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c)
Oculo-cephalic reflex (Doll's head eye phenomenon)
Stand at the head-end of the patient's bed.
Hold the head of the patient in the neutral
position firmly with both hands.
Move the head briskly, first to one side and then
to the other. Observe
the eye movements during these maneuvers -by retracting
the eyelids with the thumbs.
A positive reflex is elicited in a comatose
patient when the eyes move in an opposite direction to
the head movement as if to keep the fixation axis
straight ahead (Figure 6).
If the reflex is elicited, the brain-stem is
alive and there is no need to proceed with further
testing. In
a patient with non-functioning brain-stem, the head and
eyes will move together.
The test should be avoided in cases of recent trauma
with suspicion of cervical fracture.
The ventilator may be disconnected for 20-30
seconds while performing this test.
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| Figure
6. |
Positive
oculo-cephalic reflex. Notice the position of the eyes
in relation to the direction of head movements.
I. Head and eyes in neutral position.
IIa & IIIa.
Deviation of eyes to opposite sides when the head
is moved to the left and right respectively. IIb &
IIIb. Eyes
in neutral position, after the realignment.
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d)
Vestibulo-ocular reflex (Caloric test)
Instill about 56 ml of ice-cold water or saline into
each auditory meatus, in turn (Figure. 7).
In children, a smaller volume (10-20 ml) may be
used. Normally,
eye movements will be observed within 20-30
seconds. No
eye movements are seen in case of brain death.
Absence of eye deviation towards the tested ear
indicates a disrupted reflex arc by damage to the reflex
centers (brain-stem) or paralysis of extra-ocular
muscles. Therefore,
do not perform this test if muscle relaxants have been
administered.
Otoscopic examination must have confirmed the integrity
of the tympanic membrane.
Make sure that there is no mechanical obstacle in
the auditory canal, such as wax.
If the tympanic membrane is not intact, elicit
the reflex using cold air instead of cold water.
Testing should be done in both ears.
The test may be contraindicated in patients with
local trauma.
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Figure 7. Caloric test
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e)
Upper and lower airways stimulation (e.g., pharyngeal
and endotracheal suction)
This
test is carried out with the intention to achieve
pharyngeal and carinal stimulation.
Pass a suction catheter down into the pharynx and
the trachea up to the carina (Figure 8).
In a brain-dead patient, this will not produce
either gagging or coughing.
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Figure 8. Testing for gag
reflex.
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3.4.3
Observation Period (Interval between examinations)
After completion of the first examination, a second
examination should be conducted after the stipulated time
interval. The findings are to be recorded in the brain death
documentation form (Appendix 11) and signed by the consultants
conducting the examination.
The recommended time intervals between the first and
second examinations are given in Table 1.
Table
1. Recommended time interval between first and second
examination in various age groups.
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|
| *
Neonate (7 days - 60 days) |
48
hours |
| *
Infants (above 60 days - I year) |
12
hours |
| **
Children (above one year) |
6
hours |
| **
Adults |
6
hours |
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|
*
Two EEGs separated by the stipulated time interval
** One EEG only, at the time of first examination |
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