Background and Aims Managing Fentanyl Induced Hyperalgesia (FIH) twice in the same patient.

Methods 43 years old ASA1 female, with unremarkable surgical history, underwent wide local excision of the left breast following the diagnosis of intraductal carcinoma. Intraoperatively she received paracetamol 1g, diclofenac 75mg and fentanyl 200mcg. The surgery was uneventful. In PACU she reported “worst pain of my life”. Surgical complications were excluded. Her pain score remained 10/10 despite administering fentanyl 25mcg increments (Total 125mcg). Her pain decreased to only 7/10 after 25mg pethidine increments (Total 100mg). Finally, after administering ketamine 20mg and midazolam 2mg, the pain completely subsided. She was discharged home on oral paracetamol and diclofenac.

She presented 4 weeks later for a left mastectomy. Opioid-free anaesthesia was the chosen approach. IV induction was performed with midazolam 2mg and propofol 300mg then an LMA was inserted. Ultrasound-guided left pectoralis I+II blocks were performed using 0.5%L-bupivacaine 30 ml. Paracetamol 1g, diclofenac75 mg, and ketamine20mg were administered prior to skin incision. Dexmedetomidine infusion was administered throughout the surgery (1.5mcg/kg/h). Anaesthesia was maintained with sevoflurane whilst breathing spontaneously. In PACU patient reported postoperative pain 2/10 then discharged to ward after 30 minutes. Regular oral paracetamol, diclofenac and breakthrough pain-relief tramadol 100mg orally were prescribed. The following day she reported being more comfortable compared to her previous surgery.

Conclusions

1. After excluding surgical reasons, FIH should be considered in all patients with refractory pain despite escalating doses of fentanyl.

2. Ketamine as a suitable rescue strategy, multimodal analgesia and opioid-free anaesthesia should all be considered on suspicion of FIH.