What are the recommendations for air ambulance transport of a patient on a ventilator with a Middle Cerebral Artery (MCA) infarct and hemorrhagic transformation?

Air Ambulance Transport of Ventilated Patient with MCA Infarct and Hemorrhagic Transformation

Patients with MCA infarct and hemorrhagic transformation on mechanical ventilation can be safely transported by air ambulance if they are physiologically stabilized before departure, with meticulous attention to maintaining oxygenation (PaO₂ ≥13 kPa), normocapnia (PaCO₂ 4.5-5.0 kPa), adequate blood pressure, and head-up positioning at 20-30° to minimize intracranial pressure rises. 1

Pre-Transport Stabilization Requirements

Physiological stability is paramount before any transport attempt. A patient who is physiologically stable before departure is more likely to remain so during transfer, though constant vigilance remains essential. 1

Critical Pre-Departure Checklist:

• Ensure hemodynamic stability: Hypotensive patients must be stabilized before transport, as hypotension adversely affects neurological outcome and patients tolerate transfer poorly in this state. 1
• Optimize ventilation parameters: Obtain arterial blood gases to confirm adequate oxygenation and validate end-tidal CO₂ monitoring. 1
• Secure airway: Confirm correct tracheal tube placement and ensure adequate sedation/analgesia via continuous infusion. 1
• Establish monitoring: Arterial line for continuous blood pressure monitoring (transducer at tragus level), end-tidal CO₂, pulse oximetry, and ECG. 1

Ventilation Management During Transport

Target ventilation parameters are non-negotiable for brain-injured patients:

• PaO₂ ≥13 kPa (approximately 97 mmHg) - avoid even brief hypoxic episodes. 1
• PaCO₂ 4.5-5.0 kPa (approximately 34-38 mmHg) - maintain normocapnia. 1
• PEEP 5-10 cmH₂O - minimum 5 cmH₂O to prevent atelectasis; up to 10 cmH₂O does not adversely affect cerebral perfusion. 1
• Continuous end-tidal CO₂ monitoring is mandatory throughout transport. 1

Special Consideration for Hemorrhagic Transformation:

If clinical or radiological evidence suggests raised intracranial pressure with impending herniation, brief hyperventilation (PaCO₂ not less than 4 kPa) may be justified short-term, combined with osmotic therapy (mannitol 0.5 g/kg or hypertonic saline 2 ml/kg of 3% solution). 1

Positioning and Physical Management

Head-up tilt of 20-30° is essential to minimize ICP rises during transport. Use ambulance trolleys that allow this positioning while maintaining proper securing and padding. 1

Ensure smooth transport: Marked acceleration and deceleration have greater impact on brain-injured patients. If procedures are needed during transport, the ambulance must be brought to a complete halt. 1

Hemodynamic Management

Blood pressure targets must be maintained rigorously:

• Use isotonic saline (0.9%) exclusively for fluid management - it is the only commonly available truly isotonic crystalloid. 1
• Avoid hypotonic solutions (Ringer's lactate, Ringer's acetate, gelatins) as they increase brain water. 1
• Arterial line transducer positioning: Always measure at the level of the tragus, including when patient is head-up. 1
• Manage hypertension with increased sedation and small boluses of labetalol. 1
• Manage hypotension (after correcting hypovolemia) with alpha-agonist boluses followed by infusion (metaraminol or norepinephrine via central line). 1

Sedation and Monitoring

Maintain continuous sedation and analgesia via infusion (propofol or target-controlled infusion if available) with neuromuscular blockade to prevent agitation, coughing, or straining that could increase ICP. 1

Continuous monitoring requirements:

• Vital signs with documented neurological status (pupil size/responses) throughout transport. 1
• All monitors must be securely mounted to prevent injury during transport. 1
• Maintain standardized transfer documentation with copies retained for audit. 1

Air vs. Ground Transport Decision

Air transport is reasonable when:

• Ground transport would exceed 90-120 minutes. 1
• The patient is stabilized and safety of patient/personnel is prioritized over speed. 1
• Appropriate personnel and communication equipment accompany the patient. 1

Critical caveat: If thrombolytic therapy was administered, air transport has been demonstrated safe in studies, though arrhythmias, hypotension, and bleeding may require treatment during transit. 1

Triage Considerations

Transfer to intensive care or stroke unit with neurosurgical capabilities is recommended for patients with large territorial strokes requiring close monitoring and potential decompressive intervention. 1 If comprehensive care and timely neurosurgical intervention are unavailable locally, triage to a higher-level center is reasonable. 1

Common Pitfalls to Avoid

• Never transport actively bleeding or unstable hypotensive patients - stabilization takes precedence over transfer speed. 1
• Avoid routine supplemental oxygen unless needed to maintain SpO₂ 93-98%. 1
• Do not clamp chest drains - use Heimlich-type valve systems instead. 1
• Prevent inadvertent hyperventilation which can worsen outcomes despite seeming physiologically logical. 1
• Ensure adequate sedation to prevent blood pressure spikes from endotracheal tube discomfort. 1