What Is Anchoring Bias?
Anchoring bias is the tendency to rely too heavily on the first piece of information you receive when making decisions. In EMS, this often means that the dispatch information, a bystander's statement, or your initial visual impression of the patient becomes the "anchor" that shapes your entire assessment, even when subsequent findings suggest a different diagnosis.
How Anchoring Bias Affects EMS Calls
Consider this scenario: dispatch sends you to a "fall" at a nursing home. You arrive and find an 82-year-old woman on the floor with a hip deformity. You anchor on the mechanism (fall) and the obvious injury (fractured hip). You package the patient for transport and focus on pain management. But you miss the fact that she fell because she had a syncopal episode caused by a new-onset cardiac arrhythmia. The fall was the result, not the cause.
Anchoring bias is particularly dangerous when:
- Dispatch provides a specific chief complaint that may not be accurate
- The patient has an obvious injury that distracts from a more serious underlying condition
- First responders or bystanders provide a diagnosis rather than a description of what happened
- The patient's history of frequent calls leads you to assume this call is like the previous ones
Strategies to Overcome Anchoring Bias
The most effective strategy is to conduct a thorough, systematic assessment regardless of what you think you already know. Treat dispatch information as a starting point, not a diagnosis. Always ask yourself: "Why did this happen?" If a patient fell, investigate what caused the fall. If a patient has chest pain, consider the full differential beyond cardiac causes.
Use the "diagnostic time-out" technique. After your initial assessment, pause for 10 seconds and ask: "Is there anything else this could be? Am I missing something? What is the worst-case scenario for this patient?" This brief cognitive pause can prevent you from locking onto an incorrect diagnosis.
Practice Makes Prevention
During training and clinical rotations, deliberately practice re-evaluating your initial impressions. When you complete a patient contact, review whether your final assessment matched your initial anchor. Track how often the final diagnosis differed from the dispatch information or your first impression. Building this self-awareness over time reduces the impact of anchoring on your clinical practice.