First aid: Bleeding and hypovolaemic shock

In the third part of our series about prehospital care, Martin S Roth and colleagues focus on detection and treatment of haemorrhage

Bleeding is when one or more blood vessels are damaged and can be from arteries, veins, or capillaries. The seriousness of the haemorrhage depends on the depth of the cut, amount of bleeding, time taken to control the bleeding, and type of blood vessels damaged.

Seeing your own blood can be a shock, and onlookers watching the scene may experience shock. The caregiver is also in potential danger of becoming infected by a transmissible disease—for example, HIV or hepatitis.

External bleeding is almost always easy to identify, but internal bleeding is often more difficult to detect and treat. An average adult has about 5 l of blood and can safely lose half a litre. Rapid loss of larger volumes of blood, however, leads to hypovolaemic shock and death.

Hypovolaemic shock is a clinical state in which tissue perfusion is inadequate due to a loss of blood or plasma. A reduction in blood volume causes a fall in systolic blood pressure, which triggers a sympathetic catecholamine response. Blood flow to the peripheries is reduced. Anaerobic metabolism with lactate production occurs in tissues that are inadequately perfused and this can go on to impair the function of vital organs such as the brain, heart, and kidneys.

Physiology

Oxygen is carried in the blood in two forms. Most is carried combined with haemoglobin but a small amount is also dissolved in the plasma. Each gram of haemoglobin can carry 1.31 ml of oxygen when it is fully saturated. Every litre of blood, therefore, (which has a haemoglobin concentration of 150 g/l) can carry about 200 ml of oxygen when fully saturated (occupied) with oxygen (partial pressure 100 mm Hg). At this partial pressure, only 3 ml of oxygen will dissolve in every litre of plasma. When considering the adequacy of oxygen delivery to the tissues, the haemoglobin concentration, cardiac output, and oxygenation need to be taken into account.

Oxygen delivery to the tissues The quantity of oxygen made available to the body’s tissues in one minute is known as the oxygen delivery and is equal to the cardiac output multiplied by the arterial oxygen content.

Oxygen delivery (ml oxygen/ min)=Cardiac output (l/min)× Haemoglobin concentration (g/l)× 1.31 (ml oxygen/g haemaglobin)×% saturation

In a normal adult this works out as 5 l blood/min×200 ml oxygen/l blood=1000 ml oxygen/min. Several factors contribute to decreased oxygen supply to the tissues following haemorrhage.

When substantial amounts of blood loss occur, the fall in the oxygen carrying capacity of the blood and the reduction in blood volume cause a fall in oxygen delivery. To keep a bleeding person alive, you must ensure optimal pulmonary oxygenation and keep oxygen getting to vital organs. It is important to secure the airway (A) and breathing (B). Only then should you proceed with circulation (C).

Replacement of blood loss with crystalloids or colloids also results in dilution of the blood components or haemodilution. Initially this reduces the viscosity of blood, which improves capillary blood flow and cardiac output, increasing the supply of oxygen to the tissues. When the haemoglobin falls below 70-80 g/l the cardiac output can no longer compensate for the anaemia and blood transfusion is usually necessary.

Coping outside the hospital

• Bleeding through a break of the skin can be classified according to the type of blood vessel involved.
• Capillary—Often seen in bruises and arises slowly as a brownish colour. Always from superficial lesions, and it always stops with direct pressure. After it stops, wash it with soap and water and apply a sterile dressing
• Vein—Continuous bleeding and dark red in colour (the haemoglobin is not oxygenated)
• Artery—Intermittent bleeding and intense red colour (oxygenated haemoglobin).

Treatment

• Remember that your first concern must be your personal safety, so put a pair of disposable gloves on
• Lay the victim down, if possible with the head lower than the rest of the body
• Eliminate dirt or debris from the wound; do not remove embedded objects from the wound
• Apply direct pressure to the site of bleeding using gauze, handkerchief, tie, sanitary towel, or any clean cloth at hand. If the compress gets soaked in blood, apply another one over the previous as you will run the risk of removing the clot that is being formed. Press firmly until the bleeding stops, then wrap the compress firmly with a bandage.

ANJA NEIDRINGHAUS/AP

Only for limbs

While maintaining pressure lift the wound above the heart so that the blood pressure drops. This manoeuvre is contraindicated if you suspect that the limb is fractured

• Apply indirect pressure over the main artery supplying the blood to the wound.
• For the arm:
• Humeral artery—In the union of the medial with the distal third of the arm, right inside the biceps
• Axilary artery—With your closed fist apply pressure inside the armpit
• For the leg:
• Behind the knee
• Femoral artery—With your closed fist apply pressure over the groin.

Pressure is always applied over an artery pressed against a bone, so that with a little knowledge of anatomy you can locate and compress the artery that supplies a particular area.

Tourniquets

On rare occasions if everything else has failed, apply a tourniquet close to the wound. Once a tourniquet is applied, it should not be loosened or removed until the patient has reached medical help. Write down somewhere on the victim the time it was applied. A bandage or a tie roughly 10 cm wide can be used. Wrap the bandage several times around the limb (always between the heart and the wound). Tie a knot leaving loose ends. Get a stick and tie another knot (the stick is placed between the first and the second knot) Twist the stick until the bleeding stops and fix it so it does not loosen up. Check the tourniquet every 10 minutes. When the bleeding becomes controllable by applying direct pressure only, release the tourniquet but don’t dismantle it since it might be needed if the bleeding starts again. Once the bleeding stops you can apply a clean cloth or bandage with ice over the wound until the ambulance arrives.

Internal bleeding

Causes of internal bleeding include trauma to the chest or abdomen, fractures, bleeding duodenal or gastric ulcers, brain haemorrhage, and ectopic pregnancy. Internal bleeding must be suspected when signs of shock are present. The site of bleeding may be obvious for penetrating trauma but is often less easily found. Bleeding in the extremities can be difficult to assess in the field because it may stay in the subfascial planes. For example, a fractured femur can cause a greater than one litre blood loss without obvious external haemorrhage. Intrathoracic bleeding will cause dullness on percussion and auscultation. This can be easily confirmed with a chest x ray when the patient is in hospital. The peritoneal cavity is often a site of occult bleeding. Several litres of blood may accumulate in the abdomen before any clinically notable distension. The retroperitoneal space may also mask large volumes of blood, particularly after pelvic fractures. Because many sites of bleeding may be difficult to assess in the initial examination in the field, physical signs of shock are of paramount importance.

Signs of shock

Tachycardia, a heart rate of more than 100 beats/min, is a sensitive but not specific indicator of the state of shock. Several emergency department studies have shown similar heart rates between hypotensive and normotensive injured patients. Patients may be on ß blockers, which decrease the tachycardic response to hypotension. Up to a third of patients in shock may not be tachycardic. The presence of tachycardia does not always indicate that the patient is in shock and, more importantly, the absence of tachycardia does not indicate that shock is not present. Presentations that include abdominal pain or enlargement; tenderness and dysfunction of a limb with loss of pulses; and crushing, blunt, and penetrating trauma should always lead you to suspect internal bleeding. In such cases it is more important to hurry the emergency medical services and get the person quickly to the hospital, at which definitive care can be given.

In the emergency room

Early symptoms of hypovolaemic shock reflect the underlying pathophysiology (box 1).

The differential diagnosis of hypovolemic shock in trauma situations is tension pneumothorax, cardiac tamponade, massive pulmonary embolism, or neurogenic shock (due to spinal lesion).

Most of the above can be related to the amount of blood lost, and this can be classified into four main groups (table). Losses of up to 750 ml (class I or 15% of blood volume) do not generate symptoms. Further bleeding up to 1.5 l (class II) produces the cardiovascular signs of catecholamine release, thirst, weakness, and increased respiratory rate (tachypnoea). Systolic blood pressure begins to fall as blood loss reaches 2 l (class III shock) and often becomes unreadable after 2.5 l (class IV).

Finding the capillary refill time involves applying pressure to the nail bed until it turns white. Once the pressure is removed, the time it takes for blood to return (indicated by a pink colour returning to the nail) can be measured. Although commonly used, this test has no proved value, and a prolonged refill time does not accurately predict or correlate with blood loss.^1-4

In the emergency room, the priority is to restore the lost volume and treat shock. Two short large bore cannulas (14 gauge) should be inserted, usually at the antecubital fossae. Blood samples can be taken for full blood count and urea and electrolytes from the first. Fluid replacement takes place in three stages—volume replacement, oxygen carriage restoration, and restoration of haemostasis.

Volume replacement

What are the goals of initial volume therapy? Priniciples of fluid management emphasise efficient restoration of intravascular volume. As anaemia is better tolerated than hypovolaemia, fluid resuscitation can initially be with non-blood agents such as crystalloid (for example, sodium chloride or Hartmann’s solution) or colloid (a gelatin or starch solution). Fluid should be given until adequate diuresis and a normal blood pressure are attained. Other clinical hallmarks of suboptimal tissue oxygenation should improve (for example, mottling of the skin and coldness of hands and feet). Colloids are more efficient than crystalloids as equal intravascular volume expansion can be achieved with less, but crystalloids are cheaper than colloids.^{6 7}

Oxygen carriage and haemostatsis restoration

Once a patient has lost more than 30-40% of his or her blood volume, they need a resuscitation fluid with good oxygen carrying capability. Most oxygen is carried by haemoglobin, so restoration of oxygen carriage capacity implies red cell transfusion. There are potential setbacks in using blood (box 2).

As a third step, patients may need the replacement of coagulation factors that have been lost.

Monitoring

The volume status of a patient is best assessed by observing the vital signs and other variables after a fluid challenge of, say, 2 l of Hartmann’s solution or 1 l of gelatin solution (box 3). Fluid resuscitation should continue to produce an adequate arterial pressure and a urine flow of at least 1 ml/kg/min. Lack of improvement indicates major exsanguinating haemorrhage and the need for urgent surgical intervention and transfusion of blood. Group O blood can be immediately used in such cases.⁷

A transient response to the initial fluid challenge suggests 20-40% of blood volume may have been lost, ongoing bleeding, and the need for surgical assessment. Patients who respond with a sustained rise in blood pressure and heart rate in the absence of ongoing bleeding can be effectively managed with clear fluids.

A large proportion of patients with hypovolaemic shock will need surgical control of bleeding. The surgical team should be present in the emergency department for the assessment of such patients and to arrange definitive care. Scans of the chest and abdomen with x rays, ultrasound, or arterial angiography may help to determine the source.

Always have in mind that shock is a progressive condition that, if not treated in time, leads hopelessly to death. In the street, lay the person on their back, raise the legs, and rush the prehospital personnel—remember, if you identify any external bleeding stop it as soon as you can. In the emergency department, besides volume replacement, inotropic drugs might be needed.

Martin S Roth, first year resident, Hospital Italiano de Buenos Aires, Argentina
Email: martinsroth2828@hotmail.com

Fabian J Garcia, red cross first aid instructor,

Isabel Pinceminp, resident instructor, Hospital Municipal de San Isidro, Argentina

Samena Chaudhry, senior house officer in cardiothoracic surgery,University Hospital North Staffordshire, Stoke on Trent


studentBMJ 2005;13:133-176 April ISSN 0966-6494

1. McGee S, Abernethy WB III, Simel DL. Is this patient hypovolemic. JAMA 1999;281:1022-9.
2. Schriger DL, Baraff L. Defining normal capillary refill. Ann Emerg Med 1988;17:932-5.
3. Schriger DL, Baraff L. Capillary refill: is it a useful predictor of hypovolemic states? Ann Emerg Med 1991;20:601-5.
4. Gross CR, Lindquist RD, Woolley AC, Granieri R, Allard K, Webster B. Clinical indicators of dehydration severity in elderly patients. J Emerg Med 1992;10:267-74.
5. Finfer S, Bellomo R, Boyce N, French J, Myburgh J, Norton R; SAFE Study Investigators. A comparison of albumin and saline for fluid resuscitation in the intensive care unit. N Engl J Med 2004;350:2247-56.
6. Rivers E, Nguyen B, Havstad S, Ressler J, Muzzin A, Knoblich B, et al; Early Goal-Directed Therapy Collaborative Group. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med 2001;345:1368-77.
7. Hebert PC, Wells G, Blajchman MA, Marshall J, Martin C, Pagliarello G, et al. A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care [Correction appeared in N Engl J Med 1999;340:1056]. N Engl J Med. 1999;340:409-17.
8. Driscoll P, Skinner D, Earlam R, eds. ABC of major trauma. 3rd ed. London: BMJ Books, 2000.