 Welcome back to approach the pulmonary embolus. This is part 3. In this section, we'll discuss how to put this together to make the diagnosis. We start off by deciding the patient's risk. They can be very low risk, low risk, or high risk. Depending on what risk category the patient is in, we will use different tests to rule in or rule out a PE. In the very low risk patient, we will use a rule known as the PERC rule. In the patient with low risk, we will use the D-dimer test. And in the high risk patient, we rely on imaging. We'll discuss this in detail. First, the very low risk patient. Very low risk patient are the kind of patient that after you examine them, you're really not concerned about PE. Once you see a patient like this, you're going to apply this rule called the PERC rule. If the patient is PERC rule negative, the patient does not need further work out for a PE. The PERC rule is developed by Dr. Jeff Klein and has 8 criteria. The PERC rule only applies if the patient meets none of the criteria. They include age, tachycardia, hypoxia at any point, prior DVT or PE, recent trauma or surgery, hemoctasis, exogenous estrogen use, and clinical signs suggesting of a DVT. If the patient has none of these criteria, and your clinical suspicion is that the patient has a low probability of having PE, then you can stop your PE work up at this point. And therefore, just to reiterate, very low risk patient and if they're PERC negative, they may only need a chest x-ray, ECG and basic blood work. Often no D-dimer is done. Now that we know what to do with the very low risk patient, let's turn our attention to low risk and high risk patients. Once we divide the patient into low risk or high risk categories, we can decide to use the D-dimer to rule out PE in patients who are low risk. A negative D-dimer will rule out PE in patients who have low risk. The question is therefore, who are our low risk patients? We use different scoring system to decide whether the patient is low or high risk based on their clinical presentation. There are two main scoring systems, the well score and the Geneva score. We will discuss the well score here. The well score is a series of questions that we score about the patient's clinical presentations. They include the following. Clinical signs and symptoms compatible with the DVT, which give the patient three points. Tachycardia, which give the patient 1.5 points. Immobilization, more than three days or surgery in the past month, which give the patient 1.5 points. Previous, venous herbal embolism, 1.5. Hemoptysis and malignancy that's active also give the patient 1 point each. Then we tally up the score. There are different ways to interpret the score and here is one of them. In a patient with 4 or less than 4 in the total score, the patient is deemed low risk for a PE. If they have more than 4 on the well score, they are deemed high risk. If the patient is low risk, we discussed before we can use the D-dimer to help us. If the patient is low risk by the well score and their D-dimer is negative, our worker for the PE stops here. If the patient is low risk but their D-dimer is positive, they need to go on for further confirmatory imaging. If the patient's score is more than 4, then he or she is deemed high risk for PE. High risk patients cannot be ruled out with a negative D-dimer. We need to go further into diagnostic imaging. The imaging choice we talked about before includes a VQ scan and a CT chest. A CT scan has very high sensitivity to rule out PE. However, this test is also not perfect. In patients with extremely high risk of PE and if the CT scan is inadequate, sometimes we also add endopler ultrasound to see if there are any signs of DVT. This is fortunately a rather uncommon scenario and it's best to discuss this with your staff. Just to recap, the algorithm for diagnosing PE can be presented as follow. The patient who is very low risk and is perk negative does not need further testing. Besides basic blood work, chest x-ray and ECG. Then we use a clinical decision scoring system, either Wells or Geneva score, to split the patient into either low or high risk. In the low risk patient, a D-dimer should be drawn. If it is negative, a workup stops here. We're also mentioned here the very low risk patient who is not perk negative. They usually get lumped in with a low risk group by the Wells criteria. For the patients who are low risk and if their D-dimer is positive, we'll go on to do imaging. In the high risk patient, we do not use a D-dimer to reassure us. We often go straight to imaging. We'll talk a little bit about treatment. The treatment of the patient with the PE starts with ABC. We want to ensure that their airway is patented, their ventilation and oxygenation is adequate, and want to make sure they're not hypotensive. We use IV fluids and vasopressors if needed. In a patient with a massive PE causing cardiovascular compromise, we will consider giving thrombolytics. In those who are hemodynamically stable, we will give them anticoagulants. They can include heparin, low molecular weight heparin, and then bridging into warfarin or any other oral anticoagulants. In summary, we discuss the diagnostic approach to PE. PE sometimes is very tricky to diagnose. As patients often can have atypical symptoms and presentations, we need to maintain a low index of suspicion. We hope you find this useful. Thank you for watching.