Transcranial doppler in the diagnosis of cerebral circulatory arrest: (CONSULTANT LEVEL EXAMINATION)

Overview

The role of transcranial color coded Doppler (TCCD) in neurocritical monitoring has been illustrated in previous chapters. We will here focus on its use as a confirmatory test in the diagnosis of brain death (BD). The concept of death in Western civilization has been linked to the cessation of breathing and heart beat, irrespective of cultural and religious variability. Advances in medical technology after the Second World War and the development of critical care integrating the use of mechanical ventilators, as well as the advent of successful transplantation of vital organs, presented new ethical, legal, and medical dilemmas.

In 1968, the Ad Hoc Committee of the Harvard Medical School to Examine the Definition of BD concluded that BD is a strictly clinical diagnosis, defined as the irreversible cessation of all hemispheric, cerebellum, and brainstem neurologic functions. ^, Analyzing BD is beyond the scope of this chapter; however, readers are referred to the White Paper published by the U.S. President’s Council on Bioethics in 2009, which illustrates controversies in the diagnosis of BD, while introducing the term “ total brain failure ” and defining the irreversible cessation of whole-brain function. ^, Controversies in the diagnosis of BD and the use of the traditional cardiopulmonary standard in the organ procurement practice, known as “controlled donation after cardiac death,” have led to the development of confirmatory tests in BD diagnostic protocols. ^, These tests are recommended whenever specific elements of the clinical examination may be unreliable and are rarely implemented by law in certain countries. Patients with severe brain injury are usually treated with barbiturates; moreover, the presence of various metabolic, thermoregulatory, respiratory, and other disturbances may prevent determination of BD by clinical criteria. Confirmatory tests are used in children and neonates because clinical diagnosis of BD can be challenging in these cases. ^, Confirmatory tests are divided into those diagnosing cerebral circulatory arrest (CCA) (e.g., angiography) and those that demonstrate loss of bioelectrical activity (e.g., electroencephalography). ^,