Shock Recognition & Treatment — Lesson 5

Overview

Learning Objectives

Explain what shock is, and what goes wrong in the body when tissues don't get enough blood flow
Name the four types of shock: hypovolemic, distributive, obstructive, and cardiogenic
Spot the early and late signs of shock in a patient in the backcountry
Treat shock with what you have in the field
Decide how urgently a shock patient needs to get out

Shock is the body failing to get enough oxygen to its organs and tissues. It's common after trauma, and it gets missed a lot, because early shock looks like a pale, anxious person having a bad day, which on a hard trip describes half the group. When it's missed, treatment starts late, and late treatment is how shock kills people.

The early signs are quiet and easy to wave off. You want to spot them before the blood pressure falls, because by then you're behind.

Left alone, it only gets worse. A patient in compensated shock can look fairly well, then slide fast into decompensated shock and death if nobody treats them. Catch it early and treat it early.

What is Shock?

Definition and pathophysiology

Shock is inadequate tissue perfusion. Not enough blood reaches the tissues, cells run short on oxygen, and they can't keep up with their own metabolic demands.

Getting oxygen to the tissues comes down to one equation, the oxygen delivery relationship:

Oxygen Delivery (DO₂) = Cardiac Output (CO) × Arterial Oxygen Content (CaO₂)

In plain terms, getting oxygen to the tissues takes two things:

Enough cardiac output (heart rate × stroke volume)
Enough oxygen in the blood (hemoglobin and oxygen saturation)

Why cells need oxygen

Cells use oxygen to make ATP, the energy that runs everything they do. Cut the oxygen and they switch to anaerobic metabolism. That produces lactate, and it sets off a chain:

Lactic acidosis
Less ATP
Cells stop working, then die
Organ systems fail

How the body compensates

When perfusion first drops, the body pushes back:

Faster heart rate (tachycardia). The sympathetic nervous system speeds up the heart to hold cardiac output steady while each beat moves less blood, as it does after blood loss.

Vasoconstriction. Peripheral vessels clamp down to hold central perfusion pressure and send blood to the brain and heart.

Faster breathing (tachypnea). Breathing speeds up to pull in as much oxygen as it can.

Compensated vs. decompensated shock

Compensated shock: The compensation is working. Blood pressure is normal, but you can see the sympathetic system straining: anxiety, a fast pulse, fast breathing. Treat it here and the patient usually survives.

Decompensated shock: The compensation has failed. Blood pressure drops, mental status changes, and organs start to fail. This is a life threat.

Think of an engine pumping a hose line off a tank that's slowly draining. The operator keeps throttling up, so the pressure gauge holds steady right up until the tank's nearly dry, and then it drops fast. In shock, blood pressure is the gauge and heart rate is the throttle.

Watch the pulse, not the cuff. Low blood pressure is a late sign of shock. A normal reading doesn't rule shock out. Look for a fast heart rate and the other early signs.

Types of Shock

Shock is sorted by what's causing it. Knowing the type tells you what to go after.

Type	Cause	Example Scenario	Key Field Signs	Field Treatment Priority
Hypovolemic	Lost blood or body fluids	Bleeding, severe dehydration, burns	Fast pulse, pale skin, weak pulse, low BP (late)	Stop the bleeding, position, keep warm, evacuate
Distributive	Vessels dilate hard and lose their tone	Sepsis, anaphylaxis, neurogenic (spinal injury)	Fast pulse, flushed or blotchy skin, wide pulse pressure (early)	Treat the cause (help the patient use their own epinephrine auto-injector for anaphylaxis; spinal motion restriction for neurogenic), keep warm, evacuate
Obstructive	Something physically blocks blood flow	Tension pneumothorax, cardiac tamponade, massive PE	Fast pulse, bulging neck veins (JVD), muffled heart sounds, trouble breathing	Recognize the pattern, position of comfort, emergent evacuation. The fix happens in a hospital.
Cardiogenic	The heart fails as a pump	Heart attack (MI), severe arrhythmia	Fast pulse, fluid in the lungs (pulmonary edema), pale, weak pulse	Sit them upright if conscious, oxygen if you have it, emergent evacuation

Hypovolemic shock (the most common in the wilderness)

The body has lost volume: blood from a bleed, or other fluids from dehydration or severe burns. Treatment is to stop the bleeding, give oral fluids when it's safe, keep them flat on their back (supine) and warm, and get them out.

Distributive shock

Septic shock: A severe infection makes the vessels dilate and leak. In the wilderness it usually builds over hours, for example from an infected wound. Keep an eye on the wound everyone agreed looked fine on day two.

Anaphylactic shock: An allergic reaction releases histamine fast, and the vessels dilate hard. It needs epinephrine immediately.

Neurogenic shock: A spinal cord injury cuts the sympathetic signals that keep the vessels toned. The vessels go slack and the heart slows, so the tell is an unusual pairing, low blood pressure with a slow heart rate. It can last days to weeks. In the field, keep them flat, keep up spinal motion restriction, work hard to prevent heat loss, and evacuate.

Obstructive shock

Something physically blocks blood getting back to the heart or out of it. Think tension pneumothorax (a collapsed lung compressing the heart), cardiac tamponade (fluid around the heart), or a massive pulmonary embolism. Out here, you recognize the pattern, put them in a position of comfort, and make it an emergent evacuation. The fix happens in a hospital.

Cardiogenic shock

The heart itself fails as a pump, from a heart attack (MI) or a severe arrhythmia. It's less common in the wilderness, but you still need to recognize it. Your treatment is positioning and an emergent evacuation.

Recognizing Shock

Early (compensated) signs

They're subtle. Look for:

Fast heart rate (tachycardia): over 100 a minute at rest. It's the earliest sign you can measure.
Fast breathing (tachypnea): over 20 breaths a minute is fast and worth watching. Under 10 or over 30 is a red flag.
Anxiety and restlessness: they feel ill and scared
Pale or cool skin: from vasoconstriction. Check the core, not just the hands.
Weak pulse: less force under your fingers

Late (decompensated) signs

These mean compensation is failing and the slide toward irreversible shock has started:

Slow heart rate (bradycardia): the heart itself is failing
Low blood pressure (hypotension): systolic under 90 mmHg
Altered mental status: confusion, lethargy, loss of consciousness
Mottled skin: blotchy and bluish (cyanotic)
Cold extremities: severe peripheral vasoconstriction
Weak or absent pulse: even the central pulse is hard to feel

Vital sign thresholds

Finding	Concerning Value	Interpretation
Systolic BP	<90 mmHg	Decompensated shock (treat immediately)
Heart Rate	>100 bpm at rest	Early shock, compensating
Respiratory Rate	>20 breaths/min	Compensating for metabolic acidosis
Mental Status	Altered, confused	Not enough blood reaching the brain (emergent)

Field Treatment of Shock

Position: flat on the back (supine)

Lay the patient flat on their back. The standard for shock is four things: flat, prevent heat loss, treat the cause, evacuate. Raising the legs isn't a routine step. If there's no sign of trauma (fainting, dehydration, sepsis), you can raise the feet 6 to 12 inches (15 to 30 cm) while you wait for help, as long as it doesn't cause pain. With any trauma, keep them flat.

Flat keeps the heart and brain level, which helps blood reach the brain
Don't move a patient with a suspected spine, pelvis, or leg injury just to reposition them
Flat makes it easier to watch them and reassess

Exceptions. Someone who's struggling to breathe may need the head and torso raised a little. A conscious patient who's vomiting, or about to, may need the recovery position on their side. So does an unresponsive patient who's breathing, to keep the airway open. Airway and comfort come first.

Keep them warm

Stop the heat loss:

Get insulation under them first: a sleeping pad, a pack, spare clothing. The ground pulls heat out faster than the air does.
Get wet clothing off
Cover them with blankets or insulation
Don't let them get cold. Hypothermia makes shock worse.

Cold makes it worse. Hypothermia causes vasoconstriction and shunts blood away from the skin, which makes shock worse. Shock and hypothermia together push the death rate sharply higher.

Treat the cause

Go after whatever's driving it:

Bleeding: life-threatening bleeding from an arm or leg gets a tourniquet right away, high and tight, with the time noted. Direct pressure or wound packing handles the rest, including wounds where a tourniquet can't go.
Dehydration: oral fluids in small, frequent sips, if they're fully alert and swallowing normally
Anaphylaxis: help them use their own epinephrine auto-injector, right away
Spinal injury: maintain spinal motion restriction (neurogenic shock)

Oral fluids (when it's safe)

If a fast evacuation is on the way, hold off. If help is hours away and the patient is fully alert, swallowing normally, stable, and shows no sign of abdominal injury, they can have something to drink:

Water or a dilute electrolyte drink
Small, frequent sips, not big gulps
Do not give fluids if they're vomiting, their mental status is altered, or you suspect an abdominal injury. Fluid can make internal bleeding worse.

Monitoring

Recheck vital signs and mental status every 5 minutes while they're unstable, every 15 once they're stable:

Heart rate and rhythm
Blood pressure, if you've got a cuff
Skin temperature and color
Level of consciousness
Whether they're getting better or worse

Evacuation urgency

Any patient with signs of shock is an emergent evacuation.

Decompensated shock (low blood pressure, altered mental status): emergent. Evacuate immediately, with ALS (advanced life support) coming to meet you.
Compensated shock (fast pulse, anxiety, normal blood pressure): still emergent. The normal blood pressure won't last. Evacuate immediately, though they can tolerate a slower move better than a decompensated patient if that's what you've got.
Suspected shock from any cause: don't hold the evacuation for field treatment.

Clinical Scenarios

Scenario 1: Hemorrhagic Shock

A 35-year-old hiker is cutting firewood when the axe slips and opens a deep cut on the inside of the thigh. You get there 10 minutes later. The patient is sitting up and looks anxious. Vitals: HR 112, RR 22, BP 118/82 (baseline unknown), pale skin, and the wound is still bleeding.

What's going on: Compensated hypovolemic shock from blood loss (hemorrhagic shock). The early signs are all here: fast pulse, fast breathing, anxiety, pale skin. The blood pressure is still normal, but this patient is heading for decompensation.

What you do now:

A deep thigh wound that's still bleeding, in a patient showing shock, is life-threatening hemorrhage. Put a tourniquet on now, high and tight on the thigh above the wound, and note the time. Hold direct pressure only while you get it ready.
Lay them flat. This is trauma, so don't raise the legs.
Keep them warm: insulation under them, blankets on top.
Nothing by mouth while a fast evacuation is on the way. If the wait stretches to hours and they stay alert, small sips are fine.
Emergent evacuation. Call for a helicopter or organize a ground evacuation right away.
Recheck vitals every 5 minutes and watch for the slide into decompensated shock.

Where it goes: Control the bleeding fast and get the evacuation moving, and this patient has a good chance. Every delay raises the risk of decompensation.

Scenario 2: Anaphylactic Shock

At camp, a 28-year-old woman sits down right on a yellow jacket nest she didn't see. She's stung multiple times and runs for the tent. Within 5 minutes she says it's hard to breathe, her tongue is swelling, and she's itching all over. Vitals: HR 128, RR 28, BP 92/60. Her skin is mottled and flushed, you can hear her wheezing, and her face is swollen.

What's going on: Anaphylactic shock, a type of distributive shock, and a medical emergency. She has a severe allergic reaction plus shock: low blood pressure, a fast heart rate, and poor perfusion.

What you do now:

Help her use her own epinephrine auto-injector immediately (0.3 mg into the muscle of the outer thigh). This is what saves her life. Don't delay it.
Repeat the epinephrine in 5 to 15 minutes if she isn't improving, or if the symptoms come back.
Lay her flat. If breathing is hard, let her sit up a little. If she's breathing fine lying down, raising her feet is an option. There's no trauma here.
Manage the airway. The swelling is already narrowing it, so watch it closely.
Give supplemental oxygen if you have it.
After the epinephrine, she can take an oral antihistamine as an add-on. It is never a substitute for epinephrine.
Keep her warm.
Emergent evacuation to a hospital. Anaphylaxis can come back after it seems to settle (a biphasic reaction).
Keep watching her airway and vitals the whole time.

Epinephrine first. It's the only real field treatment for anaphylaxis. Don't hold it for any other medication.

Knowledge Check

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Summary & Key Takeaways

The short version:

Shock is inadequate tissue perfusion. The cells aren't getting enough oxygen.
A fast heart rate is often the earliest sign. Low blood pressure is a late one.
Four types: hypovolemic (the most common), distributive, obstructive, cardiogenic.
Compensated shock can look fine and still go downhill fast.
Field treatment: lay them flat, insulate underneath, prevent heat loss, treat the cause, keep checking, and evacuate.
Any suspected shock is an emergent evacuation.

What you'll actually see

In the wilderness, you'll mostly see hypovolemic shock from trauma and distributive shock from anaphylaxis or infection. A patient can be in significant shock with a normal blood pressure, so read the whole picture: fast pulse, anxiety, pale skin, weak pulse.

Glossary of Terms

Aerobic Metabolism

How cells make energy using oxygen. It produces ATP efficiently and is the normal state. When oxygen runs short, cells switch to anaerobic metabolism.

Anaerobic Metabolism

How cells make energy without oxygen. It produces lactate and less ATP. It happens in shock and hypoxia and leads to lactic acidosis.

Cardiogenic Shock

Shock from the heart failing as a pump (for example, MI or a severe arrhythmia). Less common in the wilderness.

Compensated Shock

Early shock, where the body's compensation (tachycardia, vasoconstriction) holds blood pressure near normal. The patient looks anxious but may not look critically ill.

Decompensated Shock

Late shock, where compensation has failed. Blood pressure drops, mental status changes, and organs start to fail. Life-threatening.

Distributive Shock

Shock from vasodilation and lost vascular tone (septic, anaphylactic, neurogenic). Marked by a wide pulse pressure.

Hypovolemic Shock

Shock from lost circulating volume (blood or other fluids). The most common type in trauma and wilderness emergencies.

Lactic Acidosis

Lactate building up in the blood from anaerobic metabolism during shock. It makes cell dysfunction worse and is a marker of tissue hypoxia.

Mottled Skin

Blotchy, bluish (cyanotic) skin in decompensated shock, from severe peripheral vasoconstriction and poor perfusion.

Neurogenic Shock

Shock from a spinal cord injury that knocks out sympathetic tone, so the peripheral vessels dilate. It can last days to weeks. The tell is low blood pressure with a slow heart rate.

Obstructive Shock

Shock from a physical blockage to blood flow (tension pneumothorax, cardiac tamponade, PE). It needs an emergent evacuation, and the fix happens in a hospital.

Oxygen Delivery Relationship

Oxygen delivery (DO₂) = cardiac output × arterial oxygen content. Perfusion needs both a working heart and oxygen in the blood.

Perfusion

Blood (and the oxygen it carries) flowing to the tissues. Inadequate perfusion is the core problem in shock.

Shock

Inadequate tissue perfusion and cellular hypoxia. Untreated, it leads to organ failure and death.

Tachycardia

A fast heart rate (over 100 bpm at rest). One of the earliest signs of shock, as the heart works to hold cardiac output.

Tachypnea

Fast breathing (over 20 breaths/min). In shock it comes from sympathetic activation and metabolic acidosis.

Vasoconstriction

Blood vessels narrowing to raise peripheral resistance and send blood to the vital organs. It's one of the main ways the body compensates in shock.