Toxicologic Confounders of Brain Death Determination: A Narrative Review

Role of Clinical and Multimodality Neuroimaging in the Evaluation of Brain Death/Death by Neurologic Criteria and Recent Highlights from 2023 Updated Guidelines

Purpose of Review: This review aims to provide a comprehensive overview of the diagnosis of brain death/death by neurologic criteria (BD/DNC) by emphasizing the clinical criteria established by the American Academy of Neurology (AAN) in light of their updated guidelines released in 2023. In this review, we will focus on the current implementation of ancillary tests including the catheter cerebral angiogram, nuclear scintigraphy, and transcranial Doppler, which provide support in diagnoses when clinical examination and apnea tests are inconclusive. Finally, we will also provide examples to discuss the implementation of certain imaging studies in the context of diagnosing BD/DNC. Recent Findings: Recent developments in the field of neurology have emphasized the importance of clinical criteria for diagnosing BD/DNC, with the AAN providing clear updated guidelines that include coma, apnea, and the absence of brainstem reflexes. Current ancillary tests, including the catheter cerebral angiogram, nuclear scintigraphy, and transcranial Doppler play a crucial role in confirming BD/DNC when the clinical assessment is limited. The role of commonly used imaging studies including computed tomography and magnetic resonance angiographies of the brain as well as CT/MR perfusion studies will also be discussed in the context of these new guidelines. Summary: BD/DNC represents the permanent cessation of brain functions, including the brainstem. This review article provides the historical context, clinical criteria, and pathophysiology that goes into making this diagnosis. Additionally, it explores the various ancillary tests and selected imaging studies that are currently used to diagnose BD/DNC under the newly updated AAN guidelines. Understanding the evolution of how to effectively use these diagnostic tools is crucial for healthcare professionals who encounter these BD/DNC cases in their practice.

Pharmacokinetic analysis of a phenobarbital overdose treated with urinary alkalinization alone

Phenobarbital is a long-acting barbiturate used to treat alcohol withdrawal and epilepsy. Acute overdoses present with varying levels of central nervous system depression and large overdoses can be life threatening. Phenobarbital is an attractive candidate for enhanced elimination using urinary alkalinization given it is a weak acid with a long half-life and extensive urinary elimination. Limited human data exist regarding use of urine alkalinization for the treatment of phenobarbital overdose. We present a fourteen-year-old female who was treated with urinary alkalinization alone following an intentional ingestion of 3800 mg (84.4 mg/kg) of phenobarbital tablets. Urine drugs of abuse screening was preliminary positive for barbiturates and confirmed to be phenobarbital only. The initial serum phenobarbital concentration, drawn nine hours post-ingestion, was 97.4 mcg/ml (normal range 15-40 mcg/ml). Urinary alkalinization with sodium bicarbonate was started approximately 12 h post-ingestion and stopped at 72 h post-ingestion; clinical toxicity resolved by hospital day 5. The infusion was titrated to a urinary pH of greater than 7.5. Serial serum and urine phenobarbital measurements were obtained to determine elimination half-life and urinary excretion. The elimination half-life while undergoing urinary alkalinization was 81.3 h. Prior to initiation of urinary alkalinization, the urine phenobarbital concentration was 37 mcg/ml. Approximately 8.75 h after initiation, it was greater than 200 mcg/ml at a urine pH of 8.5. Urinary alkalinization appeared to augment urinary phenobarbital excretion, though with no discernible effect on elimination half-life and unclear clinical benefit. Further research is needed to better characterize the clinical effects of urinary alkalinization for phenobarbital overdose.

Potential pharmacological confounders in the setting of death determined by neurologic criteria: a narrative review

Guidelines for the determination of death by neurologic criteria (DNC) require an absence of confounding factors if clinical examination alone is to be used. Drugs that depress the central nervous system suppress neurologic responses and spontaneous breathing and must be excluded or reversed prior to proceeding. If these confounding factors cannot be eliminated, ancillary testing is required. These drugs may be present after being administered as part of the treatment of critically ill patients. While measurement of serum drug concentrations can help guide the timing of assessments for DNC, they are not always available or feasible. In this article, we review sedative and opioid drugs that may confound DNC, along with pharmacokinetic factors that govern the duration of drug action. Pharmacokinetic parameters including a context-sensitive half-life of sedatives and opioids are highly variable in critically ill patients because of the multitude of clinical variables and conditions that can affect drug distribution and clearance. Patient-, disease-, and treatment-related factors that influence the distribution and clearance of these drugs are discussed including end organ function, age, obesity, hyperdynamic states, augmented renal clearance, fluid balance, hypothermia, and the role of prolonged drug infusions in critically ill patients. In these contexts, it is often difficult to predict how long after drug discontinuation the confounding effects will take to dissipate. We propose a conservative framework for evaluating when or if DNC can be determined by clinical criteria alone. When pharmacologic confounders cannot be reversed, or doing so is not feasible, ancillary testing to confirm the absence of brain blood flow should be obtained.

Computed Tomography Angiography (CTA) in Selected Scenarios with Risk of Possible False-Positive or False-Negative Conclusions in Diagnosing Brain Death

It is widely accepted that brain death (BD) is a diagnosis based on clinical examination. However, false-positive and false-negative evaluation results may be serious limitations. Ancillary tests are used when there is uncertainty about the reliability of the neurologic examination. Computed tomography angiography (CTA) is an ancillary test that tends to have the lowest false-positive rates. However, there are various influencing factors that can have an unfavorable effect on the validity of the examination method. There are inconsistent protocols regarding the evaluation criteria such as scoring systems. Among the most widely used different scoring systems the 4-point CTA-scoring system has been accepted as the most reliable method. Appropriate timing and/or Doppler pre-testing could reduce the number of possible premature examinations and increase the sensitivity of CTA in diagnosing cerebral circulatory arrest (CCA). In some cases of inconclusive CTA, the whole brain computed tomography perfusion (CTP) could be a crucial adjunct. Due to the increasing significance of CTA/CTP in determining BD, the methodology (including benefits and limitations) should also be conveyed via innovative electronic training tools, such as the BRAINDEXweb teaching tool based on an expert system.

Brain death/death by neurologic criteria determination: an update

PURPOSE OF REVIEW

Brain death, also known as death by neurologic criteria (DNC), is a well-established concept. In this article, we present a short history of the concept and give an overview of recent changes and a practical update on diagnosis and definitions of brain death/DNC. Unresolved issues will be discussed.

RECENT FINDINGS

There is variability in brain death/DNC determination worldwide. In recent years, successful attempts have been made to harmonize these criteria and, consequently, to improve public trust in the process and diagnosis. An international multidisciplinary collaboration has been created and it has published minimum criteria, provided guidance for professionals and encouragement to revise or develop guidelines on brain death/DNC worldwide.

SUMMARY

There are two sets of criteria for declaration of death. First, if there is neither cardiac output nor respiratory effort, then cardiopulmonary criteria are used. Second, if both the cerebrum and brainstem have completely and permanently lost all functions, and there is a persistent coma, absent brainstem reflexes and no spontaneous respiratory effort, death can be declared on the basis of brain death/DNC. Although attempts to formulate uniform criteria are ongoing, consensus has been reached on the minimum criteria. Some inconsistencies and questions remain.

Early risk stratification for progression to death by neurological criteria following out-of-hospital cardiac arrest

BACKGROUND

Some patients resuscitated from out-of-hospital cardiac arrest (OHCA) progress to death by neurological criteria (DNC). We hypothesized that initial brain imaging, electroencephalography (EEG), and arrest characteristics predict progression to DNC.

METHODS

We identified comatose OHCA patients from January 2010 to February 2020 treated at a single quaternary care facility in Western Pennsylvania. We abstracted demographics and arrest characteristics; Pittsburgh Cardiac Arrest Category, initial motor exam and pupillary light reflex; initial brain computed tomography (CT) grey-to-white ratio (GWR), sulcal or basal cistern effacement; initial EEG background and suppression ratio. We used two modeling approaches: fast and frugal tree (FFT) analysis to create an interpretable clinical risk stratification tool and ridge regression for comparison. We used bootstrapping to randomly partition cases into 80% training and 20% test sets and evaluated test set sensitivity and specificity.

RESULTS

We included 1,569 patients, of whom 147 (9%) had diagnosed DNC. Across bootstrap samples, >99% of FFTs included three predictors: sulcal effacement, and in cases without sulcal effacement, the combination of EEG background suppression and GWR ≤ 1.23. This tree had mean sensitivity and specificity of 87% and 81%. Ridge regression with all available predictors had mean sensitivity 91 % and mean specificity 83%. Subjects falsely predicted as likely to progress to DNC generally died of rearrest or withdrawal of life sustaining therapies due to poor neurological prognosis. Two of these cases awakened from coma during the index hospitalization.

CONCLUSIONS

Sulcal effacement on presenting brain CT or EEG suppression with GWR ≤ 1.23 predict progression to DNC after OHCA.

Intrathecal baclofen overdose mimicking brainstem death during deep brain stimulation surgery for pain

We describe a unique case of intrathecal baclofen overdose mimicking brainstem death, during bilateral anterior cingulate cortex deep brain stimulation (DBS) for pain. A 37-year-old man with chronic regional pain syndrome requiring an intrathecal baclofen pump underwent DBS under general anaesthesia and experienced an intraoperative generalised tonic-clonic seizure on dural opening. Once the operation was completed, the patient was noted to have fixed, dilated pupils bilaterally and was transferred for an emergency computed tomography scan of the head, which did not reveal any acute intracranial pathology. The patient was transferred to the intensive care unit for management of concurrent hypotension, bradycardia and supportive management of his low Glasgow Coma Scale (GCS) score. A trial of atropine to counter the bradycardia was unsuccessful. Intrathecal baclofen toxicity was suspected as a diagnosis of exclusion, necessitating urgent aspiration of the baclofen pump. The patient's GCS score improved after pump aspiration and he was discharged home several days later. It was noted that the intrathecal baclofen pump had been refilled several days previously and the patient had reported intermittent episodes of somnolence. In perioperative patients with intrathecal baclofen pumps in situ, baclofen toxicity should always be considered as a differential in perioperative complications, even if it is considered a rare event.

Alprazolam and lorazepam overdose and the absence of brainstem reflexes

Benzodiazepines (BZDs) rarely cause respiratory depression and death. On the other hand, high-dose BZDs may lead to profound sedation and diminished brainstem functions that mimic other structural brain lesions as described in our case: a 70-year-old unresponsive woman. She was hypothermic and had rapid shallow breathing. Her Glasgow Coma Scale score was E1V1M4, with pinpoint pupils and absent corneal, oculocephalic and oculovestibular reflexes. Other physical exams, laboratory testing and brain imaging were unremarkable. After two doses of 0.4 mg naloxone and intravenous thrombolytics were given, there were no significant responses, and the diagnosis remained a mystery. The cause of her unconsciousness was uncovered when her husband found empty bags of 80 tablets of alprazolam and lorazepam. Her consciousness and brainstem reflexes improved dramatically after 0.25 mg of intravenous flumazenil. The blood for BZDs concentration showed alprazolam 268 ng/mL (20-40 ng/mL), lorazepam 861 ng/mL (20-250 ng/mL) and their metabolites.

Brain death: a clinical overview

Brain death, also commonly referred to as death by neurologic criteria, has been considered a legal definition of death for decades. Its determination involves many considerations and subtleties. In this review, we discuss the philosophy and history of brain death, its clinical determination, and special considerations. We discuss performance of the main clinical components of the brain death exam: assessment of coma, cranial nerves, motor testing, and apnea testing. We also discuss common ancillary tests, including advantages and pitfalls. Special discussion is given to extracorporeal membrane oxygenation, target temperature management, and determination of brain death in pediatric populations. Lastly, we discuss existing controversies and future directions in the field.

Organ Procurement From Poisoned Patients: A 14-Year Survey in 2 Academic Centers

OBJECTIVES

Organ transplant from poisoned donors is an issue that has received much attention, especially over the past decade. Unfortunately, there are still opponents to this issue who emphasize that toxins and drugs affect the body's organs and do not consider organs from poisoned donors appropriate for transplantation.

MATERIALS AND METHODS

Cases of brain death due to poisoning were collected from 2 academic centers in Tehran, Iran during a period from 2006 to 2020. Donor information and recipient condition at 1 month and 12 months after transplant and the subsequent transplant success rates were investigated.

RESULTS

From 102 poisoned donors, most were 30 to 40 years old (33.4%) and most were men (55.9%). The most common causes of poisoning among donors were opioids (28.4%). Six candidate donors had been referred with cardiorespiratory arrest; these patients had organs that were in suitable condition, and transplant was successful. Acute kidney injury was seen in 30 donors, with emergency dialysis performed in 23 cases. For 51% of donors, cardiopulmonary resuscitation was performed. The most donated organs were the liver (81.4%), left kidney (81.4%), and right kidney (80.4%). Survival rate of recipients at 1 month and 12 months was 92.5% and 91.4%, respectively. Graft rejection rate at 1 month and 12 months after transplant was 0.7% and 2.21%, respectively.

CONCLUSIONS

Organ donation from poisoning-related brain deaths is one of the best sources of organ supply for people in need. If the organ is in optimal condition before transplant, there are no exclusions for use of the graft.