the highest level of deduction; a clinician generates a hypothesis and uses existing and new knowledge to find an answer) [79–11].
Some experts describe a fourth model of a naturalistic or event‐driven process of decision making (i.e., treating the patient first and then making the diagnosis) [7]. Interestingly, how and where EMS clinicians make decisions and the density of decision making during the patient journey are postulated to differ from those of other health care practitioners and are the subject of continuing research [12].
History Taking
It is essential that, regardless of the dispatch determinant, EMS crews approach each patient in the same manner [2, 4]. Field personnel should acquire a history with unbiased technique by using effective communication strategies. A balance of both subjective and open‐ended questions (e.g., “Can you describe your pain for me?”) and objective and close‐ended questions (e.g., “Is the pain sharp?”) should be used. In fact, throughout all disciplines of health care, traditional dictums state that effective history taking can lead to an accurate diagnosis in the majority of cases.
Three possible outcomes can result from taking the history of a patient dispatched with an undifferentiated dispatch code. First, the EMS clinician may identify a prehospital diagnosis related to one of the chief complaint conditions listed among the non‐priority symptoms in common dispatch algorithms [3]. It is important that the clinician does not trivialize the patient’s needs in the absence of priority symptoms, as each patient defines their own emergency. Second, the EMS clinician may establish a prehospital diagnosis that is accurate but not one of the chief complaint conditions. In these situations, EMS personnel must coordinate their prehospital care knowledge to care effectively for the patient’s needs. Third, perhaps the most frustrating, EMS clinicians may be unable to identify the specific chief complaint. This last outcome may be the first indication that the patient truly has an undifferentiated condition. At this point, it is important for the EMS clinicians to optimize the clinician–patient interaction, while minimizing the time to treatment and time to transport.
The following strategies can be used to improve diagnostic accuracy during history taking [7, 9–11].
Collect information to confirm or exclude life‐threatening conditions first; then focus on the most likely diagnosis.
Reaffirm that there are no high‐priority symptoms affecting the patient’s ability to provide accurate answers, such as hypoglycemia or receptive and expressive aphasia from a stroke.
Ensure that the patient is oriented to person, place, and time, and that there is no underlying cognitive impairment due to drug ingestion, delirium, dementia, etc.
Where feasible, sit at the patient’s side to collect a thorough history.
Use adjuncts to facilitate the history taking (e.g., drawing diagrams or using other visual aids).
Optimize communication so that the patient clearly understands the language and questions (e.g., asking simple questions).
Obtain collateral information from the next of kin, friends, or bystanders.
Allow a few moments of uninterrupted time to mentally process each patient.
Generate “most life‐threatening” and “most likely” diagnostic hypotheses.
Mentally process one patient at a time.
Avoid decision making when overly stressed or angry; take time out, regroup, and reevaluate the decision.
Move on to physical examination to augment the history that has been elicited.
Physical Examination
Sir William Osler taught that what was not found in a history was aided by completing an appropriate physical examination. The history provides 90% of the diagnosis, the physical examination provides 9%, and diagnostic tests contribute the remaining 1% of diagnostic certainty.
In the situation of the patient who remains undifferentiated despite optimizing the history, it is paramount that the EMS clinician perform a thorough and complete physical examination [4]. This begins with ensuring that a complete set of vital signs is taken and recorded. The following strategies can be used to improve the diagnostic accuracy during the physical examination process [4, 7,9–11].
Ensure that a complete and uninterrupted physical examination or secondary survey.
Clarify the history while conducting the physical examination.
Perform an environmental scan of the patient’s physical surroundings to complement the history (general surroundings, state of disarray, etc.).
Have a structured and simple differential diagnosis or impression, based on the presenting history and physical information currently available (e.g., an altered level of consciousness can be broken down into structural, metabolic, and toxicological etiologies).
Adjuncts to the History and Physical Examination: Prehospital Diagnostic Tests
In the case of the diagnostically undifferentiated patient, EMS clinicians should use appropriate prehospital diagnostic tests to facilitate the working diagnosis. This includes such tests as the fingerstick glucose assessment and a prehospital 12‐lead ECG. The following strategies can also be used to improve the clinical decision making for use of diagnostic tests [7, 9–11].
Employ any readily available decision‐making algorithms or decision rules. A classic example is the Ottawa Ankle Rules, which help emergency physicians in deciding on ordering ankle x‐rays for injured patients. Although there are very few clinical guidelines in practice for the out‐of‐hospital setting, with the increasing body of evidence, these will increase in the future.
Use existing prehospital protocols for specific therapeutic decisions whenever possible.
Use only those tests that will affect the disposition or treatment of the patient by confirming or excluding the disease hypothesis at hand.
The truly Undifferentiated Patient
The patient whose condition remains truly undifferentiated after the aforementioned maneuvers requires the same degree and level of care as those patients who have clear prehospital diagnoses. To further facilitate the care of the patient, it is important for the EMS clinicians to advocate for the patient and relay their findings and concerns to the receiving facility. The hospital staff in turn can then continue to optimize the patient interaction to identify and meet patient needs.
Transition of Care to the Receiving Facility
Just as the transition of care from the dispatcher to the paramedic occurs, there is also a transition of care between the EMS clinician and the hospital ED. It is tremendously important that this hand‐off process maintains and facilitates the continuity of patient care and does not jeopardize patient safety. EDs commonly experience the difficult situation of overcrowding and resultant long turnaround intervals for EMS staff. When EMS personnel arrive with a patient with no priority symptoms and no identifiable chief complaint, this may lead to confrontation between the charge nurse or physician and the EMS personnel. Moreover, this may lead to the receiving ED triaging the patient to the waiting room or to a lower priority than is appropriate. If the patient’s condition is truly deemed undifferentiated, then the EMS clinician must clearly state this to the receiving ED and must elaborate on what has been done to optimize the history and physical exam, and provide insight and recommendations for next steps.
Consequences of an Undifferentiated Condition
There may be no significant consequences to either the patient or EMS personnel when the patient’s condition is undifferentiated.