When you come in and look at your ‘ops list’, what thoughts spring to mind?

For me, it was always surgery. When I worked in general practice, I never really distinguished between ‘out of theatre’ procedures and ‘surgical’ procedures… because if you were on the theatre shift, your job for the day was to get everything on that list done.

In reality, though, many of our ‘ops’ are not even on surgical patients! And that’s one of the reasons why I believe all nurses should understand the different medical procedures and diseases.

We know that our patients need a lot of different procedures. Whether that’s performing x-rays, ultrasound or endoscopy to diagnose a disease… or placing something like a chest drain or oesophagostomy tube as part of their treatment, it’s our responsibility as veterinary nurses to know how to anaesthetise our medical patients for these procedures.

In the first of two posts on anaesthesia for medical procedures, we’ll be discussing all of the anaesthesia considerations for our most common endoscopy procedures! Whether your patient is having investigations into GI disease, or they’ve got a respiratory disease needing investigations, you’ll feel much better about anaesthetising them by the end of this post. 

Before we start…

Before we jump into the different endoscopic procedures and how they affect our anaesthetics, I want to remind you of a couple of fundamental principles.

The first (and I can’t say this enough) is that every one of our patients has some kind of illness or disease. And this will affect their anaesthetic considerations in some way.

This may not just be the signs they present with - they may also have concurrent cardiac disease, or endocrine disease, for example. And these comorbidities will all change the way we approach their sedation/GA.

That’s one of the reasons why thorough pre-anaesthetic assessments and  individualised anaesthetic plans are vital.

If you’ve not read last week’s post, read more about some of the fundamental medical anaesthesia principles here.

Let’s talk endoscopy!

We perform a variety of endoscopic procedures in our patients, including:

• Upper GI endoscopy: an examination of the oesophagus, stomach and duodenum

• Lower GI endoscopy: an examination of the ileum and colon

• Upper and lower GI endoscopy: an examination of all the above areas

• Bronchoscopy: an examination of the trachea, bronchi and lower airways

• Rhinoscopy: an examination of the nasopharynx and nasal cavities

• Cystoscopy: an examination of the urethra and urinary bladder

There are a ton of other fun things we can do endoscopically, such as laser treatment, stent placement and balloon dilation of strictures. I’m not going to go into detail on those things here, as they’re very specialised (and I’ll end up on a tangent about how fun endoscopy is). But just be aware that these procedures can also adjust our anaesthetic plan!

In today’s post, we’ll be focussing on the 3 most common endoscopy procedures - GI endoscopy, bronchoscopy and rhinoscopy.

Gastrointestinal endoscopy

Patients requiring GI endoscopy can present in a variety of conditions. Many have malabsorption, so are in poor body condition with weight and muscle loss. Some may have varying degrees of anorexia or hyporexia, some will have severe/ongoing vomiting or diarrhoea, and some will have gastrointestinal ulceration and haemorrhage, causing anaemia.

General considerations

Particular things to be aware of when anaesthetising these patients include:

• Fluid balance: Many of these patients will have dehydration and/or hypoperfusion due to ongoing gastrointestinal fluid losses. We need to perform a thorough hydration/perfusion assessment, correct any hypovolaemia ASAP after presentation, and correct dehydration prior to anaesthesia.

• Electrolyte and acid-base status: Our GI patients will present with varying degrees of electrolyte and acid-base abnormalities. These can vary from metabolic acidosis due to diarrhoea, to metabolic alkalosis due to vomiting. Patients with vomiting may also be hypochloraemic, and anorexic patients may be hypokalaemic, for example. These abnormalities should be addressed prior to anaesthesia.

• Albumin status: Patients with protein-losing enteropathy may have low albumin levels, impacting colloidal oncotic pressure and intravascular volume. With this comes concerns over things like blood pressure, perfusion in general, and temperature.

Pre-GA

Prior to the procedure, these patients will be fasted from 12-36 hours, depending on the area to be examined. Lower GI patients require a longer fasting time, as we need their colon to be emptied prior to the procedure. 

They are also often given bowel cleansing solutions, causing large volumes of liquid diarrhoea to be passed. This itself can have an impact on hydration status, so we need to keep a close eye on this during pre-procedure preparation.

Warming is an important consideration in these patients, especially those with poor body condition who may lose heat faster. This warming should ideally begin prior to induction.

During the procedure

Following induction, there are a few things to be aware of:

• Hypoventilation and overdistension of the stomach: In order to examine the GI tract, it must be inflated. The endoscope blows air into the oesophagus, stomach and intestines to inflate them, allowing visualisation of the mucosa. When the stomach inflates, it can push against the diaphragm, causing hypoventilation. This is often seen as hypercapnia during the procedure. If you notice your end-tidal is creeping up, check the stomach doesn’t feel too full, and if you’re worried, ask your vet to suction some of the air out.

• Regurgitation and aspiration risk: Many patients with upper GI disease have some evidence of gastro-oesophageal reflux during endoscopy. Where fluid is present within the oesophagus, this presents a regurgitation/aspiration risk during and after the procedure. If your vet notes that refluxed material is present in the oesophagus, you can ask them to suction this to minimise the risk of post-op regurgitation. If large volumes of fluid are present, or the fluid is quite thick, you can flush water down the endoscope biopsy channel, and then suction this back to flush the oesophagus.

• Medications such as omeprazole may be required during the procedure (and continued in recovery) if gastrointestinal ulceration or oesophagitis has been seen during the scope.

Post-procedure

On recovery from GA, these patients should be monitored closely for regurgitation (if an upper GI endoscopy has been performed, or if they have presented with a history of vomiting or regurgitation pre-GA).

They should receive ongoing warming until they remain normothermic, and careful attention should be paid to fluid balance.

Many of these patients will have specific nutritional requirements after their endoscopy, so it is worth double-checking with the vet if they would like a specific diet (e.g. a hydrolysed or low-fat diet) to be used after the procedure.

Endoscopy itself is not typically a painful procedure, but gas distension of the GI tract can be uncomfortable - so the vet should suction out as much air as possible from the GI tract as they withdraw the endoscope.

One thing we do need to consider, though, is that GI diseases can be painful - so even if the endoscopy isn’t painful, the patient may still need postoperative analgesia.

Bronchoscopy

Anaesthetising patients for bronchoscopy can be a challenge. These patients are presenting because they already have some kind of respiratory disease - they may be stable with a history of chronic cough, or they may be oxygen-dependent with suspected pneumonia. 

On top of their existing respiratory signs, we are then going to compromise their ventilation further by putting an endoscope in their airways!

These patients can be risky GAs and require careful pre-anaesthetic planning and close communication between team members. Here are my considerations for bronchoscopy patients.

Pre-GA

• Pre-oxygenation: We want to increase oxygen reserves as much as possible, so pre-oxygenating these patients is an important consideration.

• Maintenance: We need to think about how we’ll keep these patients asleep. Many patients will require extubation for endoscopy, and if that’s the case we can’t use inhalant anaesthesia. Larger patients can remain intubated and the endoscope passed through the ET tube (unless we need to examine the proximal trachea). However, there is still a risk of environmental gas leakage, so we need to consider alternative methods. We will place all of our bronchoscopy patients on TIVA (total intravenous anaesthesia) - typically a propofol CRI for dogs, and an alfaxalone CRI for cats (depending on the individual patient). This means preparing the CRI and a syringe driver and knowing the normal dosage ranges for maintenance.

• Bronchodilators: Many patients will require a dose of bronchodilator (e.g. terbutaline) prior to their procedure. This is done in patients where there is a higher risk of bronchoconstriction/spasm - so for that reason is something we tend to do in our feline patients. We give a dose I/M (I/V can cause marked tachycardia) around 60-90 minutes prior to the procedure. For those patients who don’t need it pre-GA, we pre-calculate an emergency dose and have a vial on hand in case it is needed during the procedure.

During the procedure

Careful monitoring of oxygenation is the main consideration during bronchoscopy. We always say ‘the anaesthetist is in charge’ - meaning if the nurse monitoring the patient isn’t happy with their oxygenation, the scope doesn’t enter the patient.

It’s really useful to agree on cut-off values for SpO2 before beginning the procedure. For example, we usually say that at 92%, the scope comes out and the patient is given time on 100% oxygen before trying again. This way, the entire team know when to stop.

During the procedure, a reliable SpO2 trace is key. If you don’t have one, don’t allow your vet to begin scoping - ask them to wait until you can reliably monitor oxygenation.

Once you’ve got a good trace, keep communicating the SpO2 level - tell them if it is dropping, and if you need to ask them to remove the endoscope temporarily, do.

If your patient has a large enough ET tube, you can pass the endoscope through the middle of the tube via a special elbow connector. This allows the patient to continue breathing 100% oxygen during the procedure.

However, if you need to extubate your patient to pass the endoscope into the trachea, we can’t do that. This means we need to find a way of giving oxygen alongside the scope. We do this by taking a rigid urinary catheter, placing an ET tube adaptor on the end, and intubating the trachea with this alongside the scope. The urinary catheter can then be attached to the breathing circuit to administer oxygen.

On recovery

Recovery is a risky time for these patients, since they are at risk of desaturation or complications such as bronchoconstriction in recovery.

Patients may need to continue oxygen therapy in recovery - if they were receiving oxygen prior to the procedure, this should be continued and their saturation regularly re-assessed.

If the patient was not oxygen-dependent prior to the procedure, their saturation should be closely monitored in the initial recovery period, and oxygen supplementation stopped when they are consistently saturating normally.

Patients should be kept quiet and calm, and their respiratory rate, pattern and effort assessed regularly in recovery, alongside thoracic auscultation and SpO2 measurement.

Rhinoscopy

Rhinoscopy is the assessment of the nose and nasopharynx. Typically, these patients will have an initial assessment of the nasopharynx with a flexible endoscope, and then a rigid rhinoscope will be placed into the nostrils to examine the nasal cavities. Nursing considerations for these patients are varied and include:

Pre-procedure

Prior to the procedure, coagulation status should be checked. Rhinoscopy and nasal biopsies run the risk of significant haemorrhage, so we need to ensure these patients can stop bleeding effectively.

This means assessing platelet levels +/- coagulation times (activated partial thromboplastin time and prothrombin time). A buccal mucosal bleeding time may also be performed in some cases.

Many patients will also have advanced imaging of the head before their rhinoscopy. This typically involves a CT scan with the administration of I/V contrast (iohexol). This can be nephrotoxic, so renal parameters should be assessed prior to the procedure. IV fluids are also given during the procedure and in recovery, to help eliminate the contrast media and avoid associated renal injury.

During the procedure

Analgesia is an important consideration during the procedure. Most rhinoscopies themselves are not especially painful, but the nose is very sensitive. Despite an appropriate anaesthetic depth, we can sometimes see reflex head-shaking or movement when beginning the procedure.

Local anaesthetic blocks are useful tools for these patients. They are also something that can (in most cases) be performed by nurses under schedule 3 - as long as those blocks don’t enter a body cavity. For our rhinoscopy patients, maxillary or infraorbital nerve blocks can be used to desensitise the nose prior to the rhinoscope being inserted.

Aspiration is another important consideration during a rhinoscopy procedure. In most cases, continuous saline irrigation is used in the nose. This comes with a significant aspiration risk - so we need to ensure we’re using a well-cuffed ET tube, packing the throat, and listening to the chest regularly for any crackles which could indicate aspiration.

If you’re using HMEs (heat and moisture exchangers), pay close attention that these don’t end up with fluid inside them, too. If you’ve got any concerns about aspiration during the procedure:

• Ask the vet to pause the endoscopy

• Check the ET tube for fluid

• Check the capnograph line and water trap for fluid

• Check the HME for fluid and change the HME as necessary

• Check the throat packs +/- change these as necessary

• Check the ET cuff is still appropriately inflated

• Suction +/- change the ET tube if needed

In recovery

Epistaxis is a risk in recovery for these patients. If there is ongoing haemorrhage from the rhinoscopy/nasal biopsy sites, recover the patient slowly and only once the haemorrhage has slowed/stopped. Medications such as tranexamic acid or phenylephrine can be applied topically (tranexamic acid can also be given systemically) to help with haemostasis. Cold packs can also be applied to the nose to try and stop haemorrhage.

Ongoing monitoring for these patients includes regular pain assessment and administration of analgesia as appropriate, as well as continued monitoring for epistaxis and aspiration.

References

1. Bovens, C. 2016. Lower airway disease in cats [Online] Vet Times. Available from: https://www.vettimes.co.uk/app/uploads/wp-post-to-pdf-enhanced-cache/1/lower-airway-disease-in-cats.pdf

2. Cox, S. 2016. Endoscopy for the Veterinary Technician. Iowa: Wiley-Blackwell.

3. Merrill, L. 2012. Small Animal Internal Medicine for Veterinary Technicians and Nurses. Iowa: Wiley-Blackwell.

4. Tucker, P.K. and MacFarlane, P. 2019. Incidence of perianaesthetic complications experienced during feline bronchoscopy: a retrospective study. Journal of Feline Medicine and Surgery, 21 (10), pp. 959-966.

5. VetEducation. 2023. Clinical use of tranexamic acid in the dog [Online]. Available from: https://veteducation.com.au/clinical-use-of-tranexamic-acid-in-the-dog/