From the Guidelines
The combination of bupivacaine, fentanyl, and adrenaline provides effective spinal cord analgesia through complementary mechanisms that enhance pain relief while reducing side effects. Bupivacaine, a local anesthetic, blocks sodium channels in nerve membranes, preventing action potential generation and transmission of pain signals. Fentanyl, an opioid, binds to mu-opioid receptors in the dorsal horn of the spinal cord, inhibiting the release of excitatory neurotransmitters like substance P and reducing pain signal transmission. Adrenaline causes local vasoconstriction, which slows the vascular uptake of both bupivacaine and fentanyl, prolonging their duration of action in the cerebrospinal fluid and at receptor sites.
According to a study published in 2024 1, the minimum local analgesic dose of bupivacaine for labor analgesia was found to be 1.99 mg, which was reduced to 0.69-0.85 mg when 5-25 µg fentanyl was added. This suggests that the combination of bupivacaine and fentanyl has a synergistic effect, allowing for lower doses of each medication to be used while still achieving effective analgesia.
The addition of adrenaline to the combination of bupivacaine and fentanyl can further enhance the duration and quality of analgesia. A study mentioned in the guidelines 1 used a small dose of adrenaline added to the local anaesthetic/opioid bolus, although the exact dose was not specified.
Some key points to consider when using this combination include:
- Bupivacaine provides dense sensory blockade
- Fentanyl enhances analgesia quality particularly for visceral pain
- Adrenaline extends the duration of the block
- Typical intrathecal doses might include bupivacaine 1.75 mg with 15 µg fentanyl, as found in a study by Whitty et al. mentioned in the guidelines 1
- Specific dosing should be tailored to the patient and procedure, taking into account factors such as the type of surgery, patient weight, and medical history.
Overall, the combination of bupivacaine, fentanyl, and adrenaline is a effective and synergistic approach to spinal cord analgesia, allowing for comprehensive pain control with minimized side effects.
From the Research
Mechanism of Action
The combination of bupivacaine, fentanyl, and adrenaline works synergistically to improve analgesia through several mechanisms:
- Bupivacaine, a local anesthetic, blocks nerve conduction and reduces pain transmission [ 2 ].
- Fentanyl, an opioid, acts on opioid receptors in the spinal cord to reduce pain perception [ 3 ].
- Adrenaline, an alpha-adrenergic agonist, enhances the effects of bupivacaine and fentanyl by reducing blood flow to the spinal cord and increasing the duration of action [ 4 ].
Synergistic Effects
The synergistic effects of the combination are demonstrated by:
- Reduced consumption of sufentanil when given epidurally with bupivacaine compared to intravenously [ 2 ].
- Improved pain relief with the addition of adrenaline to a combination of fentanyl and bupivacaine [ 4 ].
- Marked improvement in pain-relieving effect of bupivacaine and adrenaline with the addition of fentanyl [ 3 ].
Effective Concentrations
The effective concentrations of the combination are:
- Adrenaline: approximately 1.5 microg/ml [ 5 ].
- Fentanyl: 2 microg/ml [ 3 ].
- Bupivacaine: 1 mg/ml [ 3 ].
Clinical Implications
The combination of bupivacaine, fentanyl, and adrenaline has clinical implications for: