Title

A randomised controlled trial investigating the effect of adding fentanyl to low dose bupivacaine in combined spinal-epidural anaesthesia, using epidural volume extension technique in caesarean section

Date of Award

6-30-2011

Document Type

Dissertation

Degree Name

Master of Medicine (MMed)

Department

Anaesthesia (East Africa)

Abstract

Background: Epidural volume extension (EVE), is a technique whereby a small-dose intrathecal block is enhanced by an epidural injection of physiological saline. This epidural injection exerts a compression effect on the dura, which then leads to a cranial increase in sensory spread of the intrathecal local anaesthetic. The lower dose of local anaesthetic required in the EVE technique has made it possible to avoid the side effects of the conventional dose of local anaesthetic while still having the benefit of adequate anaesthesia. Several studies have been conducted in this area; these studies have either used or omitted fentanyl. The successful results demonstrated in these trials have been solely attributed to the EVE effect without taking into consideration the pharmacological effect of fentanyl on the total outcome. No study has been done to demonstrate the effect of fentanyl on the epidural volume extension block and whether adding or omitting it would make a difference on spinal block level and other characteristics.

Objective: The study aims at determining the effect of fentanyl plus low dose bupivacaine on the spinal block level of combined spinal epidural (CSE) anaesthesia utilizing the Epidural Volume Extension technique.

Study design: A randomised controlled trial

Methods

- Intervention: Forty four women scheduled for elective caesarean section were randomized to 2 groups. One group got intrathecal bupivacaine with fentanyl followed by Epidural Volume Extension with physiological saline (Fentanyl group). The second group got intrathecal bupivacaine without fentanyl followed by epidural volume extension with physiological saline (No-fentanyl group).

- Outcome measures: The outcome measures for this study were, the maximum sensory level which was measured by loss of sensation to temperature using a cold spirit swab, the motor block which was assessed using the Bromage score and the time to first request to analgesia taken as the time the patient first needed to use their PCA device or epidural supplementation intraoperatively.

Results: The sensory block level after epidural volume extension increased in both arms. The increase was more in the intervention arm (Fentanyl group) than in the control arm (Nofentanyl group). This increase was however not statistically significant P=0.19. The sensory block level after epidural volume extension in the fentanyl group was 4 levels higher than the initial intrathecal block, while in the control arm the change was 3 levels higher than the than the initial intrathecal block. The time to first request of analgesia was shorter in the no-fentanyl group than in the fentanyl group. The Bromage score for motor blockade was slightly higher in the fentanyl group compared to the no-fentanyl group. The no-fentanyl group had a higher incidence of inadequate blocks (50%) compared to the fentanyl group (13%) P=0.01. Similarly the no-fentanyl group had a higher incidence of conversion to general anaesthesia (13.64%) compared to the fentanyl group (4.55%). The fentanyl group had a higher incidence of hypotension (68.18%) compared to the no-fentanyl group (22.73%) P=0.002. The fentanyl group also had a higher incidence of respiratory discomfort (18.18%) and a higher incidence of bradycardia (27.2%) compared to the no-fentanyl group (13.64%) and (22.7%) respectively.

Conclusion: This study has shown that fentanyl has both direct and indirect effects on the block profile of low-dose bupivacaine in combined spinal epidural anaesthesia using the Epidural Volume Extension technique.

Fentanyl directly affects the maximum height of the sensory level achieved during the block, this finding was not statistically significant however we found it to be clinically significant.

Fentanyl provided better quality of anaesthesia by adding analgesic properties to the block. The fentanyl group also had a higher incidence of cardiorespiratory effects due to a higher sensory block level, demonstrated by a higher incidence of hypotension, bradycardia and respiratory distress.

This study concludes that fentanyl gives a block of superior quality when used with EVE technique compared to when it is omitted. However this technique can cause a high block which can affect patient cardiovascular and respiratory dynamics.

This document is available in the relevant AKU library

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