PULMONARY EMBOLISM

Prevention

Death from Pulmonary Embolism following major orthopedic and other surgery is largely preventable. In exceptional cases, routine blood-thinners are wisely avoided. A significant minority of surgeons fail to observe authoritative guidelines, with occasional disastrous consequences. Anticoagulation may be stopped too soon.

Death from Pulmonary Embolism following major orthopedic and other surgery is largely preventable. Venous thrombosis is abnormal clotting of blood in a vein. When such clotting occurs in major veins (Deep Venous Thrombosis, DVT), particular those draining blood from the lower half of the body, there is material risk that pieces of clot will break off and travel (embolise) through the larger veins and heart and into the arteries of the lungs (Pulmonary Embolism, PE).

Practice Point

In cases of lethal or disabling pulmonary embolism following major surgery, look for specific risk disclosure preceding consent

Among the factors that increase the probability of thromboembolism, those most often relevant to medical litigation are major surgery and immobility. More than 50% of patients undergoing major orthopedic surgery such as hip replacement or knee replacement will develop venous thrombosis, a minority will have symptoms varying from trivial to disabling, and 1-2% will die from PE ¹².

Because DVT usually produces no symptoms and often is undetected clinically ³, prevention of potentially lethal PE requires prophylaxis for all patients at risk. The previously standard approach of taking action only in the presence of evident DVT is inadequate.

Practice Point

The general intent to anticipate and prevent venous thrombosis should be documented, even though the blood-thinner heparin may be too hazardous in exceptional cases

Orthopedic and other surgeons have resisted universal blood-thinning (anticoagulation) in high risk surgery for fear of more frequent major postoperative hemorrhage. Many quality studies, including meta-analysis, have shown those fears to be groundless ⁴.

In exceptional cases, routine blood-thinners are wisely avoided. Nevertheless, bleeding into surgical wounds sometimes requires discontinuation of anticoagulation and replacement by prophylactic mechanical stimulation of legs only. Similarly, during immobilisation following acute Spinal Cord Injury, anticoagulation may be too dangerous and better option may be a clot filter in the between deep veins and heart ⁵.

A significant minority of surgeons fail to observe authoritative guidelines, with occasional disastrous consequences. Despite the development of clear Clinical Practice Guidelines ⁴ for the use of prophylactic anticoagulation following high risk surgical procedures in the majority of patients, community standards have lagged behind, particularly outside teaching centres ⁴^{,

6}. The last decade has seen limited improvement ⁷.

Practice Point

Consider whether this might be a case for a Supreme Court of Canada ruling on the appropriateness of community standards

Though far from perfectly effective, routine anticoagulation with heparin has been shown to reduce significantly the probability of DVT and PE following major surgical procedures ⁴^{,

8,

9}.

Anticoagulation may be stopped too soon. The risk does not end at hospital discharge ¹⁰, particularly under current policies of minimal necessary hospitalisation.

Traditions of anticoagulation were often established in an era when post-operative hospitalisation lasted 7-10 days or more.

Particularly where immobilisation will continue for days or weeks after release from the acute surgical unit, oral blood-thinner, usually warfarin, must be phased in almost immediately after surgery, to be stabilised by hospital discharge, and maintained until the increased risk of thrombo-embolism is over.

Practice Point

Even though appropriately administered postoperatively, anticoagulation may have been discontinued prematurely

Diagnosis

Because 1) there is still no test that is both sensitive and specific for the diagnosis of PE, and 2) erroneous diagnosis can be as dangerous as missed diagnosis, appropriate investigations are determined by clinical judgment^{11 []}.

Clinical Assessment

Probable presence of DVT (tenderness on squeezing deep leg veins, leg swelling) and absence of a more probable diagnosis for the respiratory symptoms are the strongest clinical predictors of PE. A heart-rate of more than 100, immobilisation or surgery within the preceding 4 weeks, and previous PE or DVT are intermediate clinical predictors. Current or recent malignancy and coughing up blood are least predictive.

By considering the presence or absence of each of these factors, the probability of PE can be clinically estimated to be high, moderate or low.

Diagnostic Tests

Depending on the clinical probability, one or more of these tests should be undertaken to confirm or rule out PE:

Practice Point

Tests for Pulmonary Embolism:

Diagnosis is then made or refuted on the combined clinical and investigational evidence.