Brain Stem Death as the Vital Determinant for Resumption of Spontaneous Circulation after Cardiac Arrest in Rats

BACKGROUND:Spontaneous circulation returns to less than half of adult cardiac arrest victims who received in-hospital resuscitation. One clue for this disheartening outcome arises from the prognosis that asystole invariably takes place, after a time lag, on diagnosis of brain stem death. The designation of brain stem death as the point of no return further suggests that permanent impairment of the brain stem cardiovascular regulatory machinery precedes death. It follows that a crucial determinant for successful revival of an arrested heart is that spontaneous circulation must resume before brain stem death commences. Here, we evaluated the hypothesis that maintained functional integrity of the rostral ventrolateral medulla (RVLM), a neural substrate that is intimately related to brain stem death and central circulatory regulation, holds the key to the vital time-window between cardiac arrest and resumption of spontaneous circulation. METHODOLOGY/PRINCIPAL FINDINGS:An animal model of brain stem death employing the pesticide mevinphos as the experimental insult in Sprague-Dawley rats was used. Intravenous administration of lethal doses of mevinphos elicited an abrupt cardiac arrest, accompanied by elevated systemic arterial pressure and anoxia, augmented neuronal excitability and enhanced microvascular perfusion in RVLM. This period represents the vital time-window between cardiac arrest and resumption of spontaneous circulation in our experimental model. Animals with restored spontaneous circulation exhibited maintained neuronal functionality in RVLM beyond this critical time-window, alongside resumption of baseline tissue oxygen and enhancement of local blood flow. Intriguingly, animals that subsequently died manifested sustained anoxia, diminished local blood flow, depressed mitochondrial electron transport activities and reduced ATP production, leading to necrotic cell death in RVLM. That amelioration of mitochondrial dysfunction and bioenergetic failure in RVLM by coenzyme Q10, the mobile electron carrier in mitochondrial respiratory chain, or oxygenation restored spontaneous circulation further established a causal relationship between functionality of RVLM and resumed spontaneous circulation after cardiac arrest. CONCLUSIONS/SIGNIFICANCE:We conclude that whereas necrotic cell death because of bioenergetic failure triggered by anoxia in RVLM, which precipitates brain stem death, negates resuscitation of an arrested heart, maintained functional integrity of this neural substrate holds the key to resumption of spontaneous circulation after cardiac arrest in rats

Bioenergetics Failure and Oxidative Stress in Brain Stem Mediates Cardiovascular Collapse Associated with Fatal Methamphetamine Intoxication

Background: Whereas sudden death, most often associated with cardiovascular collapse, occurs in abusers of the psychostimulant methamphetamine (METH), the underlying mechanism is much less understood. The demonstration that successful resuscitation of an arrested heart depends on maintained functionality of the rostral ventrolateral medulla (RVLM), which is responsible for the maintenance of stable blood pressure, suggests that failure of brain stem cardiovascular regulation, rather than the heart, holds the key to cardiovascular collapse. We tested the hypothesis that cessation of brain stem cardiovascular regulation because of a loss of functionality in RVLM mediated by bioenergetics failure and oxidative stress underlies the cardiovascular collapse elicited by lethal doses of METH. Methodology/Principal Findings: Survival rate, cardiovascular responses and biochemical or morphological changes in RVLM induced by intravenous administration of METH in Sprague-Dawley rats were investigated. High doses of METH induced significant mortality within 20 min that paralleled concomitant the collapse of arterial pressure or heart rate and loss of functionality in RVLM. There were concurrent increases in the concentration of METH in serum and ventrolateral medulla, along with tissue anoxia, cessation of microvascular perfusion and necrotic cell death in RVLM. Furthermore, mitochondrial respiratory chain enzyme activity or electron transport capacity and ATP production in RVLM were reduced, and mitochondria-derived superoxide anion level was augmented. All those detrimental physiological and biochemica

Sumoylation of Hypoxia-Inducible Factor-1α Ameliorates Failure of Brain Stem Cardiovascular Regulation in Experimental Brain Death

One aspect of brain death is cardiovascular deregulation because asystole invariably occurs shortly after its diagnosis. A suitable neural substrate for mechanistic delineation of this aspect of brain death resides in the rostral ventrolateral medulla (RVLM). RVLM is the origin of a life-and-death signal that our laboratory detected from blood pressure of comatose patients that disappears before brain death ensues. At the same time, transcriptional upregulation of heme oxygenase-1 in RVLM by hypoxia-inducible factor-1α (HIF-1α) plays a pro-life role in experimental brain death, and HIF-1α is subject to sumoylation activated by transient cerebral ischemia. It follows that sumoylation of HIF-1α in RVLM in response to hypoxia may play a modulatory role on brain stem cardiovascular regulation during experimental brain death.A clinically relevant animal model that employed mevinphos as the experimental insult in Sprague-Dawley rat was used. Biochemical changes in RVLM during distinct phenotypes in systemic arterial pressure spectrum that reflect maintained or defunct brain stem cardiovascular regulation were studied. Western blot analysis, EMSA, ELISA, confocal microscopy and immunoprecipitation demonstrated that drastic tissue hypoxia, elevated levels of proteins conjugated by small ubiquitin-related modifier-1 (SUMO-1), Ubc9 (the only known conjugating enzyme for the sumoylation pathway) or HIF-1α, augmented sumoylation of HIF-1α, nucleus-bound translocation and enhanced transcriptional activity of HIF-1α in RVLM neurons took place preferentially during the pro-life phase of experimental brain death. Furthermore, loss-of-function manipulations by immunoneutralization of SUMO-1, Ubc9 or HIF-1α in RVLM blunted the upregulated nitric oxide synthase I/protein kinase G signaling cascade, which sustains the brain stem cardiovascular regulatory machinery during the pro-life phase.We conclude that sumoylation of HIF-1α in RVLM ameliorates brain stem cardiovascular regulatory failure during experimental brain death via upregulation of nitric oxide synthase I/protein kinase G signaling. This information should offer new therapeutic initiatives against this fatal eventuality

The Association Between Frailty Evaluated by Clinical Frailty Scale and Mortality of Older Patients in the Emergency Department: A Prospective Cohort Study

Jin-Wei Lin,1– 3 Pei-Ying Lin,1,2 Tse-Yao Wang,1,2 Ying-Ju Chen,1,2 David Hung-Tsang Yen,1– 5 Hsien-Hao Huang1– 3 1Department of Emergency Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; 2Emergency Medicine, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan; 3Institute of Emergency and Critical Care Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan; 4Department of Nursing, Yuanpei University of Medical Technology, Hsinchu, Taiwan; 5Chang Bing Show-Chwan Memorial Hospital, Changhua City, TaiwanCorrespondence: Hsien-Hao Huang, Department of Emergency Medicine, Taipei Veterans General Hospital, No. 201, Sec. 2, Shipai Road, Beitou District, Taipei, 112201, Taiwan, Email [email protected]: Frailty epitomizes the most complex consequence of an aging population. This study aimed to evaluate the impact of frailty, measured using the Clinical Frailty Scale (CFS), on outcomes of older people in an emergency department (ED).Methods: We conducted a prospective observational study enrolling patients aged 65 years and older in a medical center of Taiwan between March 8, 2021, and November 30, 2021. The primary outcome was 90-day mortality rate. Individuals were categorized into three groups based on the CFS scores. Logistic regression was employed to examine the influence of frailty on clinical outcomes following covariate adjustment. Survival analysis was conducted using Kaplan–Meier curves and Log rank tests.Results: A total of 473 individuals were included in the study, with a mean age of 82.1 years, and 60.5% of them were males. The 90-day mortality rate was 10.6%. Among these groups, the CFS score 7– 9 group had the highest 90-day mortality rate (15.9%), followed by the CFS score 4– 6 group (8.0%) and the CFS score 1– 3 group (7.1%). The multiple logistic regression analyses demonstrated a significant impact of CFS score on prognosis, with adjusted odd ratios of 1.24 (95% CI 1.06– 1.47) for 90-day mortality, 1.18 (95% CI 1.06– 1.31) for hospitalization, and 1.30 (95% CI 1.12– 1.52) for 180-day mortality. The Kaplan–Meier curves revealed a significantly higher 90-day mortality rate for patients with high CFS scores (Log rank tests, p = 0.019).Conclusion: In the older ED population, the severity of frailty assessed by the CFS emerged as a significant and important prognostic factor for hospitalization, 90-day mortality, and 180-day mortality.Keywords: frailty, emergency service, hospital, triage, mortalit