الفهرس 
Memory and AwarenessOnly 14 pages are availabe for public view
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Abstract
”Awareness” under general anaesthesia can finally be considered as the ”invisible scar of surgery”. This unexpected and undesirable patient wakefulness under general anaesthesia has been considered as a source of pain and torture to many individuals after surgery.
The incidence of awareness in general surgical population have been estimated to be 0.1 to 0.2%. A higher incidence is reported for obstetric general anaesthesia 0.4% and can increase up to 1.0 to 1.5% in high-risk cardiac surgical patients and trauma cases.
Risk factors for awareness include:
• Patient related factors (such as unstable hemodynamics, drug addicts and alcoholics).
• Surgical factors (certain types of surgeries such as trauma, obstetric and high risk cardiac surgery) which requires caution in general anaesthetic drugs.
• Anaesthesia related factors related to umbalanced anaesthetic technique.
• Malfunctioning anaesthetic equipments especially that responsible for delivering anaesthetic gases or vapors lead to insufficient amount of the anaesthetic to ensure patient unconsciousness.
• Doctor related factors such as negligence, unchecking of the anaesthesia machine to detect any errors in vaporizes and ventilators or unattending the patient throughout the operation to detect early the clinical signs of awareness and adjust the concentrations of anaesthetic drugs.
Patients undergoing CS under general anaesthesia are at high risk of awareness. This is largely due to the use of low concentrations of volatile agents and the complete avoidance of opioid analgesia prior to delivery of the neonate. Also due to decrease in inhalational anaesthetic concentration after delivery for fear of uterine atony.
Emerging evidence has therefore aroused that intraoperative monitoring of ”depth of anaesthesia” can significantly decrease the risk of awareness especially in high risk patients.
The BIS index is the first approved and reliable monitor that enables assessment of the hypnotic component of anaesthesia. The BIS index is a processed EEG parameter calculated from several features of the cortical EEG index. This index uses a dimensionless number scaled from 100 (the awake state) to 0 (deep coma). BIS values of (40 to 60) reflect adequate hypnotic effects and has been established as the proper value for surgical anaesthesia.
Other indices similar to BIS index such as the Narcotrend index, the patient state index and the SNAP index also hold a promise for accurate assessment of anaesthetic depth. Other monitors also incorporated in DoA monitoring are the auditory evoked potential monitors which is incorporated in the A-line monitor which represent a promising parameter for monitoring DoA.
The aim of the present work was to detect intraoperative awareness during general anaesthesia for CS using the bispectral index monitoring device by comparing the hypnotic effects of midazolam supplementation or propofol infusion given after fetal delivery on bispectral index values aiming to prevent occurrence of awareness in term parturients undergoing CS under general anaesthesia.
This study was carried on 60 female patients ASA I or II physical status between 20 and 40 years of age undergoing elective CS. Routine intraoperative monitors were applied to all patients before induction of anaesthesia. In addition, BIS index VISTA™ monitor was connected to the patients via BIS Quatro™ sensor which was applied to their forehead before induction of anaesthesia.
General anaesthesia was standardized in all patients before fetal delivery. Then after fetal delivery, patients were divided into three equal study groups:
Group A (the midazolam group): 20 Patients received 0.05 mg/kg midazolam IV bolus, while maintaining isoflurane at 0.5 MAC and 1-2 µg/kg fentanyl was given.
Group B (the propofol group): 20 Patients received propofol infusion 4-6mg/kg/hr, while maintaining isoflurane at 0.5 MAC and 1-2 µg/kg fentanyl was given.
Group C (the control group): 20 Patients received 10 ml 0.9% normal saline, while maintaining isoflurane at 0.5 MAC and 1-2 µg/kg fentanyl was given.
In all groups, oxytocin 10-20 IU/L IV fluids or more were given according to presence or not of uterine atony.
Baseline BIS index values and hemodynamic variables were obtained and the subsequent changes in BIS values and maternal blood pressure and heart rate were recorded at different times throughout the operation. Also, induction to delivery time (IDT), uterine incision to delivery time (UDT) and time from cessation of isoflurane and propofol infusion to extubation were also recorded. Blood samples were drawn at baseline, after delivery of the fetus and at the end of the operation for measurement of maternal serum cortisol level.
Postoperatively: The patients were interviewed using a structured, standardized interview regarding their postoperative recall or dreaming in the PACU and on the1st postoperative day.
The study showed the following results:
The bispectral index monitor proved to be useful in monitoring the level of hypnosis in high risk obstetric surgeries.
Midazolam injection or propofol infusion given after fetal delivery significantly decreased BIS values to be within 40-60 which is considered an adequate level of hypnosis for surgery. So both drugs can be used safely and efficiently after fetal delivery to abolish maternal awareness during GA for CS.
No postoperative recall was found in the three groups of patients although the control group showed BIS values > 60 after fetal delivery indicating that the “recall test” may not be a reliable test for awareness.
There were no statistically significant differences between the three groups of patients as regards blood pressure and heart rate or as regards maternal serum cortisol levels as a measure of stress response to surgery.
Finally, management and prevention of awareness during general anaesthesia for cesearean section should be feasible and learned to avoid psychological aftereffects especially PTSD and to avoid litigation.