The absence of brain stem function is documented by conducting the following five tests:
- Absence of Pupillary reflex response to light
- Absence of Corneal reflexes
- Absence of vestibulo-ocular reflex
- Absence of cranial nerve response to pain
- Absence of gag and cough reflexes
Pupillary Reflexes: To check for absent pupillary response to light, bright pen torchlight should be used in a darkened room. It should be made sure that no eye drops to dilate the pupils have been used in the four hours previously. The pupils may not be necessarily fixed and dilated in the brainstem dead patients; however there should be no pupillary response to light.
Corneal Reflexes: Moist cotton tipped swab should be used and firm pressure should be applied to the cornea without damaging it.
Vestibulo-ocular Reflexes: testing involves instilling 20ml of ice-cold water into the external auditory canal and looking at eyeball movements of either eye for about a minute. No eyeball movement indicates absence of reflex. Presence of ruptured eardrums or discharge from the ear prevents this test from being performed.
Gag and Cough Reflexes Test: requires temporary disconnection from the ventilator. A cotton tipped swab can be used to stimulate the posterior pharynx to look for a response. Experienced ICU staff usually notice a progressive loss of response during the evolution of brainstem death when performing the routine suction of airways and oropharynx.
Grimacing of the face to a painful stimulation: is a normal response and this is absent in brainstem death situation. A firm supra-orbital pressure (trigeminal nerve) should be used to check this cranial reflex. Pin pricks should not be used to test this response.
Dolls Head Eye Phenomenon: (testing for oculo-cephalic reflex) This is one test that can be done to know if the brainstem is still alive. If this test is positive than other tests to establish brain death can be postponed. One may need to disconnect the patient from the ventilator for 15 to 20 second to perform this test. To do this test the physician holds the patients head between his hands and moves the head from side to side through1800. The clinician should hold the head to one side for 3 to 4 seconds and look at the simultaneous eye movement to that side. A similar movement is done to the opposite side and eye movement is noticed. In a normal fully alert individual and in a cadaver the eyes move with the head and there is only a very fractional delay. If the cerebral hemispheres are damaged but brain stem is still alive there will be an obvious deviation of the eyes to the opposite side for a second or two followed by a release phenomenon when the eyes will get realigned to the side of the head. This test should not be done if cervical fracture is suspected.
The plantar response: may continue to be present in brain death patients along with spinal reflexes and should not be tested. The decorticate and decerebrate posturing is absent, however on occasions it may be difficult to differentiate these from complex spinal reflexes.
Apnoea Test: The aim of apnoea test is to establish death of the respiratory centre in the brainstem (Table III). This is the ultimate test to establish brainstem death. It demonstrates that the spontaneous respiratory response fails to occur even in the absence of stimulatory drive from CO2. For this test the patient is disconnected from the ventilator for 10 minutes. However, to avoid hypoxia to vital organs, 100% oxygen is given for 5 minutes before disconnection from the ventilator. Even during the test period, 100% oxygen is given through a tracheal catheter. In the patient who is brain dead the carbon dioxide tension increase at a rate of 2mm/min (0.3 kPa/min) during apnoea testing. If the initial CO2 tension before testing is about 40mmHg (5.3 kPa) then arterial CO2 tension after 10 minutes is likely to be 60mmHg (8 kPa). However, a rise to 50mmHg in CO2 tension is acceptable and should provide sufficient stimulatory drive for spontaneous respiration in an intact respiratory centre. In patients with chronic airway disease or severe chest trauma, the apnoea test maybe difficult to perform.
In children, there remains uncertainty about the reliability of clinical brainstem testing. In neonates especially, organs for transplantation should not be removed in the first seven days of life with beating hearts. Radioisotope brain scanning has been recommended under the age of one year when brain stem death certification is required.
REQUEST FOR ORGAN DONATION
Brain death is relatively a new concept and making request for organ donation in these circumstances can be an extremely difficult task for a doctor or a nurse to undertake. If the decreased carries, a Donor Card (a card the size of a credit card expressing their desire about organ donation) the task of asking for organ donation becomes easier.
In Tamil Nadu a simple protocol was devised called Ramachandra Protocol when asking for organs. In this protocol Eyes ‘ were first requested for and only if the relatives agreed, other organs were asked for. In the tragic circumstance it was felt that by asking for the eyes first the relatives were less likely to get upset with a request for organ donation (Table-IV).
Usually the organ donation request is made in the time interval between the diagnosis of brain death and discontinuation of the ventilator. If the relatives are agreeable the process of organ donation is under taken and vital organ like heart, lungs, liver, pancreas and kidneys are removed for transplantation. Corneas should be kept moist and eyelids should be closed and retrieval surgery can be done for up to 12 hours after cardiac standstill. Other tissues like heart valves, skin, bone and cartilages can be removed for up to 48 hrs after death. The process of organ donation and transplantation requires co-ordination between different teams operating almost simultaneously and sometimes in different locations. It may require getting surgeons from different specialties together for both donor and recipient surgery.
Generally, there is no bar to organ donation and one or the other organ or tissues can be donated at any age. However, it is important to do some essential virology screening before accepting the donor. All potential donors will require a virology screen to prevent possible transmission of disease from donor to the recipient (Table.VII). The next of kin should be made aware that this is necessary; if there are any objections these should be respected. However, it does mean that donation cannot then take place.
Brain Death – Your questions answered