What medications improve pain with anesthesia?

Medications to Improve Pain Control with Anesthesia

Multimodal analgesia combining regional anesthesia with long-acting local anesthetics (bupivacaine or ropivacaine) plus adjuvants (clonidine, dexmedetomidine) and systemic non-opioid analgesics (NSAIDs, paracetamol) provides superior pain control compared to any single agent alone.

Core Strategy: Regional Anesthesia with Adjuvants

Local Anesthetic Selection

• Bupivacaine 0.25% (maximum 2.5 mg/kg) or ropivacaine 0.2% (maximum 3 mg/kg) are the preferred long-acting local anesthetics for neuraxial and peripheral nerve blocks 1
• Ropivacaine produces less intense motor block than bupivacaine while maintaining similar analgesic duration, facilitating earlier mobilization 2
• For spinal anesthesia, hyperbaric solutions produce more consistent results than plain solutions 2

Essential Adjuvants to Local Anesthetics

• Adding clonidine (1-2 mcg/kg) to local anesthetics extends blockade duration across all regional techniques 1, 3
• Neuraxial clonidine increases duration and quality of analgesia while reducing morphine consumption 3
• Dexmedetomidine added to neuraxial blocks improves both intraoperative and postoperative analgesia with reduced opioid requirements 3
• Intrathecal dexmedetomidine combined with local anesthetics provides analgesia superior to local anesthetic alone 3

Common pitfall: Higher clonidine doses increase sedation and hypotension risk without proportional analgesic benefit 4

Neuraxial Opioid Administration

Intrathecal Morphine

• Intrathecal morphine (0.05-0.5 mg) prolongs postoperative analgesia by approximately 8 hours (503 minutes) and reduces pain scores through 12 hours 5
• Decreases the number of patients requiring rescue opioid analgesia postoperatively 5
• Intrathecal morphine is similar in efficacy to intrathecal hydromorphone 3

Intrathecal Fentanyl

• Adding intrathecal fentanyl (10-50 μg) to bupivacaine improves initial analgesia and extends duration by approximately 2 hours (114 minutes) 3, 5
• Caution: When morphine is also present intrathecally, fentanyl may induce acute opioid tolerance and increase total opioid consumption 3
• Faster injection speed of intrathecal fentanyl-local anesthetic mixtures improves postoperative analgesia duration 3

Side Effect Profile

• Intrathecal morphine increases risk of nausea (NNH 9.9), vomiting (NNH 10), urinary retention (NNH 6.5), and pruritus (NNH 4.4) 5
• Respiratory depression risk with morphine 0.05-0.5 mg ranges from NNH 38-59 depending on definition used 5
• Fentanyl 10-40 μg does not significantly increase respiratory depression risk but increases pruritus (NNH 3.3) 5

Systemic Non-Opioid Analgesics

Foundation Therapy

• Combination of two non-opioid drugs (NSAID plus paracetamol or metamizole) should always be used to reduce opioid rescue requirements 3
• NSAIDs combined with paracetamol provide superior analgesia and are essential when IV rescue opioids are unavailable 3
• Metamizole (where available) at 10-15 mg/kg every 8 hours or 2.5 mg/kg/h continuous infusion after loading dose 6

Intraoperative Adjuncts

• Intraoperative IV dexamethasone reduces postoperative pain and nausea/vomiting 1
• Methylprednisolone or dexamethasone reduce postoperative swelling 3
• Intraoperative ketamine as co-analgesic reduces opioid requirements 3, 7
• IV lidocaine infusion provides multimodal analgesia benefit 3, 7

Rescue Opioid Strategy

Immediate Postoperative Period (PACU)

• IV fentanyl in divided doses (0.5-1 μg/kg) for breakthrough pain 7, 6
• Adjust dosing based on hemodynamic response and pain level 7

Ward Management

• Transition to oral analgesics as soon as possible 3
• For major surgery, consider patient-controlled analgesia (IV-PCA) with appropriate monitoring 3, 7
• Reserve opioids only for rescue when basic non-opioid analgesia is insufficient 6

Procedure-Specific Regional Techniques

Caesarean Section

• Intrathecal morphine combined with basic analgesia (NSAIDs and/or paracetamol) is the standard approach 3
• Patient-controlled epidural analgesia with ropivacaine-sufentanil is an alternative 3
• Local anesthetic wound infiltration reduces pain scores and rescue analgesia needs in first 24 hours 3

Thoracic Surgery

• Continuous paravertebral block or thoracic epidural with long-acting local anesthetic plus clonidine provides superior analgesia 3
• Paravertebral blocks provide superior analgesia compared to wound infiltration alone 1

Abdominal Surgery

• Ultrasound-guided TAP or quadratus lumborum blocks combined with clonidine 3, 7
• Continuous epidural analgesia with local anesthetic plus clonidine for open procedures 3

Critical Safety Considerations

• Calculate all local anesthetic doses based on patient weight to prevent systemic toxicity 1
• Reduce amide-type local anesthetic doses by 30% in infants under 6 months 1
• Have resuscitation equipment immediately available when performing nerve blocks 1
• Accidental intravascular injection and excessive dosing are the most common causes of local anesthetic toxicity 8
• Monitor for respiratory depression when using neuraxial opioids, particularly morphine 5