Pulmonary embolism is assessed with the two-level Wells score: more than 4 points is PE likely and the patient goes straight to a CT pulmonary angiogram, while 4 points or less gets a D-dimer with the result within 4 hours. NICE NG158, last updated 2 August 2023, adds interim anticoagulation for any delay, unfractionated heparin with consideration of thrombolysis if the patient is haemodynamically unstable, and apixaban or rivaroxaban once PE is confirmed. At the CT1 anaesthetics interview the scenario is a post-operative patient who is suddenly breathless.

Key takeaways

  • Two-level PE Wells score: more than 4 points is PE likely, 4 or less is PE unlikely (NICE NG158)
  • PE likely: CTPA immediately if possible, with interim therapeutic anticoagulation if the scan cannot be done immediately
  • PE unlikely: D-dimer with the result within 4 hours, or interim anticoagulation while waiting
  • Haemodynamic instability: continuous unfractionated heparin infusion and consider systemic thrombolysis; do not thrombolyse a stable patient even with right ventricular dysfunction
  • Confirmed PE: apixaban or rivaroxaban first line; low molecular weight heparin routes if neither suits
  • Review at 3 months; consider stopping after a provoked PE, consider continuing after an unprovoked one

How do you recognise a pulmonary embolism?

A pulmonary embolism is recognised by sudden breathlessness, pleuritic chest pain, tachycardia or haemoptysis in a patient with a reason to clot, and the anaesthetic CT1 meets it after surgery. Immobility and an operation in the previous 4 weeks are both Wells items.

Hypoxia with a clear chest film and a tachycardia that does not fit the pain score is the picture. However, the diagnosis is probabilistic until imaged, which is why NG158 makes the Wells score the first step rather than the D-dimer.

A swollen, tender calf alongside the chest symptoms scores 3 on its own and moves the patient into the likely group.

What do you do first?

The first actions in suspected PE are ABCDE with oxygen, access and an ECG, then the Wells score to decide whether the next test is a CTPA or a D-dimer. Blood pressure decides the whole pathway, because instability changes the treatment.

  • Oxygen to a target range, saturations and respiratory rate
  • Blood pressure and pulse: a hypotensive patient is on the instability pathway from the start
  • ECG, chest radiograph and a blood gas to exclude the alternatives
  • Baseline bloods including renal function and clotting, because NG158 asks for them to be reviewed within 24 hours of starting interim anticoagulation
  • Calculate and document the Wells score

How does the two-level Wells score work?

The two-level PE Wells score in NG158 adds seven items and splits at 4 points: more than 4 is PE likely, 4 or less is PE unlikely. There is no intermediate group.

  • Clinical signs and symptoms of DVT, at minimum leg swelling and pain on palpation of the deep veins: 3 points
  • An alternative diagnosis is less likely than PE: 3 points
  • Heart rate more than 100 beats per minute: 1.5 points
  • Immobilisation for more than 3 days or surgery in the previous 4 weeks: 1.5 points
  • Previous DVT or PE: 1.5 points
  • Haemoptysis: 1 point
  • Malignancy on treatment, treated in the last 6 months, or palliative: 1 point

A post-operative patient with a heart rate of 110 and no better explanation already scores 6. Working that out aloud is the kind of reasoning the station rewards.

What happens if PE is likely?

If PE is likely, with a Wells score above 4, NG158 offers a CT pulmonary angiogram immediately if possible. If the scan cannot be done immediately, interim therapeutic anticoagulation is started while waiting.

For patients with contrast allergy, severe renal impairment with an estimated creatinine clearance below 30 ml/min, or a high risk from irradiation, NG158 asks for a ventilation-perfusion SPECT scan to be assessed as the alternative, or a planar V/Q scan if SPECT is unavailable.

If the scan is negative, interim anticoagulation stops, but NG158 says to consider a proximal leg vein ultrasound if DVT is suspected, and to explain the symptoms that should bring the patient back.

What happens if PE is unlikely?

If PE is unlikely, with a Wells score of 4 or less, NG158 offers a D-dimer test with the result available within 4 hours if possible. If the result cannot be obtained within 4 hours, in any setting, interim therapeutic anticoagulation is offered while waiting.

A positive D-dimer sends the patient to the same imaging as the likely group. A negative one stops the anticoagulation and the work-up, with safety-net advice.

In practice the 4-hour clock is the part candidates miss. The guideline does not let a patient with suspected PE wait untreated for a laboratory.

What if the patient is haemodynamically unstable?

A patient with confirmed PE and haemodynamic instability is offered a continuous unfractionated heparin infusion and considered for systemic thrombolytic therapy, according to NG158. That is the recommendation that brings the anaesthetist and critical care to the bedside.

NG158 is equally clear the other way: pharmacological systemic thrombolysis is not offered to a haemodynamically stable patient, with or without right ventricular dysfunction. If they become unstable, the thrombolysis recommendation applies.

Say who makes the thrombolysis decision, where the patient is managed, and that you would prepare for cardiovascular collapse. Working under pressure is one of the three marked domains.

Which anticoagulant, and for how long?

For confirmed proximal DVT or PE, NG158 offers apixaban or rivaroxaban. If neither is suitable, the options are low molecular weight heparin for at least 5 days followed by dabigatran or edoxaban, or heparin with a vitamin K antagonist for at least 5 days or until the INR is at least 2.0 on two consecutive readings.

Special groups change the choice. Extremes of weight below 50 kg or above 120 kg prompt consideration of level monitoring; renal impairment with a creatinine clearance of 15 to 50 ml/min has its own list; below 15 ml/min it is heparin-based; active cancer is treated for 3 to 6 months with a DOAC considered.

Duration is reviewed at 3 months. NG158 says to consider stopping after a provoked event if the provoking factor has gone and the course was uncomplicated, and to consider continuing beyond 3 months after an unprovoked event, weighing recurrence against bleeding. A HAS-BLED score of 4 or more that cannot be modified prompts a discussion about stopping.

What about the swollen leg?

A suspected DVT uses the two-level DVT Wells score, and a score of 2 or more is DVT likely. NG158 then offers a proximal leg vein ultrasound with the result within 4 hours, or interim anticoagulation and a scan within 24 hours if that is not possible.

A score of 1 or less is DVT unlikely and gets a D-dimer within 4 hours, with the same interim anticoagulation rule for delay. Low-risk confirmed PE can be treated as an outpatient using a validated risk stratification tool, which NG158 introduced in 2020.

Which traps catch candidates?

The PE traps at interview are the D-dimer sent on a high-probability patient, the untreated wait for a scan, and thrombolysis offered to a stable patient because the echo showed a strained right ventricle.

  • Sending a D-dimer when the Wells score is above 4: the guideline goes straight to CTPA
  • Letting a patient wait more than 4 hours for a D-dimer or a scan without interim anticoagulation
  • Thrombolysing a haemodynamically stable patient
  • Forgetting the renal function before choosing the anticoagulant
  • Stopping every anticoagulant at exactly 3 months regardless of provocation

What is the interviewer listening for?

In a PE scenario the assessors are listening for the Wells score calculated and acted on, the interim anticoagulation rule, the instability pathway with a named decision-maker, and a first-line drug with its caveats.

  • The seven Wells items and the 4-point cut
  • CTPA immediately or D-dimer within 4 hours, and anticoagulation to cover any delay
  • Unfractionated heparin and thrombolysis considered only for instability
  • Apixaban or rivaroxaban, with weight, renal function and cancer checked first
  • A 3-month review, not a fixed stop

How this comes up at the CT1 anaesthetics interview

PE comes up in the clinical judgement station as the day-three hip replacement who becomes breathless and tachycardic on the ward, and the question is your assessment and plan. The station is one of two 15-minute stations, each marked out of 50, scored on clinical judgement and decision making, reflective practice and working under pressure.

The follow-up usually drops the blood pressure to test whether you know the thrombolysis rule and who you call. anaestheticinterview's 340-question bank includes a post-operative PE scenario with AI-marked spoken practice, which is where the NG158 pathway gets said aloud under time pressure.