Question

What are 3 pretest probability scoring systems used to evaluate patients with a suspected pulmonary thromboembolism?

Answer

There are 3 validated pretest probability scoring systems that can be used to help clinicians decide who can be sent home, who needs a D-dimer, and who goes straight to CT for suspected PTE.

Wells Criteria

Developed – 1998

Revised – 2000

Simplified – 2001

Geneva Score

Developed – 2001

Revised – 2006

Simplified – 2008

Pulmonary Embolism Rule-Out Criteria (PERC) Score

Developed – 2008

This score is used AFTER the patient is determined to be low-risk using the Well’s or Geneva score.  In patients who are low-risk and PERC negative, there is only a 1.6% false-negative rate for missed PTE.  Any one of these would deem the patient PERC positive.

Why is this so important?

Although it does help us in deciding who maybe at higher risk of PTE, I personally feel these scoring systems help us document who DOES NOT need work-up.  There are quite a few patients who come in with non-specific chest pain or shortness of breath, and you should ALWAYS entertain the idea of PTE in these patients.  But, not every single one of these patients need a d-dimer or CTA.  Better yet, some of these patients can be discharged home without any investigation if they are low-risk and PERC negative.

Below is an algorithm I modified from Jeff Kline using these clinical decision instruments.

All these images are slides from my talk at the 2015 AAPA Conference

References

1. Wells PS, Ginsberg JS, Anderson DR. Use of a clinical model for safe management of patients with suspected pulmonary embolism. Annals of Internal Medicine. 1998;129(12):997-1005. [pubmed]
2. Wells PS, Anderson DR, Rodger M. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: increasing the models utility with the SimpliRED D-dimer. Thrombosis and Haemostasis. 2000;83(3):416-20. [pubmed]
3. Wells PS, Anderson DR, Rodger M. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer. Annals of Internal Medicine. 2001;135(2):98-107. [pubmed]
4. Wicki J, Perneger TV, Junod AF, Bounameaux H, Perrier A. Assessing clinical probability of pulmonary embolism in the emergency ward: a simple score. Archives of Internal Medicine. 2001;161(1):92-7. [pubmed]
5. Le Gal G, Righini M, Roy PM. Prediction of pulmonary embolism in the emergency department: the revised Geneva score. Annals of Internal Medicine. 2006;144(3):165-71. [pubmed]
6. Klok FA, Mos IC, Nijkeuter M. Simplification of the revised Geneva score for assessing clinical probability of pulmonary embolism. Archives of Internal Medicine. 2008;168(19):2131-6. [pubmed]
7. Kline JA, Courtney DM, Kabrhel C. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. Journal of Thrombosis and Haemostasis. 2008; 6(5):772-80.  [pubmed]

LISTEN TO THE PODCAST HERE

This is actually a special episode for the PAINE Podcast as I have the opportunity to do a joint-interview podcast with Chip Lange from TOTAL EM.  This was the first time I got to dabble with a conversational-style podcast and I think it went pretty good.  Chip and I had a great time doing it and will most definitely be doing more of these in the future.

One of the many saying my Army Airborne Ranger dad has instilled in me growing (and one that I still use today) is the seven “P” approach to accomplishing tasks:

Proper

Planning

and

Preparation

Prevents

Piss

Poor

Performance

What is nice about this saying is that it applies very nicely to the steps of intubation as well.

Prepare

You need to to have everything at the bedside you MIGHT need prior to any intubation attempt.  This includes equipment, medications, and any personnel or team members who will assist.  If you even suspect this could be a difficult airway, you should have your plan B and plan C options in the room to ward off the evil spirits.

• Endotracheal tubes (3 sizes), stylets, bougies, syringes
  • Test the balloons on all the tubes
• Laryngoscope
  • Multiple blades and handles
  • Check the lights
  • If using video, plug it in and make sure it turns on
• Patent IV lines x 2
• Suction
• Cardiac and pulse oximetry monitor
• Bag-valve mask
• End-tidal CO2 monitor
• Medications
  • Drawn up and labeled
  • Concentration read aloud

This also gives you the opportunity to talk with you team about the plan for intubation (how many attempts, progression should plan A, steps of what will happen during the intubation and everyone’s roles during the procedure, etc..), as well as reviewing assisting maneuvers (external laryngeal manipulation, etc.).

Preoxygenate

In order to decrease any deoxygenation-related issues during the intubation attempt, your patient should recieve 100% oxygen at 15 liters per minute through a non-rebreather mask for 3-5 minutes.  This will properly de-nitrogenate and super-saturate all the hemoglobin and give you the time you need to visualize and intubate.

Position

“EAR HOLE TO CHEST HOLE”

For ideal visualization, you want to position your patient so that their external auditory meatus lined up to the sternal notch

Premedicate

There are several different medications you can give for premedication purposes to modify the physiologic response during intubation (lidocaine, opiates, atropine, defasculating agents, etc..), but the main one is the sedative.  It is generally poor form to paralyze someone before you sedate them.  There are several medications you can choose from for sedation in intubation:

• Ketamine – 1-2mg/kg IV
  • My ideal sedative
• Etomidate 0.3mg/kg IV
  • Less hemodynamic compromise
  • Can cause adrenal suppression
• Propofol – 1.5-3mg/kg IV
  • Can cause hemodynamic instability

Paralyze

There are 2 choices for classes of paralytics:

• Depolarizing
  • Succinylcholine – 1.5-2mg/kg IV
  • Rapid onset, shortest duration of action
  • Caution in burn/crush injuries, hyperkalemic patients
• Non-Depolarizing
  • Rocuronium – 1.2mg/kg IV
  • Vecuronium – 0.3mg/kg IV

Pass The Tube

Once you patient is properly sedative and paralyze, you can proceed to laryngoscopy.

Post-intubation Assessment

Capnography

This is used for confirmation of correct placement of the endotracheal in the trachea and tests for end-tidal CO2.  There are 2 main types:

• Qualitative
  • Color change calorimeter
  • Attaches to end of endotracheal tube and detects CO2 by changes in exhaled pH

GOLD IS GOOD

• Quantitative
  • Continuous Waveform Capnography
    • Gold standard
    • Gives you a visual waveform to see if the ventilations are adequate

Securing the Tube

Once you know you are in the right spot and have been confirmed by capnography, you need to secure the tube.  There are different ways to achieve and I often defer to the respiratory therapist or nurse on how they want it secured.  There are commercial devices that lock the tube in place and secure using velcro straps, all the way to the old standby of adhesive tape.  This is a great site that shows several different ways you can secure the endotracheal tube (http://aam.ucsf.edu/article/securing-endotracheal-tube).

Radiography

Chest xray is the gold standard for the radiographical confirmation of endotracheal placement, as well as ensuring the proper depth.  The ideal position for the tube depth should be 3-5cm from the carina or at T3-4 position.

Josh Farkas (PulmCrit) did a great review on endotracheal tube positioning and depth just last week.

Ultrasound is being used more frequently as a confirmatory tool for endotracheal tube placement.

Great review by EmDocs on ultrasound for endotracheal tube confirmation.

Sedation/Analgesia

Now that the tube is in place, secured, and confirmed, you are done right?  WRONG!!!  Your patient now has a tube shoved into the tracheal and it is a tad uncomfortable.  Postintubation sedation/analgesia is PARAMOUNT for good patient care.

• Sedation
  • Ketamine – 0.1-0.5mg/kg bolus and 0.1-0.5mg/kg/hr infusion
  • Propofol – 5mcg/kg bolus and 5-50mcg/kg/hr infusion
  • Midazolam – 0.05mg/kg bolus and 0.025mg/kg/hr infusion
• Analgesia
  • Fentanyl – 2mcg/kg bolus and 1mcg/kg/hr infusion
  • Hydromorphone – 0.5-1mg/kg bolus and 0.5-3mg/kg/hr infusion
  • Morphine – 5-10mg/kg bolus and 2-30mg/hr infusion

You should be shooting for a Richmond Agitation Sedation Scale (RASS) of -1 to -3 for adequate sedation following intubation.

Really good intubation checklist from Scott Weingart of EmCrit

References

1. http://lifeinthefastlane.com/ccc/rapid-sequence-intubation/
2. http://emcrit.org/podcasts/emcrit-intubation-checklist/
3.  Weingart SD, Levitan RM.  Preoxygenation and Prevention of Desaturation During Emergency Airway Management.  Annals of Emergency Medicine.  2012;59(3):165-175.
4. http://www.capnography.com/Emergencydevice/emergencyintubtion.htm
5. http://www.capnography.com/new/emergency-intubations
6. http://www.capnography.com/new/emergency-intubations?id=216
7. http://lifeinthefastlane.com/ccc/capnography-waveform-interpretation/
8. http://www.derangedphysiology.com/main/core-topics-intensive-care/mechanical-ventilation-0/Chapter%201.2.3/endotracheal-tube-detail
9. http://emcrit.org/podcasts/post-intubation-sedation/
10. https://coreem.net/core/post-intubation/

LISTEN TO THE PODCAST HERE

Epidemiology

Dyspnea is one of the more common complaints that will bring a patient to the ED for evaluation.  The most recent data from the CDC shows more than 3.7 million visits to the ED in the United States for shortness of breath alone and more than 11 million for dyspnea-related complaints (cough, chest pain, etc.).

Pathophysiology

There are 3 global processes that have to function in series to prevent a patient from becoming short of breath:

• Ventilation
  • Airflow through the tracheobronchial tree to the terminal alveoli
  • Ventilation without perfusion = Dead space
    • Anatomic = trachea, main bronchi
    • Physiologic = terminal alveoli
• Perfusion
  • Blood flow through the pulmonary arteries to the terminal capillaries
  • Perfusion without ventilation = Intrapulmonary shunt
    • Anatomic = right-to-left shunt
    • Physiologic = terminal alveoli
• Gas Exchange
  • Capillary-alveoli interface to exchange oxygen and carbon dioxide
    • Determined by arterial-alveoli gradient

5 Main Causes of Hypoxemia

• V/Q Mismatch (most common)
  • PNA, PTE, pulmonary edema, asthma, COPD
• Hypoventilation
  • Drug overdose, neuromuscular disease (GBS, ALS, MG)
• Right-to-Left Shunt
  • Intracardiac
    • PFO, ASD, VSD
  • Vascular
    • PTE, AVM
  • Alveolar
    • PNA, atelectasis, pulmonary edema, ARDS
• Low Inspired Oxygen
  • Altitude, fire,
• Diffusion Abnormality
  • COPD, interstitial lung disease

Bedside Evaluation

Vitals

• Blood Pressure
  • Often hypertensive due to stress
  • Can also be the precipitating factor
• Heart Rate
  • Often tachycardic due to stress and system trying to increase cardiac output for oxygen demand
  • If bradycardic à think overdose
• Respiratory Rate
  • Will be tachypnic
    • > 40 bpm is ominous and respiratory failure could be imminent
  • if bradypnic à think overdose
• Temperature
  • If febrile, then infectious causes go up on differential
• Pulse oximetry
  • Common practice is to give all dyspneic patients oxygen
    • Lots of research on oxygen in ACS

History

• Onset
• Severity
• Events leading up to this episode
  • Triggers, compliance with medications
• Allergies
• Past History
  • Medical problems, previous episodes
• Chest pain
• Trauma
• Fever
• Hemoptysis
• Cough
• Tobacco history
• Medications

Physical Exam

Rapid examination should be performed (often while getting the history) to evaluate for impending respiratory collapse:

• Altered mental status
  • Lethargy to combative
• Fatigue of breathing
• Audible stridor
• Cyanosis
• Tripod position
• Retractions or accessory muscle use
• Fragmented speech
• Inability to lie supine
• Diaphoresis

Any of the above findings should raise your threshold to intubate.

Once these have been evaluated and ruled-out, you can begin a focused physical exam to address the causes of acute dyspnea:

• Pulmonary
  • Breath sounds
    • Wheezing, diminished, equal, crackles, rales
• Cardiovascular
  • Rhythm
    • Tachycardia, irregular
  • Murmurs
  • S₃/S₄
  • Distant/muffled heart sounds
  • Edema/JVD
• Skin
  • Diaphoresis
  • Capillary refill
  • Urticaria

Work-Up

• Chest Radiograph
• EKG
• Ultrasound
  • EM Resident Blog – Ultrasound in Acute Dyspnea – Part 1
  • EM Resident Blog – Ultrasound in Acute Dyspnea – Part 2
  •  

• Labs
  • D-Dimer
  • Brain Naturetic Peptide (BNP)
    • If < 100 pg/mL à > 90% NPV for CHF
    • If > 500 pg/L à > 90% PPV for CHF
  • ABG
    • Needed to calculate the A-a gradient

Differential Diagnosis

• Upper Airway
  • Angioedema
  • Foreign body
  • Anaphylaxis
  • Infections
  • Trauma
• Pulmonary
  • PTE
  • COPD
  • Asthma
  • Edema
  • PTX
  • Pneumonia
  • Trauma
  • Hemorrhage
  • Effusion
• Cardiac
  • Acute decompensated heart failure
  • ACS
  • Cardiomyopathy
  • Dysrhythmias
  • Valvulopathies
  • Effusion/tamponade
• Neurologic
  • Neuromuscular
    • GBS, MG, ALS
• Metabolic/Toxic
  • Overdose
  • Carbon monoxide poisoning
  • Acute chest syndrome in sickle cell disease
• Miscellaneous
  • Anxiety
  • Ascites

Management

Three main primary goals for the emergent management of acute dyspnea:

• Optimize arterial oxygenation
  • Provide supplemental oxygen
  • Continuous cardiac and pulse oximetry monitoring
• Determine need for emergent airway management
  • Bring airway supplies to the bedside
    • Non-invasive ventilation is an option
    • Include difficult airway adjuncts as well
• Determine most likely cause and initiate treatment
  • Start work-up (as outlined above)
  • Don’t let a definitive diagnosis preclude starting treatment

References

1. National Hospital Ambulatory Medical Care Survey: 2011 Emergency Department Summary. http://www.cdc.gov/nchs/data/ahcd/nhamcs_emergency/2011_ed_web_tables.pdf.  Accessed on November 15^th,2016.
2. Petersson J, Glenny RW. Gas exchange and ventilation-perfusion relationships in the lung. The European Respiratory Journal. 2014;44(4):1023-41. [pubmed]
3. Simon PM, Schwartzstein RM, Weiss JW, Fencl V, Teghtsoonian M, Weinberger SE. Distinguishable types of dyspnea in patients with shortness of breath. The American Review of Respiratory Disease. 1990;142(5):1009-14. [pubmed]
4. Schabowski S, Lin C. Dyspnea. In: Sherman SC, Weber JM, Schindlbeck MA, Rahul G. P. eds. Clinical Emergency Medicine, 1e. New York, NY: McGraw-Hill; 2014. http://accessemergencymedicine.mhmedical.com/content.aspx?bookid=991&Sectionid=55139128 . Accessed November 16, 2016.
5. Fertel BS. Respiratory Distress. In: Cydulka RK, Cline DM, Ma O, Fitch MT, Joing S, Wang VJ. eds. Tintinalli’s Emergency Medicine Manual, 8e. New York, NY: McGraw-Hill; 2016. http://accessemergencymedicine.mhmedical.com/content.aspx?bookid=1759&Sectionid=128948449 . Accessed November 16, 2016.
6. Schneider HG, Lam L, Lokuge A. B-type natriuretic peptide testing, clinical outcomes, and health services use in emergency department patients with dyspnea: a randomized trial. Annals of Internal Medicine. 2099;150(6):365-71. [pubmed]
7. Ahmed A, Graber MA. Evaluation of the adult with dyspnea in the emergency department.  In: UpToDate, edited by Hockberger RS, Grayzel J.  UpToDate, Waltham, MA. 2016.  https://www.uptodate.com/contents/evaluation-of-the-adult-with-dyspnea-in-the-emergency-department?source=see_link#H29. Accessed November 16, 2016.