Royal Army College

Lesson Overview

The earlier lessons dealt with the quickest killers: catastrophic bleeding, then airway and breathing. This lesson takes up the next link, the C of MARCH and ABCDE: circulation, the moving of blood and oxygen to every organ. When that supply fails, the casualty is in shock, a condition that can kill even when the visible injury looks slight.

Shock is dangerous precisely because it is quiet. A wound that sprays bright blood demands action from anyone. Shock does its work without drama, behind a face that may still be talking, while the casualty empties inside or the heart loses its grip. The skill here is not heroics but noticing: reading a pattern of small signs early, while they can still be answered, and keeping watch so you see the casualty change before the change becomes a collapse.

This is the knowledge layer. The hands-on skills it touches, controlling bleeding, positioning a casualty, taking and recording observations, are taught and certified in person under qualified instruction, and you do only what you are trained and currently authorised to do. You are a trained first responder, not a medic: your task is to recognise, to do the few things that buy time, and to keep help coming, never to attempt the advanced procedures that belong to qualified medical care. The clinical detail is confirmed by the College's medical staff and follows current internationally recognised practice. The care described is owed to anyone who needs it, by their need alone, friend or stranger, in keeping with the humanitarian footing of the Royal Kaharagian Army as a small home-defence and relief force.

By the end you will be able to explain what shock is and why it is dangerous, recognise its early signs, manage it correctly within your scope, carry out a secondary survey and a SAMPLE history, record the vital signs a first-aider can take, and monitor a casualty so you notice when they change.

Key Terms

Circulation: the movement of blood around the body by the heart and blood vessels, carrying oxygen to the organs and tissues.
Perfusion: the delivery of oxygen-carrying blood to an organ or tissue. Good perfusion keeps an organ alive and working; poor perfusion starves it.
Shock: a life-threatening failure of the circulation, in which the body can no longer perfuse its organs. Untreated, it leads to organ failure and death.
Hypovolaemic shock: shock caused by too little fluid in the circulation, most often from blood loss; the commonest cause in an injured soldier, and why stopping bleeding is the first treatment for shock.
Compensation: the body's early defence against shock, narrowing the blood vessels and speeding the heart to hold pressure up and protect the vital organs. It hides shock until it can no longer cope, and then the casualty falls fast.
Capillary refill: the time the colour takes to return to a fingernail or fingertip after it has been pressed white. A return slower than about two seconds suggests poor perfusion.
AVPU: a quick four-step scale of a casualty's level of response, recording whether they are Alert, respond to Voice, respond only to Pain, or are Unresponsive.
Vital signs: the simple, repeatable measures of a casualty's state that a first-aider can record over time, including the level of response, the breathing rate, the pulse, the skin, and the capillary refill.
Secondary survey: a careful head-to-toe examination carried out after the immediate threats to life have been dealt with, to find injuries or signs missed in the first rush.
SAMPLE history: a short, ordered way of gathering the key facts about a casualty: Signs and symptoms, Allergies, Medications, Past medical history, Last oral intake, Events leading up to the incident.
Lethal triad: the dangerous trio of becoming cold, becoming acidic inside, and losing the ability to clot, each one worsening the others, which is why warmth and speed matter so much in a bleeding casualty.

What circulation is, and what shock is

The heart pumps blood through the vessels, and the blood carries oxygen to every part of the body. Each organ needs a steady supply; the brain and the heart fail soonest without it. The delivery of that blood is perfusion. When the body can no longer perfuse its organs, that failure is shock. The word does not mean fright or the jolt of bad news; it means a circulation failing to keep the body's cells supplied, and it is a true threat to life.

Picture the circulation as three things working together: a pump (the heart), the pipes (the blood vessels), and the fluid in them (the blood). Shock arises when any one of the three fails, which gives a simple way to hold its causes in mind:

Too little fluid, most often from bleeding, external or hidden in the chest, abdomen, pelvis, or a broken thigh; or from heavy fluid loss through serious burns, prolonged vomiting or diarrhoea, or being unable to drink. This is hypovolaemic shock, shock from low volume, and for a soldier it is by far the commonest kind.
Widened pipes, where the vessels relax so the same volume no longer fills them and the pressure falls, as in a severe allergic reaction, a spinal injury, or an overwhelming infection.
Pump failure, from a heart attack or a chest injury that stops the heart filling.

On operations the commonest cause by far is blood loss. Controlling bleeding is therefore the first and most important treatment for shock, and this lesson follows directly from the bleeding drills of Lesson 03.

The danger of shock is that it builds. Early on the body compensates, tightening the vessels and driving the heart faster to keep the vital organs supplied, and the casualty may look only a little unwell. Compensation is real and powerful, and it is also a trap: it holds the outward signs steady while the inner state worsens. This is precisely the window in which sound first aid does most good. If the cause is not addressed, compensation fails, and a point comes after which no treatment will recover the casualty. The fall is not gentle; the casualty who looked "stable" can slide to collapse in minutes. Recognise shock before that point, not after it.

Recognising shock

Shock rarely announces itself with one dramatic sign. You read it from a pattern, and the signs change over time in a fairly orderly way, so a first-aider who knows the order can place a casualty along it and judge how far the shock has gone. Read the picture, not a single reading.

Look for the following, roughly in the order they tend to appear:

pale, cool, clammy skin, often with sweating, as blood is drawn from the surface to protect the core; the skin feels cold and damp even on a warm day, and the colour drains from the lips and the inside of the eyelids;
a fast pulse, as the heart speeds up to compensate; early in shock it is fast and still fairly full, but as shock deepens it weakens and turns thready, faint and easily lost under the finger, which is a worse sign than speed alone;
fast, shallow breathing, as the body tries to take in more oxygen for the blood that is left;
thirst, a real and telling symptom of a circulation short of fluid, and worth asking about;
restlessness, anxiety, or agitation, an early change in the brain that often comes before any obvious drop in alertness; a casualty who becomes oddly anxious, fidgety, or "not themselves" may be showing you early shock;
a slow capillary refill: press a fingernail or fingertip until it whitens, release, and watch the colour return; longer than about two seconds is a warning sign of poor perfusion;
and, as a late and serious sign, the restlessness gives way to drowsiness, confusion, and a falling level of consciousness. The brain is among the last organs the body will let starve, so a real change in alertness means the shock is already advanced.

Set out as a progression, the picture looks like this:

   EARLY (compensating) ........................ LATE (failing)

   anxious, restless        --->   drowsy, confused, slipping away
   skin pale, cool, clammy  --->   skin grey, cold, sweating
   pulse fast, still full   --->   pulse fast then WEAK and thready
   breathing a little fast  --->   breathing fast and shallow, then gasping
   thirsty, alert           --->   thirst ignored, response falling
   refill a touch slow      --->   refill clearly delayed

   The body holds the line on the left, then loses it on the right.
   Act on the LEFT. Do not wait for the right.

A low blood pressure is a serious sign but a dangerous one to wait for: the body holds the pressure up until it suddenly cannot. (A first-aider rarely measures blood pressure in the field anyway; you read its proxies, the pulse, the refill, and the skin.) This is especially true of the young and fit, who compensate well and can look stable until they collapse. Do not be reassured by a casualty who "looks all right" if the mechanism of injury, a fall, a blast, heavy bleeding, a crushed limb, a hard vehicle impact, tells you shock is likely. Treat the mechanism, not only the appearance: if the story of the injury could have caused serious bleeding, inside or out, assume shock is on its way and prepare for it before the signs grow loud.

Managing shock

The management of shock follows from its causes, and the order matters. Each step costs little and gives much; together they hold the line until the help that shock truly needs can reach the casualty.

Control the cause, above all the bleeding. Shock from blood loss will not improve while the casualty is still bleeding. Stop catastrophic bleeding first, by direct pressure, wound packing, or a tourniquet as taught in Lesson 03, and reassess that it has truly stopped, because a controlled wound can break through with movement. Where the cause is something you cannot fix, such as bleeding inside the abdomen, recognising it and moving quickly to those who can is itself the treatment: you cannot stop that bleeding, but you can shorten the time to the surgeon who can.
Lay the casualty down. Lying flat is easier on a failing circulation than sitting or standing, and it spares the casualty the dizziness and faint of trying to hold the head up on a low pressure. Keep them still; the work of moving costs oxygen they cannot spare. Do not prop them upright, and do not march a shocked casualty about.
Keep them warm. A cold casualty does worse. This is treatment, not comfort: cold thickens the blood, worsens bleeding, and deepens shock. Insulate them from the ground first, which steals heat quickly into the cold earth, then cover them from above with blankets, a coat, or a foil casualty blanket, and remove or cover wet clothing where you safely can. This is the H of MARCH, and it matters as much for the shocked casualty as for the cold one. The reason is the lethal triad: a bleeding casualty allowed to grow cold falls into a vicious circle in which cold, acidity from poor perfusion, and loss of clotting each feed the next. Warmth breaks into that circle, and speed shortens the time it has to turn.
Reassure them. Fear and pain make shock worse, driving the heart faster and the casualty more agitated. Speak calmly, explain what you are doing, and stay with them. A casualty who hears a steady voice settles; one who hears panic deteriorates. Reassurance is treatment, not courtesy, and it costs you nothing but attention.
Give nothing by mouth. A casualty who may need surgery, or whose consciousness is slipping, must not be given food or drink, however much they say they are thirsty. A full stomach and a dulled airway invite choking, and a stomach full of water delays the anaesthetic that surgery to stop the bleeding may need. Moisten dry lips if you must, but do not let them eat or drink.
Call for help early, and keep checking. Shock needs more than first aid can give, so summon medical help or evacuation at once, not after you have run out of ideas. Until help arrives, monitor closely: the casualty's condition will change, and the trend you record will be among the most useful things you hand over.

A clear word on the limit of your scope. The definitive treatment for serious shock from blood loss is the replacement of lost volume and the stopping of the bleeding at its source: intravenous or intraosseous fluids, blood and blood products, and surgery. None of these is a first-responder task. Fluids through a drip, in particular, are a medical procedure, given by a qualified medic or doctor, and certified in person; do not attempt them, and do not regard their absence as a failure on your part. Your job is the part only the person on the spot can do: control the cause you can reach, lay the casualty down, keep them warm, reassure them, give nothing by mouth, monitor the trend, and get them to those who can do more. Done well, that buys the minutes in which the advanced care becomes possible.

The secondary survey: a head-to-toe check

Once the immediate killers have been dealt with, the airway open, breathing supported, catastrophic bleeding stopped, shock being managed, and only then, you carry out the secondary survey: a careful examination from head to toe to find what the first rush did not. The primary sequence is fast and aimed at what kills in minutes; the secondary survey is slower and aimed at what was hidden, a second wound behind the first, a fracture, a swelling filling quietly with blood. If at any point you find a new threat to life, stop and return at once to the airway-breathing-circulation drill of Lesson 02. The fuller examination never takes priority over a fresh threat to life, and the survey can always be resumed once the new threat is held.

Work methodically and in the same order every time, so that order becomes a habit you cannot accidentally break under stress. Move down the body in turn:

   HEAD-TO-TOE SECONDARY SURVEY  (gentle, in order, both sides)

   1. Head and face   scalp, behind the ears, eyes, nose, mouth; fluid or blood
   2. Neck            deformity, swelling, the windpipe central; tenderness
   3. Chest           both sides rise together? bruising, wounds, a flail area
   4. Abdomen         gently feel all four quarters for tenderness, rigidity
   5. Pelvis          do NOT rock it; look and note pain (a hidden blood store)
   6. Back/spine      log-roll only if trained and safe; feel down the spine
   7. Arms            both, shoulder to fingertip; pulse, movement, feeling
   8. Legs            both, hip to toe; the thigh can hide enough to shock
   9. All over        a medical-alert bracelet, an exit wound, the armpits

   LOOK and gently FEEL at each step: bleeding, swelling, bruising,
   deformity, tenderness, wetness. Expose only what you must; cover again.

At each part, look and gently feel for bleeding you had not seen, swelling, bruising, deformity, tenderness, or wetness. Tell the casualty what you are about to do and where you are about to touch, both because it is kinder and because their flinch or their answer is part of the examination. Expose only what you must, protecting the casualty's modesty and warmth, which you are also guarding for the sake of the shock, and cover them again as you go. Remember where serious bleeding hides: the chest, abdomen, pelvis, and a fractured thigh can each hold enough blood to cause shock with little showing outside, so the survey is also a search for the silent stores that explain a shock you cannot otherwise account for. Check, too, for the easily missed: a medical-alert bracelet or necklace that may explain a collapse, an exit wound behind an entry wound, and the back, the buttocks, and the armpits.

The vital signs a first-aider can record

A casualty is described not only by their injuries but by a handful of simple measures of how their body is coping, and the value of these measures is that you can take them again and again and watch them move. Within your training and where you are equipped, record the vital signs a first-aider can take, noting the time against each so the next set can be compared with the last:

Level of response, on the AVPU scale. Decide whether the casualty is Alert (awake and aware), responds to Voice (rouses or answers when you speak), responds only to Pain (stirs only to a firm pinch of the shoulder, no more), or is Unresponsive. A casualty sliding down this scale, from Alert towards Voice or Pain, is getting worse, and in a shocked casualty that slide is an alarm.
Breathing rate and effort. Count the breaths over a measured time and note whether they are fast or slow, deep or shallow, easy or laboured. Fast, shallow breathing fits with shock; very slow or gasping breathing is a grave sign.
Pulse rate and character. Feel the pulse, count it over a measured time, and note not only how fast it is but its character: full and strong, or fast, weak, and thready? A pulse climbing in rate and fading in strength is the signature of worsening shock.
Skin colour and temperature. Note whether the skin is a normal colour or pale, grey, or blue-tinged, and whether it feels warm and dry or cold and clammy. Cool, pale, sweating skin supports a picture of shock.
Capillary refill. Press a nail bed or fingertip until it blanches, release, and time the return of colour; longer than about two seconds suggests poor perfusion. Take it the same way each time so your comparisons are fair.

Hold these on a simple casualty card so nothing is forgotten and the trend is visible at a glance. A rough layout, which you can rule out on any card or notebook, looks like this:

   +-----------------------------------------------------------+
   | CASUALTY CARD                          Name/ID: __________ |
   | Mechanism / what happened: ______________________________ |
   | Catastrophic bleeding controlled?  [ ] Yes  How: ________  |
   +-----------------------------------------------------------+
   |  TIME      |  ____  |  ____  |  ____  |  ____  |           |
   |  AVPU      |  A V P U | A V P U | A V P U | A V P U |       |
   |  Breathing |  __/min  | __/min  | __/min  | __/min  |       |
   |  Pulse     |  __/min  | __/min  | __/min  | __/min  |       |
   |  rate/char |  full/thr| full/thr| full/thr| full/thr|       |
   |  Skin      |  col/temp| col/temp| col/temp| col/temp|       |
   |  Cap refill|  __ sec  | __ sec  | __ sec  | __ sec  |       |
   +-----------------------------------------------------------+
   | SAMPLE: S____ A____ M____ P____ L____ E____                |
   | Treatment given / time: _________________________________ |
   +-----------------------------------------------------------+

The card is not paperwork for its own sake. It forces you to take each sign, it dates each one so a trend appears across the columns, and it becomes the single sheet you hand over when help arrives, so the next carer sees at once not just how the casualty is but which way they are going.

The SAMPLE history

Alongside the examination, gather a short history. The body tells you what is wrong now; the history often tells you why, and what to watch for. The word SAMPLE keeps it ordered and complete. Take it from the casualty if they can speak, or from family, comrades, or bystanders if they cannot, and take it as you work rather than as a separate interview; most of it can be asked while your hands carry out the survey.

S, Signs and symptoms: what you can see and measure (the signs), and what the casualty tells you they feel (the symptoms), such as pain, breathlessness, dizziness, or thirst. Ask where it hurts, how badly, and whether anything makes it better or worse.
A, Allergies: known allergies, especially to medicines, and any sign that an allergic reaction may itself be the problem. An allergy is also a warning to the medic about what not to give.
M, Medications: what the casualty takes regularly, and any recent change. Some medicines, such as blood thinners, change how an injury behaves and how it must be treated; a blood-thinner can turn a modest bleed into a serious one and is vital for the medic to know.
P, Past medical history: existing conditions and past serious illness or surgery that may bear on the present, such as heart disease, diabetes, asthma, or a previous operation on the part now injured.
L, Last oral intake: when they last ate or drank, which matters if surgery and anaesthesia may follow, and which is one more reason you give a shocked casualty nothing by mouth.
E, Events: what happened, the mechanism of injury or the story of the illness, which often points straight to the injuries to look for. The events also tell you whether to expect shock, as a heavy fall or a blast should put you on guard for it.

Write down what you learn, or pass it on accurately, ideally onto the same casualty card as the vital signs. A clear SAMPLE history saves time and prevents harm; you will use it again when you give a formal handover (Lesson 07).

Monitoring and reassessment

A casualty is not a photograph but a moving picture. The pulse quickens, breathing tires, shock emerges as blood quietly accumulates inside, a tourniquet loosens with movement, the level of consciousness slips. The single inspection that looked reassuring can be wrong minutes later. So you monitor, and you reassess, on a rhythm rather than only when something catches your eye, because the whole danger of shock is that it changes the casualty faster than a casual glance will catch.

Watch and, where you are trained and equipped, record the vital signs described above: the level of response on the AVPU scale, the breathing rate and effort, the pulse rate and character, the skin colour and temperature, and the capillary refill. Note the time against each, and check again at intervals and, without fail, after any move, because moving a casualty is when a controlled bleed breaks loose or a borderline circulation tips over. Reassess sooner in a casualty you have judged seriously hurt; a stable-looking casualty can be checked less often, but never abandoned. What matters most is not a single set of numbers but the trend: a pulse climbing and weakening, a casualty growing drowsier, skin turning greyer, refill lengthening, all warn of deterioration and that help cannot come too soon. Equally, a trend that holds steady or improves after you have stopped the bleeding and kept the casualty warm is real reassurance, honestly earned. Keep these notes; two sets of observations ten minutes apart say more than any one set alone, and they become the heart of your handover (Lesson 07).

In Practice: A Casualty Who "Looks All Right" After a Roadside Collision

On a cold road at the edge of a market town, two vehicles have collided. You reach a national who is conscious, talking, even walking about, with no dramatic wound, asking only for a drink of water. You could be reassured, and be wrong. The mechanism, a hard impact at speed, tells you to look harder whatever the cheerful face says.

You persuade them to sit, then to lie down, and begin your checks calmly, telling them what you are doing. The signs gather into a pattern: skin pale and clammy though the day is cold, pulse fast and not as full as it should be, capillary refill slow, thirsty and a little agitated, plucking at their coat. You recognise shock, most likely from bleeding inside that you cannot see, and you act on the early picture. With no external bleeding to fix, you turn to what is in your scope: you insulate them from the cold ground, cover them well against the lethal triad of cold and delay, reassure them in a steady voice, and, despite the thirst, give them nothing by mouth, explaining gently why. You call for help at once, telling the responders plainly that this is a shocked casualty who needs urgent transfer.

Your secondary survey, worked head to toe in order, finds bruising spreading across the abdomen, a silent store filling where you cannot stop it. Your SAMPLE history reveals they take a blood-thinning medicine, which makes that hidden bleed more dangerous still. You write both onto the casualty card. You monitor them while you wait, and across two sets of observations their pulse has climbed and weakened and they have grown a shade harder to rouse on the AVPU scale, a trend you note with the times against it. When help arrives you hand over all of it plainly: the mechanism, the rising pulse, the abdominal bruising, the blood-thinner, the card. You did not treat the cheerful appearance; you treated the mechanism, the early signs, and the trend, and in doing so you may have bought the minutes that saved a life.

Check Your Understanding

What is shock, and why can a casualty in early shock look only mildly unwell? Name the body's defence that hides it, and say what this tells you about when to act.
List the steps of managing shock in order, explain why controlling the cause (especially bleeding) comes first, and say in plain terms why keeping the casualty warm matters as much as it does.
What is the difference between the primary sequence and the secondary survey, what must you do if you find a new threat to life during the secondary survey, and which vital signs would you record so that you could later show a trend?

Reflection (write a short paragraph): You are monitoring a casualty whose first set of observations looked steady, but ten minutes later their pulse is faster and weaker and they are harder to rouse. Why is the trend in a casualty's signs more telling than any single set of numbers, and how should this change both what you do for them now and what you tell the arriving medic?

Summary

Circulation delivers oxygen-carrying blood to the organs; when that delivery fails, the casualty is in shock, which can kill even when the injury looks slight. Picture the circulation as pump, pipes, and fluid, and shock as the failure of any of the three.
Shock most often comes from blood loss, hypovolaemic shock; it can also come from fluid loss, widened vessels (severe allergy, spinal injury, infection), or failure of the heart. In an injured soldier bleeding is the commonest cause, so stopping bleeding is the first treatment for shock.
Recognise shock from a pattern that worsens in order: anxiety and restlessness, pale, cool, clammy skin, a fast pulse that later weakens to a thready one, fast breathing, thirst, slow capillary refill, and, as a late sign, drowsiness and confusion. The body compensates and hides shock; the fit compensate best and can collapse suddenly, so treat the mechanism, not only the appearance.
Manage shock within your scope: control the cause (above all bleeding), lay the casualty down, keep them warm against the lethal triad of cold, acidity, and poor clotting, reassure them, give nothing by mouth, and call for help early. Intravenous fluids, blood, and surgery are medical procedures, certified in person, not first-responder tasks.
After the immediate killers are dealt with, carry out a gentle head-to-toe secondary survey, record the vital signs a first-aider can take (AVPU, breathing, pulse rate and character, skin, capillary refill) on a casualty card, and gather a SAMPLE history. Then monitor and reassess on a rhythm: the trend in the casualty's signs is what warns you they are getting worse, and it is the heart of the handover you will make in Lesson 07.

Circulation, Shock, and Assessing the Casualty