PBL 8 Flashcards
What is a pulmonary Embolism? WHat is it usually secondary to?
Pulmonary embolism is blockage in one or more arteries in your lungs. In most cases, pulmonary embolism is caused by blood clots that travel to your lungs from another part of your body — most commonly, your legs. Pulmonary embolism is a complication of deep vein thrombosis (DVT), which is clotting in the veins farthest from the surface of the body.
What are the common signs and symptoms of a pulmonary embolism? (3)
- Shortness of breath. This symptom typically appears suddenly, and occurs whether you’re active or at rest.
- Chest pain. You may feel like you’re having a heart attack. The pain may become worse when you breathe deeply, cough, eat, bend or stoop. The pain will get worse with exertion but won’t go away when you rest.
- Cough. The cough may produce bloody or blood-streaked sputum.
What are the three main symptoms of a pulmonary embolism? (3)
What are the less common symptoms of a pulmonary embolism? (7)
3 main:
- Sudden shortness of breath
- Chest Pain
- Cough with bloody sputum
Other:
- Wheezing
- Leg swelling, usually in only one leg
- Clammy or bluish-colored skin
- Excessive sweating
- Rapid or irregular heartbeat
- Weak pulse
- Lightheadedness or fainting
What gets stuck in the arteries of the lungs in a pulmonary embolism? (4) How many blockages do there tend to be?
What is PE secondary to DVT known as?
Blockages to the lungs in PE:
- Usually a blood clot
- Occasionally fat from within the marrow of a broken bone
- Occasionally part of a tumor
- Occasionally air bubbles
It’s rare to experience a solitary pulmonary embolism. In most cases, multiple clots are involved.
Because pulmonary embolism almost always occurs in conjunction with deep vein thrombosis, most doctors refer to the two conditions together as venous thromboembolism (VTE).
What are the risk factors for DVT and Pulmonary Embolism? (14)
- Damage to the inside of a blood vessel due to trauma or other conditions
- Changes in normal blood flow, including unusual turbulence, or partial or complete blockage of blood flow
- Hypercoagulability/family history of blood clots
- Prolonged immobility
- Older age
- Dehydration
- Recent surgery
- Heart Disease
- Pregnancy/recent childbirth
- Cancer
- Previous blood clots
- Smoking
- Being overweight
- Oestrogen supplements in the pill/HRT
Why does older age predispose to blood clots? (3)
Older people are at higher risk of developing clots. Factors include:
- Valve malfunction. Tiny valves in your larger veins keep your blood moving in the right direction. However, these valves tend to degrade with age. When they don’t work properly, blood pools and sometimes forms clots.
- Dehydration. Older people are at higher risk of dehydration, which may thicken the blood and make clots more likely.
- Medical problems. Older people are also more likely to have joint replacement surgery, cancer or heart disease.
Why does surgery increse y our risk of blood clots\? What type of surgery is particularly risky?
Surgery is one of the leading causes of problem blood clots, especially joint replacements of the hip and knee. During the preparation of the bones for the artificial joints, tissue debris may enter the bloodstream and help cause a clot. Simply being immobile during any type of surgery can lead to the formation of clots. The risk increases with the length of time you are under general anesthesia.
Why does pregnancy increase the risk of blood clots?
Why do certein types of cancer increase the risk of blood clots? Which types of cancer and cancer treatment are particularly risky?
Pregnancy. The weight of the baby pressing on veins in the pelvis can slow blood return from the legs. Clots are more likely to form when blood slows or pools.
Cancer. Certain cancers — especially pancreatic, ovarian and lung cancers — can increase levels of substances that help blood clot, and chemotherapy further increases the risk. Women with a history of breast cancer who are taking tamoxifen or raloxifene also are at higher risk of blood clots.
What tests might you order to help confirm a diagnosis of pulmonary embolism? (7)
- CXR - may appear normal in PE, but can rule out other conditions.
- Lung scan (ventilation/perfusion rate)
- Spiral (helical) computerized tomography (CT) scan with contrast agent.
- D-dimer blood test - increased D-dimer, increased risk of clotting
- Ultrasound.
- MRI (reserved for pregnant women and those whose kidneys would be damaged by the dyes in CT)
- Pulmonary angiogram (difficult to perform, used when other tests do not give a definitive answer)
Describe a lung scan. In what situation is this test less reliable?
Lung scan. This test, called a ventilation-perfusion scan (V/Q scan), uses small amounts of radioactive material to study airflow (ventilation) and blood flow (perfusion) in your lungs. First, you inhale a small amount of radioactive material while a special camera designed to detect radioactive substances records air movement in your lungs. Then a small amount of radioactive material is injected into a vein in your arm. Images taken after the injection show whether you have a normal or diminished flow of blood to your lungs. This test is less reliable if you’re a smoker.
What arterial blood gases would you expect to see in Pulmonary Embolism? Is this exclusive to PE?
pO2 will be lowererd - hypoxaemia. This also occurs in other conditions which present in a similar way to PE, so it is not exclusive to PE.
Very often seen in combination with hypocapnoea (reduced blood co2) and alkylosis.
What is hypocarnoea, and what usually causes it?
Hypocapnia or hypocapnea also known as hypocarbia is a state of reduced carbon dioxide in the blood. Hypocapnia usually results from deep or rapid breathing, known as hyperventilation.
In Pulmonary embolism (PE), what is the extent of the hypoxaemia (surprisingly) not related to?
The severity of the hypoxaemia is not related to the extent of the damage to the vasular bed of the lungs - except when the lungs are very severly compromised with 40% or more of the vascular bed affected by the clot.
Which two drugs are commonly used to treat clots? Why is one given before the other? What are the risks of these medication?
What type of clot treating drug is set aside for emergency situations and why?
Anticoagulants. The drugs heparin and warfarin (Coumadin) prevent new clots from forming. Heparin works quickly and is usually delivered with a needle. Warfarin (Coumadin) comes in pill form and doesn’t start working until a few days after your first dose. Risks include bleeding and easy bruising.
Clot dissolvers (thrombolytics). While clots usually dissolve on their own, certain medications can dissolve clots quickly. Because these clot-busting drugs can cause sudden and severe bleeding, they usually are reserved for life-threatening situations.
Which surgical procedures are sometimes used in the treatment of blood clots? When are they indicated? (3)
- Clot removal. If you have a very large clot in your lung and you’re in shock, your doctor may use a catheter to suction out the clot. It can be difficult to remove a clot this way, and this procedure isn’t always successful.
- Vein filter. A catheter can also be used to place a filter in the inferior vena cava. This filter catches and stops blood clots moving toward your lungs. Filter insertion is typically reserved for people who can’t take anticoagulant drugs or when these drugs don’t work well enough.
- Surgery. If you’re in shock and thrombolytic medication isn’t working quickly enough, your doctor might attempt emergency surgery. This happens infrequently, and the goal is to remove as many blood clots as possible, especially if there’s a large clot in your pulmonary artery.
- What preventative measures are taken in hospitals to try and avoid the complication of clotting before and after operations?(4)
- Which patients are given a preventative medication as soon as they present in A&E? (4)
- Anticoagulant therapy. A heparin injection, is given to anyone at risk of clots before and after an operation — as well as to people admitted to the hospital with a heart attack, stroke, complications of cancer or burns. Oral warfarin can be given for a few days before major elective surgery to reduce your risk of clots.
- Graduated compression stockings steadily squeeze your legs, helping your veins and leg muscles move blood more efficiently. They offer a safe, simple and inexpensive way to keep blood from stagnating after general surgery.
- Use of pneumatic compression. This treatment uses thigh-high or calf-high cuffs that automatically inflate every few minutes to massage and squeeze the veins in your legs.
- Physical activity. Moving as soon as possible after surgery can help prevent pulmonary embolism and speed your overall recovery.
Which test would you most likely use to diagnose DVT? Why?
Doppler ultrasound: Using high-frequency sound waves, this system can visualize the large, proximal veins and detects a clot if one is present. Painless and without complications, this is the most commonly used method to diagnose deep vein thrombosis. However, sometimes the test can miss a clot, especially in the smaller veins.
Which clots may require more aggressive treatment with thrombolytics? How is this treatment administerd and what drugs are used?
Blood clots located in the femoral vein near the groin that extend into the iliac vein in the abdomen may require more aggressive treatment with thrombolytic (thrombo=clot + lysis=breakdown) therapy. Clot-busting drugs (alteplase [Activase], streptokinase [Streptase]) may be injected directly into the clot itself.
Who would you not prescribe anticoagulants? What alternative treatment for a DVT would you give them?
Those who have gastrointestinal bleeding (bleeding from the stomach or bowel), intracranial bleeding (bleeding in the brain), or who have had recent major trauma potentially could bleed to death if anticoagulation medications are prescribed. The alternative for leg DVT treatment in these situations may be an inferior vena cava filter.
Other than medication, what can be used after a DVT has occured? What does this help to prevent? How long should this be used for?
Compression stockings are useful in preventing a complication of a leg blood clot called postthrombotic syndrome or postphlebitis syndrome, in which the affected leg swells and becomes chronically painful. These stockings may be purchased over-the-counter or can be custom fitted. It is recommended that they be worn for at least a year after the diagnosis of deep venous thrombosis.
- What is the other name for warfarin?
- What can affect the levels of warfarin needed? (3)
- What blood test is done to monitor Warfarin dosage? How often?
- Warfarin (Coumadin)
- dose needs to be individualized for each person, and blood clotting must monitored routinely since changes in diet, activity, and the administration of other medications may affect the levels of warfarin.
- Blood tests (usually INR, or international normalized ratio) are done routinely to monitor the blood thinning effects. Ideally, the INR should be kept in a range between 2.0 and 3.0. Blood tests are done weekly until the INR stabilizes and then are done every two weeks to every month.
- What is the name of the heparin-like drug given as a short term initial treatment for blood clots?
- How is this given, and what is the dosage?
- When might this be used as a long term treatment?
- Enoxaparin (Lovenox) is a low molecular weight heparin injected beneath the skin to thin the blood.
- The dose is usually 1milligram per kilogram of weight injected twice daily or 1.5 milligrams per kilogram injected once daily.
- Enoxaparin may be used over the long-term in some patients with cancer.
- What is the name of the condition in which nearly all of the venous return from the leg is obstructed by clots in the iliac and femoral veins?
- How is this treated?
- Phlegmasia Cerulea Dolens describes a situation in which a blood clot forms in the iliac vein of the pelvis and the femoral vein of the leg, obstructing almost all blood return and compromising blood supply to the leg.
- In this case surgery may be considered to remove the clot, but the patient will also require anti-coagulant medications.
Describe platelets: shape, size and main function
Platelets are flattened discs that appear round when viewed from above, spindle shaped in section or or in a blood smear. They average about 4um in diamaeter and are roughly 1um thick. Platelets are a major participant in a vascular clotting system that also includes plasma proteins and the cells and tissues of the blood.
How long does a platelet last in the bloodstream? How are they removed from the bloodstream? What is the normal platelet concentration? Where are platelets found on mass? Why?
Platelets are continuously replaced. Each platelet circulates for 9-12 days before being removed by phagocytes, mianly in the spleen. Each microliter of circulating blood contains 150000-500000 platelets; 350000/uL is the average concentration. Roughly one third of the platelets in the body at any moment are held in the spleen and other vascular organs rather than in the bloodstream. The reserves are mobilised during a circulatory crisis, such as severe bleeding.
What is the medical terms platelet concentration which is too low? What concentration is considered too low? What causes this? What are the signs for this?
What is the medical terms platelet concentration which is too high? What concentration is considered too high? What causes this?
The normal platelet count in adults ranges from 150,000 to 450,000/microL
- Low platelet count: Thrombocytopenia is defined as a platelet count less than 150,000/microL (150 x 109/L). This generally indicates excessive platelet destruction or inadequate platelet production. Signs include bleeding along the digestive tract, within the skin and occasionally inside the CNS.
- High platelet count: Thrombocytosis, platelet counts can exceed 500,000/uL. Results from accelerated platelet formation in response to infection, inflammation or cancer.
What are the functions of platelets? (3)
- The release of chemicals important to the clotting process. By releasing enzymens and other important factors at the appropriate times, platelets help initiate and control the clotting process.
- The formation of a temporary patch in the walls of damaged blood vessels. Platelets clump together at an injury site, forming a platelet plug which can slow the rate of blood loss while clotting occurs.
- Active contraction after clot formation has occurred. Platelets contain filaments of actin and myosin. After a blood clot has formed, the contraction of platelet filaments shrinks the clot and reduces the size of the break in the vessel wall.
What is the name for platelet production, and where does it occur? What type of cells produce platelets, and how do they do this? How many platelets can one cell produce?
Platelet production or thrombocytopoeisis, occurs in the bone marrow. Normal bone marrow contains a number of megakaryocytes, enormous cells (up to 160um in diameter) with large nuclei. During their development and growth, megakaryocytes manufacture structural proteins, enzymes and membranes. They then begin shedding cytoplasm in small membrane enclosed packets. A mature megakaryocyte gradually loses all its cytoplasm, producing about 4000 platelets before the nucleus in engulfed by phagocytes and broken down for recycling
What is the rate of megakaryocyte activity and platelet formation stimulated by? (3)
- Thrombopoietin (TPO) or thrombocyte stimulating factor, a peptide hormone produced in the kidneys (and perhaps other sites) that accelerates platelet formation and stimulates the production of megakaryocytes
- Interleukin 6 (IL6) a hormone that stimulates platelet formation
- Multi- CSF, which stimulates platelet production by promoting the formation and growth of megakaryocytes.
What is haemostasis? What are the three stages of haemostasis?
The process of haemostasis, the cessation of bleeding, halts the loss of blood through the walls of damaged vessels. At the same time, it establishes a framework for tissue repair. Haemostasis consists of three phases, the vascular phase, the platelet phase and the coagulation phase.
However the boundaries of these phases are somewhat arbitrary. In reality, haemostasis is a complex cascade in which many things happen at once, and all of them interact to some degree.
If a blood vessel wall is damaged, the vascular phase of haemostasis begins. What happens to the blood vessel wall? Why does this happen? How long does this effect last?
Cutting the wall of a blood vessel triggers a contraction in the smooth muscle fibres of the vessel wall. This local contraction of the vessels is a vascular spasm, which decreases the diameter of the vessel at the site of injury. Such a constriction can slow or even stop the loss of blood through the walls of a small vessel. The vascular spasm lasts about 30 minutes, a period called the vascular phase of haemostasis.
