Short title: Anaesthetic mechanisms in the CNS Where and how do anaesthetics act? Mec.

General anaesthesia is a balance of hypnosis, amnesia, analgesia, and immobility, including the inhibition of noxious autonomic reflexes. Local anaesthesia implements the latter two elements in a conscious patient. This review article discusses several important aspects of anaesthesia, beginning with basic concepts such as the minimum alveolar concentration and afterwards developing into a discussion about the mechanisms of action of anaesthetics on a cellular level, introducing electrophysiological investigations in the brain to study hypnosis and amnesia, in the dorsal horn of the spinal cord to study analgesia and the inhibition of noxious reflexes, and in the ventral horn of the spinal cord to study immobility, separately. In accordance with the results of electrophysiological patch clamp studies, researchers have confirmed that the modulation of neurotransmission input from dorsal afferent neurons into the dorsal horn of the spinal cord and effects on the spinal reflex arc from the dorsal horn to ventral horn motor neurons are important anaesthetic action mechanisms. Accordingly, intraoperative body movement of patients is not a sign of insufficient muscle relaxation, but rather insufficient analgesia. In conclusion, sufficient analgesia is a correct strategy (rather than muscle relaxant administration) for performing intraoperative patient immobility and for providing patients with good and safe intraoperative anaesthesia management by protecting them from noxious reflexes and stress including autonomic reactions such as hypertension and tachycardia.

Tranexamic acid: an alternative to aprotinin as antifibrinolytic therapy in pediatric congenital heart surgery.

OBJECTIVE: There has been concern about the usage of aprotinin, an antifibrinolytic drug that was often used in pediatric cardiac surgery until 2006. At our center, these concerns led to the replacement of aprotinin with tranexamic acid for antifibrinolytic treatment. METHODS: In this retrospective observational study, two groups of pediatric patients were studied during two different periods, receiving either aprotinin (n=70) or tranexamic acid (n=70) upon cardiac surgery. Data were collected from children with cyanotic heart defects, children who weighed less than 10 kg, and children who underwent re-operation. RESULTS: There was no difference in terms of blood loss or amount of erythrocyte concentrates and fresh frozen plasma transfused. Only the intraoperative amount of platelet concentrate received by children in the tranexamic acid group was 29 ml (p=0.013) higher. There was no significant difference in the length of stay at the intensive care unit, in renal function values, or in the rate of rethoracotomy. CONCLUSIONS: The results of this study suggest that tranexamic acid represents an adequate alternative to aprotinin in congenital cardiac surgery.