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BRAIN DEATH

By: Riahialam M , MDAnesthesiology and Critical Care Department

Shiraz University of Medical SciencesReference: Uptodate v19.2

Prerequisite Define Cause Imaging R/O Electrolyte or Ph disturbance,

endocrine problems, severe shock R/O Intoxication or drug poisoning R/O False Positive: Locked-in

syndrome, GBS T>= 36C SBP>=100 even by vasopressour

infusion

Neurologic Exam Deep Coma

No Motor Response No Pupil Response To Light (Pupil

size 4-9 mm) Neg. Corneal Reflex Neg. Occulovestibular Reflex Neg. Jaw Jerk No Cough during ETT Suction Neg. sucking or Rooting Reflex Apnea test

Movement present in brain death Some of spinal cord or peripheral nerve

Movement in facial nerve region, Finger Flexion, Tonic Neck reflex (with flexion in neck some

movement appear in body like shoulder add. Elbow flex. , Pron. Or supine. Wrist, flex. of trunk, LAZARUS sign),

Triple flexion in hip, ankle & knee after foot stimulation like babinski sign,

Some opisthotonic movement in trunk, Pos. Abd. Superfascial or deep Reflexes, Undulating Toe Sign, Pos. pronation extension reflexes upper limb

Caloric test T difference between the body and the injected

water creates convective current in the endolymph of the horizontal semicircular canal

Warm Water (>=44°C) endolymph in the ipsilateral horizontal canal rises, causing an increased rate of firing in the vestibular afferent nerve. This situation mimics a head turn to the ipsilateral side. Both eyes will turn toward the contralateral ear, with horizontal nystagmus to the ipsilateral ear.

Cool Water (<=30°C), the endolymph falls within the semicircular canal, decreasing the rate of vestibular afferent firing. The eyes then turn toward the ipsilateral ear, with horizontal nystagmus (quick horizontal eye movements) to the contralateral ear.

Caloric test COWS = Cold Opposite , Warm

Same (Fast direction nystagmus)

In comatose patients with cerebral damage, the fast phase of nystagmus will be absent .

If both phases are absent, this suggests the patient's brainstem reflexes are also damaged .

Apnea Test Done after other criteria: Core temperature

≥36ºC, SBP≥100 mmHg, eucapnia (PaCO2 35 to 45 mmHg), absence of hypoxia, and euvolemic status

O2 100% in 10 min , PEEP 5, till PaO2=200 or PaCo2>=40 , when SaO2>95 ABG is done

Pt Disconnected from M.V , O2 6 lit/min administrated with Canola at level of carina or T-piece or CPAP 10 cmH2o with O2 12 lit/min

PaCO2 >= 60 mmHg or 20 mmHg above baseline and PH<7.28 with no Respiratory effort, in 8-10 min

Note Apnea Test Not Valid for : chronic

↑PaCo2, Cervical Spine Injuries, Test discontinued: If SBP<90 or

Sao2<85 for 30sec, or Cardiac Arrhythmia appears.

Another choice for these pt. is CPAP. New method is M.V with O2+CO2

3.5% , Fr:4/min, and observe pt respiratory effort detected by respirator, pressure trigger is better

Repeat test? Newborn 7d-2m >>> 48hr

later Infant 2m-1y >>> 24hr

later Child 1y-18y >>> 12hr later Adult >>> 6hr Resuscitated or Hypoxic

encephalopathy >>> 24hr later

Note Resuscitated after cardiac arrest, we

recommend observation for at least 24 hours from the time of the arrest, as spontaneous improvement in brainstem reflexes can occur hours after cardiac arrest.

In patients received induced hypothermia, the recovery time may be further extended, as some motor and brainstem reflexes may recover after being absent for three days.

Perform an ancillary test of brain blood flow with such patients;

Electrophysiologic parameters may also be affected by induced hypothermia.

2010 American Academy of Neurology guideline update published in found insufficient evidence to determine a minimally acceptable observation period.

Ancillary Tests When the cranial nerves cannot be adequately

examined When neuromuscular paralysis is present When heavy sedation is present When the apnea test is not valid (high carbon

dioxide retainers) or cannot be completed When confounders render the clinical

examination unreliable, e.g., multiple organ failure and the presence of a sedating or paralyzing drug that may be very slow to clear

To shorten the duration of the observation period Infants <1 year; two positive tests are required

for those <2m. 

Ancillary Tests EEG Evoked potentials — Somatosensory

evoked potentials (SSEPs) and brainstem auditory evoked potentials (BAEPs)

Brain blood flow —Transcranial Doppler, MR angio, CT angio, Nuclear medicine, 4vessel cerebral angio is the traditional "gold standard"

Other tests — The atropine test examines the HR response to intravenous injection of 3 mg atropine. An increase in HR of <3%supports the diagnosis of brain death

Brain Death Mimics

Locked-in syndrome

Hypothermia

Drug intoxication

Guillain-Barré syndrome

Prognosis In adults, there are no published

reports of recovery of neurologic recovery after a diagnosis of brain death as outlined above

Brain ischemia leads to sympathetic nervous system collapse leading to vasodilation and cardiac dysfunction

Pulmonary edema and diabetes insipidus are frequent early consequences of brain death and may also precipitate cardiopulmonary failure   

Prognosis In one series, all 73 patients meeting the

clinical criteria for brain death suffered cardiac asystole despite full cardiorespiratory support; 97 percent died within seven days

One case series of 175 patients surviving longer than one week after diagnosis of brain death challenges this tenet. In this series, 80 patients survived two weeks, 44 survived four weeks, 20 survived two months, and seven survived six months. Those with long survivals were very young (two newborns). 

The End