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Abstract
40 patients ASA I of both sexes scheduled for elective abdominal operation were included in the current study. All patients were examined preoperatively to assess their degree of fitness to both anesthesia and surgery. Informed consent was obtained from all patients. Routine laboratory investigations were obtained according to the need of each patient.
Premedication with midazolam 0.01 - 0.1mg/kg is given before surgery. Routine intraoperative monitoring was used as:
• Non invasive blood pressure monitor.
• Five leads electrocardiography.
• Pulse oximetry.
• Capnography.
• Anesthesia agent monitors showing both inspiratory and expiratory concentration of anesthetic agent.
• Baseline values of systolic/diastolic blood pressure, heart rate and oxygen saturation were obtained before induction.
• AEP index by AEP Monitor/2
Following preoxygenation for 3 minutes via face mask, patients received fentanyl 2 micrograms/kg IV, followed by propofol 2.5 mg/kg as intravenous bolus dose. Lastly, atracurium 0.5mg/kg while patients were breathing oxygen. When proper muscle relaxation was achieved, patients were intubated with oral cuffed endotracheal tube. The tube was secured and connected to a Drager Anesthetic machine.
After intubation with proper sized cuffed tube, patient’s lungs were ventilated with a tidal volume of 10 ml/kg and respiratory rate of 12 breaths/ minutes. Adjustment was made to maintain end tidal CO2 33 - 36 mmHg. Muscle relaxation was maintained with increments of atracurium 10 mg each.
Then patients were randomly divided into two groups:
Group One:
Maintenance of patients of this group were achieved by propofol infusion 2 - 6 mg/kg/h. guided by hemodynamic response and 0.1 mg/kg atracurium every 20 minutes.
Group Two:
Maintenance of patients of this group was achieved by isoflurane 1-2 MAC (which equal to 1.2 - 2.4 Vol. %), N2O in O2 and atracurium 0.1mg/kg every 20 minutes.
During surgery, all patients were monitored for response of intubation, light anesthesia throughout the maintenance period.
Responses were managed by administration of a bolus dose of fentanyl
During maintenance, patients were also monitored for hypotension with the systolic arterial pressure < 80 mmHg, and/or bradycardia HR < 45 beats/minute for > 1 minute. Hypotension was treated with fluids and 50% decrements in propofol infusion rate or isoflurane concentration. If decrease was unsuccessful, vasopressor drug (ephedrine 0.1mg/kg) was administered. For bradycardia, propofol was decreased and anticholinergic drug (atropine 0.01mg/kg) were administered.
Towards the end of suergery, isoflurane vaporizer had been closed, propofol pump closed, flowmeter increased to 6 liter/min. mechanical ventilation was discontinued at the end of surgery and residual curarization was antagonized by neostigmine 0.04 - 0.08 mg/kg and atropine 0.01mg/kg, and patients were ventilated by hand and assisted until spontaneous and adequate respiration was achieved, (respiratory rate > 8 breath/min. and/or end carbon dioxide tension < 50mmHg). Extubation was performed followed by oxygenation by face mask.
The current study compared the level of consciousness during anesthesia by two different anesthetic techniques during elective abdominal operations.
Monitoring of anesthetic depth was done by the autonomic responses (heart rate, blood pressure) versus auditory evoked potential index. It was found that the auditory evoked potential index is more sensitive and gives a more predictive value regarding adequate depth of anesthesia than depending on the vital signs alone. We also found that TIVA group is associated with a high incidence of awareness when compared to the inhalational group depending on the auditory evoked potential index.