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A P a t i e n t ’s G u i d e t o A n t i t h r o m b o t i c a n d T h r o m b o l y t i c T h e r a p y
in Neonates and Children
AMERICAN COLLEGE OF CHEST PHYSICIANS
A Patient’s Guide to Antithrombotic and
Thrombolytic Therapy in Neonates and Children
PAT I E N T E D U C AT I O N G U I D E
AMERICAN COLLEGE OF CHEST PHYSICIANS
How does blood circulate through the body?
"! The heart pumps blood through blood vessels in the body.
"! Blood is pumped by the right side of the heart to the lungs where it gathers oxygen.
"! After blood picks up oxygen in the lungs, it returns to the left side of the heart where it is
pumped into the aorta, the largest blood vessel in the body.
"! The aorta branches into smaller arteries and takes this oxygen-containing blood, along with
nutrients, to all tissues and organs of the body.
"! The arteries taper down to narrower capillaries where oxygen and other nutrients can be
given off to various tissues. Once this has happened, the capillaries join to form a network
of veins that transport the blood back to the right side of the heart.
"! The oxygen-poor blood then re-enters the lungs to gather more oxygen before returning to
the left side of the heart through the pulmonary veins for another cycle through the body.
Are there special problems with blood circulation in newborns?
"! Newborns have a hole between the right side and left side of the heart that allows blood to
go around the lungs, which are not used before birth (oxygen is given by the placenta prior
to birth). This hole normally closes in the weeks after birth, but in many children with heart
disease, it stays open for months or years.
What is a normal (or helpful) blood clot?
"! Blood clotting is a normal process that occurs when a blood vessel is damaged to prevent
bleeding from the site of injury.
"! If a blood vessel is cut, blood flows out of the vessel where it comes into contact with
powerful substances that stimulate blood clotting, and the leak is sealed.
"! The plug forms a scab, during which time the blood vessel is repaired.
What is an abnormal (or harmful) blood clot?
"! An abnormal blood clot (usually referred to as a blood clot) is a solid mass consisting of
blood cells and other material that forms inside a blood vessel and blocks the flow of blood.
What kinds of harmful blood clots exist?
Venous clots
"! Deep vein thrombosis (DVT)
-
Blood clots occurring in the veins
"! Pulmonary embolism (PE)
-
Venous clots that break off and travel, becoming stuck in the lungs.
"! Cerebral sinovenous thrombosis
-
Blood clots in veins draining the brain
A P a t i e n t ’s G u i d e t o A n t i t h r o m b o t i c a n d T h r o m b o l y t i c T h e r a p y
in Neonates and Children
AMERICAN COLLEGE OF CHEST PHYSICIANS
"! Intracardiac clots
-
Blood clots in the heart. These can break off and travel as “emboli,” potentially causing “embolic strokes”
"! Paradoxical embolus or paradoxical stroke
-
In children with holes between the right side and the left side of the heart, venous clots can
break off and travel through to the arteries. This is called a paradoxical embolus. If it goes to
the brain, it is called a paradoxical stroke.
"! Superficial thrombosis or phlebitis
-
Blood clots that occur in the surface veins, not the deep veins. They are less serious, do not
break off, and cannot travel to the lungs to cause a PE.
Arterial clots
"! Blood clots may occur in arteries and usually cause the affected body part to become
ischemic (lack of oxygen to the tissues) or if severe, cause infarction (tissue death)
"! Arterial ischemic strokes
-
Blood clots in the arteries to the brain
What are the major risk factors for blood clots in newborns?
"! Medical procedures, especially lines in arteries or veins.
"! The exceptions are the following:
-
Arterial ischemic strokes, which happen frequently for no known reasons
-
Clots in the kidney veins that can also occur for no known reason
What are the major risk factors for blood clots in children?
"! Being sick with other major problems, including cancer, heart disease, or after major
surgery
"! Lines put into big veins to give fluid or drugs (vascular cannula) also cause many clots
in children.
How common are blood clots in newborns and children?
"! Overall, blood clots in newborns and children are less common than in adults, and there
may be many reasons for this. Because of this, and because of the difficulty of performing
clinical research in children, we do not know nearly as much about the best way to diagnose or treat blood clots in newborns and children as we do about how to diagnose and
treat them in adults.
What symptoms does a blood clot cause?
"! The symptoms caused by blood clots vary a lot depending on the where it is, how big it is,
and what the clot is doing to the surrounding tissues or body organs.
"! Clots in veins often cause pain and swelling of the affected area. In children, they often
cause no obvious symptoms.
"! Clots in the lungs (pulmonary emboli) often cause difficulty breathing or chest pain. These
symptoms can come and go or be very minor, even with big emboli that could cause death.
"! Arterial clots usually cause the affected area to be cold, have no pulse, and painful.
A P a t i e n t ’s G u i d e t o A n t i t h r o m b o t i c a n d T h r o m b o l y t i c T h e r a p y
in Neonates and Children
AMERICAN COLLEGE OF CHEST PHYSICIANS
"! Arterial ischemic strokes often cause loss of movement or speech, but they can also cause
seizures or cause no obvious symptoms.
"! Cerebral sinovenous thrombosis often causes headache, seizures, or occasionally, loss of
movement or speech, as well.
"! In otherwise healthy children, in whom blood clots are rare, the signs and symptoms of blood
clots are often easily confused with other more common medical conditions.
"! In sick children, in whom blood clots are more common, the signs and symptoms may often
be hidden by the signs and symptoms of the underlying medical problems.
How is a blood clot diagnosed?
"! There is no simple blood test that can diagnose a blood clot, and they are rarely seen on plain
radiographs.
"! Clots in arteries can sometimes be diagnosed by simple clinical assessment of the patient,
but this is almost never true for clots in veins.
"! Blood clots are diagnosed by the use of medical imaging techniques such as ultrasound,
CT scan, or MRI. A special test called ventilation/perfusion scanning may be required for
pulmonary emboli.
"! Each test has specific advantages and disadvantages. Often, a combination of tests is required.
"! In children, testing is difficult because sometimes a general anesthetic is required to enable
the imaging test to be performed properly.
How is a blood clot treated?
"! Treatment for blood clots consists of two parts: (1) immediate treatment, and (2) long-term
treatment.
- Immediate treatment—The goals of immediate treatment of clots in arteries are to reduce
ischemia and relieve symptoms. For clots in veins, the goals are to prevent the clot from
becoming larger, prevent clots from breaking off and causing emboli, and, of course, to relieve
symptoms; however, clots in veins cause few, if any, symptoms in children.
-
Long-term treatment—The goals of long-term treatment are to prevent recurrent clots and
lessen symptoms such as pain and swelling that occur from damaged veins. Any damage
already caused by ischemia or infarction (tissue death) will not be fixed by long-term treatment.
The long-term problems of arterial clots are called chronic arterial insufficiency, and the longterm consequences of venous clots are called postthrombotic syndrome.
"! Blood thinner—A blood clot is often treated with a blood thinner (anticoagulant therapy).
The major side effect of blood thinners is that they increase the risk of abnormal bleeding. The
length of treatment depends on where the blood clot is located (in general, clots in arteries
are treated for shorter time than clots in veins), the treatment required for the child’s underlying illness, the ability to give the treatment to the child, and the likely risk of bleeding for the
child.
"! Clot-busting drugs—For very severe blood clots, more powerful clot-busting drugs (throm-
bolytic therapy) can be given. These drugs have a much higher risk of bleeding then blood
thinners and are only used when the likely benefits outweigh the risks.
"! Surgery—Occasionally, surgery is required to remove a blood clot. This is most common for
intracardiac clots in children after major heart surgery.
A P a t i e n t ’s G u i d e t o A n t i t h r o m b o t i c a n d T h r o m b o l y t i c T h e r a p y
in Neonates and Children
AMERICAN COLLEGE OF CHEST PHYSICIANS
"! Antiplatelet drugs—For clots in arteries, antiplatelet drugs are often given, which usually
cause less bleeding than blood thinners. An antiplatelet drug stops the platelets (small cells in
the blood) from working.
"! Observation—Occasionally, blood clots in newborns and children are not treated but just
observed.
What are the most commonly used blood thinners in children?
"! Heparin and warfarin have been used for more than 50 years in adults and more recently in
children. Patients who take either of these drugs require blood testing to measure the bloodthinning effects of the drug and adjust (increase or decrease) the dose to achieve the desired
blood-thinning effect.
"! Heparin is given by injection into the veins through a “drip”; therefore, it is used mostly with
patients in the hospital. Heparin has the advantage that it can be “turned off” very quickly by
stopping the drip or by giving a specific antidote.
"! Warfarin is taken by mouth; therefore, it is used most commonly when treatment is given out-
side the hospital. Warfarin takes a few days to work properly and needs a few days to easily be
turned off, so planning is required around any surgical procedures. Warfarin can be reversed
quickly if necessary.
"! Low-molecular-weight heparins are derived from heparin and have been used as blood thin-
ners in the last 15 years. They are given by injection under the skin, once daily or twice daily,
and require less frequent testing than heparin or warfarin. However, there is no good way to
turn them off quickly (less than 12 hours).
What are the most commonly used antiplatelet drugs in children?
"! Aspirin, dipyridamole, and clopidogrel. Each of these drugs has specific considerations.
Are there special considerations for blood thinners and antiplatelet drugs in children?
"! None of these drugs was specifically designed for use in newborns or children, so there are
often practical issues when prescribing these drugs in children.
"! Special strategies have been developed to assist with giving these drugs to newborns and
children of different ages, as well as monitoring the results. Therefore, most big children’s hospitals have developed special “anticoagulation clinics” to support children and their families.
Combining the treatment of blood clots with the treatment of childhood cancer, heart disease, or other major illness in the context of normal (or abnormal) growth and childhood development requires specialist consideration and usually a close working relationship between
the doctors, nurses, parents, and children.
Are there other blood-thinning drugs used in children?
"! There are many other blood thinning drugs used in adults (eg, fondaparinux, dabigatran,
rivaroxaban, apixaban); however, the safety and effectiveness of these drugs in children is not
known. Clinical trials need to be performed in children to learn more about how to use these
drugs.
A P a t i e n t ’s G u i d e t o A n t i t h r o m b o t i c a n d T h r o m b o l y t i c T h e r a p y
in Neonates and Children
AMERICAN COLLEGE OF CHEST PHYSICIANS
For additional information:
Antithrombotic therapy and prevention of thrombosis: American College of Chest Physicians evidence-based
clinical practice guidelines, 9th edition. Chest. 2012;141(2 suppl):48S-52S.
www.chestpubs.chestjournal.org
American College of Chest Physicians
www.chestnet.org
CHEST Journal
www.chestjournal.org
These materials are for informational and educational purposes only. They are not intended to replace the medical advice of a qualified
health-care provider. Please see your doctor if you are having medical problems associated with the health issues described in this guide. American College of Chest Physicians © 2012