75 | 4 things I wish I'd known earlier about caring for pyothorax patients
This episode’s topic is a messy, kind of gross, but oh-so-satisfying one - yep, today we’re chatting all things pyothorax nursing.
We’ll discuss what pyothorax is, the common causes, and the clinical signs, diagnostics, and nursing management - so you can care for these patients confidently.
Plus, I’ll share the biggest lessons I’ve learned from (too many!) years of caring for these patients, so you can spend less time learning the hard way, and more time giving great care.
First things first - what IS a pyothorax?
Pyothorax refers to the presence of purulent exudate (pus) inside the pleural space.
To recap from episode 73, the pleura are thin membranes that cover the inside of the thoracic wall, and the outer surface of the lungs and other intra-thoracic structures. These membranes, and the small space between them, allow the lungs to move without friction as the patient breathes.
In a pyothorax patient, the pleural space fills with purulent fluid, compressing the lungs.
What happens when a patient gets a pyothorax?
As our patients’ lungs can’t expand, they hypoventilate and can’t deliver enough oxygen-rich air to their alveoli. This means they also can’t deliver enough oxygen from the alveoli into the bloodstream to supply cells and tissues, since there isn’t enough oxygen there in the first place, meaning our patients become hypoxaemic.
These patients commonly present in respiratory distress, and need careful and prompt stabilisation, treatment and nursing care. But we’re getting ahead of ourselves - we’ve not chatted about WHY our patients get pyothorax yet, and which patients we commonly see the disease in!
Ok, so that’s what a pyothorax is - but what causes it?
Like many of our other medical disorders, there are a ton of reasons why a patient can develop pyothorax, and these vary somewhat depending on species.
Cats commonly develop pyothorax due to:
Bite wounds: Cats who have outdoor access or are prone to fighting are at the highest risk. Puncture wounds can introduce bacteria directly into the thoracic cavity, but as most bite wounds are very small, these can go unnoticed until clinical signs develop.
Migrating foreign bodies: Any foreign material that enters the airways can migrate through lung tissue and enter the pleural space, causing infection. This is a more common cause of disease in dogs, but we can still see this in cats, too. Common foreign bodies include grass seeds or other small fragments of plant material.
Parapneumonic spread: It isn’t just foreign bodies that move into the pleural space - bacteria from inside the lungs can spread to cause pyothorax, too.
Haematogenous spread: This is rare, but possible. Haematogenous spread refers to bacteria from elsewhere in the body travelling via the bloodstream and causing infection in the pleural space, too.
And then we have dogs. In general, we don’t see pyothorax in dogs anywhere near as often as we do in cats - but it does happen, and usually for different reasons. Common causes include:
Inhaled foreign bodies: It’s peak grass seed season as I am recording this, and in the last week we’ve already scoped out two airway grass seeds - so it’s probably no surprise that this is a common cause of canine pyothorax. Dogs running through fields of grass, wheat, barley, etc, will often inhale grass seeds which can then lodge in their lower airways and migrate into the pleural space where they cause infection.
Oesophageal perforation: I promise I am not blaming every canine pyothorax on foreign bodies, but oesophageal perforation - usually due to foreign body ingestion, particularly something sharp - is another cause of pyothorax. The gastrointestinal tract is not a sterile tract, and any perforation will lead to contamination and infection. Oesophageal perforations will also cause pneumothorax, as we mentioned last week, so these patients are especially high-risk.
Ruptured pulmonary or thoracic abscesses: Though they’re rare, intrathoracic abscesses can develop due to chronic infection, secondary to oesophageal perforation. If these rupture, the infection isn’t protected within the abscess capsule any more, and leaks freely into the pleural space.
Surgical complications: Hopefully, this isn’t something any of us see, but post-op thoracotomy patients (or chest drain placements for other pleural space diseases) are at risk of developing pyothorax, especially if asepsis was compromised during surgery or postoperative management.
Frustratingly, in many cases, we won’t identify a specific underlying cause from these lists. Most cases are idiopathic, where we don’t identify a clear source of infection.
If you’ve been where a while, you’ll know this is one of my least favourite medical terms, because we’re basically calling ourselves idiots who can’t find a cause. But regardless of whether we identify that underlying cause or not, our patient management is the same - prompt triage and stabilisation, and intensive ongoing care.
What signs do we see in pyothorax patients?
These patients usually present in respiratory distress, with signs such as:
Tachypnoea
Orthopnoea
Shallow breathing with a restrictive pattern
Increased abdominal effort
Alongside this, they usually have a history of more systemic clinical signs, including:
Lethargy
Depressed mentation
Weakness
Anorexia or hyporexia/inappetence
Pyrexia
Signs of dehydration
Clinical examination usually reveals muffled heart and lung sounds on auscultation, especially ventrally, as the fluid settles at the bottom of the chest. Patients may also show other cardiorespiratory changes, such as:
Bradycardia or tachycardia
Weak or bounding pulses
Pale or injected mucous membranes
Prolonged or very rapid CRT
Hypotension
These patients need to be stabilised promptly before we think about any further diagnostics, and that’s where we come in as nurses.
How do we stabilise these patients without stressing them out and tipping them over the edge?
Just like our other pleural space disease patients, pyothorax cases require careful stabilisation to prevent stress exacerbating their dyspnoea and significantly increasing their oxygen demand.
Add to this that these patients are usually cats - and we all know how poorly tolerant of handling, examination and veterinary treatment these guys are in general, anyway - so they’re even more challenging!
Prioritise a hands-off and stress-free approach initially, but know that it’ll only get you so far - there’s fluid sitting inside the pleural space impeding ventilation, so our patient will only improve to the extent the lungs are compressing them.
If I had a pyothorax cat in front of me right now, I’d approach them exactly like this:
Alert the vet if they do not already know about the case
Determine if they are critical and need emergency intervention (eg, you cannot wait due to concerns they may arrest)
If they are, prioritise IV access (if the patient is that unwell, they won’t be putting up a fight for this) and prepare intubation equipment and emergency drugs
If they are not, place the patient in an oxygen kennel and monitor them closely from a distance.
Consider clipping for an IV and applying local anaesthetic cream if the patient tolerates this without becoming highly stressed or more dyspnoeic.
If the patient is stressed, discuss with the vet and consider anxiolytic medication (eg, butorphanol) IM where appropriate.
Prepare equipment for IV catheter placement (if not performed already), emergency bloodwork, and thoracocentesis whilst the medication takes effect.
And once your patient is more stable, it’s time to think about diagnostics.
This usually starts with standard bloodwork and a point-of-care ultrasound scan (POCUS) to identify pleural fluid and guide thoracocentesis.
Speaking of thoracocentesis, like our other pleural space diseases, this is performed both for diagnostic AND therapeutic purposes. As well as relieving the pressure on the lungs and improving ventilation, we’ll collect samples for analysis to determine the type of pleural space disease our patient has.
Depending on where you are in the world, you’ll either perform this procedure under veterinary direction, or assist with it, carefully draining fluid whilst minimising excessive suction on the pleural space, as this can damage the delicate pleural lining.
Samples of the fluid collected are placed in both plain and EDTA tubes and submitted for cytology (which can also be performed in-house) and culture and sensitivity testing.
What about ‘proper’ imaging?
Thoracic x-rays will show areas of pleural effusion, retraction of the lung lobes, and pleural thickening. If available, however, CT is preferred - this gives us much more information about both the pleural space and the lung fields.
Both X-ray and CT images will be of far better quality if we drain the patient first, as this will ease ventilation and allow us to assess the lung fields more thoroughly. Usually, these patients are anaesthetised after initial stabilisation and centesis, for chest drain placement and more thorough imaging.
Ok, so you know your patient has pyothorax. How will you manage them?
Treating and caring for patients with pyothorax is varied, encompassing both medical and surgical management alongside chest drain management and supportive care.
These patients are often complex, but there are lots of great skills we can use when caring for them.
Let’s start by looking at medical management.
Alongside oxygen therapy and respiratory support, antibiotics are the main treatment. Appropriate IV antibiotics are given based on pleural fluid culture results; multiple antibiotics are often required/
These patients also need supportive treatment including intravenous fluid therapy (based on hydration status), analgesia, antiemetics and appetite stimulants if needed.
Then we’ve got chest drains to think about.
We mentioned back in episode 73 that not every pleural space disease patient needs a chest drain, but pyothorax patients absolutely do.
Whilst we will manage them medically with antibiotics, we also need to get as much of that purulent content out of the pleural space as we can. We can also lavage the pleural space to try and loosen consolidated pus, making it easier to remove.
Most patients will have bilateral chest drains placed. These must be handled aseptically and very carefully to prevent complications. Nursing considerations when managing chest drains include gentle drainage, aseptic handling and management, cleaning and redressing the drain sites regularly, and preventing patient interference. This is essential because if they damage their drain, it can let air in, rapidly causing a pneumothorax.
How do we perform pleural lavage?
To loosen that accumulated pus, we instil around 10ml/kg of warmed, sterile, isotonic crystalloid solution into the pleural space via the chest drains.
This fluid is left in place for around 10-15 minutes (depending on how the patient responds) and, during this time, the patient is encouraged to move around (if possible) and their respiratory rate, pattern and effort are monitored closely.
Once the dwell time has passed, the fluid is drained - usually, we’ll get more fluid out than we’ve instilled, and the fluid will appear more like diluted pus.
What if drainage and lavage aren’t enough?
Whilst medical management is fine for most patients, it isn’t always enough - severe cases may need surgery.
This is indicated in patients with persistent or localised effusion not responding to lavage, patients with foreign bodies or ruptured abscesses, or patients severely affected and not clinically improving despite medical management.
Usually, patients will require an exploratory thoracotomy with debridement and flushing/decontamination of the pleural space, and potentially a lung lobectomy if needed.
Post-op nursing for these patients is intensive, including pain management, nutritional support, hydration management, careful respiratory monitoring and chest drain care.
I used to feel so unsure when caring for these patients.
I knew what to do (because I was told), but I would feel very ‘out of my depth’ while I did it.
But 18 years later, with a lot more experience and confidence under my belt, I know we’re not here to just tick boxes and carry out vet orders - nurses and technicians play a vital role in managing pyothorax patients.
Here are the four biggest lessons I’ve learned over the years, and the things I wish I knew back then to help me care for these patients more confidently:
1: You often won’t know why it happens, and that’s fine.
Don’t get bogged down in why - the important thing is that there is an infection present needing management. Yes, imaging may show something specific, such as a foreign body or abscess (indicating surgery may be needed), but if not, it doesn’t really matter THAT much.
You’ll still have fluid for culture, you’ll still treat the patient with appropriate antibiotics, you’ll still place and manage a chest drain, and you’ll still nurse the patient the same way.
2: Don’t rush these patients into imaging.
X-rays won’t give you THAT much useful information - a point-of-care ultrasound or even a diagnostic thoracocentesis will give you just as much (if not more) info.
What’s more, these procedures usually need less restraint, and are better tolerated - so they’ll keep your patient’s stress levels down, too.
3: Don’t overthink draining - it’s not as complicated as it seems.
I always used to panic about draining chest drains.
“How will I know when to drain it?!”
“What should I look for?”
“When should I be worried?”
In reality, it’s way simpler than I initially thought. Drain your patient every 4-6 hours, depending on the volumes you’re getting out of the drains, and monitor the patient’s respiratory status regularly. If it changes, recheck the drain and see if more frequent emptying is needed.
4: Infection makes these guys feel pretty miserable, so supportive care is essential.
The infection, pyrexia, dehydration and anorexia we often see in pyothorax patients make them feel lousy, but luckily for them (and us!), it’s the nursing care, along with drainage, that really helps these patients.
So there you have it - that’s the lowdown on caring for patients with pyothorax as a vet nurse.
These cases are demanding, but they also let us use nearly every clinical skill we have, from emergency triage and stabilisation, to assisting with diagnostics and procedures, supportive care and monitoring, and client education and support.
As nurses and technicians, our role in caring for these patients is vast, and we really are essential to their recovery. Hopefully you’re feeling way more confident about caring for these patients after this episode - so go out there, get stuck in and use your skills!
Did you enjoy this episode? If so, I’d love to hear what you think. Take a screenshot and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout-out and share it with a colleague who’d find it helpful!
Thanks for learning with me this week, and I’ll see you next time!
References and Further Reading
Barrs, V.R. and Beatty, J.A., 2009. Feline pyothorax: a retrospective study of 27 cases in Australia. Journal of Feline Medicine and Surgery, 11(10), pp.803–810.
Bonagura, J.D. and Twedt, D.C., 2020. Kirk’s Current Veterinary Therapy XV. 15th ed. St. Louis, MO: Elsevier.
Clarke, D.L. and King, L.G., 2009. Thoracic drainage in small animals. Veterinary Clinics of North America: Small Animal Practice, 39(5), pp.849–862.
Demetriou, J.L., Foale, R.D., Ladlow, J., McGrotty, Y., Faulkner, J. and Kirby, B.M., 2002. Canine and feline pyothorax: a retrospective study of 50 cases in the UK and Ireland. Journal of Small Animal Practice, 43(9), pp.388–394.
Fossum, T.W., 2019. Small Animal Surgery. 5th ed. St. Louis, MO: Elsevier.
King, L.G. and Boag, A., 2007. Textbook of Small Animal Emergency Medicine. Ames, IA: Wiley-Blackwell.
Nelson, R.W. and Couto, C.G., 2020. Small Animal Internal Medicine. 6th ed. St. Louis, MO: Elsevier.
