Timely diagnosis of brain death (BD) is critical as it prevents unethical and futile continuation of support of vital organ functions when the patient has passed. Furthermore, it helps with avoiding the unnecessary use of resources and provides early opportunity for precious organ donation. The diagnosis of BD is mainly based on careful neurological assessment of patients with an established underlying diagnosis of neurological catastrophe capable of causing BD. Ancillary testing, however, is tremendously helpful in situations when the presence of confounders prevents or delays comprehensive neurological assessment. Traditionally, four-vessel digital subtraction angiography and computed tomography angiography have been used for blood flow (BF) examinations of the brain. The lack of BF in the intracranial arteries constitutes conclusive evidence that the brain is dead. However, there is an apparent discrepancy between the BF and sufficient cerebral perfusion; several studies have shown that in 15% of patients with confirmed clinical diagnosis of BD, BF is still preserved. In these patients, cerebral perfusion is significantly impaired. Hence, measurement of cerebral perfusion rather than BF will provide a more precise assessment of the brain function. In this review article, we discuss a brief history of BD, our understanding of its complex pathophysiology, current Canadian guidelines for the clinical diagnosis of BD, and the ancillary tests-specifically CT perfusion of the brain that help us with the prompt and timely diagnosis of BD.
Background: Treatment of refractory status epilepticus (RSE) is often titrated to achieve EEG burst suppression. However, optimal burst suppression characteristics are largely unknown. We used an unsupervised machine learning algorithm to predict RSE outcome based on the quantitative burst suppression ratio (QBSR). Methods: We conducted principal component analysis (PCA) as a linear combination of 22 QBSR features from non-anoxic adult RSE patients at the Winnipeg Health Sciences Centre. We also determined the most predictive components that significantly differed between survivors and non-survivors. Results: Using 135,765 QBSRs from 7 survivors and 10 non-survivors, PCA identified a predominantly non-survivor cluster of 8 patients (75% non-survivors). The first 2 PCA components comprised 75% data variance. The most important first component feature was skewness of QBSR distribution in the right or left hemisphere (0.52 each). The most important second component feature was third QBSR quantile of the left hemisphere (0.49). Only right hemispheric QBSR features significantly differed between groups: QBSR skewness for the first component (Benjamini-Hochberg adjusted p=0.038) and average QBSR for the second component (0.32, Benjamini-Hochberg adjusted p=0.046). Conclusions: Our pilot study shows that RSE patient survival may be impacted by QBSR, with differential hemispheric EEG burst suppression characteristics predicting poor RSE outcome.
Background: Ancillary testing assist in the diagnosis of brain death. While traditionally, lack of blood flow (BF) in the intracranial arteries constitutes conclusive evidence that the brain is dead, there is apparent discrepancy between the BF, and sufficient cerebral perfusion; In 15% of patients with confirmed clinical diagnosis of brain death, BF is still preserved. In these patients, cerebral perfusion is significantly impaired suggesting that cerebral perfusion rather than BF more accurately assesses brain function. We aim to present a history of brain death, its pathophysiology, and ancillary tests utilized for its diagnosis- specifically CT Perfusion studies. Methods: A literature search using titles and key terms was conducted for articles containing brain death ancillary testing diagnosis, and CTP as primary focus. Results: Across selected studies, CTP diagnosed brain death with 100% positive predictive value, as none of the patients were proven not-dead on follow-up. The early prediction of mortality outcome in these patients with proven high mortality rate may help decisions for withdrawal of life support. It may also facilitate procurement of organs for transplants. Conclusions: Although clinical assessment is the gold standard method of brain death determination, CTP has shown promising results that could alter our current clinical approach.
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