The Pre-brief
Traumatic Brain Injury (TBI) is a major global health problem. In the United States, it is the leading cause of death in children and young adults. Patients with severe TBI who present to the ED are acutely ill and have high rates of morbidity and mortality. Ideally, patients who suffer from severe TBI should be transported and cared for in a specialized trauma facility. In reality, many of these patients initially present to small hospitals with scarce resources and long transportation time to the nearest level I trauma facility. Clinicians who care for this sick cohort of patients should vigilantly prevent any secondary injuries that can result in long term neurocognitive impairment and disability1.
Types of injuries
Severe traumatic brain injury is defined as head trauma with a Glasgow Coma Score (GCS) of 3 to 8. There are two types of brain insults in severe TBI. The primary injury results from the direct impact of trauma on the brain parenchyma resulting in tissue and vessel damage. Secondary injury, which is the focus of the emergency management of TBI, is induced by episodes of hypoxia, hypotension, and seizures. Secondary brain insults are amenable to prevention or reversal, especially early in the disease course2.
Why is my patient getting worse?
The hallmark of preventing a secondary injury in patients with TBI is maintaining adequate oxygenation and cerebral perfusion pressure. This process should ideally start from where these patients are initially encountered. Prehospital clinicians should take extra precautions to prevent hypoxia or hypo-/hypercapnia. Keep oxygen saturations above 90% and maintain normocapnia with target PCO2 in the 35-40 range3. Prehospital intubation of patients with severe TBI is a topic of debate as many of these patients suffer from multiple facial and other injuries that can create a difficult airway, potentially resulting in prolonged intubation or multiple intubation attempts, which can further contribute to hypoxia. However, several of the studies implying worse outcomes are confounded by the level of experience of the intubator – more experienced prehospital teams may allow for early prevention of secondary injury. If patients are found to be hypoxic in the prehospital setting, some advocate for basic airway techniques such as bag-valve-mask (BVM) or inserting a supraglottic airway adjunct to maintain adequate oxygenation.
Watch that CPP (Ya you know me)
Cerebral perfusion pressure (CPP) is equal to mean arterial pressure (MAP) minus intracerebral pressure (ICP) (CPP= MAP-ICP). A MAP between 80-100 mm Hg is enough to maintain a CPP> 60 mmHg which is the goal number for most patients with severe TBI. If you have the ability and resources to do so, place an A-line for close blood pressure monitoring. Take extra steps to avoid hypotension and control any sources of blood loss. Elevated ICP can be reduced by elevating the head of the bed to 30-45 degrees while maintaining cervical spine precautions.
I did what you told me, but my patient is still getting worse!
When your patient is showing signs of impending herniation such as progressive neurological decline, unilateral posturing, cranial nerve abnormalities, or hemodynamic instability, a few measures can be pursued to emergently reduce ICP. While awaiting neurosurgical intervention, patients can be given a 500 mL bolus of hypertonic saline (3% solution or greater), or mannitol 1 g/kg. Proceed with caution when using mannitol as it can cause hypotension, further compromising the ICP. If you didn’t do so by now, insert a foley catheter and replace any urinary losses with saline solution to avoid hypotension. I’m a big fan of using optic ultrasound to assess for elevated ICP by measuring the optic nerve sheath diameter. An outer diameter of 5mm or less tends to indicate a normal ICP (but may not rule out elevated ICP completely).
What other important things I need to do?
Seizure prophylaxis and avoiding fever prevent ICP elevation. Although emergent antiepileptic prophylaxis decreases the incidence of early seizures, it does not prevent the later development of epilepsy after TBI. Check the sugar and keep that in the normal range. Don’t forget about coagulopathy. Reverse anticoagulation in order to avoid ongoing bleeding.
The Debrief
- Patients with severe TBI are at high risk for long term neurological disability. Management should be targeted at preventing secondary injuries.
- Avoid hypoxia and hypotension
- Control external bleeding and reverse anticoagulation
- Watch closely for signs or symptoms of elevated ICP. Give mannitol or hypertonic saline. DO NOT HYPERVENTILATE. There is a theoretical use for hyperventilation as a salvage therapy, but it only works for a short term.
- Finally, these patients have high rates of morbidity and mortality. They should be transferred to a trauma facility where they can be managed by a specialized multidisciplinary team.
References
