Residency · Residency · Emergency Medicine

Prehospital Care and Medical Oversight

Introduction

Emergency physicians serve as the medical directors and oversight authorities for prehospital emergency medical services (EMS) systems. Understanding the structure, capabilities, and limitations of prehospital care is essential for effective collaboration between the ED and field providers. Medical oversight -- both online (direct) and offline (indirect) -- ensures that paramedics and EMTs deliver evidence-based care within defined protocols.

EMS System Structure

Levels of Prehospital Providers

The Emergency Medical Responder (EMR) provides basic first aid, CPR, and AED use with limited interventions. The Emergency Medical Technician (EMT-Basic) performs BLS skills including splinting, oxygen administration, and assisted medications such as epinephrine auto-injector, aspirin, and nitroglycerin assist. The Advanced EMT (AEMT) can establish IV access, perform basic fluid resuscitation, and administer select medications including D50, glucagon, and nebulized bronchodilators. The Paramedic operates at the highest level with advanced airway management (including RSI in many systems), 12-lead ECG interpretation, synchronized cardioversion, needle decompression, chest tube insertion (in some systems), and broad pharmacologic capability.

Response Models

Tiered response systems deploy BLS and ALS units based on dispatch acuity, optimizing resource allocation. Fire-based, third-service, and hospital-based EMS models each carry distinct advantages in staffing, response time, and clinical integration. Community paramedicine is an expanding model in which paramedics provide preventive care, chronic disease management, and post-discharge follow-up.

Medical Oversight

Online (Direct) Medical Control

Online medical control provides real-time physician consultation via radio or phone for high-acuity decisions such as field termination of resuscitation and medication orders outside protocol. The emergency physician must understand local protocols to provide effective guidance. Base station physicians should avoid "cookbook" orders and instead engage in shared decision-making with experienced field providers.

Offline (Indirect) Medical Control

Offline medical control encompasses protocol development, including standing orders, treatment algorithms, and clinical guidelines written and regularly updated by the EMS medical director. Quality improvement involves systematic review of prehospital care reports, run data, and patient outcomes. Education and credentialing includes ongoing training, skills verification, and continuing medical education requirements. Scope of practice determinations define which procedures and medications each provider level may utilize.

<image>Flowchart illustrating the relationship between EMS medical director, online medical control physician, and field paramedics showing lines of authority and communication pathways</image>

Key Prehospital Interventions and Evidence

Airway Management

Supraglottic airways (SGAs) are the first-line advanced airway in many EMS systems, and studies including the PART Trial and AIRWAYS-2 have shown comparable outcomes to endotracheal intubation in cardiac arrest. Prehospital RSI requires robust training, continuous quality improvement, and first-pass success rates above 90 percent to justify implementation. Bag-valve-mask ventilation remains a reasonable strategy, particularly when transport times are short.

Trauma Care

Tourniquet application for life-threatening extremity hemorrhage is a critical BLS and ALS skill, and early application improves survival. Pelvic binders for suspected pelvic ring injuries reduce hemorrhage volume. Spinal motion restriction has shifted from rigid backboards to selective immobilization based on validated clinical criteria such as the NEXUS and Canadian C-Spine Rule.

Cardiac Care

Prehospital 12-lead ECG with STEMI identification and cath lab activation reduces door-to-balloon time significantly. Early defibrillation is the single most impactful intervention for witnessed VF and pulseless VT cardiac arrest. Prehospital blood product administration is emerging in select systems for hemorrhagic shock.

<image>Illustration of a prehospital 12-lead ECG showing STEMI criteria with annotations for paramedic-level interpretation and hospital notification pathway</image>

Dispatch and Communication

Emergency Medical Dispatch (EMD) uses structured protocols such as MPDS to prioritize calls, allocate resources, and provide pre-arrival instructions including CPR coaching and choking interventions. Crew Resource Management (CRM) principles applied to prehospital settings reduce communication errors during handoff. Structured handoff tools such as MIST (Mechanism, Injuries, Signs/vitals, Treatment) improve information transfer from EMS to the ED.

Medicolegal and Ethical Considerations

Patient refusal of care requires paramedics to assess decision-making capacity in the field, and documentation of informed refusal is critical. Field providers must honor valid advance directives including Do Not Resuscitate orders and POLST forms, with state-specific regulations applying. Field termination of resuscitation follows protocols that define criteria (such as asystole without ROSC after 20 minutes of ALS in normothermic medical arrest), and medical control may be required.

<image>Decision algorithm for EMS field termination of resuscitation showing inclusion and exclusion criteria with medical control consultation steps</image>

Quality Improvement in EMS

The Cardiac Arrest Registry to Enhance Survival (CARES) provides benchmarking data for out-of-hospital cardiac arrest outcomes. High-performance CPR metrics include a chest compression fraction above 80 percent, rate of 100 to 120 per minute, depth of 5 to 6 cm, and full recoil. Response time intervals (call-to-dispatch, dispatch-to-scene, scene-to-hospital) are tracked and optimized. Morbidity and mortality review of sentinel events drives protocol updates.

Clinical Pearls

The emergency physician's role extends beyond the ED walls, and active engagement in EMS medical direction improves prehospital care quality. Supraglottic airways are noninferior to endotracheal intubation in cardiac arrest and should be first-line in most EMS systems. Prehospital STEMI identification with cath lab pre-activation significantly reduces time to reperfusion. Structured handoff communication between EMS and the ED reduces information loss and improves patient safety. Field termination of resuscitation, when protocol-driven, reduces futile transports and ED resource utilization.

References

1. Gausche-Hill M, et al. "EMS Medical Directors: Roles and Responsibilities." Prehospital Emergency Care. 2015;19(4):559-568.
2. Wang HE, et al. "Effect of a Strategy of Initial Laryngeal Tube Insertion vs Endotracheal Intubation on 72-Hour Survival in Adults With Out-of-Hospital Cardiac Arrest (PART Trial)." JAMA. 2018;320(8):769-778.
3. Cone DC, et al., eds. Emergency Medical Services: Clinical Practice and Systems Oversight. 3rd ed. Wiley; 2021.
4. Mell HK, et al. "Emergency Medical Services Response Times in Rural, Suburban, and Urban Areas." JAMA Surgery. 2017;152(10):983-984.

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