Anesthesia for traumatic brain injury (TBI)

The treatment of TBI is a lesson of humility to the medical profession.

In spite of the advances - in treatment and transport, diagnostic techniques , surgical  procedures ,anesthetic  and  intensive care-,  brain trauma  places an enormous challenge  because of the complexity and  uniqueness of the central nervous system. 

If we resume our present state of the art  of  its treatment, the most we can do is to try to improve the delivery of O₂ and nutrients by  fluid and hemodynamic resuscitation and by treating  increased ICP. We can also evacuate hematomas and  lift  depressed fractures and decompress the brain.

Secondary injury can be minimized .

 But nothing can be done to repair the  nervous tissue.

Almost 100% of persons with  severe TBI  and as many as two thirds of those with moderate head injury will be permanently disabled  and will not return to their previous level of function.

Anesthesiologists participate in almost every  step of the treatment  of the patient with TBI.

In fact  ,one of the best things that can happen to such a patient is to meet an anesthesiologist as early as possible. Anesthesiologists are not only experts in airway management  and in intracranial blood volume but also in the stabilization of vital functions and the  normalization of homeostasis.

I am not going to write about the surgical pathologies and the pathophysiological changes that occur after head trauma,and I'll  go directly to the treatment.

Emergency  assessment (Simultaneously with resuscitation maneuvers) .

-Neurological assessment and spine inmobilization

  GCS(specifying every one of the 3 responses)

  Pupils

-Other organs, specially  internal  bleeding, lung injury, pneumothorax

Any bleeding which causes or may cause instability threatens the perfusion of every organ and specially the brain. Brain perfusion must be ensured  ,even in the presence of  uncontrolled bleeding. Ignoring  this fact can result in the survival of a brain death  patient.

A high degree of suspicion is essential in every step of the treatment.

Internal hemorrhages  previously undetected can suddenly  destabilize the patient.

As increased ICP causes frequently hypertension, the normotensive or hypotensive patient has to rise our suspicion  of present bleeding.

Airway and Ventilation

Intubation  equals  anesthesia induction, in the ER, the CT scan or in the street.

Once intubated, during transport or in the  OR, the patient will be treated with the same principles of care in every stage ,the most important goals being the optimization of brain perfusion and oxygenation,the avoidance of hypotension and hypoxia, the treatment of increased ICP and the prevention of further neurological  damage.

There are multiple metabolic factors involved in TBI unrelated to this simplistic hydrostatic approach ,many of them still unknown.

Indications  of intubation

To protect the airway from aspiration,to ensure normoxia and normo-hypocapnia.

GCS<8

Ventilatory failure

Irregular respirations

Deterioraring  level of consciousness

Face fractures

Bleeding into mouth

Seizures

Significant lung/chest injury

Shock

Combative

Need of transport

Intubation

When preparing to intubate the patient, take in account:
  -Increased ICP- Drugs are used to blunt the rise of ICP caused by laryngoscopy and intubation.

  -Prediction of difficult intubation-face trauma, laryngeal trauma, and anatomically abnormal airway .

 -Hemodynamic stability-will determine which drugs we are going to use.

 -Cervical spine injury

 -Full stomach

If  there is no predicted difficulty, rapid sequence induction with Sellick' maneuver.

The choice of drugs and its doses will be determinated  by the  hemodynamic  state.

Normovolemic  patients ,(normo or hypertensive) can be intubated with propofol 1-2 mg/kg or thiopental 3-4 mg/kg. 

Muscle relaxant :Succinylcholine 1.5 mg/kg or Rocuronium 1 mg/kg.

If the patient is hypovolemic, Etomidate 0.2-0.3 mg/kg or ketamine 1-1.5 mg/kg .

In predicted difficult intubation in non –cooperative patients the options  include fiberoptic intubation,intubating LMA,light wand,retrograde intubation,cricothiroidotomy .

Please see the excellent site of  difficult intubation in trauma patients  by Tom Trimble.

Cervical spine injury is always suspected- After removing the anterior part of the Philadelphia collar,an assistant  stabilizes the head in a neutral position  without flexion and with minimal extension.Another assistant performs cricoids pressure to avoid passive reflux.

Mechanical  ventilation – After intubation ,patients are ventilated to ensure normoxia and mild hyperventilation.

During the first hours following TBI, unnecessary hyperventilation is  avoided  because aggravates  the already reduced   CBF .

 In the case of asymmetric  neurological signs, hyperventilation is recommended  to reduce ICP ,albeit the risk of ischemia.

PEEP can be used as needed as it has minimal effect on ICP

Cardiovascular resuscitation

Hypotension  or hypoxia increase morbidity and mortality from severe traumatic brain injury.

Hypotension is defined as a systolic BP of 90 mmHg or less.  The CPP  should  be between 60 to 70 mmHg. Higher CPP's  are associated with an increased incidence of ARDS.

Fluid resuscitation (via 2 wide bores peripheral IV's)  is guided by  heart rate,

blood pressure , arterial wave contour , systolic variation (delta down) and capillary refill. Central venous pressure is not routinely monitored and urinary output is affected by mannitol.

Isotonic crystaloids
Assess coagulation function .(PT,PTT,Fibrinogen,TEG)
Early use of blood components.
FFP/PRBC >1:2 ratio reduce mortality
High platelets ratio improved survival in massive transfusion associated with TBI
Consider early use of cryoprecipitate or fibrinogen concentrate as needed
Tranexamic acid has shown to reduce risk of death, less progression of IC hemorrhage.

Serum glucose concentration should be kept between 140-180 mg/dL to avoid neuroglucopenia.Brain metabolism is impaired at levels below 108 mg /dL.

Vasopressors   are used  during fluid resuscitation  to shorten  the occurrence of  hypotension We generally use phenylephrine bolus 1.5 mcg/kg.

Management of increased ICP

Increased ICP over 20 mmHg is a predictor of  worse neurological outcome.

-Posture- Torso up  10-30 degrees.(remember to keep the transducer at ear level) and avoid  lateral deviation of  the head which can compromise venous return.

-Hyperventilation-see above

-Diuretics- Mannitol 1 g/kg  if lateralization signs or trastentorial herniation.Osmolarity kept under 320 mOsm/L. Not to  be used in hemodinamically unstable patients, produces hypotension. May mildly affect coagulation.

-Hypertonic saline- 5ml/kg of a 3% solution.

-Induced moderate hypertension, may produce cerebral vasoconstriction, thus reducing the intracranial blood volume.

-CSF drainage.

-Barbiturates-In refractory cases, needs vasopressor support.

-Decompressive craniotomy.

Temperature  - Treat hyperthermia aggressively. Hypothermia is not recommended.


After the initial resuscitation, the patient is taken to CT scan .Patients with unstable hemodinamics due to bleeding which need emergency extracranial surgery, are taken directly to the OR.
In patients with suspicion of  blunt injury of the neck vessels, a CT angio is performed.The patients at risk are:
neck hematoma,Lefort lll,abnormal neurological examination with normal head CT scan,seat belt injury,massive epistaxis.Although this lesions  are not frequent,can be devastating, and a prompt intervention in the neuroradiology suit can be life saving.

 

Operating room management

As in other stages, keep  goals of treatment.

Remember aggressive treatment of hypotension,hypoxia.

Try to improve operating conditions.

Almost all patients arrive intubated to the OR .Check depth and fixation of tube, lines.

In multiple trauma patients,be aware of sudden hemodynamic or respiratory decompensation  from  previously undiagnosed sources of bleeding , pneumothorax.

Bleeding- Check   frequently : operating field, suctions , CUSA,  monitors. Communication with surgeon is essential.

Bleeding  can be profuse ,so be ready .The main problems are underestimation of blood loss and unreadiness.

Early  blood orders and  available blood in the OR .

In massive bleeding, inform blood bank .

Arterial  wave contour and systolic variation are  the most important parameters for diagnosing hypovolemia and for continuous assessment of  volume  replacement.

In a  second place, pH and bicarbonate. Do fine tuning of the Ht  and other components when bleeding  is stopped and volemia corrected.
Common problems: 

Brain bulging

Causes: the hematoma itself ,brain edema, problems of positioning ,trendelemburg, jugular vein compression , turning of the neck, hypoventilation, PEEP, hypoxemia, hypotension

Iatrogenic use of hypotonic fluids before surgery

Treatment . After correcting  extracranial  factors ,  hyperventilate ,reduce inspiratory time,give another dose of mannitol  or hypertonic saline and /or furosemide

The surgeon may drain CSF from the ventricle.

If it does not help,  deepen the anesthesia with thiopental, which generally demands  the concomitant use of vasopressors

Monitoring

EKG, arterial line, pulse oximetry, esophageal  temperature, ETCO2 and agents, urinary output, TOF.

Brain monitoring in the OR is seldom used in trauma patients in our hospital.
All patients will have a subdural or intraventricular catheter placed for ICP monitoring.

Laboratory- Arterial  blood gases, electrolytes, glucose ,Ht. Coagulation profile, tromboelastogram.

Maintenance.  Balanced anesthesia  . Isoflurane or sevoflurane  are used at concentrations  lower  than 1 MAC. Opioids:fentanyl
TIVA- is another option.It is not associated with improved neurological outcome compared with balanced anesthesia with volatile agents.

Muscle relaxation.  Rocuronium ,vecuronium or atracurium.

Postoperative course-

After the postoperative CT scan , all  severe TBI and craniotomy patients are admitted  to neurosurgical intensive care.

Patients with one or more of these conditions are ventilated after surgery:

Severe traumatic brain injury,multiple trauma patients , massive transfusion, hypothermia, brain swelling, difficult hemostasis.

Please  consult the guidelines of the Brain trauma foundation and the page of Open Anesthesia

I wish to thank  Prof.Jean F.Soustiel, Deputy Director of the Dept.of Neurosurgery, for the revision  of this guidelines  and for his useful  suggestions and comments.