Unequal Pupils at 8,000 Feet
A 24-year-old woman fell 20 feet. She is intubated, sedated, and paralyzed. GCS before intubation was 6. She has a left pupil 5 mm and nonreactive, right pupil 3 mm and reactive. BP is 152/78, HR is 58, SpO2 is 99%, temperature is 36.4°C. She has a right temporal contusion. You are at a rural hospital and need to fly 45 minutes to a trauma center at a cabin altitude of 6,000 ft. She has received 1 L of normal saline and is on 40% FiO2. No family is present.
1. What is your interpretation of her exam, and what are your immediate priorities before takeoff?
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Interpretation The unequal, nonreactive left pupil with bradycardia and hypertension is a Cushing response and indicates elevated intracranial pressure with herniation. The right temporal contusion suggests a traumatic brain injury, possibly with an expanding hematoma.
Immediate priorities
- Secure the airway and confirm tube position; avoid hypoxia and hypercapnia.
- Maintain cerebral perfusion: keep MAP adequate, avoid hypotension, and target CPP roughly 60–70 mmHg.
- Elevate the head of the bed 30 degrees and keep the neck midline.
- Give hyperosmolar therapy now: 3% saline 3–5 mL/kg or mannitol 0.5–1 g/kg if blood pressure is adequate.
- Target PaCO2 35–40 mmHg; brief hyperventilation to 30–35 mmHg only for active herniation.
- Control pain, sedation, temperature, and glucose; avoid hypotension during transport.
Reasoning The pupil and vital signs are herniation signs, not just a head injury. Treatment must lower intracranial pressure and protect perfusion while arranging definitive neurosurgical care. Hyperventilation is a bridge for active herniation, not a routine ventilator setting.
2. How do you set the ventilator and hemodynamics? Include target numbers and the reasoning.
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Ventilator
- FiO2 to keep SpO2 94–98%; avoid prolonged hyperoxia.
- Respiratory rate to keep PaCO2 35–40 mmHg, using capnography as a trend but not as a substitute for blood gas when available.
- Tidal volume 6–8 mL/kg predicted body weight; avoid high peak pressures.
- Keep PEEP modest so it does not impair venous return.
Hemodynamics
- Target MAP at least 80 mmHg and CPP 60–70 mmHg.
- Treat hypotension with isotonic fluid and, if needed, norepinephrine.
- Avoid systolic BP below 100 mmHg.
- Keep head neutral; avoid tight cervical collars or tape that compresses jugular veins.
Reasoning Both hypoxia and hypotension worsen secondary brain injury. Ventilation should be normocapnic except during active herniation. Cerebral perfusion depends on MAP minus ICP, so pressure support is as important as sedation and osmotherapy.
3. During flight her BP rises to 190/100 and the left pupil dilates further. What do you do?
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Interpretation This is worsening intracranial hypertension with progressive herniation.
Actions
- Check the airway: confirm tube position, suction, and verify the ventilator is not causing hypercapnia or high airway pressures.
- Ensure adequate sedation and analgesia; paralysis alone does not blunt pain or agitation.
- Hyperventilate briefly to a PaCO2 of 30–35 mmHg.
- Repeat hyperosmolar therapy: 3% saline 3–5 mL/kg or mannitol if the pressure and volume status allow.
- Keep the head midline and elevated; loosen cervical straps.
- Notify the trauma center and request neurosurgical readiness; do not delay definitive decompression.
Reasoning A rising blood pressure with a dilating pupil is a herniation emergency. The goal is to lower ICP immediately while correcting reversible causes such as hypoxia, hypercapnia, or tube obstruction. Hyperventilation and osmotherapy are temporizing; definitive care is surgical decompression.