Evaluation of the adequacy of general anesthesia in cesarean section by bispectral index

Abstract

Background: Awareness and recall, though not common, are the major hazards of general anesthesia, especially in Cesarean section (C/S) because of the absence of benzodiazepine and opioids for a significant time during anesthesia. In this study, the Bispectral Index (BIS), end-tidal isoflurane, and hemodynamic parameters were examined to evaluate the depth of the routine general anesthetic technique in C/S.

Methods: This study was carried out on 60 parturient patients undergoing elective C/S. A standardized anesthetic technique was applied: induction with Thiopental (4-5 mg/kg) and Succinylcholine (1.5-2 mg/kg) as well as maintenance with O2, N2O, and isoflurane. Electrocardiogram, heart rate, blood pressure, Spo2, end-tidal isoflurane concentration, BIS, and any clinical signs of inadequate depth of anesthesia such as movement, sweating, lacrimation, coughing, and jerking were continuously monitored and recorded at 16 fixed time points during anesthesia.

Results: A median BIS of less than 70 (range: 42-68) was obtained on all occasions during surgery; however, at each milestone, at least 20% of the patients had BIS values above 60. Hemodynamic parameters increased significantly in some patients, especially during laryngoscopy and intubation. No patient experienced recall or awareness.

Conclusion: The currently used general anesthetic technique in our center appears inadequate in some milestones to reliably produce BIS values less than 60, which are associated with lower risk of awareness. Therefore, with respect to such desirable outcomes as good Apgar and clinical status in neonates, we would recommend the application of this method (if confirmed by further studies) through larger dosages of anesthetic agents.

Keywords: Awareness; Bispectral index; Cesarean section; Recall.

Figure 1

The mean values of mean arterial blood pressure (MAP) (white squares) and heart rate (HR) (black triangles) at predetermined time points at designated events along with the measurement of the Bispectral Index (BIS) (black squares) are depicted herein. Base: Baseline; Induc: After induction; Intub: Intubation; Si: Skin incision; Del: Delivery; U/ct: Uterine curettage; U/cl: Uterine closure; Abd/l: Abdominal lavage; P/cl: Peritoneal closure; SQ/cl: Subcutaneous closure; Isf/dc: Cessation of isoflurane; S/cl: Skin closure; Rev: Reversal administration; O-eye: Eye opening

Figure 2

The Bispectral Index (BIS) values (25, 50, and 75 percentile) at predetermined time points are illustrated herein. Base: Baseline; Induc: After induction; Laryn: Laryngoscopy; Intub: Intubation; Si: Skin incision; Rm: Retraction of rectus muscles; Del: Delivery; U/ct: Uterine curettage; U/cl: Uterine closure; Abd/l: Abdominal lavage; P/cl: Peritoneal closure; SQ/cl: Subcutaneous closure; Isf/dc: Cessation of isoflurane; S/cl: Skin closure; Rev: Reversal administration; O-eye: Eye opening; Box: First quartile, median, third quartile; Box whiskers: The lowest datum still within 1.5 IQR of the lower quartile, and the highest datum still within 1.5 IQR of the upper quartile, IQR=3rd quartile-1st quartile; ○: Datum within 1.5-3 IQR of the upper quartile (between inner and outer fences; *Datum outer than 3 IQR of the upper quartile (above outer fence