Magister Scientiae Dentium - MSc(Dent) / AIM:The aim of this study was to review the data available from the Department of Health(DOH), on pre-school paediatric patients treated under Dental General Anaesthesia(DGA), at public health facilities in the Western Cape (WC) in order to ascertain the type and nature of treatment provided.METHODOLOGY:This retrospective descriptive study reviewed the records on the Department of Health(DoH) Database of 16 732 pre-school patients treated under dental general anaesthesia in the period 1 January 2005 until 31 December 2007. A questionnaire was also completed telephonically with 22 dentists from the district dental health clinics.Summary descriptive statistics were calculated from data collected and comparisons were drawn between services available at the health districts and academic hospitals.RESULTS:Of the 58 255 procedures recorded for pre-school patients in the district health clinics in the Western Cape, 99.94% were for extractions provided and 0.5% for restorations.The average number of teeth extracted was 10.4 (SD ±3.9).The average rate of DGA per 1000 of the population was 1.06. Only 9% (2) of dentists at district clinics reported that pre-DGA prevention was provided and 5% (1) reported including post-DGA prevention. The Academic Hospital at Tygerberg Oral Health Centre was the only facility in the Western Cape that provided comprehensive dental treatment for pre-school patients which included restorations, extractions, pre and post DGA prevention. Red Cross Children’s Hospital provided treatment for pre-school patients under DGA that included extractions, pre- and post DGA, but no restorative treatment. CONCLUSION:The demand for DGA in pre-school patients in the WC was high. The lack of prevention associated with DGA in the public health service is the most likely reason the retreatment rate under DGA was reported by dentists as being 77%. There was an absence of protocol regarding DGA for pre-school patients in the public health service.RECOMMENDATIONS:Guidelines formulated were recommended for use in the public service for pre-school patients being treated under DGA and includes the provision of preventive interventions such as regular topical fluoride applications, oral hygiene instruction and dietary advice.

Bien que l’anesthésie générale soit un outil indispensable dans la chirurgie médicale d’aujourd’hui, ses mécanismes sous-jacents précis sont encore inconnus. Au cours de la sédation induite par le propofol les actions anesthésiques à l’échelle microscopique du neurone isolé conduisent à des changements spécifiques à l’échelle macroscopique qui sont observables comme les signaux électroencéphalogrammes (EEG). Pour une concentration faible en propofol, ces changements caractéristiques comprennent une augmentation de l’activité dans les bandes de fréquence delta (0.5-4 Hz) et alpha (8 13 Hz) dans la région frontal, une l’activité augmentée de delta et une l’activité diminuée de alpha dans la région occipitale. Dans cette thèse, nous utilisons des modèles de populations neuronales thalamo-corticales basés sur des données expérimentales. Les effets de propofol sur les synapses et sur les récepteurs extra-synaptiques GABAergiques situés dans le cortex et le thalamus sont modélisés afin de comprendre les mécanismes sous-jacents aux changements observés dans certaines puissances de l’EEG spectrale. Il est démontré que les modèles reproduisent bien les spectrales caractéristiques observées expérimentalement. Une des conclusions principales de ce travail est que l’origine des delta rythmes est fondamentalement différente de celle des alpha rythmes. Nos résultats indiquent qu’en fonction des valeurs moyennes des potentiels de l’état du système au repos, une augmentation ou une diminution des fonctions de gain thalamo-corticale résulte respectivement en une augmentation ou une diminution de alpha puissance. En revanche, l’évolution de la delta puissance est plutôt indépendant de l’état du système au repos; l'amélioration de la puissance spectrale de delta bande résulte de l’inhibition GABAergique synaptique ou extra-synaptique pour les fonctions de gain non linéaire à la fois croissante et décroissante. De plus, nous cherchons à identifier les paramètres d’un modèle de thalamo-corticale en ajustant le spectre de puissance de modèle pour les enregistrements EEG. Pour ce faire, nous considérons la tâche de l’estimation des paramètres dans les modèles qui sont décrits par un ensemble d’équations différentielles ordinaires ou bien stochastiques avec retard. Deux études de cas portant sur des données pseudo-expérimentales bruyantes sont d’abord effectuées pour comparer les performances des différentes méthodes d’optimisation. Les résultats de cette élaboration montrent que la méthode utilisée dans cette étude est capable d’estimer avec précision les paramètres indépendants du modèle et cela nous permet d’éviter les coûts de calcul des intégrations numériques. En considérant l’ensemble, les conclusions de cette thèse apportent de nouveaux éclairages sur les mécanismes responsables des changements spécifiques qui sont observées pendant la sédation propofol-induite dans les modèles de EEG. / Although general anaesthesia is an indispensable tool in today’s medical surgery, its precise underlying mechanisms are still unknown. During the propofol-induced sedation, the anaesthetic actions on the microscopic single neuron scale lead to specific changes in macroscopic-scale observables such as electroencephalogram (EEG) signals. For low concentration of propofol these characteristic changes comprised increased activity in the delta (0.5-4 Hz) and alpha (8-13 Hz) frequency bands over the frontal head region, but increased delta and decreased alpha power activity over the occipital region. In this thesis, we employ thalamo-cortical neural population models, and based on the experimental data, the propofol effects on the synaptic and extrasynaptic GABAergic receptors located in the cortex and thalamus are modelized to understand the mechanisms underlying the observed certain changes in EEG-spectral power. It is shown that the models reproduce well the characteristic spectral features observed experimentally. A key finding of this work is that the origin of delta rhythm is fundamentally different from the alpha rhythm. Our results indicate that dependent on the mean potential values of the system resting states, an increase or decrease in the thalamo-cortical gain functions results in an increase or decrease in the alpha power, respectively. In contrast, the evolution of the delta power is rather independent of the system resting states; the enhancement of spectral power in the delta band results from the increased synaptic or extra-synaptic GABAergic inhibition for both increasing and decreasing nonlinear gain functions. Furthermore, we aim to identify the parameters of a thalamo-cortical model by fitting the model power spectrum to the EEG recordings. To this end, we address the task of parameter estimation in the models that are described by a set of stochastic ordinary or delay differential equations. Two case studies dealing with noisy pseudo-experimental data are first carried out to compare the performance of different optimization methods. The results of this elaboration show that the method used in this study is able to accurately estimate the independent model parameters while it allows us to avoid the computational costs of the numerical integrations. Taken together, the findings of this thesis provide new insights into the mechanisms responsible for the specific changes in EEG patterns that are observed during propofol-induced sedation.

The thesis is focused on perioperative use of opioids during caesarean section. The general part is concerned with pharmacology of opioids due to their practical use during general and regional anaesthesia and postoperative analgesia with particular focus on remifentanil. Emphasis is put on the placental transfer of opioids into breast milk which has the possible influence on postnatal adaptation of the newborns and breastfeeding/lactation. The first part of the research describes current anaesthetic practice and opioid use in obstetrics in the Czech Republic according to the OBAAMA-CZ study in 2011. The second study on a unique group of 151 parturients showed that bolus application of remifentanil at a dose of 1 μg/kg at the time of 30 seconds before induction of general anaesthesia for caesarean section significantly stabilizes maternal hemodynamic parameters (blood pressure, heart rate) and reduces the stress response to tracheal intubation and skin incision. On the contrary, no influence on depth of anaesthesia (monitored by BIS) was found. But we demonstrated a slight effect of remifentanil on the assessment of postnatal adaptation of newborns at first minute after delivery. However, this attenuation was very short and in the fifth minute the results were already fully comparable to the control...

The thesis is focused on perioperative use of opioids during caesarean section. The general part is concerned with pharmacology of opioids due to their practical use during general and regional anaesthesia and postoperative analgesia with particular focus on remifentanil. Emphasis is put on the placental transfer of opioids into breast milk which has the possible influence on postnatal adaptation of the newborns and breastfeeding/lactation. The first part of the research describes current anaesthetic practice and opioid use in obstetrics in the Czech Republic according to the OBAAMA-CZ study in 2011. The second study on a unique group of 151 parturients showed that bolus application of remifentanil at a dose of 1 μg/kg at the time of 30 seconds before induction of general anaesthesia for caesarean section significantly stabilizes maternal hemodynamic parameters (blood pressure, heart rate) and reduces the stress response to tracheal intubation and skin incision. On the contrary, no influence on depth of anaesthesia (monitored by BIS) was found. But we demonstrated a slight effect of remifentanil on the assessment of postnatal adaptation of newborns at first minute after delivery. However, this attenuation was very short and in the fifth minute the results were already fully comparable to the control...