (the heart squeezed by fluid around it) (fluid squeezing the heart). Sodium bicarbonate does NOT fix the upstream break, does NOT improve survival (per BICAR-ICU and other large trials), and can cause harm (fluid overload, shifting the oxygen-hemoglobin curve so oxygen sticks to red cells instead of unloading into tissues). Lactate drops naturally when you fix blood flow (perfusion)—not when you cover up the number with base.
·Low urine (under 0.5 mL per kilogram per hour) means the kidneys are shutting down because they aren't getting enough blood flow—it's a downstream effect of shock, not the cause. The body sacrifices the kidneys to save the heart and brain. Fluids alone do NOT fix blood flow (perfusion) if the real problem is a broken pump (cardiogenic shock—the heart can't move blood forward, so fluids back up and flood the lungs) or a blockage (obstructive shock—like a blood clot in the lungs or fluid squeezing the heart shut). Fix the TYPE of shock first. Once blood flow is restored, mean arterial pressure (MAP—the average pressure pushing blood through the body) rises above 65 mmHg, and lactate drops, urine output comes back on its own. Forcing fluids into a broken system makes things worse.
·Vital signs are flags, not diagnoses. A pressure of 80/50 and heart rate of 120 are red flags screaming something is broken, but they don't tell you WHY—bleeding (hypovolemic shock), a weak pump (cardiogenic shock), infection (distributive shock from sepsis), or a blockage (obstructive shock like a pulmonary embolism (a clot lodging in a lung artery) or cardiac tamponade (the heart squeezed by fluid around it)). Use vitals PLUS the clinical picture (skin color and temperature, neck veins flat or bulging, lung sounds wet or clear, mental status alert or confused, bedside ultrasound showing the heart and lungs) PLUS history (Did this start after vomiting for days? After chest pain? After a long car ride where a clot could form?) to figure out which ONE part of the circulation broke. Then fix THAT part. The numbers improve when you fix the cause—not the other way around. Chasing numbers without fixing the break is like mopping the floor while the pipe is still leaking.

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