in that it may mislead the clinician into assuming that no priority symptoms are present when in reality there are one or more. The result may obviously affect the patient, whose problem is potentially minimized or underestimated, and for whom inappropriate or ineffective protocols are applied. This may convey actual risk to the patient if it leads to a negative interaction between EMS clinician and patient, resulting in mistrust and, in some cases, no transport to a hospital [4].
EMS personnel must compile a massive amount of information in a relatively short period. They must incorporate this information with their prehospital clinical skills and baseline knowledge in their clinical decision making, which is necessary to assess and treat patients effectively. Similar to emergency physicians, EMS clinicians become expedient decision makers, using strategies to improve efficiency and thoroughness. They sometimes call on certain rules of thumb, shortcuts, and abbreviated thinking to make fast, efficient, and accurate decisions, or what clinical decision experts term “heuristics” [4]. Various ethnographic and descriptive studies exploring medical errors, adverse events, and near misses in EMS have shown that EMS clinician decision making is a predominant factor influencing patient safety in EMS [5, 6].
When EMS clinicians are interacting with a patient, there is clinical reasoning related to both the line of medical inquiry, such as the history, physical examination, and diagnostic tests, and the clinical decision making (i.e., the cognitive process of using data to evaluate, diagnose, and treat the patient) [8]. Clinical reasoning is a tremendously complex process and is under intense continuing investigation. There is no single model of clinical decision making that adequately relates to the very complex environment that exists in the emergency setting. Rather, there are several models or strategies that individuals use in clinical decision making or cognitive performance including:
pattern recognition or skill‐based (e.g., making a diagnosis immediately on entering the room, which is frequently unconscious, automatic, and based on years of experience)
rule based (e.g., advanced cardiac life support algorithms)
hypothetical deductive or knowledge based (considered 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
