Sometimes the best CPD is some that you hadn’t considered attending in the first place. I’d seen the Exhibitor Stream at BSAVA Congress and had noticed the Docsinnovent lecture, but hadn’t made concrete plans to attend until I’d stopped by their stand and had a chat with Chris Geddes, Dawn Sheppard and Muhammed Nasir.
Most people have probably heard about their v-gel product for rabbits, but I hadn’t seriously considered their cat product, nor their forthcoming dog product. Why? Probably for the same reason as everyone else – I’m not at all comfortable intubating rabbits, but intubating cats and dogs? No problem.
Well, maybe I was missing a trick. It turns out the reason Docsinnovent came up with the v-gel was not for ease of insertion at all, but to avoid some of the problems that can occur with ET tubes. In cats, not causing laryngeal spasm or tracheal rupture is a big bonus. In dogs, I was told, managing reflux and regurgitation will be a major benefit.
I’ll admit, I wasn’t initially convinced – after all, reflux is rare, isn’t it? Regurgitation’s even rarer, I thought – that’s why we starve our patients, and why we tube them, and that sorts things out nicely, doesn’t it? When was the last time you saw a patient regurgitate under an anaesthetic? Still, it sounded like there was more to learn. So, a few hours later I was listening to “Reflux and regurgitation: what can you do to protect your small animal patients during anaesthesia?” with Ivan Crotaz and Muhammad Nasir.
By the end of it, I felt like I had met Luke Skywalker, except he’d just finished telling me: “Incredible. Every word you just said was wrong.”
Full credit to Ivan and Muhammed: unlike Luke Skywalker, they spent the hour courteously, respectfully and effectively taking attendees on a tour of just how reflux and regurgitation works, and how often (and why!) it happens in the first place – and why it’s a bigger problem than I realised.
Muhammed discussed data from the human side, and I was impressed at just how extensive the research was – thousands of patients over decades, with anywhere from 10 to 80 percent of patients having some form of reflux- or regurgitation-related complication. Obviously this depends significantly on quite a few comorbidities and complicating or emergency situations, but Ivan went through a review of the more limited veterinary data, which showed reflux in 13 to 55 percent of patients (33 percent in cats!). There was more going on than I thought.
It was pointed out that as a surgeon, I’m poking around inside the patient, and unless I happen to be looking down the throat in the middle of a bitch spay, I’m probably not actively looking for reflux. Neither is the veterinary nurse – they’re busy monitoring the anaesthetic, and unless they have a pressing reason to look down the throat, they’re taking the clinical parameters externally.
Many of the issues that increase the risk of reflux and regurgitation are connected directly to the upper and lower oesophageal sphincter. Ivan’s descriptions of the function and anatomy of the oesophagus were excellent. Essentially, a combination of anatomical and physiological factors ensures the “valves” don’t release acid or bile into the oesophagus.
Unfortunately, many things can interfere with this mechanism. There are breed predilections (deep or barrel-chested animals), and risks from obesity (one more reason not to like fat bitch spays!) – with interesting things having an effect. I was surprised to hear that right lateral recumbency increases the risk of reflux, for instance. And while “legs over” turning won’t cause a stomach twist, it can increase the risk of reflux significantly – as will leaving a patient’s head stretched out straight.
It will surprise no one that pushing up on the stomach or increasing pressure in the cranial abdomen may increase your risk of reflux, and with it oesophagitis, post-operative pain, oesophageal strictures, laryngospasm and aspiration pneumonia. Longer periods of fasting can increase risks – in fact, the American Animal Hospital Association now recommends five hours starving before anaesthesia.
Canine v-gel will have a small channel that directs reflux well out of the airway – it’s a clever design, and you can insert a small catheter and flush (and suction) the oesophagus with saline (and acid binders) to prevent mucosal injury. Until it’s available, an oesophageal tube can be used alongside an ET tube to direct reflux away from the vulnerable oropharynx. It’s worth noting that according to Ivan and Muhammed, while a mildly cuffed low pressure ET tube is helpful, it’s not an ironclad defence against aspiration.
I’m going to be actively looking for reflux now, and not just regurgitation. We’re likely to be getting some v-gels in for our high-risk patients, now that I know who they are. Fasting recommendations are going to be overhauled as well. Ivan’s recommendations for pre-anaesthetic medication in at-risk patients (proton pump inhibitors or H2 blockers) are also going to get a trial.
