Nasopharyngeal method for selective brain cooling and development of a time-resolved near-infrared technique to monitor brain temperature and oxidation status during hypothermia

Mild hypothermia at 32-35oC (HT) has been shown to be neuroprotective for neurological emergencies following severe head trauma, cardiac arrest and neonatal asphyxia. However, HT has not been widely deployed in clinical settings because: firstly, cooling the whole body below 33-34°C can induce severe complications; therefore, applying HT selectively to the brain could minimize adverse effects by maintaining core body temperature at normal level. Secondly, development of an effective and easy to implement selective brain cooling (SBC) technique, which can quickly induce brain hypothermia while avoiding complications from whole body cooling, remains a challenge. In this thesis, we studied the feasibility and efficiency of selective brain cooling (SBC) through nasopharyngeal cooling. To control the cooling and rewarming rate and because core body temperature is different from brain temperature, we also developed a non-invasive technique based on time-resolved near infrared spectroscopy (TR-NIRS) to measure local brain temperature. In normal brain, cerebral blood flow (CBF) and energy metabolism as reflected by the cerebral metabolic rate of oxygen (CMRO2) is tightly coupled leading to an oxygen extraction efficiency (OEF) of around ~33%. A decoupling of the two as in ischemia signifies oxidative stress and would lead to an increase in OEF beyond the normal value of ~33%. The final goal of this thesis is to evaluate TR-NIRS methods for measurements of CBF and CMRO2 to monitor for oxidative metabolism in the brain with and without HT treatment. Chapter 2 presents investigations on the feasibility and efficiency of the nasopharyngeal SBC by blowing room temperature or humidified cooled air into the nostrils. Effective brain cooling at a median cooling rate of 5.6 ± 1.1°C/hour compared to whole body cooling rate of 3.2 ± 0.7 was demonstrated with the nasopharyngeal cooling method. Chapter 3 describes TR-NIRS experiments performed to measure brain temperature non-invasively based on the temperature-dependence of the water absorption peaks at ~740 and 840nm. The TR-NIRS method was able to measure brain temperature with a mean difference of 0.5 ± 1.6°C (R2 = 0.66) between the TR-NIRS and thermometer measurements. Chapter 4 describes the TR-NIR technique developed to measure CBF and CMRO2 in a normoxia animal model under different anesthetics at different brain temperatures achieved by whole-body cooling. Both CBF and CMRO2 decreased with decreasing brain temperature but the ratio CMRO2:CBF (OEF) remained unchanged around the normal value of ~33%. These results demonstrate that TR-NIR can be used to monitor the oxidative status of the brain in neurological emergencies and its response to HT treatment. In summary, this thesis has established a convenient method for selective brain cooling without decreasing whole body temperature to levels when adverse effects could be triggered. TR-NIRS methods are also developed for monitoring local brain temperature to guide SBC treatment and for monitoring the oxidation status of the brain as treatment progresses

Role of Calpains in Axonal Injury and Degeneration

Axonal injury and degeneration, whether primary or secondary, contribute to the morbidity and mortality seen in many acquired and inherited central nervous system (CNS) and peripheral nervous system (PNS) disorders, such as traumatic brain injury (TBI), spinal cord injury, cerebral ischemia, neurodegenerative diseases, and demyelinating and hereditary neuropathies. The calpain family of proteases has been causally linked to many of these acute and chronic disorders. In particular, previous studies have suggested that pathologic calpain activity may be responsible for axonal dysfunction and degeneration. Even though the immediate cause of increased intra-axonal calpain activity varies, the downstream effects of calpains may be similar. To address the role of calpains in axonal injury, I have relied on two animal models: nerve transection and optic nerve stretch. First, I demonstrated that overexpression of the endogenous calpain inhibitor, calpastatin, in transgenic mice provided biochemical and morphological protection to transected PNS axons, and biochemical protection to CNS axons. I then studied the role of calpains in synaptic dysfunction in transected PNS axons. There was no detectable protection of synaptic function with calpastatin overexpression. Next, I developed and characterized a new in vivo model of optic nerve stretch that isolates mechanical strain primarily to axons of retinal ganglion cells in the rat. This model of optic nerve stretch recapitulates the signature pathology seen in axons after human TBI, which is transport disruption. Within my study of optic nerve stretch, I used both the pharmacologic calpain inhibitor MDL-28170 and adeno-associated viral vector-mediated overexpression of calpastatin to examine the role of calpains in impairment of retrograde transport after mechanical stretch of axons. Calpastatin overexpression, but not short-duration MDL-28170, protected retrograde axonal transport. Taken together, my dissertation work extends our understanding of the pathologic role of calpains in axonal injury and degeneration

Vliv hypotermie na úspěch resuscitace a neurologické postižení po dlouhodobé srdeční zástavě léčené metodou Emergency Preservation and Resuscitation

6 Souhrn: Úspěšnost resuscitace obětí srdeční zástavy je stále neuspokojivá. Srdeční zástava způsobená traumatem a následným vykrvácením má za použití konvenčních technik resuscitace velmi špatnou prognózu. Většina těchto pacientů umírá přímo na místě, přestože poranění by mohla být při patřičném vybavení chirurgicky ošetřitelná. Emergency Preservation and Resuscitation (EPR) je nová resuscitační metoda, která využívá masivní infuze ledové tekutiny do tepenného řečiště k navození hypotermie jako hlavního ochranného mechanismu (Emergency Preservation). Navozená hypotermie pro období srdeční zástavy umožňuje získat čas pro převoz raněného do zdravotnického zařízení. Po chirurgické kontrole krvácení je odložená resuscitace následně zahájena s využitím mimotělního oběhu (Resuscitation), obdobně jako je tomu v srdeční chirugii. Ve výzkumu jsme nejprve využívali model na psu, který nejlépe odpovídá klinické praxi. Zjistili jsme, že hloubka hypotermie koreluje s dobou zástavy, po níž je ještě možné docílit příznivého neurologického výsledku. Co nejčasnější navození hypotermie po nastalé zástavě je spojeno s příznivějšími výsledky. Úloha léků se jeví jako omezená. Prodloužená doba krvácení před zástavou není překážkou úspěchu EPR. Krevní deriváty a energetické substráty mohou mít kladný vliv. V nově vyvinutém...5 Summary: Currently, the outcomes from traumatic exsanguination cardiac arrest (CA) show that over 50% of deaths due to trauma occur at the scene, where medical care is limited. Less than 10% of patients who become pulseless from trauma survive. However, in an appropriate setting, some of those traumatic injuries could be surgically repairable. Emergency preservation and resuscitation (EPR) is a novel approach for resuscitation of exsanguination CA victims. EPR uses deep hypothermic preservation for prolonged CA to buy time for transport, damage control surgery, and delayed resuscitation with cardiopulmonary bypass (CPB). Initially, we used a dog model to maximize clinical relevance. We showed that the efficacy of EPR is related to the depth of hypothermia and duration of CA. Pharmacologic adjuncts tested to augment hypothermia generally failed. Extended hemorrhagic shock did not prevent the success of EPR vs. conventional resuscitation if extended post-resuscitative hypothermia was provided. Oxygenation of the flush allowed extending of survivable duration of deep hypothermic CA. Because of the lack of molecular tools available for use in dogs, we developed a rat EPR model to study the cellular and molecular mechanisms underlying deep hypothermic neuroprotection to allow us to define specific targets for...Department of Neurosurgery and Neurooncology First Faculty of Medicine and Central Military HospitalNeurochirurgická a neuroonkologická klinika 1. LF UK a ÚVN PrahaFirst Faculty of Medicine1. lékařská fakult

Brain Injury

The present two volume book "Brain Injury" is distinctive in its presentation and includes a wealth of updated information on many aspects in the field of brain injury. The Book is devoted to the pathogenesis of brain injury, concepts in cerebral blood flow and metabolism, investigative approaches and monitoring of brain injured, different protective mechanisms and recovery and management approach to these individuals, functional and endocrine aspects of brain injuries, approaches to rehabilitation of brain injured and preventive aspects of traumatic brain injuries. The collective contribution from experts in brain injury research area would be successfully conveyed to the readers and readers will find this book to be a valuable guide to further develop their understanding about brain injury

Cardiac Arrhythmias

The most intimate mechanisms of cardiac arrhythmias are still quite unknown to scientists. Genetic studies on ionic alterations, the electrocardiographic features of cardiac rhythm and an arsenal of diagnostic tests have done more in the last five years than in all the history of cardiology. Similarly, therapy to prevent or cure such diseases is growing rapidly day by day. In this book the reader will be able to see with brighter light some of these intimate mechanisms of production, as well as cutting-edge therapies to date. Genetic studies, electrophysiological and electrocardiographyc features, ion channel alterations, heart diseases still unknown , and even the relationship between the psychic sphere and the heart have been exposed in this book. It deserves to be read

Evaluation of metabolism of adenosine triphosphate as a novel biomarker of tissue ischaemia in vivo.

Introduction Ischaemia is often a medical emergency, clinical signs and symptoms vary dependant on organ or organ system affected. Timely restoration of oxygen delivery to affected tissues is paramount to preventing morbidity and mortality. Current diagnostic aids are non-specific and often late markers of ischaemia where there has been irreversible tissue damage. Metabolism of adenosine triphosphate (ATP) is altered during periods of ischaemia and intermediate nucleosides such as adenosine, inosine and hypoxanthine are released into the systemic circulation in demonstrable quantities. Development of an amperometric biosensor sensitive to these purine nucleosides, produced early in ischaemia prior to cell death, gives potential for purine nucleosides to be a clinically relevant biomarker. Methods A series of prospective observational cohort studies have been designed to provide pilot data on purine nucleoside changes, measured in real-time in vivo in populations of both surgical and non-surgical patients where a simple test for early identification of ischaemia would be clinically useful expedite diagnosis and prevent patient harm. Results There was no significant variation from baseline readings in purine nucleosides in systemically obtained samples intra-operatively in patients who are anaesthetised with general anaesthetic. There were significant increases in nucleosides in blood samples obtained locally within acutely ischaemic tissue. Elevated purine nucleosides were also identified in patients with critical limb ischaemia and following some types of brain injury. Conclusions Reliable determination of purine nucleosides in vivo remains challenging; multiple factors may interfere with quantification in vivo. Results here have identified purine nucleosides may have a role in acute and chronic limb ischaemia as well as traumatic brain injury. This requires further validation in populations of patients in clinical practice. Expansion to further areas of ischaemia may also be of clinical value

Evaluation of spasticity in experimental models of ischemic stroke

Strokes are one of the most common causes of lifelong physical impairment, with about 35% of the patients suffering from post-stroke spasticity (PSS). In contrast to the long and successful history of experimental stroke, rodent models of PSS are sparse and insufficiently characterized [275]. Motivated by this gap in stroke studies, this thesis focused on the development of a PSS mouse model and the long-term effects after strokes within the primary motor area (MOp), secondary motor area (MOs), and internal capsule. For longitudinal determination of PSS, sensorimotor behavioral tests, and equivalent to the measurement in the patient, electrophysiological measurements of the Hoffman reflex were performed. For this purpose, in addition to a longitudinal H-wave measurement, a novel direct nerve H-wave measurement was established in the mouse. For the quantitative determination of the PSS, the ratio of H- and M-wave as well as the rate-dependent depression were measured, which allow an objective measurement of PSS. The experiments revealed that a lesion within the MOp leads to motor deficits, without development of PSS, whereas a lesion within the MOs and internal capsule leads to mild and strong PSS, respectively, after 56 days. In the established internal capsule stroke model for the induction of PSS, an onset of PSS was detected electrophysiologically after 14 days. The sensorimotor deficit score correlated with the PSS measurement, i.e. animals with a PSS showed a reduced recovery of motor function. It was demonstrated that, in addition to the grid walk test, the cylinder test represents behavioral tests that still detect a motor deficit 56 days after a lesion and are sensitive to the motor deficits that occur in PSS. In addition to electrophysiolgical and sensorimotor changes, structural changes were also analyzed, which included examination of secondary neurodegeneration in addition to lesion description. Within the first 28 days after lesion within the MOp microglia/- macrophages were found mainly in the ipsilesional in subregions of the thalamus, which suggested a secondary neurodegeneration. Within the spinal cord, this aggregation of microglia/macrophages and thus evidence of selective secondary degeneration was particularly evident in the dorsal corticospinal tract, an important descending motor pathway. The knowledge gained will serve as a basis for further studies, which will include a precise characterization of secondary neurodegeneration at the spinal cord level and neuronal tracing to evaluate the influence of the cortico- as well as reticolospinal tracts