Claudio Scherle

Brain death diagnosis and apnea test safety

The apnea test is a mandatory examination for determining brain death (BD), because it provides an essential sign of definitive loss of brainstem function. However, several authors have expressed their concern about the safety of this procedure as there are potential complications such as severe hypotension, pneumothorax, excessive hypercarbia, hypoxia, acidosis, and cardiac arrhythmia or asystole. These complications may constrain the examiner to abort the test, thereby compromising BD diagnosis. Nevertheless, when an appropriate oxygen-diffusion procedure is used, this technique is safe. We review here the prerequisites to begin the test, its procedure, potential complications, and the use of alternative ancillary tests. We recommend that the apnea test be retained as a mandatory procedure for the diagnosis of BD. In those situations when the apnea test is terminated by the examiner for some reason or when it is impossible to carry it out in a patient due to the presence of some pathologic condition, alternative ancillary tests should be used to confirm BD.

TCD diastolic velocity decay and pulsatility index increment in PVS cases.

BACKGROUND Functional neuroimaging has provided new insights for assessing cerebral function in persistent vegetative state patients (PVS). Compared to controls, positron emission tomography and single photon emission tomography have shown a substantial reduction of global brain cerebral glucose metabolism and perfusion in PVS. Doppler ultrasonography (TCD) assesses local blood flow velocity and direction in the proximal portions of large intracranial arteries; it is a noninvasive technique, and it can be carried out at the bedside. To date, few studies have applied TCD to study PVS. METHODS We assessed intracranial circulation by TCD in five PVS patients. The cause of brain insult was hypoxic encephalopathy in four cases, and the other suffered an embolic cerebral infarct causing a top of the basilar artery syndrome. The sample volume was set at 12 mm; power output and gain settings were maximized as needed. The temporal bone acoustic window was not suitable for intracranial vessel insonation in all patients. As an alternative, the internal carotid artery siphon was assessed by orbital insonation between 55-70 mm. RESULTS Systolic velocity was within a normal range, between 44 and 62 cm/second in all cases. However, the diastolic amplitude was reduced, as well as the end diastolic velocity, and the pulsatility index was increased in all patients. CONCLUSIONS We conclude that TCD diastolic velocity decrement and PI augmentation in our cases might be related to uncoupling of cerebral blood flow and cerebral metabolic rate, arising from reduced cerebral glucose consumption and oxygen uptake, after extensive brain injury.

TCD Systolic Spikes in a Malignant MCA Infarct

IntroductionMalignant MCA infarction results in significant space occupying effect and intracranial pressure (ICP) increment. Due to the high mortality rate in such patients, the term malignant MCA infarction was coined.MethodsWe studied a patient who developed a sudden onset of slurred speech, right hemiplegia, and decreased level of arousal. Two days later CT scan showed a massive cerebral infarct, involving the left MCA territory.ResultsA transcranial Doppler exam showed a normal flow pattern in the right hemisphere, but in the left hemisphere systolic spikes without diastolic flow were observed in internal carotid artery, anterior cerebral artery, as well as in the MCA.ConclusionsThe pathophysiologic mechanisms leading to BD might asymmetrically begin in cerebral hemispheres in malignant MCA infarcts.

Coexistence of vasospasm and microembolism detected by transcranial Doppler ultrasonography in a patient with subarachnoid haemorrhage

Delayed cerebral ischaemia as a clinical expression of vasospasm is one of the main complications of subarachnoid haemorrhage. In some cases, ischaemic manifestations can be related to cerebral emboli, but the relationship between vasospasm, damaged endothelial lining, and embolism, remains to be proven. The case is presented of a 56-year-old female patient who, 5 days after the clipping of an aneurysm in the left middle cerebral artery (MCA), suffered transient ischaemic attacks (TIAs) of this arterial territory. Transcranial Doppler ultrasonography showed an increment of the left MCA mean flow velocity, and 12 microembolic signals were detected in 30 mins. The coexistence of microemboli signals with severe vasospasm in the same arterial segment might suggest a causal relationship between cerebral embolism, severity of vasospasm, and TIAs.

Subsequent bilateral thalamic haemorrhage

Simultaneous or subsequent bilateral thalamic haemorrhage is rare, and most reported cases are from Asian countries. An 80-year-old white Cuban man, with a history of arterial hypertension, suffered sudden onset of right hemiparesis. Computed tomography (CT) scan showed a left posteromedial thalamic haemorrhage. Two days later his condition suddenly deteriorated: blood pressure was 220/105 mm Hg, he was stuporous and tetraplegic, respiration was ataxic, and his gaze was fixed and deviated downward and inward. CT scan showed haemorrhages in both thalami, extending to the ventricles. 32 h later the patient died. There are few previous publications of simultaneous or subsequent bilateral thalamic haemorrhages and this is the first report involving a Hispanic patient. Prognosis in patients with bilateral thalamic haemorrhage is poor, and the mechanism underlying the development of subsequent and symmetrical bleeding is not clear.

Duplicated middle cerebral artery.

Duplicated middle cerebral artery (DMCA) is an anomalous vessel arising from the internal carotid artery. The incidence DMCA is relatively law, and an association between this anomaly and cerebral aneurysms has been documented. There is a controversy whether DMCA may have perforating arteries. This is an important fact to consider in aneurysm surgery. We report the case of a 34-year-old black woman who suffered a subarachnoid hemorrhage and the angiography a left DMCA, and an aneurysm in an inferior branch of the main MCA. The DMCA and the MCA had perforating arteries. The aneurysm was clipped without complications. The observation of perforating arteries in our patient confirms that the DMCA may have perforating arteries. This is very important to be considered in cerebral aneurysms surgery. Moreover, the DMCA may potentially serve as a collateral blood supply to the MCA territory in cases of MCA occlusion.