Chapter 2: Cardiovascular System

Section 2b: Bleeding

Uncontrolled bleeding is a threat to life. If significant amounts of blood are lost e.g. half to a third of normal blood volume (normal blood volume of a 70 Kilo subject is 5.6 litres). Then the blood pressure drops and the heart's ability to produce a normal pulse is lost. It responds by increasing its rate of pumping.

If a blood vessel is damaged, such as an artery it will be under high pressure. The simplest way of controlling this bleeding is by direct pressure to the wound and then a pad can be secured by a dressing and hence the situation remedied. The blood vessels themselves tend to respond to injury by curling up to the extent that the leaking hole is closed. This control of bleeding is further reinforced by the body producing a plug of red cells which stick to the hole and this is further reinforced by clotting factors forming a rigid framework and hence some kind of repair is achieved.

Loss of sufficient amount of blood to derange the pulse and blood pressure will result in a condition known as shock. The subject will respond to this state of affairs by becoming pale, sweaty, anxious or confused and will feel cold to the touch. The normal signs one would expect e.g. a pulse of 60 at the radial or wrist, blood pressure of 120/80mmHg will be progressively deranged, the pulse will increase for example to 100 and the blood pressure will drop for example to 100/80mmHg. In early shock the lower figure -120/80mmHg may become slightly higher - 120/90mmHg. This is because the body's response to the situation is for the high-pressure vessels to stiffen and contract and this acts to maintain pressure but reduce flow. For this reason the pulse is very difficult to feel. Part of the response of the skin to this situation is that the blood supply is reduced and it is therefore cold. This can be confirmed when the pulse is taken, the capillary return test indicates this. The test is done by squeezing a finger tip until it whitens and then noting the time it takes to pink up again, normally 2 seconds, shock 3 seconds +. Sweating is also part of the response and indicates that adrenaline a stress and survival hormone has been produced in response to this injury.

If this state of affairs continues the blood supply to certain organs can be reduced to the point where they are seriously damaged. The most important ones are the kidneys. As blood is progressively lost, the subject will lose consciousness and ultimately the heart will stop pumping (cardiac arrest). The treatment then is that external bleeding should be controlled immediately it has occurred by local pressure.

If the subject has lost significant blood then, the treatment is to give 2 litres of Saline intravenously or replace with blood if available (if necessary this treatment will need to be repeated). This requires a plastic tube to be inserted into a vein, which is the part of the circulation that propels fluid back towards the right side of the heart. This procedure can be life saving. In the case of error i.e. a normal subject does not require 2 litres of Saline and it is given by mistake, it will not cause any harm. The act replacing fluid, which returns the circulation to normal and controlling bleeding will result in the following -

1. heart function returns to normal
2. the pulse slows down
3. the blood pressure comes back up to normal
4. the vital organs are spared a potentially serious insult

Other important points:-

1. If inappropriate amounts of intravenous fluids are given in the management of shock for example more than 2 litres of saline given rapidly in a person who has normal vital signs i.e. pulse 60, blood pressure 120/80 or so, the first sign of them coming into difficulty would be anxiousness followed by breathlessness either difficulty in breathing and or increased rate of breathing.

This is due to the fact that the fluid which has been given inappropriately has leaked out of the circulation of the lungs i.e. from the vessels in the lungs into lung tissue making them stiffer which increases the difficulty in breathing and also reduces the efficiency of the lungs. This can progress to become life threatening with the subject starting to cough up pink frothy fluid from the lungs and losing consciousness. The treatment for this is first of all to avoid it by only giving appropriate amounts of fluid intravenously and observing the subject for the return of pulse and blood pressure to normal. In this situation one would not continue with aggressive fluid replacement treatment. If, however, the situation has arisen then the fluid should be stopped immediately, the subject sat up to improve the efficiency of breathing, given oxygen and even some drugs to improve the breathing. These drugs would be Morphine, which helps reduce the pressure on the lungs, which is one of the mechanisms by which the fluid leaks into the lungs. It also makes the subject feel better. A drug known as a diuretic promotes removal of fluid from the lungs by increasing the amount of urine production by the kidneys and so reducing the excess fluid the subject has in their circulation.

2. Bleeding can be regarded as two types either external where it is visible to the observer or internal. Usually the latter results from damage of an organ or a blood vessel to an organ. Bleeding into the body cavities can occur for example following injury to the abdomen, chest or the pelvis and can result in serious or even fatal shock. Bleeding into the abdomen is usually recognised by the subject complaining of abdominal pain and touching the abdomen even gently can provoke severe pain (peritonism). Bleeding into the chest can result in the collapse of a lung which may not be immediately life threatening. Bleeding into the area between the lung and the heart can impair the heart action. This will result in the heart producing a smaller volume pulse which is increasingly more difficult to feel, the heart sounds becoming quieter and the veins becoming filled with blood because the blood returning to the heart has not been pumped out of it. (Cardiac tamponade)

This can be evident on examining the neck where the neck veins, which are normally not visible, can become very obvious and firm. This situation is called cardiac tamponad and can be remedied by removing the blood from the space between the heart and the lungs using a long needle and syringe, this is not a procedure commonly done and requires expert care.