The Effects of Small Intravenous Doses of Midazolam on Explicit Recall and the Bispectral Index after Fetal Expulsion in a Cesarean Section under General Anesthesia

Noh, Gyu Jeong; Jeon, Woo Jae

Abstract

BACKGROUND: Explicit recall in a cesarean section under general anaesthesia can be a terrifying experience and may cause psychological sequelae. Administering low doses of midazolam, we investigated the changes of the bispectral index (BIS) and the occurrence of explicit recall of specific events after fetal expulsion in a cesarean section under general anesthesia.
METHODS
The investigation was carried out on 30 ASA 1 or 2 parturients who underwent a cesarean section under general anesthesia. Anesthesia was maintained with 50% N2O in oxygen and 0.75% of isflurane. We randomly allocated parturients into a control group (n = 10), group A (n = 10), and B (n = 10). Neither midazolam nor any other drugs except oxytocin were administered in the control group. In the group A and B, midazolam 0.02 and 0.03 mg/kg respectively, were injected immediately after umbilical cord clamping. An isolated forearm test were done to all the parturients at 5, 10, and 20 minutes after fetal expulsion. We assessed the changes of the BIS at 1, 2, 3, 4, 5, 10, 15, and 20 minutes after fetal expulsion, at discontinuance of isoflurane administration and extubation. The wav file, "clench your left or right hand" was binaurally played, simultaneously with the isolated forearm test. The wav file, "one, two, three, four, five" was also binaurally played 15 minutes after fetal expulsion. We interviewed all the parturients the next day and assessed the occurrence of explicit recall.
RESULTS
The BIS values after fetal expulsion in the control group and group A was maintanied above 60 and group B, below 60 (P < 0.05). The lowest median BIS value was 54.5 in the group A, 36.4 in the group B (P < 0.05). There were two parturients in the control group and in the group A, respectively, who showed explicit recall. The results of the isolated forearm test were negative for all groups. The extubation times and PAR scores failed to show significant differences among the three groups.
CONCLUSIONS
The authors confirmed the occurrence of explicit recall for specific events after fetal expulsion. The BIS values after fetal expulsion could be maintained below 60 until the end of surgery,and explicit recall could be prevented when we injected midazolam 0.03 mg/kg immediately after fetal expulsion.