Analgesia for pancreatitis

Providing analgesia for the pancreatitis case always raises a few questions. Are we talking acute or chronic cases? Let’s look at both and address those queries with some practical tips for case management.

In the acute setting I think we see three grades of pancreatitis. Those that respond well to partial mu agonists and dietary change, those that require full mu agonists and hospitalisation and those really sick cases that require intensive care. It’s the last category I tend to see most.

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Opioids

Opioids are our first line analgesics in pancreatitis with full mu agonists such as methadone being preferred over partial agonists like buprenorphine. Buprenorphine may be appropriate for those mild cases. We no longer worry about spasm of the sphincter of Oddi (which is not actually present in the vast majority of dogs) which was always voiced as a reason to avoid full mu agonists such as morphine and methadone. Reasons to avoid full mu agonists would be the fact that they can make nausea worse and so I would always work to reduce our dose and frequency where possible by looking at some of the following strategies. We know maropitant is useful in reducing morphine-associated vomiting and so it makes sense to add this therapy in our pancreatitis cases. My first line opioid is methadone at 0.3mg/kg IV – but I always add an adjunct for a multimodal approach and that would be lidocaine as a CRI. Other opioid options are fentanyl as a CRI which avoids the sedation you see with intermittent boluses of methadone. Rates for fentanyl are 2-5mcg/kg/hr. Some US colleagues see butorphanol as an effective analgesic when used as a CRI but cost tends to limit this in the UK.

Lidocaine CRI

Lidocaine has an anti-inflammatory effect with peripheral and central actions. In an inflammatory disease such as pancreatitis we are limited with options that provide a reduction in those factors that act to sensitise nociceptors (see queries over NSAIDs below) and so lidocaine is a suitable adjunct to our opioid therapy. Rates of lidocaine are quoted from 25-100mcg/kg/min – although in conjunction with opioids it is rare to exceed 50mcg/kg/min and below 25mcg/kg/min may not be effective. Exercise caution with doses in hypoproteinaemic cases – lidocaine is highly protein bound and where plasma proteins are low, there is more free drug available so you need to reduce your dose.

Lidocaine is useful to reduce your opioid dose or frequency of dosing. There is a question over whether lidocaine has a prokinetic effect in dogs and whether it may exacerbate nausea. I would always bear this in mind if after 24 hours the dog looks more nauseous – it may be worth reducing the lidocaine rate in these cases.

Maropitant

Yes – to reduce nausea. Is it analgesic? I hope to see at some point some definitive evidence that it is analgesic. (The MAC reduction studies are out there but remember that MAC reduction does not necessarily mean analgesia). Theory is that it inhibits substance P and therefore reduces activation of pain processing. Could it work synergistically with opioids or other analgesics? This is a watch this space question.

NSAIDs

Whilst I love NSAIDs and see a real value in reduction of inflammation in pancreatitis cases, we do need to consider the degree of gastro-intestinal inflammation occurring concurrently with acute pancreatitis.

How about those osteoarthritis cases which suffer with bouts of pancreatitis but are painful with their OA? I can see a role for cautious NSAID use in these cases and am sure many of you have experience of such cases.

Paracetamol

In lieu of NSAIDs and in an attempt to reduce our opioid use, I will always add paracetamol to an analgesic plan for dogs (not cats). This is not for an anti-inflammatory effect as we know this is not the predominant mechanism of action. In cases where you have given an opioid and the dog looks a little more comfortable, but you feel the pain scores could be lower, this is where I use paracetamol. Half an hour later, you will see a more comfortable dog.

For dogs that will not tolerate NSAIDs in the chronic setting, paracetamol can be effective and you can read more here about long term use of paracetamol in dogs.

Ketamine CRI

So far I’ve structured this post in the order I would think about these cases. I’m a big fan of ketamine as a CRI – particularly as many of these patients have had low grade pain for a while and could have a component of central sensitisation. Rates for ketamine are listed in this post. I use ketamine alongside opioids, in a very similar manner to how I would use lidocaine – going for that multimodal approach which allows us to use lower doses of all drugs and therefore reduce side effects.

Local anaesthesia

In those cases that are refractory to analgesia, epidural delivery of opioids and local anaesthetics can have a dramatic effect in breaking the cycle of pain. This can be done as a single injection or for continuous delivery an epidural catheter can be placed. If pancreatitis cases are being sedated for diagnostics then this is the time to think about an epidural.

Specifics for cats

Different opioids suit different cats and in my experience cats with pancreatitis or triaditis respond well to buprenorphine. If the cat is particularly sick, these are the cases were I will reduce my buprenorphine dose from 0.02mg/kg to 0.01mg/kg – otherwise you will have a very sedated kitty.

A ketamine CRI works wonders for those cats that are still uncomfortable after opioids – rates are the same as for dogs – 0.3mg/kg/hr (5mcg/kg/min).

In lieu of an NSAID, I find gabapentin an effective adjunct. Work in people shows that it is an effective visceral analgesic – we don’t have the evidence in cats. Dose would be 5-10mg/kg TID.

In summary, our aim is to improve comfort in these cats whilst at the same time avoiding sedation and reducing nausea. With a multimodal approach this is possible.

This post was written by Carl Bradbrook.

Matt & Carl established Zero Pain Philosophy to provide educational resources to veterinary professionals enabling optimal management of pain.

Matt Gurney is an RCVS & European Specialist in Veterinary Anaesthesia & Analgesia and works at Anderson Moores Veterinary Specialists. Matt is Vice-President of the European College of Veterinary Anaesthesia & Analgesia.

Carl Bradbrook is an RCVS & European Specialist in Veterinary Anaesthesia & Analgesia and is President of the Association of Veterinary Anaesthetists. Carl works at Anderson Moores Veterinary Specialists.