PULMONARY EMBOLISM Flashcards
How many people have a DVT in UK every year?
1 in 1’000
If untreated how many of those with a DVT will develop a PE?
1 in 10
How many PE’s happen as a hospital inpatient? How many deaths?
1/2
25’000 deaths every year
What is the usual cause?
A DVT
Explain how a DVT causes a PE?
In almost all cases, the cause is a blood clot (thrombus) that has originally formed in a deep vein (known as a DVT). This clot travels through the circulation and eventually gets stuck in one of the blood vessels in the lung. The thrombus that has broken away is now called an embolus (and can therefore cause an embolism). Most DVTs come from veins in the legs or pelvis. Occasionally, a PE may come from a blood clot in an arm vein, or from a blood clot formed in the heart.
What other causes, other than blood clots can it be?
• Fatty material from the marrow of a broken bone (if a large, long bone is broken - such as the thigh bone (femur).
• Foreign material from an impure injection - for example, with drug misuse.
• Amniotic fluid from a pregnancy or childbirth (rare).
• A large air bubble in a vein (rare).
• A small piece of cancerous material (tumour) that has broken off from a larger tumour in the body.
Rare causes: RV thrombus – post MI/ Septic emboli – R sided endocarditis/ Fat, air or amniotic fluid embolism/ Neoplastic cells/ Parasites
What is Virchow’s triad?
- Altered blood flow
- Altered vessel
- Altered blood constituents = hypercoagulability
- Blood flow
These include turbulence, stasis, mitral stenosis, and varicose veins.
- Damage to vessel
Injuries and/or trauma to endothelium includes damage to the veins arising from shear stress or hypertension.
- Hypercoaguability
Hyperviscosity, deficiency of antithrombin III, nephrotic syndrome, changes after severe trauma or burn, disseminated cancer, late pregnancy and delivery, race, age, smoking, and obesity
Problems: what happens?
- Lung tissue is ventilated but not perfused = increased intrapulmonary dead space and decreased gas exchange. After a few hours, the lung tissue then stops producing surfactant => lung collapse => increased hypoxaemia.
- Decreased cross-sectional area of pulmonary arterial bed => increased pulmonary arterial pressure (pulmonary hypertension) and a decreased cardiac output
Zone of lung no longer perfused => can infarct but often doesn’t because lungs are still supplied with O2 by bronchial circulation and the airways
What are the risk factors?
• Immobility: surgery or from illness or injury o Surgery: Recent surgery esp abdo/pelvic or hip/knee replacement o Leg fracture o Prolonged bed rest/reduced mobility • Travel • Prev. DVT (or PE) • Blood clotting disorders (clot more easily) i.e. Thrombophilia • Other disorders that make you clot more easily: nephrotic syndrome, antiphopholipid • Contraceptive pill or HRT • Cancer or heart failure • Older people (over 60yrs) • Pregnancy/ post partum • Obesity • Smoking • Male • Dehydration • Malignancy
What are the key symptoms?
Acute breathlessness - Pleuritic chest pain (worse on inspiration) - Haemoptysis - Dizziness - Syncope (RHF) - Dyspnoea (RHF) - Cough
What is the onset?
Suddenly
What symptoms will a small PE cause?
- No symptoms at all (common).
- Breathlessness - this can vary in degree from very mild to obvious shortness of breath
- Chest pain which is pleuritic, meaning sharp pain felt when breathing in. Often you feel like you can’t breathe deeply, as this causes you to catch your breath. This happens because the blood clot may irritate the lining layer (pleura) around the lung. Shallow breathing is more comfortable.
- Coughing up blood (haemoptysis).
- A mildly raised temperature (fever).
- A fast heart rate (tachycardia).
