Field Management: Prehospital Care

Joshua B. Gaither

GENERAL PRINCIPLES

The goal of prehospital management of moderate to severe traumatic brain injury (TBI) is to prevent secondary brain insult (e.g., due to hypoxia, hypotension, hypoglycemia, or inadvertent hyperventilation following intubation), and by reducing secondary brain injury, improve patient outcome [1].

Aims of Prehospital (Field) Care

Goal-directed patient care includes: rapid patient assessment, intervention to prevent secondary brain injury, early transport (scene time less than 10–15 minutes), and direct transport to an appropriate trauma receiving facility.

ASSESSMENT

Scene Assessment

Assuring scene safety and donning appropriate personal protective equipment is the first step in management of TBI.

• Initial assessment and management of the patient may have to wait until the scene is safe.

• If the patient is trapped, work with other rescue personnel to formulate extrication plan and ensure responder safety.

Patient Assessment

Initial assessment should focus on identification and management of life threatening injuries using a structured assessment:

• Airway—Evaluate the ability to maintain an open airway while limiting cervical spine motion.

• Breathing—Evaluate the respiratory rate and pattern, and evaluate for external chest injury.

• Circulation—Identify significant external hemorrhage and access perfusion. Measure blood pressure (BP) and heart rate (HR). Evaluation of peripheral pulses or capillary refill time may also be used if BP cannot be obtained.

• Disability—Document blood glucose, Glasgow Coma Score (GCS), pupil size and reactivity, and evidence of seizure or focal motor deficits.

• Exposure—Remove clothing to evaluate for life-threatening injury. Avoid hypothermia or hyperthermia.

Common problems identified during patient assessment: airway obstruction, hypoventilation, hypoxemia, hypo- or hypertension, and reduced level of consciousness. Extracranial injuries such as life-threatening external hemorrhage, tension pneumothorax, and spinal cord injury are common. Spinal injury should be assumed in all patients with head injury.

PATIENT MANAGEMENT

Goals of patient management—The management strategy outlined in the following is based on the treatment recommendations released by the Brain Injury Foundation (BIF) and focuses on the rapid identification and correction of hypoxia, hypotension, hypoglycemia, and prevention of hyperventilation [2].

Airway Management

• Goal: Prevent Hypoxia

• Management:

Basic Airway Management: Insertion of an oropharyngeal airway (OPA) or nasopharyngeal airway (NPA) and application of a nonrebreather (NRB) mask with high-flow oxygen.

Advanced Airway Management: Insertion of a supraglottic airway or endotracheal intubation (ETI).

• Indications:

Evidence of upper airway obstruction.

Advanced airway management should be considered when insertion of an OPA/NPA and ventilation with a bag-valve mask (BVM) with high-flow oxygen does not maintain oxygen saturation greater than 90%.

• Complications: Prehospital ETI can lead to inadvertent hypoxia, and unrecognized esophageal intubation is fatal. Increased intracranial pressure (ICP), aspiration of gastric contents, and hypo- or hypertension can also occur.

Discussion

In patients with airway obstruction, insertion of an OPA/NPA can be sufficient to open the airway and allow effective oxygenation and ventilation. Successful prehospital ETI requires both provider expertise and involved medical oversight. Evidence for the benefit of advanced airway management is conflicting; some studies have shown improved morbidity and mortality with prehospital ETI [3,4], while other others have not [5,6]. Supraglottic airways are an alternative to ETI and are easy to insert and achieve faster time to ventilation than ETI [7]. Advanced airway management requires use of End-tidal CO₂ (EtCO₂) to ensure tube placement and prevent hyperventilation.

Breathing/Ventilation

• Goal: Ensure adequate oxygenation (O₂ saturation greater than 90%) and ventilation (EtCO₂ = 35–45)

• Management:

Administer high flow oxygen by NRB mask, if inadequate oxygenation, assist ventilation with a BVM.

Optimal ventilation may be best achieved when continuous O₂ saturation and EtCO₂ monitoring is utilized.

• Indications: O₂ saturation less than 90% despite use of high flow oxygen indicates the need for assisted ventilation.

• Complication: Hyperventilation (EtCO₂ less than 35) is associated with significant increase in morbidity and mortality.

Discussion

Hypoxia and hyperventilation (low CO₂) increase mortality following TBI [8]. Inadvertent hyperventilation is common in intubated patients and if available, EtCO₂ monitoring should be utilized. Adjust the ventilation rate and tidal volume to reach a goal EtCO₂ of 35 to 45. If EtCO₂ is not available the goal respiratory rate for patients with TBI is as follows: Adults: 10 breaths/min, Children (2–14 years):15 breaths/min, neonates (0–1 years):25 breaths/min. Use of a pressure controlled bag for ventilation can reduce the risk of hyperventilation and lung injury.

Circulatory Management Goal

• Goal: Maintain systolic blood pressure (SBP) greater than 90.

• Management: Administer isotonic 500 mL crystalloid fluid boluses to maintain a SBP greater than 90.

• Indications: SBP less than 90 or if a significant drop in SBP occurs.

• Complications: hypothermia, coagulopathy, volume overload, pulmonary edema, and respiratory failure.

Discussion

A single episode of hypotension doubles the risk of mortality in severe TBI [9]. The BIF recommends that SBP be maintained above 90 mmHg. However, in the prehospital setting across large populations with TBI mortality is the lowest when SBP is near 140 [10]. Therefore, when an initial BP is obtained that is less than 140 and subsequent BP values decrease, field providers should consider starting fluid resuscitation. Use of vasopressors and administration of hypertonic fluids in the field have thus far been impractical or not associated with a clear mortality benefit [11–14].

Disability

• Goal: Identify and treat hypoglycemia. Identify neurologic injury and increased ICP.

• Management:

Administer dextrose to maintain a normal blood glucose level.

Routine hyperventilation is no longer recommended to decrease ICP; however, it may be beneficial in patients who demonstrate signs of herniation.

• Indications: Blood glucose less than 70 in adults or less than 50 in children.

• Complications: Hyperventilation will reduce ICP but does so at the expense of reduced cerebral blood flow, and therefore should only be administered when clinically indicated, and should be monitored via capnography.

Discussion

Historically, the prehospital treatment of increased ICP has been the mainstay of TBI management. However, the BIF has significantly reduced the emphasis on treatment of increased ICP in favor of treating or preventing other causes of secondary injury. Assess periodically for signs of raised ICP (i.e., declining GCS, pupil dilatation and/or reduced reactivity, increasing systemic hypertension with reflex bradycardia). Providers could consider a 30° head-up tilt of spinal board if evidence of increased ICP is present. Current data does not support prehospital administration of mannitol or hypertonic saline [12,13].

Spinal Immobilization

All head-injured patients require application of spinal motion restriction techniques. Common tools used to prevent spinal motion include the application of a cervical collar and immobilization of the patient on the transport stretcher. Long spinal boards can be used to facilitate spinal motion restriction and patient extraction.

Patient Destination

Trauma patients have improved outcomes when treated in a facility with an experienced trauma team, ready access to neuroimaging, and ideally neurosurgery on site [14]. Air transport may be required for long transport distances.

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