How to manage intraoperative pain in a patient undergoing Total Abdominal Hysterectomy (TAH) under spinal anesthesia with inadequate visceral or peritoneal analgesia?

Management of Intraoperative Pain During TAH Under Spinal Anesthesia

Your management approach using IV ketamine, midazolam, propofol, and dexmedetomidine infusion was appropriate for rescue analgesia when spinal anesthesia failed to provide adequate visceral coverage, though converting to general anesthesia or adding regional blocks would have been more definitive options.

Understanding the Problem

The pain you encountered represents inadequate visceral analgesia despite adequate somatic blockade at T6-T7. This is a recognized limitation of spinal anesthesia for abdominal hysterectomy, as visceral pain from peritoneal traction and organ manipulation requires higher sensory levels or additional interventions 1.

Why Your Spinal Failed for Visceral Pain

• Bupivacaine 20 mg with morphine 0.1 mg intrathecal provides excellent somatic analgesia but may not reliably block visceral afferents, particularly with significant surgical manipulation 1
• T6-T7 level may be insufficient for complete visceral coverage during TAH, as some studies suggest higher blocks or combined techniques are superior 1
• Intrathecal morphine (0.1 mg) primarily provides postoperative analgesia rather than intraoperative visceral coverage 2

Optimal Intraoperative Rescue Strategy

First-Line: Systemic Adjuncts (What You Did)

Ketamine 25-50 mg IV boluses were an excellent choice, as intrathecal ketamine has been shown to prolong analgesia compared to fentanyl in abdominal surgery 2. Your dosing was appropriate.

Dexmedetomidine infusion provides both analgesia and anxiolysis. Neuraxial dexmedetomidine improves intraoperative and postoperative analgesia when combined with bupivacaine 2. Your IV infusion at 4 µg at 6.4 cc/hr was reasonable for systemic effect.

Midazolam 1.5-2 mg total provided anxiolysis and amnesia. While intrathecal midazolam is inferior to other adjuvants 2, IV midazolam for sedation during inadequate regional anesthesia is acceptable 1. However, avoid excessive sedation that could compromise airway protection 3, 4.

Propofol 25 mg provided brief sedation but does not address the underlying pain mechanism 3.

Second-Line: Regional Rescue Options

Intraperitoneal local anesthetic instillation by the surgeon can reduce intraoperative visceral pain and improve early postoperative pain scores 2. Ask the surgeon to instill 20-30 mL of 0.25% bupivacaine intraperitoneally.

Local anesthetic wound infiltration by the surgeon reduces pain scores and rescue analgesia requirements 2. This can be done during closure.

TAP block (transversus abdominis plane) can be performed intraoperatively and significantly reduces both intraoperative anesthetic requirements and postoperative pain 2, 5. Bilateral TAP blocks with 20 mL of 0.25% bupivacaine per side would have been ideal 5.

Third-Line: Conversion to General Anesthesia

If pain persists despite systemic adjuncts, convert to general anesthesia with:

• Propofol or volatile anesthetic for unconsciousness
• Maintain spontaneous ventilation or secure airway with LMA/ETT
• Continue opioid-sparing multimodal approach 2

What You Should Have Done Differently

Prevention Strategy (For Next Time)

Use intrathecal fentanyl 25 mcg in addition to bupivacaine and morphine for better initial intraoperative analgesia 2, 6. Fentanyl provides superior intraoperative visceral coverage compared to midazolam (367 vs 254 minutes of analgesia) 6.

Consider combined spinal-epidural (CSE) technique, which provides the best analgesia for abdominal hysterectomy with only 2/40 patients experiencing discomfort 1. The epidural component allows intraoperative rescue with local anesthetic or opioid boluses.

Preoperative gabapentin 600-1200 mg reduces postoperative narcotic consumption and improves pain scores 2. This should be given 1-2 hours before surgery.

Preoperative paracetamol 1000 mg IV or PO decreases postoperative narcotic requirements 2. This is safe and inexpensive.

Critical Pitfalls to Avoid

Sedation Without Airway Control

Never deeply sedate a patient with inadequate anesthesia without securing the airway. Your incremental dosing was appropriate, but excessive midazolam or propofol could lead to airway obstruction 3, 4.

Ignoring Surgical Communication

Communicate immediately with the surgeon when pain occurs. Request gentler tissue handling, consider pausing for additional analgesia, or ask for local anesthetic infiltration 2.

Undertreating Visceral Pain

Visceral pain requires different management than somatic pain. Systemic opioids, ketamine, or regional techniques targeting the peritoneum are necessary 1. Simply increasing sedation without addressing the pain mechanism is inadequate.

Missing the Fentanyl Opportunity

Adding intrathecal fentanyl to your initial spinal would have prevented this scenario entirely, providing 6+ hours of superior intraoperative analgesia 6. The concern about acute opioid tolerance only applies when fentanyl is combined with morphine in the presence of additional intraoperative opioids 2.

Postoperative Considerations

Your patient already has intrathecal morphine 0.1 mg, which provides excellent postoperative analgesia for 12-24 hours 2. Ensure multimodal analgesia with:

• NSAIDs (ibuprofen or ketorolac) unless contraindicated 2
• Paracetamol 1000 mg every 6 hours 2
• Monitor for respiratory depression from intrathecal morphine for 24 hours 2
• Avoid excessive systemic opioids given the intrathecal morphine already on board 2