Chapter 10 Pulmonary emboli and venous thromboses
PULMONARY EMBOLI
Pulmonary embolism (PE) is a diagnosis to be made in the emergency department. If diagnosed and treated appropriately, the mortality is of the order of 8–10%, with most patients dying of comorbidity. If the diagnosis is not made initially, the mortality rises to about one-third of cases1 and patients have a three-fold higher rate of in-hospital adverse events.2
Risk factors
Note: Only 6% of patients with PE have no recognised coexistent illness or risk factor.
Diagnosis and differential diagnosis
The diagnosis is often difficult and approaches to diagnosis remain in a state of flux. Classical signs and symptoms occur only occasionally, and most are non-specific. Clinical judgment enhances the ability of investigations to predict PE, and is now used in most PE investigation algorithms, in association with calculation of pre-test probability (PTP) of PE based on symptoms, signs and risk factors.4
Pre-test probability (PTP)2
| Signs of DVT | 3 |
| PE most likely cause | 3 |
| Active cancer | 1.5 |
| Recent immobilisation (bed rest of 3 days or more, leg plaster for 2 weeks or more, surgery within 3 weeks) | 1.5 |
| Tachycardia (PR > 100/min) | 1 |
| History of haemoptysis | 1 |
PTP is considered high if over 6, intermediate for a score of 3–6, and low for a score of 2 or less.
PE rule-out criteria (PERC)
A gestalt suspicion of low probability of PE together with a refinement of Wells criteria4 has been developed and trialled to exclude PE in outpatient populations.5,6 These PE rule-out criteria (PERC) are: age < 50 years, pulse < 100/min, SaO2 ≥ 95%, no haemoptysis, no oestrogen use, no surgery/trauma requiring hospitalisation within 4 weeks, no prior venous thromboembolism (VTE) and no unilateral leg swelling.
In a large multicentre study, the combination of low suspicion and negative PERC reduced the probability of VTE to below 2% in those with low suspicion of PE.6
Investigations
The Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study found that, although an abnormal (low, intermediate or high probability) ventilation/perfusion lung scan was very sensitive (98%) for PE, it was not nearly as specific (10%) as previously thought, and only a minority of patients with PE had high probability scans.7 Ultrasonography of leg veins (to look for deep vein thrombosis (DVT)) and pulmonary angiography should be used much more liberally when there is strong clinical suspicion of PE.
Troponin I
Several studies have suggested the use of troponin I in PE to predict the occurrence of complications. Elevated troponin I appears to reliably predict haemodynamic instability and complicated clinical course.8–10 Others have suggested B-type natriuretic peptide (BNP) may be a better predictor.11
