الفهرس 
NEURO-ANATOMY OF PAINOnly 14 pages are availabe for public view
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Abstract
Pain is defined as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage” Nociception is made up of four processes: Transduction, transmission, modulation, and perception. Sensory neurons synapse in substantia Gelatinosa, secondary neurons cross midline and ascend in anterolateral column, and then branches go to reticular formation, and then terminate in ventrobasal nucleus of thalamus. Tertiary neurons go to sensory cortex.
Opioids are powerful analgesics all descended from morphine, all activate mu receptors and varying degrees of delta and kappa receptors. Opioid receptors are distributed throughout the CNS. Both supraspinal and spinal opioid receptors produce antinociception.
Neuroaxial opioids are widely used in adults and paediatrics although they have unpleasant non-analgesic effects including hypotension, respiratory depression, nausea, vomiting, urine retention, and pruritis. Risk factors for respiratory depression after intrathecal opioid administration include advanced age, poor general condition, use of water-soluble opioid, marked changes in thoraco-abdominal pressure, lack of tolerance to opioids, and concomitant administration by other routes of opioids or other CNS depressant drugs.
The stress response to surgery comprises a number of hormonal changes initiated by neuronal activation of the hypothalamic-pituitary-adrenal axis. The overall metabolic effect is catabolism of stored body fuels. In general, the magnitude and duration of the response are proportional to the extent of surgical injury. Regional anaesthesia with local anaesthetics or opioids inhibits the stress response to surgery and can influence postoperative outcome by beneficial effects on organ function.
The use of regional anaesthesia in patients undergoing cardiac surgery- both adults and paediatrics- is well established although it may has many Adverse effects such as infection, pruritis, hemodynamic changes, respiratory depression, and the most dangerous is permanent neurologic damage secondary to neuroaxial hematoma formation, since these patients receive heparin intra-operatively for cardiopulmonary bypass, the use of regional anaesthesia remain controversial, and this fear has so far restricted the use of intrathecal or epidural anaesthesia in cardiac surgery.
The present study was conducted –at Ain Shams University Hospitals- on 45 pediatric patients who were subjected to elective cardiac surgery for closure of ventricular or atrial septal defects (VSD or ASD), the patients were randomly divided into 3 groups, 15 patients each. Preparation and induction were the same in the 3 groups, then, Group no. (1): received general anaesthesia alone in the form of isoflurane, pancuronium and fentanyl for maintenance of anesthesia. Group no. (2): received intrathecal fentanyl immediately after induction with maintenance of anaesthesia by isoflurane and pancuronium. Group no. (3): received Caudal injection of fentanyl immediately after induction with maintenance of anaesthesia by isoflurane and pancuronium.
The study aimed to compare pediatric patients receiving general anaesthesia alone to those receiving combined general and regional anaesthesia as regard intra-operative hemodynamic stability, stress response, acid-base balance, arterial blood gases, and postoperative time to extubation and ICU stay. The study also aimed to estimate the incidence of postoperative complications attributed to regional anaesthesia.
The study found that the use of epidural or spinal anaesthesia in pediatric patients attenuate the stress response, with consequent greater hemodynamic stability and shorter extubation time when compared to general anaesthesia alone and postoperative intravenous opioid analgesia.
The risks of regional anaesthesia in these patients include undesired side effects (pruritis, nausea and vomiting), hypotension, respiratory depression, and neuroaxial hematoma formation. The incidence of side effects dos not appear to be significant. Hypotension associated with regional blockade in adult patients is uncommon in infants and young children. Postoperative respiratory depression is greatly reduced by avoiding intravenous opioids and using prudent doses of spinal or epidural opioids.
The risk of neuroaxial hematoma formation is small but serious. This risk can be reduced by employing reasonable safeguards. Appropriate precautions include selecting patients with normal coagulation function, abandoning the regional anaesthesia technique if needle placement is difficult, and delaying the surgery in the event of return of blood via the regional anaesthesia needle or catheter. Maximize the interval between needle placement and heparin administration to be at least 45-60 minutes, and if epidural catheter is used, it should be removed only after normal coagulation function has been restored after surgery.
This work also concluded that regional anaesthesia may facilitate early tracheal extubation immediately after surgery and maybe even in the operating room and so reduces the complications and the expense associated with mechanical ventilation in the post-operative period.
All children were stable and fully awake after the surgery and had no respiratory or neurological complications.
This study finally concluded that regional anaesthesia can play a major role in pediatric cardiac surgery but fear of complications specially neuroaxial hematoma formation and subsequent neurological damage still needs more and more studies applied to larger number of patients to ensure safety of regional anaesthesia in pediatric and adult cardiac surgery.