Clinical Case 043: Post-op pain puzzle

This case comes from Dr Jonathan Ramachenderan.

59 yo man presents with a small bowel obstruction likely secondary to adhesions. He has a background history of 4 previous laparotomies for recurrent bowel obstructions and Chronic Back pain with a spinal fusion 10 years previously.

He appears chronological older than his age and currently takes 100mg BD of Morphine Sulfate, Tramadol SR 150mg BD, Paracetamol SR 775mg TDS and Duloxetine 30mg. His renal and liver function is normal and he is intolerant of NSAID due to gastric irritation.

The procedure is long due to difficult division of adhesions and takes 5hours. He requires 30mg of Morphine intraoperatively and receives 100mg of Tramadol and 1gram of Paracetamol. Ketamine is considered but not given.

Possible alternatives: TAP blocks, Continued Ketamine boluses and or infusion

2 hours later he is in extreme pain, moaning, uncomfortable and unmanageable on the ward. You are called to assess and manage him.

Ketamine infusion is started (0.1-0.2mg/kg/hr) [80kg = 8-16mls/hr of Ketamine 200mg in 200mls] PCA bolus is increased to 2mg with a background of 3mls (3mg) an hour

There are multiple calls through the night as the patient’s analgesia isn’t adequate. He is uncomfortable and obviously distressed when you see him the next morning. He isn’t able to move in the bed and simply lifting his gown to examine him is painful. He has used 200mg of morphine in 16hours.

TAP block is preformed for the patient’s acute pain (Tranversus Abdominis Plane identified under ultrasound and 20mls of 0.25% bupivacaine is infiltrated bilaterally). TAP Blocks are described here at the NYSORA site,  evidence for their efficacy is here from Anaesthesia-Analgesia  2007, McConnell Et al.

His opioid is rotated (morphine to fentanyl) and opioid requirement is revisited and an equivalency is calculated (200mg oral morphine = 1200mcg fentanyl/ 24hours). He is then given a background of 50mcg/hour with a 20mcg bolus.

Methadone is also started intravenously 10mg BD.

Ketamine is continued at 0.1mg/kg/hr.

His pain relief is instant following the TAP block on the ward. The opioid rotation helps to alleviate his pain and as his oral intake begins, he is re-started unto a lower oxycontin dose (75mg BD) with breakthrough oxycodone. His ketamine is first to come down as his pain remits and his fentanyl PCA is soon to follow. He is also commenced unto his regular tramadol with pregabalin 50mg TDS.

On discharge the “Reverse analgesic ladder” is described and handed over. The patient’s preoperative opioids are given together with his oral “as required” opioids titrated down over 1-2 weeks. This is on a baseline of multimodal analgesia. Importance of multimodal analgesia is that multiple analgesic agents are additive and synergistic in their action and opioid sparing.

Great Case JR!  We will run a second post discussing the theory and practicality of managing post op pain in chronic pain patients soon.  Love to hear your feedback and pearls around this scenario.  Thanks – Casey.


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