From the Guidelines
The correct answer is "all of the above." Adrenaline (epinephrine) and corticosteroids are both used in peripheral nerve blocks for multiple beneficial effects. Adrenaline slows the absorption of local anesthetic agents by causing vasoconstriction, which keeps the anesthetic at the injection site longer, prolonging the duration of the nerve block and reducing systemic absorption that could lead to toxicity. Additionally, both adrenaline and corticosteroids have pharmacologic properties that contribute to analgesia. Corticosteroids like dexamethasone have potent anti-inflammatory properties, as seen in a study by Zhang et al. 1, where the combination of ropivacaine, dexamethasone, and dexmedetomidine resulted in a significantly longer duration of analgesia compared to other groups. This is further supported by Maher et al. 1, who found that the addition of dexamethasone to ropivacaine in intercostal nerve blocks prolonged the duration of analgesia and reduced opioid requirements.
- Key benefits of using adrenaline and corticosteroids in peripheral nerve blocks include:
- Prolonged duration of analgesia
- Reduced systemic absorption of local anesthetics
- Anti-inflammatory effects of corticosteroids
- Potential for reduced opioid requirements
- Typical concentrations of epinephrine used are 1:200,000 to 1:400,000, and corticosteroids like dexamethasone are typically used in doses of 4-8 mg.
- The combination of adrenaline and corticosteroids in peripheral nerve blocks can provide effective post-procedural pain management by targeting multiple mechanisms of pain and inflammation, as supported by recent studies 1.
From the Research
Rationale for Using Adrenaline and Corticosteroids in Peripheral Nerve Blocks
- Adrenaline slows the absorption of blocking agents, which can prolong the duration of the block and reduce the risk of systemic toxicity 2, 3.
- Both adrenaline and corticosteroids have pharmacologic activity that can produce analgesia, contributing to pain relief 2, 4.
- Corticosteroids have potent anti-inflammatory properties, which can be beneficial in reducing inflammation and promoting healing in peripheral nerve pathologies 5, 6.
Mechanisms of Action
- Adrenaline works by constricting blood vessels, which delays the absorption of local anesthetics and prolongs their duration of action 3.
- Corticosteroids have anti-inflammatory effects, which can reduce swelling and promote healing in peripheral nerves 5, 6.
- The combination of adrenaline and corticosteroids can provide synergistic effects, enhancing the duration and efficacy of peripheral nerve blocks 4.
Clinical Applications
- Adrenaline is commonly used as an additive to local anesthetics in peripheral nerve blocks to prolong the duration of the block and reduce systemic toxicity 2, 3.
- Corticosteroids are used in peripheral nerve blocks to provide anti-inflammatory effects and promote healing in peripheral nerve pathologies 5, 6.
- The use of corticosteroids in peripheral nerve blocks is supported by evidence from systematic reviews and clinical trials, which demonstrate their efficacy in reducing pain and inflammation 5, 4, 6.