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.
2 hours later he is in extreme pain, moaning, uncomfortable and unmanageable on the ward. You are called to assess and manage him.
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.
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.
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.
First10EM Journal Club: October 2018
Clinical Case 050: Think Better, Do Better
Dabigatran – Clexane you can swallow
About The Author
Casey Parker
I am a GP working in Broome, NW of Western Australia. I work as a hospital DMO (District Med Officer) doing Emergency, Anaesthestics, some Obstetrics and a lot of miscellaneous primary care. Also on the web as @broomedocs | + Casey Parker | Contact
great case JR and talk about a multimodal analgesic cake approach!
firstly well done for getting on top of the post op pain in the end. can be very tricky in the chronic pain patient
I have to ask why the dose of ketamine infusion was so low? There are published series of palliative care patients being run on 20-40mg ketamine per hour for up to several weeks as a SC infusion…often in an outpatient or home setting. analgesic doses are cited often at 0.5mg/kg onwards.
Also reading the case, this patient was a sitting duck for opioid withdrawal given his chronic requirements, it seems a lot of the post op symptoms were related to that, right?
does that explain the use of methadone?
I’ve been using lots of norspan in recent years, to switch some of my chronic pain (the oxycontin/panadeine forte crowd) over to a patch formulation with less abuse potential
Works a treat
Until of course they get an acute problem and require opiates in hospital…
For this chap I’d have considered TAP blocks at the end of the case, plus a fentanyl/ketamine PCA post-op (how was he in recovery before hitting the ward?
Methadone’s also pretty useful – have you used the IV form at induction – seems to give good relief for up to 16hrs post op
Thoughts?
Hey Tim!
Hows the anaesthetising going?
Totally agree with your management post operatively. TAP blocks would have worked well, catheters even better.
As you will see in the upcoming discussion he was placed unto a morphine PCA in which he used solidly in the first 16hours -> this didn’t seem to work at all, appearing to worsen his pain -> opioid induced hyperalgesia.
He was also allodynic and hyperalgesic as a result of “wind up” or central sensitisation which even when touched he nearly jumped of the bed.
From my memory he was fine in recovery.
I haven’t used methadone on induction but with this case and a few others I am happy to use it when required, another one added to my repertoire!
Thanks Minh
The use of a Ketamine at a sub anaesthetic dose (0.1-0.2mg/kg) was used here for a couple of reasons.
Firstly to help with Opioid induced hyperalgesia (he was using more and more morphine with little clinical improvement of pain), secondly to help reduce the “wind up” pain the patient was experiencing due to the lack of appropriate analgesia and thirdly to reduce the progression to chronic post surgical pain.
-> the discussion to follow will explain a little more!
Yes he absolutely was a sitting duck. The point of the case and the what struck me as we managed him post operatively was how early identification and perioperative and post operative planning would have produced a different outcome
Perioperative use of a NMDA antagonist such as Ketamine or preoperative pregabalin/gabapentin would have helped immensely to reduce the incidence of wind up, chronic post surgical pain and reduce his acute opioid consumption.
So to complicate his pain further he was most likely experiencing opioid withdrawal during his heightened pain misadventure. The use of IV methadone was indeed indicated here and worked amazingly well. Methadone is also a weak NMDA antagonist helping to reduce OIH and wind up.
Hope that helps. The discussion will have some meat and evidence.