Bispectral index values during spinal anesthesia using hyperbaric bupivacaine with intrathecal or intravenous fentanyl for cesarean section

Background: it has been shown that bispectral index (bis) may reduce during spinal anesthesia. the aim of this study was comparing bis scores during spinal anesthesia using hyperbaric bupivacaine alone or with intrathecal or intravenous fentanyl for cesarean section. methods: in this double-blind randomized controlled clinical trial, 140 pregnant women with american society of anesthesiologists (asa) class i or ii were randomly assigned to receive 1-2.5 ml hyperbaric 0.5% plus normal saline (b), 2-2.5 ml hyperbaric 0.5% plus 20 μg fentanyl intrathecally (bfit), or 2.5 ml hyperbaric 0.5% plus 100 μg fentanyl intravenously (bfiv). bis was measured using electroencephalography (eeg) findings and recorded at the baseline and 5th, 10th, 15th, 30th,, 45th, and 60th minutes after spinal injection. the heart rate (hr), mean arterial pressure (map), signal quality index (sqi), and temperature were also recorded during surgery. results: a total number of 140 subjects completed the study and underwent analysis. the recorded bis was significantly different between the three groups at all time points (p = 0.004). at all the times, the bis values were lower in the bfiv group compared to other groups (p < 0.05). the bis scores in group b were significantly higher in most time points compared to other groups. after spinal anesthesia, the changing trend of bis reduced until the 30th minute for the bfit group and until the 45th minute for the b and bfiv groups. conclusions: although the bis scores began to decrease during spinal anesthesia using hyperbaric bupivacaine alone or with intrathecal or intravenous fentanyl for cesarean section, the greatest reduction from baseline bis values occurred with adding intravenous fentanyl. moreover, maximum reductions of bis scores appeared at 30 and 45 minutes after induction of spinal anesthesia.