Bispectral index values at Sevoflurane concentrations of 1% and 1.5 % in lower segment cesarean section under general anaesthesia

Abstract

BACKGROUND: General anesthesia is needed for caesarean section in situations such as obstetric emergencies (ecclampsia, acute fetal distress etc) or when spinal anesthesia is contraindicated (patient refusal, thrombocytopenia etc). Regardless of indication, it is desirable to keep dose of volatile anesthetics to a minimum so as to decrease their effects on the neonate without causing a risk of awareness in the, mother.
OBJECTIVES: 1. To compare efficacy of 1% and 1.5% Sevoflurane as inhalational anaesthetic for maintenance of general anaesthesia in cesarean section.
2. To ascertain the optimum concentration of sevoflurane required to prevent awareness in lower segment caesarean section under general anesthesia.
3. To use Bispectral index to determine if lower concentration of sevoflurane can be used effectively in lower segment cesarean section.
STUDY DESIGN: A prospective observational study
PARTICIPANTS: 50 parturients planned for elective under general anesthesia
METHODS: Patients were divided into two groups. Group A received 1% sevoflurane with N2O for maintenance of anesthesia while group B received 1.5% sevoflurane with N2O. BIS, HR, NIBP, SpO2, EtCO2 and Etsevo were recorded at 16 designated points throughout the procedure. Post-operatively patients were interviewed for any recall of intraoperative events.
RESULTS: From the time of skin incision until uterine closure, average values for BIS were higher for group A (Sevoflurane 1%) than for group B (Sevoflurane 1.5%) but values in both groups were below 60. From abdominal mopping till the end of procedure, values for group A continued to be higher than that for group B and values in group A reached above 60 in some patients. None of the patients had any intraoperative awareness as confirmed by post-operative interviews.
CONCLUSIONS: Sevoflurane 1.5% with N2O for maintenance of general anesthesia seems to be adequate for preventing intraoperative awareness during LSCS under while Sevoflurane 1% may be inadequate for maintenance of anesthesia in some patients.
IMPLICATIONS: Sevoflurane 1.5% seems better choice than Sevoflurane 1% for maintenance of general anesthesia in LSCS