BIS for recognition of brain-death in potential organ donors

Background and aim of study

BIS is based on EEG monitoring. Although it has been created for assessing depth of sedation or anaesthesia it can give information on damaged brain activity. The aim of study was to check out whether BIS index can indicate brain-death and what kind of BIS record is observed in patients with clinical symptoms of brainstem death.

Methods

Five BIS records of patients with clinically defined symptoms of brain-death were analysed. In all patients' CT scans showed deep and irreversible damage of brain (massive intracerebral haemorrhage). Tests for absence of brainstem reflexes and persistent apnoea had been carried out and patients were qualified for transplantation procedure. BIS was monitored before and during apnoea test and pain stimuli.

Results

In two cases the range of BIS was initially 0 (0–3). BIS monitor alarmed of EEG flat line. No response on pain stimuli nor on apnoea test were observed in one case. In the second patient BIS increased during apnoea test to 90. In the other three cases initially BIS was over 0 (15–45) and during apnoea test increased to over 90. No reaction on pain stimuli was observed. In those cases where reaction on apnoea test was recorded, BIS significantly decreased after apnoea test.

Discussion

The attempts for using BIS in patients with a severely damaged brain as prediction of brain-death have been already described. However there were no investigations on BIS records in patients with diagnosed brain-death. It is underlined in many guidelines for recognition of brain-death that such investigation as EEG must be assessed by highly trained specialists. Therefore the use of a more simple device for recognition of brain-death could be helpful and might increase the number of organ donations. It is especially needed in haemodynamically unstable patients in whom the apnoea test is difficult to perform because it may cause rapid decrease in blood pressure to an unmeasurable level and even circulatory arrest. Although in two cases BIS confirmed diagnosis of brain-death, in three other patients BIS was significantly higher than 0 and device did not recognise EEG flat line. Probably strong artefacts were the cause of it: the electrical activity of heart, autonomous nervous system impulsation and transmissible trembling of upper half of corps caused by heart work, which can be especially observed in non ventilated patients.

Conclusion

These observations all together make the use of BIS for diagnosis of brain-death in potential organ donors impossible and in our opinion unreliable. Too many factors can influence BIS record and this is unacceptable when used for defining the patient's death.