When a patient's blood count, amount of blood, or red blood cells falls too low, he may need a blood transfusion. We generally say that 9 grams of hemoglobin is the cutoff level, with normal being between 13 and 15 grams for most healthy people. But for many reasons, including religious (Jehovah Witnesses refuse any blood transfusion), the choice of no blood or of, under certain circumstances, blood be given. Frequently, when a patient knows he will be needing blood, he will give his own blood in advance or have friends or relatives donate for him.
As far as coagulation is concerned, I am going to show you a schematic version of the clotting pathway, which includes factors IV and VII through XIII. I never remember all the specifics myself and always have to refer to specialists or books to understand all the pathways, but I thought you might be interested to see how much is involved in forming a blood clot and stopping bleeding when you get a scratch or cut. The factors and their synonyms are:
| I | = | Fibrinogen |
| II | = | Prothrombin |
| III | = | Tissue Factor |
| IV | = | Calcium Ion |
| V | = | Proaccelerin (labile factor) |
| VII | = | Serum Prothrombin Conversion Accelerator Factor (stable factor) |
| VIII | = | Antihemophilic Factor |
| IX | = | Christmas Factor |
| X | = | StuartPrower Factor |
| XI | = | Plasma Thromboplastin Antecedent |
| XII | = | Hageman Factor |
| XIII | = | Fibrin Stabilizing Factor and then there are platelets. |
We sometimes refer to the expression “consumption coagulopathy,” which means that, because of continued bleeding and the body's attempt at stopping the bleeding by forming blood clots, many clotting factors are used up or consumed, and this must be managed by physicians with in-depth knowledge of the clotting pathways and their replacements.
In certain situations like hemophilia, kidney disease, and Von Willebrand's disease, special factors are needed and must be supplied by the hematologists. Another problem is disseminated intravascular coagulation or DIC, the name for a number of conditions which cause severe problems with coagulation and can lead to death if not rapidly and appropriately corrected. Some of the things that can cause DIC are massive bleeding, problems with labor and delivery, severe infections, burns, liver disease, crush injuries, and malignancies. DIC is a difficult problem to counteract and sometimes results in death, even in the most experienced hands.
Now let us turn to the whole area of transfusions. Blood contains substances which are called antigens, and, without being more specific, we have to receive a blood transfusion with blood containing pretty much the same antigens as our own. Otherwise, severe “allergic” reactions and even death can occur. The first blood group discovery was made in 1901 with the determination of A, B, and O types. Later on, many other subgroups, such as Rh, Kell, Lewis, and Duffy, were discovered, making it much safer to receive blood transfusions. In the early 1980's, with the beginning of the AIDS epidemic, we were unable to identify contaminated blood. Now we can determine contaminated HIV positive or AIDS blood, making the blood supply safe and dependable.
In conclusion, let me review briefly the hemostatic process, or how bleeding stops without our external help. After a minor injury causes an opening in a vein or an artery small artery called an arteriole, the vessel contracts and partially closes off. Then, a mass of platelets join together to form a plug--like a finger in a dike which stops the bleeding and allows the hole to heal with a collagen scar (see Chapter 21). So the next time you have a cut and are bleeding, think about all these considerations I have mentioned, and by the time you have reread this chapter the bleeding had better have stopped; if not see a doctor!
Chapter 19
PULMONARY EMBOLISM
Blood clots in veins where they shouldn't be found,
Can be a great problem if they should abound.
And if they break loose and go to the lung,
A patient may die with the reason unsung.
More than half a million will get this bad disease,
With blood clots from their pelvis, or their ankles to their knees.
And ten percent will die within an hour, sad to say.
So one must make the diagnosis soon, with no delay.
And of the 90% who live beyond the very first hour,
About a third will die in spite of all the medical power.
So face it, blood clots in your veins, are a very serious matter,
And shouldn't be taken lightly or be treated by a Mad Hatter.
If you are diagnosed and treated with the proper drugs
The doctor can dissolve the most pernicious of the clogs.
And using anticoagulants, (blood thinners to the public,)
You'll probably survive to next New Year and be able to
drink some bubblic!
In reviewing the literature for this chapter, I was surprised to find that so many people have pulmonary emboli and that a large proportion of them die of the disease. When a large clot breaks loose in a vein and travels through the venous system to the heart and through the right side of the heart into the lungs, death may be instantaneous when the body is unable to get oxygen. There are other factors involved that we don't need to consider, but it's important to note that almost 50% of patients dying in the hospital have some degree of pulmonary emboli. If the diagnosis is made, then ninety percent will survive; if the diagnosis is not made, only seventy percent will survive, so it is important to know the signs and symptoms and be sure that your physician knows about them and starts appropriate therapy rapidly.
But let's go back a few steps. Who develops these blood clots, and why do they develop? Normally, blood flows continuously from the legs into the large vein in the abdomen and chest, the vena cava. But under certain circumstances, blood flow is diminished and sets up a background for co-agulation or clotting to occur. As long ago as the 1880s the famous German physician Rudolf Virchow determined that three factors were responsible, for the occurrence of blood clots or thrombosis. They are known today as Virchow's triad and consist of (1) stasis or slowing down of blood flow in the vein, (2) injury to the vein, and (3) an increased tendency for the blood to clot, called hypercoagulability.
The causes of this triad are many, but the main ones that concern us here are those related to surgery. When a patient has an operation, he often is lying down for a prolonged period with no muscle activity; the patient is often paralyzed by the anesthesiologist so that the surgeon can operate in a motionless field. This operative inactivity and the postoperative bed rest are highly conducive to stasis in the veins, and thrombosis or formation of clots can occur more readily. This problem may be more common as we get older, and it takes longer to recover and ambulate.
When