ANALYSIS OF DEFECTS IN THE FORENSIC MEDICAL ASSESSMENT OF CHANGES DISCOVERED DURING THE EXAMINATION OF PERSONS WHO DIED FROM TRAUMATIC BRAIN INJURY.

OBJECTIVE: The aim: To identify the main groups of expert defects that arise during the forensic assessment of changes detected during the examination of persons who died from a traumatic brain injury (TBI). PATIENTS AND METHODS: Materials and methods: A total of 102 repeated commission forensic medical examinations with changed conclusions in corpses with TBI were analyzed. Data processing and analysis were conducted using statistical methods. RESULTS: Results: The examined forensic medical assessments of TBI with changed conclusions in corpses were categorized into the following groups: defects in estab¬lishing the diagnosis of TBI - 17.65±7.4%; defects in establishing the mechanism of TBI - 35.3±9.3%; defects in establishing the duration of TBI - 39.22±9.5%: sober - 20±12.4%; with alcohol intoxication - 80±12.4%. A combination of defects was found in 7.83±5.2% of cases. Defects that directly affected the experts' incorrect establishment of the diagnosis, mechanism, and duration of TBI were also identified. CONCLUSION: Conclusions: The largest number of changed conclusions during the forensic medical examination of corpses in cases of TBI was due to the wrongly established duration of the trauma, accounting for 39.2±9.5%, with the vast majority of cases (80±12.4%) observed against the background of alcohol intoxication. The mechanism of trauma accounted for 35.3±9.3% of the changed conclusions. The main defects were incomplete collection of material for histological examination (90.2±5.8%) and incorrect interpretation of the results of histological examination (76.48±8.2%), along with the violation of the method of sectional examination (68.6±9.0%). Different groups of expert defects predominated in the cases with an incorrectly established diagnosis of TBI, duration of trauma, and mechanism.

THE PROBLEMS OF CRIMINAL LIABILITY OF PHARMACEUTICAL EMPLOYEES IN THE CONTEXT OF CERTAIN FORMS OF COLLABORATIVE ACTIVITIES.

OBJECTIVE: The aim: Based on the specifics of the criminal legislation, which provides liability for collaborative activity, it is necessary to offer an adequate understanding of the limits of the criminal liability of pharmaceutical employees for these criminal offenses, as well as to determine the characteristics of the components of these criminal offenses related to the pharmaceutical activities carried out by pharmaceutical employees. PATIENTS AND METHODS: Materials and methods: The conducted research is based on the analysis of the provisions of the criminal legislation of Ukraine and Georgia. CONCLUSION: Conclusions: The main problems of criminal liability for collaboration activities by pharmaceutical employees are connected to the following: without clari-fication of the aforementioned criminal offenses, it is impossible to specify the limits of criminal liability.

ANALYSIS OF DEFECTS IN THE DIAGNOSIS OF TRAUMATIC BRAIN INJURY FOR THE DECEASED WITHIN 24 HOURS FOLLOWING ADMISSION.

OBJECTIVE: The aim: To conduct the analysis of medical records with the diagnosis of traumatic brain injury for the deceased within 24 hours following admission to Clinical Emergency Hospital. PATIENTS AND METHODS: Materials and methods: The study was aimed at a retrospective analysis of 102 cases of the lethality of the deceased within 24 hours following admission to Clinical Emergency Hospital for 2012-2019 in cases of traumatic brain injury. Medical histories of the deceased and data from the forensic autopsy had been analyzed. RESULTS: Results: There were 62 cases (60.8%) of isolated traumatic brain injury, and 40 cases (39.2%) of combined traumatic brain injury. The following defects were identified in the diagnosis: absence of a complete description of the local status with external injuries on the head, absence of a complete and qualitative assess¬ment and objectification of hemodynamics and the function of external breathing using laboratory indicators and electrocardiography, absence of neuroimaging. CONCLUSION: Conclusions: The percentage of diagnostic defects prevailed among traumatic brain injury patients who died from acute blood loss. The maximum number of diagnostic defects for the patients with traumatic brain injury was observed in the polytrauma department, and the minimum - in the neurological department. The maximum number of defects of a diagnostic nature as a whole fall on those patients who were admitted to the hospital in the interval I - 6:00 a.m. - 9:59 a.m. and in the interval IV - 6:00 p.m. - 9:59 p.m.

GAT inhibition preserves cerebral blood flow and reduces oxidant damage to mitochondria in rodents exposed to extreme hyperbaric oxygen.

Oxygen breathing at elevated partial pressures (PO2's) at or more than 3 atmospheres absolute (ATA) causes a reduction in brain γ-aminobutyric acid (GABA) levels that impacts the development of central nervous system oxygen toxicity (CNS-OT). Drugs that increase brain GABA content delay the onset of CNS-OT, but it is unknown if oxidant damage is lessened because brain tissue PO2 remains elevated during hyperbaric oxygen (HBO2) exposures. Experiments were performed in rats and mice to measure brain GABA levels with or without GABA transporter inhibitors (GATs) and its influence on cerebral blood flow, oxidant damage, and aspects of mitochondrial quality control signaling (mitophagy and biogenesis). In rats pretreated with tiagabine (GAT1 inhibitor), the tachycardia, secondary rise in mean arterial blood pressure, and cerebral hyperemia were prevented during HBO2 at 5 and 6 ATA. Tiagabine and the nonselective GAT inhibitor nipecotic acid similarly extended HBO2 seizure latencies. In mice pretreated with tiagabine and exposed to HBO2 at 5 ATA, nuclear and mitochondrial DNA oxidation and astrocytosis was attenuated in the cerebellum and hippocampus. Less oxidant injury in these regions was accompanied by reduced conjugated microtubule-associated protein 1A/1B-light chain 3 (LC3-II), an index of mitophagy, and phosphorylated cAMP response element binding protein (pCREB), an initiator of mitochondrial biogenesis. We conclude that GABA prevents cerebral hyperemia and delays neuroexcitation under extreme HBO2, limiting oxidant damage in the cerebellum and hippocampus, and likely lowering mitophagy flux and initiation of pCREB-initiated mitochondrial biogenesis.

Impact of the European Union on access to medicines in low- and middle-income countries: A scoping review.

This Scoping Review synthesises evidence of the impacts of European Union (EU) law, regulation, and policy on access to medicines in in non-EU low- and middle-income countries (LMICs), and the mechanisms and nature of those impacts. We searched eight scholarly databases and grey literature published between 1995-2021 in four languages. The EU exerts global influence on pharmaceuticals in LMICs in three ways: explicit agreements between EU-LMICs (ex. accession, trade, and economic agreements); LMICs' reliance on EU internal regulation, standards, or methods (ex. market authorisation); 'soft' forms of EU influence (ex. research funding, capacity building). This study illustrates that EU policy makers adopt measures with the potential to influence medicines in LMICs despite limited evidence of their positive and/or negative impact(s). The EU's fragmented internal and external actions in fields related to pharmaceuticals reveal the need for principles for global equitable access to medicines to guide EU policy.

Esta revisión exploratoria sintetiza la evidencia disponible sobre el impacto que ejercen las leyes, las políticas y las regulaciones de la Unión Europea (UE) sobre el acceso a los medicamentos en países de bajo y mediano ingreso (PBMI) que no pertenecen a la UE. La búsqueda se realizó en ocho bases de datos académicas, incluyendo literatura gris. Se incluyeron publicaciones en cuatro idiomas entre 1995 y 2021. Como resultado principal se encontró que la UE ejerce su influencia sobre los productos farmacéuticos en los PBMI a través de tres mecanismos principales: i) acuerdos explícitos entre la UE y los PBMI, por ejemplo, acuerdos de ascensión a la UE o tratados comerciales, ii) utilización de la normativa, estándares o métodos de la UE por parte de los PBMI (reliance) para, por ejemplo, autorizar el ingreso de nuevos medicamentos a partir de la autorización previa por parte de la UE) y, iii) formas blandas de influencia de la UE, por ejemplo, a través de financiación a la investigación o al desarrollo de capacidades locales. Esta revisión revela que los tomadores de decisión de la UE adoptan medidas que, a pesar de la escasa evidencia que sustenta su impacto, positivo o negativo, tienen el potencial de influir en el acceso a los medicamentos de los PBMI. El accionar fragmentado de la UE respecto a los productos farmacéuticos, tanto a nivel interno como externo, son una clara muestra de la necesidad de crear principios que guíen las políticas de la UE frente al acceso equitativo a los medicamentos a nivel global.

THE PROBLEMS OF DEFINITION OF THE ABETTING IN THE COMISSION OF THE OFFENCES INVOLVING THREATS TO PUBLIC HEALTH (PART 1 OF ARTICLE 9 OF THE COUNCIL OF EUROPE CONVENTION ON THE COUNTERFEITING OF MEDICAL PRODUCTS AND SIMILAR CRIMES INVOLVING THREATS TO PUBLIC HEALTH).

OBJECTIVE: The aim: based on the features of the notion of "abetting the commission of crimes established in accordance with the Convention" provided for in Part 1 of Art. 9 of the Medicrime Convention, it is necessary to offer an adequate understanding of the notion of "abetting" and define the types of criminal offenses (crimes) that are the "subject" of such abetting. PATIENTS AND METHODS: Materials and methods: the research is based on an analysis of the provisions of the Medicrime Convention and the criminal law of Ukraine. The following methods were used: dialectical method; hermeneutic method; systemic-and-structural method; and comparative-legal method. RESULTS: Results: at the legislative level, there is a problem of designating the relevant socio-legal phenomena with adequate concepts and interpretations of these concepts. In the current criminal legislation of Ukraine, there is no definition of the concept of "abetting", which is used in Part 1 of Art. 9 of the Medicrime Convention. Therefore, in the implementation of the requirements provided for in Part 1 of Art. 9 of the Medicrime Convention, each Party takes the necessary legislative and other measures to recognize abetting in committing any crimes, established under this Convention, as a crime, therefore we should take into account the existence of two alternative ways to explain the meaning of "abetting": 1) to recognize at the legislative level that "abetting" and "incitement" are synonyms, and therefore the meaning of the term "abetting" can be explained by using the term "inclination"; 2) to recognize at the legislative level that the concept of "abetting" has a meaning different from the concept of "incitement", and covers not only "inclination", but also "coercion", "motivation" and "encouragement". CONCLUSION: Conclusions: the main disadvantage of using the concept of "abetting" in the text of the Ukrainian translation of the Medicrime Convention is that without an independent explanation of this concept at the legislative level, its content should be determined depending on the meaning of the term "inciter" under Part 4 of Art. 27 of the Criminal Code of Ukraine), and means inciting a person to commit any of the crimes specified in the Medicrime Convention.

Essential Medicines in Universal Health Coverage: A Scoping Review of Public Health Law Interventions and How They Are Measured in Five Middle-Income Countries.

Very few studies exist of legal interventions (national laws) for essential medicines as part of universal health coverage in middle-income countries, or how the effect of these laws is measured. This study aims to critically assess whether laws related to universal health coverage use five objectives of public health law to promote medicines affordability and financing, and to understand how access to medicines achieved through these laws is measured. This comparative case study of five middle-income countries (Ecuador, Ghana, Philippines, South Africa, Ukraine) uses a public health law framework to guide the content analysis of national laws and the scoping review of empirical evidence for measuring access to medicines. Sixty laws were included. All countries write into national law: (a) health equity objectives, (b) remedies for users/patients and sanctions for some stakeholders, (c) economic policies and regulatory objectives for financing (except South Africa), pricing, and benefits selection (except South Africa), (d) information dissemination objectives (ex. for medicines prices (except Ghana)), and (e) public health infrastructure. The 17 studies included in the scoping review evaluate laws with economic policy and regulatory objectives (n = 14 articles), health equity (n = 10), information dissemination (n = 3), infrastructure (n = 2), and sanctions (n = 1) (not mutually exclusive). Cross-sectional descriptive designs (n = 8 articles) and time series analyses (n = 5) were the most frequent designs. Change in patients' spending on medicines was the most frequent outcome measure (n = 5). Although legal interventions for pharmaceuticals in middle-income countries commonly use all objectives of public health law, the intended and unintended effects of economic policies and regulation are most frequently investigated.

THE PROBLEMS OF CRIMINALIZATION OF THE SIMILAR CRIMES INVOLVING THREATS TO PUBLIC HEALTH (ARTICLE 8 OF THE COUNCIL OF EUROPE CONVENTION ON THE COUNTERFEITING OF MEDICAL PRODUCTS AND SIMILAR CRIMES INVOLVING THREATS TO PUBLIC HEALTH).

OBJECTIVE: The aim: Medicrime Convention is a first international treaty against counterfeit medical products and similar crimes involving threats to public health. There are problems in criminalization of those acts that are listed in Art. 8 of the Medicrime Convention because the term of "similar crimes" is absent in the current criminal legislation of Ukraine. PATIENTS AND METHODS: Materials and methods: The conducted study is based on the analysis of the provisions of the Medicrime Convention, the criminal legislation of Ukraine. The following methods: dialectical method; hermeneutic method; system-and-structural method; comparative-and-law method were used. RESULTS: Results: Comparison of the provisions of the Medicrime Convention allows to state that crimes in its Articles 5-8 that are different from those provided for in Art. 5-7 of this Convention and form independent types of actions, are at least "placing on the market" of medicinal products and medical devices provided in subparagraph "a" of paragraph 1 of Art. 8 and "commercial use of original documents" specified in subparagraph "b" of paragraph 1 of Art. 8. It's an assumption that Art. 5-8 of the Medicrime Convention provide for such independent types of crimes involving threats to public health as: 1) manufacturing of counterfeit medical products, active substances, excipients, parts, materials and accessories as well as medicinal products, medical devices, active substances and excipients; 2) the supplying, the offering to supply, the brokering, the trafficking, the keeping in stock, importing and exporting of counterfeit medical products, active substances, excipients, parts, materials and accessories; 3) the making of false documents or the act of tampering with documents; 4) placing on the market of medicinal products, medical devices; 5) the commercial use of false documents. CONCLUSION: Conclusions: The term of "similar crimes" in Art. 8 of the Medicrime Convention covers multi-ordinal intentional acts that constitute different types of independent crimes involving threats to public health, as well as special kinds of some of them. These types of crimes are not the same (identical).

Increased Antiseizure Effectiveness with Tiagabine Combined with Sodium Channel Antagonists in Mice Exposed to Hyperbaric Oxygen.

Hyperbaric oxygen (HBO2) is acutely toxic to the central nervous system, culminating in EEG spikes and tonic-clonic convulsions. GABA enhancers and sodium channel antagonists improve seizure latencies in HBO2 when administered individually, while combining antiepileptic drugs from different functional classes can provide greater seizure latency. We examined the combined effectiveness of GABA enhancers (tiagabine and gabapentin) with sodium channel antagonists (carbamazepine and lamotrigine) in delaying HBO2-induced seizures. A series of experiments in C57BL/6 mice exposed to 100% oxygen at 5 atmospheres absolute (ATA) were performed. We predicted equally effective doses from individual drug-dose response curves, and the combinations of tiagabine + carbamazepine or lamotrigine were tested to determine the maximally effective combined doses to be used in subsequent experiments designed to identify the type of pharmacodynamic interaction for three fixed-ratio combinations (1:3, 1:1, and 3:1) using isobolographic analysis. For both combinations, the maximally effective combined doses increased seizure latency over controls > 5-fold and were determined to interact synergistically for fixed ratios 1:1 and 3:1, additive for 1:3. These results led us to explore whether the benefits of these drug combinations could be extended to the lungs, since a centrally mediated mechanism is believed to mediate hyperoxic-induced cardiogenic lung injury. Indeed, both combinations attenuated bronchoalveolar lavage protein content by ~ 50%. Combining tiagabine with carbamazepine or lamotrigine not only affords greater antiseizure protection in HBO2 but also allows for lower doses to be used, minimizing side effects, and attenuating acute lung injury.

Adrenoceptor blockade modifies regional cerebral blood flow responses to hyperbaric hyperoxia: protection against CNS oxygen toxicity.

Exposure to extreme hyperbaric oxygen (HBO2) >5-6 atmospheres absolute (ATA) produces baroreflex impairment, sympathetic hyperactivation, hypertension, tachycardia, and cerebral hyperemia, known as phase II, culminating in seizures. We hypothesized that attenuation of the effects of high sympathetic outflow would preserve regional cerebral blood flow (rCBF) and protect against HBO2-induced seizures. To explore this possibility, we tested four adrenoceptor antagonists in conscious and anesthetized rats exposed to HBO2 at 5 and 6 ATA, respectively: phentolamine (nonselective α1 and α2), prazosin (selective α1), propranolol (nonselective ß1 and ß2), and atenolol (selective ß1). In conscious rats, four drug doses were administered to rats before HBO2 exposures, and seizure latencies were recorded. Drug doses that provided similar protection against seizures were administered before HBO2 exposures in anesthetized rats to determine the effects of adrenoceptor blockade on mean arterial pressure, heart rate, rCBF, and EEG spikes. All four drugs modified cardiovascular and rCBF responses in HBO2 that aligned with epileptiform discharges, but only phentolamine and propranolol effectively increased EEG spike latencies by ~20 and 36 min, respectively. When phentolamine and propranolol were delivered during HBO2 at the onset of phase II, only propranolol led to sustained reductions in heart rate and rCBF, preventing the appearance of epileptiform discharges. The enhanced effectiveness of propranolol may extend beyond ß-adrenoceptor blockade, i.e., membrane stability and reduced metabolic activity. These results indicate that adrenoceptor drug pretreatment will minimize the effects of excessive sympathetic outflow on rCBF and extend HBO2 exposure time.NEW & NOTEWORTHY Blocking adrenergic receptors with phentolamine (nonselective α1 and α2), prazosin (selective α1), propranolol (nonselective ß1 and ß2), and atenolol (selective ß1) modified cardiovascular and regional cerebral blood flow (rCBF) responses in hyperbaric oxygen (HBO2) at 6 atmospheres absolute (ATA); however, only phentolamine and propranolol extended EEG spike latencies. When these two agents were delivered at the onset of sympathetic hyperactivation, only propranolol reduced heart rate and rCBF throughout the exposure and prevented epileptiform discharges. These data validate the strong role of adrenergic control of cardiovascular function and rCBF in extreme HBO2 and the potential use of antiadrenergic drugs to prevent seizures.

S-nitrosylation of GAD65 is implicated in decreased GAD activity and oxygen-induced seizures.

Breathing oxygen at partial pressures ≥2.5 atmospheres absolute, which can occur in diving and hyperbaric oxygen (HBO2) therapy, can rapidly become toxic to the central nervous system (CNS). This neurotoxicity culminates in generalized EEG epileptiform discharges, tonic-clonic convulsions and ultimately death. Increased production of neuronal nitric oxide (NO) has been implicated in eliciting hyperoxic seizures by altering the equilibrium between glutamatergic and GABAergic synaptic transmission. Inhibition of glutamic acid decarboxylase (GAD) activity in HBO2 promotes this imbalance; however, the mechanisms by which this occurs is unknown. Therefore, we conducted a series of experiments using mice, a species that is highly susceptible to CNS oxygen toxicity, to explore the possibility that NO modulates GABA metabolism. Mice were exposed to 100% oxygen at 4 ATA for various durations, and brain GAD and GABA transaminase (GABA-T) activity, as well as S-nitrosylation of GAD65 and GAD67 were determined. HBO2 inhibited GAD activity by 50% and this was negatively correlated with S-nitrosylation of GAD65, whereas GABA-T activity and S-nitrosylation of GAD67 were unaltered. These results suggest a new mechanism by which NO alters GABA metabolism, leading to neuroexcitation and seizures in HBO2.

Antiepileptic drugs prevent seizures in hyperbaric oxygen: A novel model of epileptiform activity.

Breathing oxygen at sufficiently elevated pressures can trigger epileptiform seizures. Therefore, we tested the hypothesis that pre-treatment with FDA-approved antiepileptic drugs could prevent seizure onset in hyperoxia at 5 atmospheres absolute. We selected drugs from two putative functional categories, Na+-channel antagonists and GABA enhancers, each administered intraperitoneally at four doses in separate groups of C57BL/6 mice. The drugs varied in efficacy at the doses used. Of the five tested Na+-channel antagonists, carbamazepine and lamotrigine more than tripled seizure latency compared to values seen in vehicle controls. Primidone, zonisamide and oxcarbazepine were less effective. Of the four GABA reuptake inhibitors, tiagabine and vigabatrin also increased seizure latency by more than three times control values; valproic acid was less effective, and the GABA synthesis promoter gabapentin was intermediate in effectiveness. We infer that Na+-channel function and GABA neurotransmission may be critical targets in the pathophysiology of CNS O2 toxicity. Because these essential components of neuronal excitation and inhibition are also implicated in the pathogenesis of other seizure disorders, including generalized epilepsy, we propose that, at some level, common pathways are involved in these pathologies, although the initiating insults differ. Furthermore, hyperoxic exposures are not known to cause the spontaneously-recurring seizures that characterize true clinical epilepsy. Nonetheless, experimental studies of hyperbaric oxygen toxicity could provide new insights into molecular mechanisms of seizure disorders of various etiologies. In addition, the neuropathology of hyperbaric oxygen is particularly relevant to the hypothesis held by some investigators that oxidative stress is an etiological factor in clinical epilepsies.

Effects of striatal nitric oxide production on regional cerebral blood flow and seizure development in rats exposed to extreme hyperoxia.

The endogenous vasodilator and signaling molecule nitric oxide has been implicated in cerebral hyperemia, sympathoexcitation, and seizures induced by hyperbaric oxygen (HBO2) at or above 3 atmospheres absolute (ATA). It is unknown whether these events in the onset of central nervous system oxygen toxicity originate within specific brain structures and whether blood flow is diverted to the brain from peripheral organs with high basal flow, such as the kidney. To explore these questions, total and regional cerebral blood flow (CBF) were measured in brain structures of the central autonomic network in anesthetized rats in HBO2 at 6 ATA. Electroencephalogram (EEG) recordings, cardiovascular hemodynamics, and renal blood flow (RBF) were also monitored. As expected, mean arterial blood pressure and total and regional CBF increased preceding EEG spikes while RBF was unaltered. Of the brain structures examined, the earliest rise in CBF occurred in the striatum, suggesting increased neuronal activation. Continuous unilateral or bilateral striatal infusion of the nitric oxide synthase inhibitor N(ω)-nitro-L-arginine methyl ester attenuated CBF responses in that structure, but global EEG discharges persisted and did not differ from controls. Our novel findings indicate that: 1) cerebral hyperemia in extreme HBO2 in rats does not occur at the expense of renal perfusion, highlighting the remarkable autoregulatory capability of the kidney, and 2) in spite of a sentinel increase in striatal blood flow, additional brain structure(s) likely govern the pathogenesis of HBO2-induced seizures because EEG discharge latency was unchanged by local blockade of striatal nitric oxide production and concomitant hyperemia.

Baroreceptor afferents modulate brain excitation and influence susceptibility to toxic effects of hyperbaric oxygen.

Unexplained adjustments in baroreflex sensitivity occur in conjunction with exposures to potentially toxic levels of hyperbaric oxygen. To investigate this, we monitored central nervous system, autonomic and cardiovascular responses in conscious and anesthetized rats exposed to hyperbaric oxygen at 5 and 6 atmospheres absolute, respectively. We observed two contrasting phases associated with time-dependent alterations in the functional state of the arterial baroreflex. The first phase, which conferred protection against potentially neurotoxic doses of oxygen, was concurrent with an increase in baroreflex sensitivity and included decreases in cerebral blood flow, heart rate, cardiac output, and sympathetic drive. The second phase was characterized by baroreflex impairment, cerebral hyperemia, spiking on the electroencephalogram, increased sympathetic drive, parasympatholysis, and pulmonary injury. Complete arterial baroreceptor deafferentation abolished the initial protective response, whereas electrical stimulation of intact arterial baroreceptor afferents prolonged it. We concluded that increased afferent traffic attributable to arterial baroreflex activation delays the development of excessive central excitation and seizures. Baroreflex inactivation or impairment removes this protection, and seizures may follow. Finally, electrical stimulation of intact baroreceptor afferents extends the normal delay in seizure development. These findings reveal that the autonomic nervous system is a powerful determinant of susceptibility to sympathetic hyperactivation and seizures in hyperbaric oxygen and the ensuing neurogenic pulmonary injury.

Baroreflex-mediated cardiovascular responses to hyperbaric oxygen.

The cardiovascular system responds to hyperbaric hyperoxia (HBO2) with vasoconstriction, hypertension, bradycardia, and reduced cardiac output (CO). We tested the hypothesis that these responses are linked by a common mechanism-activation of the arterial baroreflex. Baroreflex function in HBO2 was assessed in anesthetized and conscious rats after deafferentation of aortic or carotid baroreceptors or both. Cardiovascular and autonomic responses to HBO2 in these animals were compared with those in intact animals at 2.5 ATA for conscious rats and at 3 ATA for anesthetized rats. During O2 compression, hypertension was greater after aortic or carotid baroreceptor deafferentation and was significantly more severe if these procedures were combined. Similarly, the hyperoxic bradycardia observed in intact animals was diminished after aortic or carotid baroreceptor deafferentation and replaced by a slight tachycardia after complete baroreceptor deafferentation. We found that hypertension, bradycardia, and reduced CO--the initial cardiovascular responses to moderate levels of HBO2--are coordinated through a baroreflex-mediated mechanism initiated by HBO2-induced vasoconstriction. Furthermore, we have shown that baroreceptor activation in HBO2 inhibits sympathetic outflow and can partially reverse an O2-dependent increase in arterial pressure.

S-nitrosylation therapy to improve oxygen delivery of banked blood.

From the perspectives of disease transmission and sterility maintenance, the world's blood supplies are generally safe. However, in multiple clinical settings, red blood cell (RBC) transfusions are associated with adverse cardiovascular events and multiorgan injury. Because ∼85 million units of blood are administered worldwide each year, transfusion-related morbidity and mortality is a major public health concern. Blood undergoes multiple biochemical changes during storage, but the relevance of these changes to unfavorable outcomes is unclear. Banked blood shows reduced levels of S-nitrosohemoglobin (SNO-Hb), which in turn impairs the ability of stored RBCs to effect hypoxic vasodilation. We therefore reasoned that transfusion of SNO-Hb-deficient blood may exacerbate, rather than correct, impairments in tissue oxygenation, and that restoration of SNO-Hb levels would improve transfusion efficacy. Notably in mice, administration of banked RBCs decreased skeletal muscle pO2, but infusion of renitrosylated cells maintained tissue oxygenation. In rats, hemorrhage-induced reductions in muscle pO2 were corrected by SNO-Hb-repleted RBCs, but not by control, stored RBCs. In anemic awake sheep, stored renitrosylated, but not control RBCs, produced sustained improvements in O2 delivery; in anesthetized sheep, decrements in hemodynamic status, renal blood flow, and kidney function incurred following transfusion of banked blood were also prevented by renitrosylation. Collectively, our findings lend support to the idea that transfusions may be causally linked to ischemic events and suggest a simple approach to prevention (i.e., SNO-Hb repletion). If these data are replicated in clinical trials, renitrosylation therapy could have significant therapeutic impact on the care of millions of patients.

Brain oxygenation and CNS oxygen toxicity after infusion of perfluorocarbon emulsion.

Intravenous perfluorocarbon (PFC) emulsions, administered with supplemental inspired O(2), are being evaluated for their ability to eliminate N(2) from blood and tissue prior to submarine escape, but these agents can increase the incidence of central nervous system (CNS) O(2) toxicity, perhaps by enhancing O(2) delivery to the brain. To assess this, we infused a PFC emulsion (Oxycyte, 6 ml/kg iv) into anesthetized rats and measured cerebral Po(2) and regional cerebral blood flow (rCBF) in cortex, hippocampus, hypothalamus, and striatum with 100% O(2) at 1, 3, or 5 atmospheres absolute (ATA). At 1 ATA, brain Po(2) stabilized at >20 mmHg higher in animals infused with PFC emulsion than in control animals infused with saline, and rCBF fell by ~10%. At 3 ATA, PFC emulsion raised brain Po(2) >70 mmHg above control levels, and rCBF decreased by as much as 25%. At 5 ATA, brain Po(2) was ≥159 mmHg above levels in control animals for the first 40 min but then rose sharply; rCBF showed a similar profile, reflecting vasoconstriction followed by hyperemia. Conscious rats were also pretreated with PFC emulsion at 3 or 6 ml/kg iv and exposed to 100% O(2) at 5 ATA. At the lower dose, 80% of the animals experienced seizures by 33 min compared with 50% of the control animals. At the higher dose, seizures occurred in all rats within 25 min. At these doses, administration of PFC emulsion poses a clear risk of CNS O(2) toxicity in conscious rats exposed to hyperbaric O(2) at 5 ATA.

Nitric oxide-mediated central sympathetic excitation promotes CNS and pulmonary O2 toxicity.

In hyperbaric oxygen (HBO(2)) at or above 3 atmospheres absolute (ATA), autonomic pathways link central nervous system (CNS) oxygen toxicity to pulmonary damage, possibly through a paradoxical and poorly characterized relationship between central nitric oxide production and sympathetic outflow. To investigate this possibility, we assessed sympathetic discharges, catecholamine release, cardiopulmonary hemodynamics, and lung damage in rats exposed to oxygen at 5 or 6 ATA. Before HBO(2) exposure, either a selective inhibitor of neuronal nitric oxide synthase (NOS) or a nonselective NOS inhibitor was injected directly into the cerebral ventricles to minimize effects on the lung, heart, and peripheral circulation. Experiments were performed on both anesthetized and conscious rats to differentiate responses to HBO(2) from the effects of anesthesia. EEG spikes, markers of CNS toxicity in anesthetized animals, were approximately four times as likely to develop in control rats than in animals with central NOS inhibition. In inhibitor-treated animals, autonomic discharges, cardiovascular pressures, catecholamine release, and cerebral blood flow all remained below baseline throughout exposure to HBO(2). In control animals, however, initial declines in these parameters were followed by significant increases above their baselines. In awake animals, central NOS inhibition significantly decreased the incidence of clonic-tonic convulsions or delayed their onset, compared with controls. The novel findings of this study are that NO produced by nNOS in the periventricular regions of the brain plays a critical role in the events leading to both CNS toxicity in HBO(2) and to the associated sympathetic hyperactivation involved in pulmonary injury.

Pharmacologically augmented S-nitrosylated hemoglobin improves recovery from murine subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: S-nitrosylated hemoglobin (S-nitrosohemoglobin) has been implicated in the delivery of O(2) to tissues through the regulation of microvascular blood flow. This study tested the hypothesis that enhancement of S-nitrosylated hemoglobin by ethyl nitrite inhalation improves outcome after experimental subarachnoid hemorrhage (SAH). METHODS: A preliminary dosing study identified 20 ppm ethyl nitrite as a concentration that produced a 4-fold increase in S-nitrosylated hemoglobin concentration with no increase in methemoglobin. Mice were subjected to endovascular perforation of the right anterior cerebral artery and were treated with 20 ppm ethyl nitrite in air, or air alone for 72 hours, after which neurologic function, cerebral vessel diameter, brain water content, cortical tissue Po(2), and parenchymal red blood cell flow velocity were measured. RESULTS: At 72 hours after hemorrhage, air- and ethyl nitrite-exposed mice had similarly sized blood clots. Ethyl nitrite improved neurologic score and rotarod performance; abated SAH-induced constrictions in the ipsilateral anterior, middle cerebral, and internal carotid arteries; and prevented an increase in ipsilateral brain water content. Ethyl nitrite inhalation increased red blood cell flow velocity and cortical tissue Po(2) in the ipsilateral cortex with no effect on systemic blood pressure. CONCLUSIONS: Targeted S-nitrosylation of hemoglobin improved outcome parameters, including vessel diameter, tissue blood flow, cortical tissue Po(2), and neurologic function in a murine SAH model. Augmenting endogenous Po(2)-dependent delivery of NO bioactivity to selectively dilate the compromised cerebral vasculature has significant clinical potential in the treatment of SAH.

Autonomic activation links CNS oxygen toxicity to acute cardiogenic pulmonary injury.

Breathing hyperbaric oxygen (HBO2), particularly at pressures above 3 atmospheres absolute, can cause acute pulmonary injury that is more severe if signs of central nervous system toxicity occur. This is consistent with the activation of an autonomic link between the brain and the lung, leading to acute pulmonary oxygen toxicity. This pulmonary damage is characterized by leakage of fluid, protein, and red blood cells into the alveoli, compatible with hydrostatic injury due to pulmonary hypertension, left atrial hypertension, or both. Until now, however, central hemodynamic parameters and autonomic activity have not been studied concurrently in HBO2, so any hypothetical connections between the two have remained untested. Therefore, we performed experiments using rats in which cerebral blood flow, electroencephalographic activity, cardiopulmonary hemodynamics, and autonomic traffic were measured in HBO2 at 5 and 6 atmospheres absolute. In some animals, autonomic pathways were disrupted pharmacologically or surgically. Our findings indicate that pulmonary damage in HBO2 is caused by an abrupt and significant increase in pulmonary vascular pressure, sufficient to produce barotrauma in capillaries. Specifically, extreme HBO2 exposures produce massive sympathetic outflow from the central nervous system that depresses left ventricular function, resulting in acute left atrial and pulmonary hypertension. We attribute these effects on the heart and on the pulmonary vasculature to HBO2-mediated central sympathetic excitation and catecholamine release that disturbs the normal equilibrium between excitatory and inhibitory activity in the autonomic nervous system.