Sam David Shemie

In comatose patients at risk of death by neurologic criteria (DNC), spinal-mediated movements (SMM) and movements of unclear neuroanatomic origin (MUO) are

OBJECTIVES: To describe temporal trends and instantaneous relationships between middle cerebral artery (MCA) cerebral blood flow velocity, cerebral oxygen saturation (Csat), cerebral fractional tissue oxygen extraction (cFTOE), and systemic arteriovenous oxygen difference (AV o ₂ ) during the first 24 hours following congenital heart disease (CHD) surgery requiring cardiopulmonary bypass (CPB). DESIGN: Prospective observational study conducted from August 2021 to June 2022. SETTING: Single-center pediatric cardiac ICU in Canada. PATIENTS: Fifteen ventilated neonates and infants admitted to the PICU following CHD surgery requiring CPB. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Bilateral transcranial Doppler (TCD) assessments of the MCA were performed at seven predefined time points during the first 24 hours following CPB, with time 0 defined as the end of CPB. A total of 87 simultaneous measurements of systemic oxygen saturation, Csat, TCD-derived parameters, and AV o ₂ were analyzed. The nadir in MCA velocities occurred at a mean of 9.3 hours ( sd , 1.7 hr) post-CPB and coincided with the lowest Csat and the highest AV o ₂ difference and cFTOE. Lower MCA mean velocities were associated with higher AV o ₂ difference and increased cFTOE. CONCLUSIONS: In neonates and infants following CPB, MCA velocities reach its lowest point approximately 9 hours post-CPB, coinciding with the highest AV o ₂ difference and previously published nadir of cardiac output. These findings could suggest a period of relative cerebral hypoperfusion. Future studies should evaluate whether targeted interventions guided by multimodal cerebral monitoring can mitigate the risk of acute and long-term brain injury in this vulnerable population.

There are two anatomic formulations of death by neurologic criteria accepted worldwide: whole-brain death and brainstem death. As part of the Canadian Death Definition and Determination Project, we convened an expert working group and performed a narrative review of the literature. Infratentorial brain injury (IBI) with an unconfounded clinical assessment consistent with death by neurologic criteria represents a nonrecoverable injury. The clinical determination of death cannot distinguish between IBI and whole-brain cessation of function. Current clinical, functional, and neuroimaging assessments cannot reliably confirm the complete and permanent destruction of the brainstem. No patient with isolated brainstem death has been reported to recover consciousness and all patients have died. Studies suggest a significant majority of isolated brainstem death will evolve into whole-brain death, influenced by time/duration of somatic support and impacted by ventricular drainage and/or posterior fossa decompressive craniectomy. Acknowledging variability in intensive care unit (ICU) physician opinion on this matter, a majority of Canadian ICU physicians would perform ancillary testing for death determination by neurologic criteria in the context of IBI. There is currently no reliable ancillary test to confirm complete destruction of the brainstem; ancillary testing currently includes evaluation of both infratentorial and supratentorial flow. Acknowledging international variability in this regard, the existing evidence reviewed does not provide sufficient confidence that the clinical exam in IBI represents a complete and permanent destruction of the reticular activating system and thus the capacity for consciousness. On this basis, IBI consistent with clinical signs of death by neurologic criteria without significant supratentorial involvement does not fulfill criteria for death in Canada and ancillary testing is required.

Purpose Decompressive craniectomy immediately reduces intracranial pressure by increasing space to accommodate brain volumes. Any delay in reduction of pressure and signs of severe intracranial hypertension requires explanation. Clinical Features We present the case of a 13-yr-old boy presenting with a ruptured arteriovenous malformation resulting in a massive occipito-parietal hematoma and increased intracranial pressure (ICP) refractory to medical management. This patient ultimately underwent a decompressive craniectomy (DC) for alleviation of increased ICP, despite which the patient’s hemorrhage continued to worsen to the point of brainstem areflexia suggestive of possible progression to brain death. Within hours of the decompressive craniectomy, the patient displayed a relatively sudden, marked improvement in clinical status, most notably a return in pupillary reactivity and significant decrease in measured ICP. A review of postoperative images after the decompressive craniectomy suggested increases in brain volume that continued beyond the initial postoperative period. Conclusion We urge caution to be taken in the interpretation of the neurologic examination and measured ICP in the context of a decompressive craniectomy. In the patient described in this Case Report, we propose that ongoing expansion of brain volume following a decompressive craniectomy beyond the initial postoperative period, possibly secondary to the stretch of skin or pericranium (used as a dural substitute for expansile duraplasty), can explain further clinical improvements beyond the initial postoperative period. We call for routine serial analyses of brain volumes after decompressive craniectomy to confirm these findings.

This 2023 Clinical Practice Guideline provides the biomedical definition of death based on permanent cessation of brain function that applies to all persons, as well as recommendations for death determination by circulatory criteria for potential organ donors and death determination by neurologic criteria for all mechanically ventilated patients regardless of organ donation potential. This Guideline is endorsed by the Canadian Critical Care Society, the Canadian Medical Association, the Canadian Association of Critical Care Nurses, Canadian Anesthesiologists’ Society, the Canadian Neurological Sciences Federation (representing the Canadian Neurological Society, Canadian Neurosurgical Society, Canadian Society of Clinical Neurophysiologists, Canadian Association of Child Neurology, Canadian Society of Neuroradiology, and Canadian Stroke Consortium), Canadian Blood Services, the Canadian Donation and Transplantation Research Program, the Canadian Association of Emergency Physicians, the Nurse Practitioners Association of Canada, and the Canadian Cardiovascular Critical Care Society.