🫀 Physiological Adaptation · Lesson 8 of 10 · 7 min

Four Kinds of Shock and the First Hour of Sepsis

🩸 Hypovolemic shock wants fluid. Cardiogenic shock drowns in it. Both have low blood pressure. The exam asks which bag you hang, and the wrong answer is a very plausible one.

💡 Key idea

Compensation hides shock behind a normal blood pressure: watch heart rate, pulse pressure, skin and urine. Fluids for hypovolemic and septic; not for cardiogenic, except right ventricular infarction, which needs fluids for preload and no nitrates; obstructive needs the block relieved. Neurogenic shock is the slow, warm one.

🧠 Why it matters

Shock is inadequate tissue perfusion. COMPENSATORY stage: tachycardia, narrowing pulse pressure, cool clammy skin, anxiety, decreased urine output; the blood pressure can still look normal. PROGRESSIVE and REFRACTORY stages: hypotension (MAP below 65), confusion, oliguria, metabolic acidosis with rising lactate, and organ failure. HYPOVOLEMIC (hemorrhage, burns, dehydration): isotonic fluids and blood, stop the loss. CARDIOGENIC (massive MI, heart failure): the pump fails, so fluids worsen pulmonary congestion; inotropes, diuretics and sometimes mechanical support, except in right ventricular infarction, where the failing right ventricle needs preload: cautious fluid boluses and no nitrates or diuretics. OBSTRUCTIVE (tension pneumothorax, cardiac tamponade, massive pulmonary embolism): a physical block to filling or outflow drops cardiac output, often with distended neck veins; relieve the block with needle decompression or a chest tube, pericardiocentesis, or thrombolysis or embolectomy, because fluids alone will not fix it. DISTRIBUTIVE shock has three types. SEPTIC: sepsis is organ dysfunction caused by a dysregulated response to infection; septic shock is sepsis that needs vasopressors to keep MAP 65 or higher and has a lactate above 2 despite adequate fluids; the first hour bundle is lactate measurement (remeasure if above 2), blood cultures drawn before antibiotics, broad-spectrum antibiotics within one hour, rapid 30 mL/kg of crystalloid for hypotension or a lactate of 4 or more, and vasopressors (norepinephrine first), started during or after fluids, to keep MAP 65 or higher. ANAPHYLACTIC: intramuscular epinephrine first, then fluids and airway support. NEUROGENIC (spinal cord injury at or above T6): the classic shock with BRADYCARDIA and warm dry skin, from lost sympathetic tone; treat with fluids, vasopressors and atropine. Universal nursing care: oxygen, two large-bore IVs, hourly urine output of at least 0.5 mL/kg/hr (about 30 mL/hr in adults), continuous monitoring, and keeping the client warm.

🏥 In the real world

🧊 A client bleeding after surgery has a blood pressure of 118/88 and a heart rate of 126, with cool skin and 15 mL of urine in the last hour. A new nurse reads the pressure as fine. The experienced nurse reads a pulse pressure of 30, tachycardia and oliguria as compensated hemorrhagic shock, and the client goes back to the operating room before the pressure ever falls. The blood pressure is the last number to move.

📌 Takeaways

Early shock: tachycardia, narrow pulse pressure, cool skin, low urine, normal BP
Sepsis hour one: cultures, antibiotics, 30 mL/kg fluids, lactate, norepinephrine if MAP under 65
Cardiogenic shock gets inotropes and diuretics, not fluid boluses; obstructive needs the block relieved; neurogenic is bradycardic

📖 Terms in this lesson

Cardiogenic shock: Shock caused by a failing heart pump, treated with inotropes rather than large fluid boluses.

Septic shock: Sepsis needing vasopressors to keep MAP at 65 mmHg or more, with lactate above 2 mmol/L despite fluids; hour one: lactate, cultures, antibiotics, 30 mL/kg crystalloid and vasopressors.

Minimum urine output: Adults should make at least 30 mL/hr (0.5 mL/kg/hr) and children at least 1 mL/kg/hr; less for two hours means poor kidney perfusion, as in shock, dehydration or magnesium toxicity, and is reported before the creatinine rises.

Epinephrine: The first drug for anaphylaxis, 0.3 to 0.5 mg IM (1 mg/mL) into the outer thigh, and 1 mg IV every 3 to 5 minutes in cardiac arrest; expect tachycardia and hypertension, and check the concentration twice because the two strengths differ tenfold.

✅ Test yourself

Which client findings indicate the compensatory stage of hypovolemic shock?

Blood pressure 80/40, heart rate 140, confusion and no urine output
Heart rate 124, blood pressure 112/88, cool skin, urine 20 mL/hr
Heart rate 56, warm dry skin, blood pressure 90/60
Fever, flushed skin, bounding pulses, heart rate 110, blood pressure 96/50

Answer: B · Heart rate 124, blood pressure 112/88, cool skin, urine 20 mL/hr

Tachycardia, narrowed pulse pressure, cool skin and reduced urine output with a near-normal pressure are compensation; the first set is late shock, the third is neurogenic, and the fourth, with fever, flushed skin and bounding pulses, is early warm septic shock.

A client with septic shock has a MAP of 58 after receiving 30 mL/kg of crystalloid. Which intervention does the nurse anticipate next?

Oral antibiotics once cultures return
Diuretics to prevent fluid overload
A norepinephrine infusion
Another 30 mL/kg crystalloid bolus

Answer: C · A norepinephrine infusion

Persistent hypotension after adequate fluids calls for vasopressors, with norepinephrine as the first choice.

Why are large fluid boluses avoided in cardiogenic shock?

Extra volume worsens pulmonary edema
The client is not hypotensive
Fluids cause hyperkalemia
Fluids interfere with inotropic medications

Answer: A · Extra volume worsens pulmonary edema

In cardiogenic shock the problem is the pump, not volume; added fluid backs up into the lungs.

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