As people increasingly rely on hospitals’ Emergency Departments to treat minor injuries, it has become more difficult for Emergency Physicians to identify dangerous and/or life-threatening issues. Physicians often use clinical decision rules to stratify patients in terms of risk— usually, these rules have been trialed with excellent methods at a specific site, then validated at multiple other sites. In some circumstances, the preponderance of evidence results in these rules being accepted as the standard of care.
There are hundreds of clinical decision rules and instruments, but in this article I will discuss a few very common ones that have become the current standard of care, and are used to evaluate patients who might have serious illness or injuries.
The Canadian Head CT Rule and the New Orleans Criteria are two rules for head trauma patients. Both attempt to reduce unnecessary radiation from CT scans by helping the physician determine which minor head injury patients may require a head CT, and which do not.
The Canadian Head CT rule suggests that head CTs should be performed for patients who meet any of the following criteria:
• 65 years or older
• Less than normal mental status 2 hours after injury
• Suspected open or depressed skull fracture
• Any sign of basal skull fracture (swelling/bleeding around the eyes, blood or clear fluid in the ear)
• Two or more episodes of vomiting
• 30 or more minutes of amnesia before impact
• Dangerous mechanism (pedestrian struck, ejection from motor vehicle, fall from 3+ feet or 5+ stairs)
The New Orleans Head CT Criteria suggests that head CTs should be performed for patients who meet any of the following criteria:
• 60 years or older
• Deficits in short-term memory
• Visible trauma above the clavicle
• Any episode of vomiting
• Drug or alcohol intoxication
Applying the rules to inappropriate patients is a common mistake made by physicians. Conversely, both the Canadian and New Orleans Head CT rules may prove insufficient— some patients are not covered by either rule because they fall outside the age range, or because they are on a medication for which there was not enough data in the study to derive conclusions (eg. a blood thinner). If either one of these rules supports no head CT after a head injury, that physician has a very strong case that the standard of care was met— even in the circumstance that a patient has a bad outcome.
The NEXUS and Canadian C-spine rules have similar goals— to decrease the level of radiation administered to patients with neck injuries. The NEXUS rule states that a patient does not require further imaging if he/she displays:
• No neurological deficit
• Normal mental status
• No midline spinal tenderness
• Not intoxicated
• No other major injury (eg. broken long bone) that could distract from their neck pain
The Canadian C-spine Rule suggests that no imaging is required if the patient is:
• Under 65 years old
• Has no extremity sensation abnormalities
• Did not have a dangerous mechanism of injury (eg. a rollover motor vehicle accident)
In addition, the patient must demonstrate one “low risk factor” in order to negate the need for imaging, such as sitting up in the ER, walking at any time, delayed neck pain, or no midline neck tenderness; and be able to move his/her neck 45 degrees to the left and right.
The NEXUS and Canadian C-spine rules can be applied incorrectly, similarly to the head CT criteria. Knowing the studies and the inclusion and exclusion criteria is key to applying these studies to an individual patient.
The HEART score helps determine which patients with chest pain are low-risk enough to send home, and is becoming popular enough to be considered a standard of care. Risk-stratification is done by evaluating:
• The patient’s history
• Number of risk factors for heart attacks
• A single troponin (a blood test that shows heart-muscle damage)
Patients with a score of 3 or less have a 0.9-1.7% risk of a negative cardiac outcome in 30 days. This is essentially as good, or better than, a stress test in establishing risks. Many physicians have taken this to mean that they can safely discharge patients with chest pain for follow-up with their primary care doctor after one troponin if the patient’s HEART score is less than 3.
HEART is quickly replacing one of the previous standards, the Cincinnati chest pain protocol, which initially required 4 sets of troponin lab tests every 3 hours. If all 4 of those labs were normal, then a Cardiology follow-up with a stress test within 72 hours was required. (This has been modified, with evidence, in some locations to include two troponins 3 hours apart, followed by cardiology follow-up for a stress test within 72 hours if both lab tests are normal).
Common errors in the application of the HEART score involve not taking into account all of a patient’s risk factors, or applying the scoring system to some patients with chest pain specifically excluded in the initial study or validation study (eg. patients with active congestive heart failure).
Since chest pain accounts for more than 20% of Emergency Physician malpractice liability, it is no wonder that multiple other scoring systems and tools exist to help Emergency Physicians mitigate the risk of a bad outcome.
Chest Pain and Shortness of Breath
The Pulmonary Embolism Rule-out Criteria (PERC) rule is used, and has become a standard of care, for ruling out a blood clot in the lung as a source of chest pain or shortness of breath. The PERC rule states that a patient has a 1.4%risk of a blood clot in the lungs in the next 90 days if he/she meets the following criteria:
• Under 50 years old
• Heart rate under 100
• Oxygen saturation (on room air) greater than 95%
• No prior history of blood clots
• No recent trauma or surgery
• Not vomiting blood
• Does not take estrogen
• Does not have unilateral leg swelling
Since 1.4% is a better rate of detecting disease than even a CT scan (~2%), a patient with a negative PERC rule requires no further workup for a blood clot in the lungs. The usual next step for a low-risk patient with a positive PERC rule would be a d-dimer blood test to look for evidence of clotting in the blood. Unfortunately, this test is very non-specific.
Note that application of the PERC rule is not perfect— 1.4% of the patients it is applied to will have a blood clot. However, PERC remains the standard of care because it is more reliable than actual testing (CT scan) which additionally involves the risks of radiation and intravenous dye. It is important to remember that the test is unidirectional: while a negative PERC evaluation allows a physician to avoid further testing, a positive PERC does not force the doctor to order more testing.
Emergency Physicians practice with rules like these on a daily basis, both to protect themselves from liability and to limit over-testing and over-admission of patients. Many other rules exist, some for diseases with major comorbidities, and some for relatively minor processes. A working knowledge of these rules and their applications can help you decide if a case has merit, and whether the standard of care was met for any of these common patient complaints.
 PRIMARY STUDY: Stiell IG, Wells GA, Vandemheen K, et al. The Canadian CT Head Rule for patients with minor head injury. Lancet 2001;357:1391-1396
 PRIMARY STUDY: Haydel MJ, Preston CA, Mills TJ, Luber S, Blaudeau E, DeBlieux PM. Indications for computed tomography in patients with minor head injury. N Engl J Med 2000;343:100-105
VALIDATION STUDY: Stiell IG, Clement CM, Rowe BH, Schull MJ, Brison R, Cass D, Eisenhauer MA, McKnight RD, Bandiera G, Holroyd B, Lee JS, Dreyer J, Worthington JR, Reardon M, Greenberg G, Lesiuk H, MacPhail I, Wells GA. Comparison of the Canadian CT Head Rule and the New Orleans Criteria in patients with minor head injury. JAMA. 2005 Sep 28;294(12):1511-8.
 PRIMARY STUDY: Hoffman JR, Wolfson AB, Todd K, Mower WR.Selective cervical spine radiography in blunt trauma: methodology of the National Emergency X-Radiography Utilization Study (NEXUS). Ann Emerg Med. 1998 Oct;32(4):461-9.
VALIDATION STUDY: Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI. Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. National Emergency X-Radiography Utilization Study Group. N Engl J Med. 2000 Jul 13;343(2):94-9. Erratum in: N Engl J Med 2001 Feb 8;344(6):464.
 PRIMARY STUDY: Stiell IG, Wells GA, Vandemheen KL, Clement CM, Lesiuk H, De Maio VJ, Laupacis A, Schull M,
McKnight RD, Verbeek R, Brison R, Cass D, Dreyer J, Eisenhauer MA, Greenberg GH, MacPhail I, Morrison L, Reardon M, Worthington J. The Canadian C-spine rule for radiography in alert and stable trauma patients. JAMA. 2001 Oct 17;286(15):1841-8.
VALIDATION STUDY: Stiell IG, Clement CM, Mcknight RD, et al. The Canadian C-spine rule versus the NEXUS low-risk criteria in patients with trauma. N Engl J Med. 2003;349(26):2510-8.
VALIDATION STUDY: Backus BE, Six AJ, Kelder JC, Bosschaert MA, Mast EG, Mosterd A, Veldkamp RF, Wardeh AJ, Tio R, Braam R, Monnink SH, van Tooren R, Mast TP, van den Akker F, Cramer MJ, Poldervaart JM, Hoes AW, Doevendans PA. A prospective validation of the HEART score for chest pain patients at the emergency department. Int J Cardiol. 2013 Oct 3;168(3):2153-8.
 Karcz A, Holbrook J, Auerbach BS, et al. Preventability of malpractice claims in emergency medicine: a closed claims study. Ann Emerg Med. 1990;19:865-943
 PRIMARY STUDY: Kline JA, et al. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost 2004; 2: 1247–55.
VALIDATION STUDY: Kline JA, et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost 2008; 6: 772–80.
Expert Witness Bio E-080148
This qualified expert of Emergency Medicine obtained his BA in Biology from Brandeis University, his MBA in Healthcare Administration and his MD from the University of Pennsylvania. He completed his Residency in Emergency Medicine and is Board Certified in Emergency Medicine. He is a Member of the American College of Emergency Physicians and the American Academy of Emergency Medicine. He has 15 Publications on Emergency Medicine and is Currently an Assistant Professor of Emergency Medicine at a Medical School in the Mid-Atlantic and is the Current Chief of Emergency Medicine at a Community Hospital in Maryland.
BA, Biology, Brandeis University
MBA, Healthcare Administration, University of Pennsylvania (The Wharton School)
MD, University of Pennsylvania School of Medicine
Residency, Emergency Medicine, University of Maryland
Board Certified: Emergency Medicine
Member, American College of Emergency Physicians
Member, American Academy of Emergency Medicine
Publications: 12 Articles, 2 Abstracts, 1 Book Chapter
Former, Attending Physician, University of Pittsburgh
Former, Clinical Instructor, John Hopkins School of Medicine
Former, Assistant Professor Johns Hopkins School of Medicine
Former, Assistant Director of Emergency Medicine, Howard County General Hospital
Current, Assistant Professor, Medical School in the Mid-Atlantic
Current, Chief of Emergency Medicine, Community Hospital in Maryland