Comparison of subarachnoid block with bupivacaine and bupivacaine with fentanyl on entropy and sedation: A prospective randomized double-blind study

Abstract

Background and Aims:We studied the state entropy to monitor the sedative effect of subarachnoid block (SAB) using bupivacaine alone or combination of bupivacaine and fentanyl. The effect of use of fentanyl via the subarachnoid route on the sedation level was also studied using the entropy scores and the decrease in the requirement of propofol used as an adjuvant sedative drug.Materials and Methods:In this prospective randomized double-blind study, 30 patients of age 18-70 years requiring SAB were enrolled for the study. Patients with any known allergy to study drugs, contraindication for SAB, obesity, neurological or psychiatric disease on concurrent medication and refusal were excluded from the study. Patients were randomly allocated into two groups: Group C: SAB was administered with 2.5 mL (12.5 mg) of 0.5% hyperbaric bupivacaine; Group D: SAB was administered with 2.5 mL of 2 mL (10 mg) of 0.5% hyperbaric bupivacaine and 0.5 mL (25 μg) fentanyl. Propofol infusion was started if the state entropy (SE) value was ≥75, at the rate of 100 μg/kg/min till the SE value reaches in the range of 60-75 (recorded as onset time). Thereafter the infusion rate was titrated to maintain SE value between 60 and 75. The level of sedation was measured with SE and Ramsay sedation (RS) scale.Results:The demographic profile and baseline parameters, were comparable in two groups (P > 0.05). After SAB, decrease in SE and response entropy was noted in both the groups and fall was significant in Group D (P < 0.0001). The total propfol required in thew two groups were comparable being 3.97 ± 2.14 mg/kg in Group C and 3.41 ± 2.34 mg/kg in Group D (P = 0.342). The change in the mean RS values was from 1.17 ± 0.38 to 1.69 ± 0.47 in Group D (P = 0.06), whereas in Group C it was from 1.03 ± 0.18 to 1.43 ± 0.50 (P = 0.041) within 20 min of SAB.Conclusion:Subarachnoid block causes sedation per se, but the level of sedation is not clinically significant and the sedation caused is not enough to avoid sedative agents for allaying anxiety in patients intraoperatively. The sedative effect of SAB was enhanced by adding intrathecal fentanyl probably because of better quality of SAB. SE showed good correlation with RS scaling system. Therefore, SE may be used as reliable tool to titrate sedation in patients undergoing surgery under SAB.

Comparison of fentanyl and nalbuphine as adjuvants to intrathecal 0.5% bupivacaine in lower limb surgeries: A randomised double-blind prospective study

“…The lack of any change in entropy values may be due to the absence of significant systemic absorption of study drugs from the intrathecal space. This is in contrast to Varma et al’s (2014) study, which observed a significant reduction in both entropies after spinal anaesthesia administration with bupivacaine. Varma et al (2014) also noticed a further reduction in entropy by adding fentanyl adjuvant to bupivacaine.…”

“…This is in contrast to Varma et al’s (2014) study, which observed a significant reduction in both entropies after spinal anaesthesia administration with bupivacaine. Varma et al (2014) also noticed a further reduction in entropy by adding fentanyl adjuvant to bupivacaine.…”

“…As the conversion of conscious sedation to hypnosis may cause adverse effects, monitoring is essential. Evidence is available on entropy monitors to detect sedation due to spinal bupivacaine and fentanyl (Varma et al 2014), but sources addressing entropy on nalbuphine are few. Therefore, we conducted this trial to compare the analgesic effect, entropy and haemodynamics between nalbuphine and fentanyl in lower limb surgeries.…”

“…Entropy is used to monitor sedation (Kwon et al 2012) and depth of anaesthesia (Varma et al 2014). An extensive literature search revealed few studies on intrathecal fentanyl using entropy (Syed Othman et al 2016, Varma et al 2014), but scarce sources on nalbuphine. Therefore, this study aimed to compare the analgesic efficacy (primary outcome) and effect on entropy (secondary outcome) between nalbuphine and fentanyl as adjuvants added to 3 mL of 0.5% hyperbaric bupivacaine for the subarachnoid block in lower limb surgery.…”

“…It also augments postoperative analgesia and has no documented evidence of neurotoxicity (Ahmed et al 2016, Mukherjee et al 2011). Spinal anaesthesia blocks the somatosensory drive to the thalamocortical regions, which reduces excitability and thereby decreases brain arousal (Varma et al 2014). Opioid adjuvants cause further reduction in the level of consciousness and awakening.…”