Block-dependent sedation during epidural anaesthesia is associated with delayed brainstem conduction

Doufas, Anthony G.; Wadhwa, Anupama; Shah, Yunus M.; Lin, Chum-Ming; Haugh, Gilbert S.; Sessler, Daniel I.

doi:10.1093/bja/aeh192

Cited by 41 publications

(27 citation statements)

References 33 publications

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“…Depression of brainstem activity by epidural anesthesia was also confirmed in humans. 18 The present study supports the deafferentation hypothesis and provides strong evidence against the classical criticism that spinal anesthetics could directly affect the brainstem through rostral diffusion in the cephalo-spinal fluid. In fact, there was no pharmacological agent that could diffuse in our transected animals.…”

Section: Discussionsupporting

confidence: 86%

Spinal cord injury immediately decreases anesthetic requirements in rats

et al. 2011

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Study design: Pharmacologically blocking the spinal cord produces sedative effects and reduces anesthesia requirements in patients and animals. Whether spinal cord injury also reduces anesthesia requirements remains unclear. Methods: We retrospectively analyzed data from urethane-anesthetized rats 15 to assess anesthesia requirements immediately after complete thoracic transection of the spinal cord. The depth of anesthesia was monitored up to 12 h after spinal transection by the reflexes to noxious stimuli and by electrophysiological recordings from the infragranular layers of the primary somatosensory cortex. Whenever animals displayed electrophysiological and/or behavioral signs of activation, we delivered an additional dose of anesthesia. Anesthetic requirements in animals receiving spinal transection (n ¼ 11) were compared with control animals receiving 'sham' lesion (n ¼ 9). Results: The cumulative dose necessary to maintain a stable level of anesthesia was significantly lower in transected animals compared with control animals. By about 7 h after spinal cord injury, on average the cumulative dose of urethane was only 1.13 ± 0.14 of the original dose, compared with 1.64 ± 0.19 of the original dose in control animals. Conclusions: Spinal transection immediately decreased anesthetic requirements in rats. To establish whether these results are relevant for patients with spinal cord injury will require further investigation.

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Section: Discussionsupporting

confidence: 86%

Spinal cord injury immediately decreases anesthetic requirements in rats

et al. 2011

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“…This is based on the observation that sedation during epidural analgesia seems to depend on sensory block level [2]. Sensory deafferentation was ruled out as the cause of sedation in this study because there was no difference between the median anaesthetic block levels of the two groups.…”

Section: Discussionmentioning

confidence: 95%

“…A minimal dose of intravenous sedative agents such as midazolam and propofol is often used to reduce patients' anxiety with minimal influence on haemodynamic variables. Neuraxial anaesthesia with local anaesthetics alone has been reported to reduce sedative requirements but with significant sedation achieved only with a high sensory block level, which may result in haemodynamic instability [1][2][3][4][5][6]. Intrathecal fentanyl is often combined with a local anaesthetic agent to enhance and prolong the sensory block produced by spinal anaesthesia [7,8], and a recent study reported the sedative effect of intrathecal fentanyl as monitored using Bispectral Index (BIS) [9].…”

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confidence: 99%

The effect of intrathecal fentanyl on Cerebral State Index‐guided sedation during spinal anaesthesia*

Kim

Kim²,

Shin

et al. 2009

Anaesthesia

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SummaryThis study investigated the effect of intrathecal fentanyl on the dose of propofol during sedation guided by Cerebral State Index monitoring. Seventy patients were randomly assigned to receive either fentanyl 25 lg (n = 35) or normal saline (n = 35) with hyperbaric bupivacaine 12.5 mg for spinal anaesthesia. Propofol was infused to maintain a Cerebral State Index value of 65-75 for 30 min. The propofol infusion time and dose required to reach a Cerebral State Index value of 75 were recorded together with the time required to reach a Cerebral State Index value higher than 90 after cessation of sedation. The onset time for sedation was faster and the recovery time was slower in the fentanyl group compared to those in the saline group (p = 0.018 and 0.027, respectively). The propofol doses required for onset and maintenance of sedation were significantly lower in the fentanyl group compared to those in the control group (p = 0.018 and < 0.001, respectively). In conclusion, adding intrathecal fentanyl 25 lg during spinal anaesthesia significantly reduced the dose of propofol required for sedation and prolonged the subsequent recovery time. During spinal anaesthesia, conscious sedation can be provided for patient comfort. A minimal dose of intravenous sedative agents such as midazolam and propofol is often used to reduce patients' anxiety with minimal influence on haemodynamic variables. Neuraxial anaesthesia with local anaesthetics alone has been reported to reduce sedative requirements but with significant sedation achieved only with a high sensory block level, which may result in haemodynamic instability [1][2][3][4][5][6]. Intrathecal fentanyl is often combined with a local anaesthetic agent to enhance and prolong the sensory block produced by spinal anaesthesia [7,8], and a recent study reported the sedative effect of intrathecal fentanyl as monitored using Bispectral Index (BIS) [9]. The level of sedation can be monitored using the Observer's Assessment of Alertness ⁄ Sedation scale (OAA ⁄ S) and other commercially available monitors such as BIS, entropy and the Cerebral State Index (CSI), which uses the spontaneous EEG to calculate a numerical index between 100 and 0. The CSI has been reported to distinguish between graduated levels of propofol anaesthesia [1,10].The purpose of this study was to investigate the effect of intrathecal fentanyl on the dose of propofol required for sedation guided by CSI monitoring and the OAA ⁄ S scale in patients undergoing lower extremity surgery. We hypothesised that the addition of intrathecal fentanyl would decrease the propofol dose for an adequate level of sedation during spinal anaesthesia. MethodsThis study was approved by our Institutional Review Board and informed consent was obtained from all patients. Seventy patients of ASA physical status 1 or 2, undergoing lower extremity surgery, were assigned by random number in sealed envelopes to either a fentanyl group (n = 35) or the saline group (n = 35). Exclusion criteria included age kg.m )2 over 65 years,

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“…Hodgson and Liu [11] observed that epidural lidocaine reduced by 34% the sevoflurane required to produce adequate depth of anaesthesia but intravenous lidocaine that had similar plasma lidocaine concentration to epidural did not. Doufas et al [12] found that sedation during epidural anaesthesia depended on sensory block level and was associated with detectable block-dependent alterations in the brainstem auditory evoked responses. In addition, the effects of the other neuraxial block or spinal anaesthesia were studied by Pollock et al [13] who showed that observer sedation scoring and self-sedation scores for patients were significantly decreased in patients who received spinal anaesthesia compared with control patients who did not.…”

Section: Discussionmentioning

confidence: 99%

Haemodynamic effects of thoracic epidural anaesthesia during induction of anaesthesia: an investigation into the effects of tracheal intubation during target‐controlled infusion of propofol*

et al. 2005

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SummaryWe compared haemodynamic changes following induction of anaesthesia with propofol during tracheal intubation with and without epidural anaesthesia. Nineteen patients were divided into two groups to receive epidurally administered saline (Group C) or lidocaine 1.5% (Group E). The propofol infusion was started to produce blood concentrations of 3 lg.ml )1 , and following fentanyl and vecuronium administration, tracheal intubation was performed. Mean arterial blood pressure (MBP), heart rate (HR), Bispectral index and effect-site propofol concentration were recorded. Time to loss of consciousness was significantly shorter in Group E than in Group C. The effect-site propofol concentration at loss of consciousness was significantly lower in Group E than in Group C. MBP and HR were significantly lower following propofol induction in both groups, and were significantly increased following intubation in Group C but not in Group E. In conclusion, epidural anaesthesia did not produce profound hypotension following induction of anaesthesia and produced a reduction in the haemodynamic response to tracheal intubation during a target controlled infusion of propofol.

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Block-dependent sedation during epidural anaesthesia is associated with delayed brainstem conduction

Abstract: Sedation during epidural anaesthesia depends on sensory block level and is associated with detectable block-dependent alterations in the brainstem auditory evoked responses. Sensory deafferentation may reduce CNS alertness through mechanisms related to brainstem neural activity.

Cited by 41 publications

References 33 publications

Spinal cord injury immediately decreases anesthetic requirements in rats

Spinal cord injury immediately decreases anesthetic requirements in rats

The effect of intrathecal fentanyl on Cerebral State Index‐guided sedation during spinal anaesthesia*

Haemodynamic effects of thoracic epidural anaesthesia during induction of anaesthesia: an investigation into the effects of tracheal intubation during target‐controlled infusion of propofol*

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