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BRAIN DEATH

SV Khadilkar, KA Jagiasi

 

INTRODUCTION

Brain death is defined as “Irreversible cessation of all functions of the entire brain including the brain stem”. In adults, the
chief causes of brain death are traumatic brain injury and subarachnoid haemorrhage.4 The declaration of brain death requires not only a series of careful neurological tests but also the establishment of the cause of coma, the ascertainment of irreversibility, the resolution of any misleading clinical neurological signs, the recognition of confounding factors, the interpretation of the .ndings on neuroimaging and the performance of any confi.rmatory laboratory tests that are deemed necessary.

1 Diagnostic criteria for clinical diagnosis of brain death.


2 Prerequisites
1. Absence of clinical brain function when the proximate cause is known and demonstrably irreversible.
2. Clinical or neuroimaging evidence of an acute CNS catastrophe that is compatible with the clinical diagnosis of brain death.
3. Exclusion of complicating medical conditions that may confound clinical assessment [i.e. no severe electrolyte, acid base or endocrine disturbance.]
4. No drug intoxication or poisoning.
5. Core temperature greater or equal to 32 degrees Celsius

The central considerations in the diagnosis of brain death are
1. Absence of cerebral functions.
2. Absence of brain stem functions including spontaneous respiration.
3. Irreversibility of the state.

Absence of cerebral function is judged by presence of unconsciousness and total lack of spontaneous unconscianess movements and of motor and vocal responses to all visual, auditory and cutaneous stimulation. Absence of brain stem
function is judged by absence of pupillary responses to light and pupils at mid position with respect to dilatation
(4-6 mm), absence of spontaneous eye movements, absence of corneal re.exes, absence of caloric responses, absence of gag reflex and coughing in response to tracheal suctioning, sucking and rooting re.exes, decerebrate responses to noxious stimuli and absence of respiratory movements. Lack of respiratory drive at a PaC02 that is 60 mm Hg or 20 mm Hg above normal baseline values is also necessary.

Conditions interfering with the clinical diagnosis of brain death.
1. Facial trauma
2. Toxic levels of any sedative drugs, aminoglycosides, tricyclic antidepressants, anticholinergics, antiepileptics,
chemotherapeutic agents or neuromuscular blocking agents.When these factors are operating, some con.rmatory tests are recommended.
3. Clinical reflexes that can be seen in a case with brain death.2 a. Babinski re.ex b. Deep tendon re.exes, super.cial abdominal reflexes, triple .exion response. c. Spontaneous movements of limbs other than pathologic .exion or extension response. d. Respiratory like movements (shoulder elevation and adduction, back arching and intercostal expansion without signi.cant tidal volumes). e. Sweating, blushing, tachycardia f. Normal blood pressure without pharmacologic
support or sudden increases in blood pressure.

 

Confirmatory Laboratory Tests
Brain death is a clinical diagnosis.
A repeat clinical evaluation at another time, usually six hours later is recommended, but this interval is arbitrary. A confirmatory test is not mandatory but is desirable in patients in whom specific components of clinical testing cannot be reliably performed for one reason or the other.
1. Conventional cerebral Angiography.
2. Technetium-99m hexamethylpropyleneamineoxime brain scan.
3. Electroencephalography
4. Transcranial Doppler Ultrasonography.
5. Somatosensory evoke potentials.
After the clinical criteria of brain death have been met, the physician should inform the next of kin who can be approached about organ donation.
The family should be told in unequivocal terms that the patient is dead. Mechanical ventilation, fluids and blood pressure medication are administered. only to procure organs in the event that permission for donation is given. Management of a brain dead patient in preparation for donation is complicated and advice from a neurologist specialized in neurological critical care or from an anaesthesiologist should be strongly considered.

Major immediate threats to organs are
1. Pulmonary oedema, requiring pulmonary artery catheter placement and treatment with positive end-expiratory pressure ventilation.
2. Hypotension, requiring adequate fluid resuscitation and vasopressors
3. Polyuria from diabetes insipidus, requiring desmopressin.

When mechanical ventilation and supports are continued because of ethical or legal objections to their discontinuation, what usually follows is an invariant heart rate from a differentiated sinoatrial node, structural myocardial lesions leading to a marked reduction in the ejection fraction, decreased coronary perfusion the need for increasing use of inotropic drugs to maintain blood pressure and a fragile state that leads to cardiac arrest within days or weeks.

 

REFERENCES
1. Eelco FM Wijdicks. The diagnosis of Brain Death. The New Engl J Med 2001; 344 : 1215-21.
2. The quality standards sub-committee of the American Academy of Neurology. Practice parameters for determining
brain death in adults. Neurology 1995; 45 : 1012-14.
3. Uniform Determnation of Death, uniform laws Annotated (ULA) 589 West 1993 and West supp 1997.
4. WIjdicks EFM Determing brain death in adults. Neurology

 
 

PROSPECTIVE OBSERVATIONAL COHORT STUDY OF TIME SAVED BY PREHOSPITAL THROMBOLYSIS FOR ST ELEVATION MYOCARDIAL INFARCTION DELIVERED

Thrombolysis delivered by paramedics with support from the base hospital can meet the national targets for early thrombolysis. The system has been shown to work well and can be introduced without delay.

BMJ, 2003; 327 : 22.

 
 

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