Bleeding

Bleeding is the loss of blood from the body. Hemorrhage (AE) or haemorrhage (BE) is the medical term for bleeding. In common usage, a hemorrhage means particularly severe bleeding; although technically it means escape of blood to extravascular space. The complete loss of blood is referred to as exsanguination.

Children are put more in danger by bleeding as they have less blood to lose. The average adult human will be in medical danger after 1 litre (2 pints) and could die of hypovolemic shock if more blood is lost.

The human body generates blood at a rate of about 2 litres (2 quarts) per week. The technique of blood transfusion is used to replace severe quantities of lost blood.

Causes, prevalence, and risk factors

Hemorrhage generally becomes dangerous, or even fatal, when it causes hypovolemia (low blood volume) or hypotension (low blood pressure). In these scenarios various mechanisms come into play to maintain the body's homeostasis. These include the "retro-stress-relaxation" mechanism of cardiac muscle, the baroreceptor reflex and renal and endocrine responses such as the renin - angiotensin - aldosterone effect.

Death from hemorrhage can generally occur surprisingly quickly. This is because of 'negative feedback'. An example of this is 'cardiac repression', when poor heart contraction depletes blood flow to the heart, causing even poorer heart contraction. This kind of effect causes death to occur more quickly than expected.

Types of bleeding

minor traumatic bleeding: bleeding from small and superficial wounds; the loss of blood is not dangerous and the bleeding will stop spontaneously; the main risk is the wound itself (dysfunction of the organs involved and infection);
severe traumatic bleeding: the flow of blood can soak a paper or cloth hankerchief in a few seconds; in such a situation, the bleeding will cause death in a few minutes;
externalised bleeding: the blood flow through a natural orifice, such as the nose, the ears, the mouth (spitting and vomitting blood), the vagina (except for the natural menstruation), the urethra and the anus; the blood comes from the interior of the body and reveals a hidden trauma or a disease;
internal bleeding: the blood flows inside the body; it cannot be seen, but can be suspected by shock symptoms.

Further, bleeding can be categorized by the type of the damaged blood vessel:

arterial bleeding occurs from arteries, the major blood vessels which carry oxygen-rich blood from the heart throughout the body. This type of bleeding is characterized by spurts with each beat of the heart, is bright red in color (although blood darkens when it meets the air) and is usually severe and hard to control. Arterial bleeding requires immediate attention.
venous bleeding occurs from veins, vessels which return the blood to the heart. Venous bleeding is characterized by a steady flow and the blood is dark, almost maroon in shade. Venous bleeding is easier to control than arterial bleeding.
capillary bleeding occurs from capillaries, the smallest of our body’s blood vessels. It is usually slow, oozing in nature and this type of bleeding usually has a higher risk of infection than other types of bleeding. It is much easier to control than other types of bleeding.

Hemorrhage in the brain

Internal bleeding can occur in any part of the brain. Blood may accumulate in the brain tissues itself, or in the space between the brain and the membranes covering it. The bleeding may be isolated to part of one hemisphere (lobar intracerebral hemorrhage) or it may occur in other brain structures, such as the thalamus, basal ganglia, pons, or cerebellum (deep intracerebral hemorrhage).

An intracerebral hemorrhage can be caused by a traumatic brain injury or abnormalities of the blood vessels (aneurysm or angioma). When it is not caused by one of these conditions, it is most commonly associated with high blood pressure (hypertensive intracerebral hemorrhage). In some cases, no cause can be found.

Blood irritates the brain tissues, causing swelling (cerebral edema). It can collect into a mass called a hematoma. Either swelling or a hematoma will increase pressure on brain tissues and can rapidly destroy them.

Symptoms vary depending on the location of the bleed and the amount of brain tissue affected. The symptoms usually develop suddenly, without warning, often during activity. They may occasionally develop in a stepwise, episodic manner or they may get progressively worse.

First aid

Minor traumatic bleeding

The minor traumatic bleeding stops spontaneously, the loss of blood is not dangerous in itself. But the wound can still endanger the life of the casualty. See Wound.

Severe traumatic bleeding

Follow the basic principles of first aid. Only after you have surveyed the scene; conducted a primary patient survey (considering the patient's airway, breathing, and circulation); and made a call to the emergency services; should you attempt additional treatment yourself.

ask someone to call for help, or do it yourself if you are alone; describe the general state of the casualty (alert or unalert, breathing or not) and the wound itself;
follow the instructions given by the Emergency medical services.

A major technique of first aid is to control bleeding through direct pressure with the hand (possibly protected by a plastic bag, a glove or other material); it can be replaced when necessary by the application of a bandage over the wound. If the casualty is conscious and alert, he can press on the wound himself for a short time (e.g. the time needed for a bystander to get protection for the hands, something to make a bandage).

Where application of direct pressure is not possible (e.g. there is a foreign body inside the wound, or a broken bone comes outside, or the wound is too large for the hand), then it is possible to compress the artery against a bone, between the wound and the heart (see Pressure point).

In extreme cases of an injured limb, a tourniquet may be used. If medical care is delayed (after a few hours), the injured limb must generally be amputated afterwards, just below the level the tourniquet is applied; this is "losing a limb to save a life". This risk is very low in the urban environment of a developed country (the delay before a rescue team arrives is generally a few minutes after the call), but must be taken into account in wilderness or in countries that do not have organised prehospital medical services. Some first aid instruction no longer teaches the use of the tourniquet because the risk may be greater than the benefit; some other consider that saving a life is above the rest. However, this should always be the last choice.

Externalised bleeding

The only minor situation is a spontaneous nosebleed, or a nosebleed caused by a slight trauma (such as a child putting his finger in the nose). Just sit down, slightly tilt your head forward, and pinch the bridge of your nose. Do not blow your nose! Keep doing this for about ten minutes, which is the time the clot forms correctly (a shorter compression is not efficient). Consult a doctor when the bleeding does not stop or starts again.

Any other situation (including nosebleed due to a severe nose trauma or to a head trauma) must be considered as an emergency: place the person in a comfortable situation (lying or seated), call for help and follow the instructions.

Internal bleeding

Main article: Internal bleeding

The shock symptoms are not specific to an internal bleeding, but are always a medical emergency. In such a situation, the role of a bystander is to lay the person down, and call for help.

Risk of blood contamination

Concerning the direct exposure of the first-aider's skin to the blood: the skin is watertight, so if the skin is not wounded (skin disease or very recent wound), there is no risk of contamination by a disease of the casualty. Before any further activity (especially eating, drinking, touching the eyes, the mouth or the nose), the hand must be carefully and softly washed with clear water, then bathed five minutes in diluted bleach (sodium hypochlorite).

However, to avoid any risk, it is highly recommended to protect the hands, e.g. by a plastic bag or a cloth, before pressing the wound. If there is nothing to protect the hands, examine your hand to be sure it is not wounded, or use a distant compression of the artery (pressure point with your hand if you know the anatomic references, or a tourniquet).

In case of blood exposure, even on safe skin, the first-aider should go to the emergency service, where an anti-retroviral therapy will be started just in case.

Notes

Before the advent of modern medicine the technique of bloodletting, or phlebotomy, was used for a number of conditions: causing bleeding intentionally to remove a controlled amount of excess or "bad" blood.

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