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Tag: Respiratory

  • Pulse oximetry is great, but know its limitations

    Pulse oximetry is great, but know its limitations

    Pulse oximetry is a very useful diagnostic and monitoring tool that has become commonplace in veterinary clinics. It measures the percentage of haemoglobin saturated with oxygen, and is an indirect measure of arterial oxygen levels.

    pulse ox
    Dog with pulse oximetry.

    However, here are several important points to help you understand the limitations of pulse oximetry.

    Causes for false readings

    Falsely low readings:

    • motion artefact
    • peripheral vasoconstriction/low tissue perfusion from hypothermia or shock
    • pigmentation of mucous membranes
    • thick hair coat

    Falsely high readings:

    • haemoglobin abnormalities (carboxyhaemoglobin and methaemoglobin, for example)

    False sense of security

    Pulse oximetry can give us a false sense of security. We hold on to the adage “95% and above means everything is going along swimmingly”, but that couldn’t be further from the truth:

    Dog with pulse oximetry
    Pulse oximetry can give us a false sense of security.
    • It does not detect hypoventilation or apnoea: it can take several minutes for apnoea to result in hypoxaemia that is detected on pulse oximetry; therefore, it cannot be used as a sole measure of respiratory adequacy. This is best measured by capnography.
    • A common misconception is the oxygen saturation will drop with patients with anaemia. This is incorrect. The haemoglobin present in the decreased number of red blood cells will still be saturated to normal levels. However, this cannot be interpreted as the patient having adequate oxygen delivery to its tissues.
    • One last point: due to the oxyhaemoglobin dissociation curve, any drop below 94-95% is significant and warrants investigation. At 95% SpO2 the partial pressure of oxygen in the arterial blood is 80mmHg (normal), but at 90% SpO2 the partial pressure is 60mmHg (severe hypoxaemia) – for only a small percentage decrease, there is an exponential reduction in arterial oxygen content. This is even more important when patients are receiving oxygen therapy as the patient’s SpO2 should be 99-100% normally. So when a patient has an SpO2 of 95%, but is on high rates of oxygen, then significant respiratory compromise/disease must be present for an SpO2 of 95% or lower to occur.
  • Anaesthetic risks: when complacency sets in

    Anaesthetic risks: when complacency sets in

    Adverse events during anaesthesia in otherwise young and healthy patients is a rare occurrence. However, with low incidence of adverse events could come an increased risk of complacency on the part of the veterinary team.

    Take the following case as an example:

    Clicky
    Clicky the cat with Gerardo and his team.

    “Clicky” is a young and healthy cat that underwent a routine dental prophylaxis procedure. A few days after the procedure, she developed respiratory difficulties and presented to our emergency clinic.

    Possible problems

    She was diagnosed as having severe subcutaneous emphysema, most likely from a tracheal wall compromise that would have occurred as an adverse event from tracheal intubation.

    We need to handle cats very gently while they are intubated as their tracheas are nowhere near as robust as their canine counterparts.

    Overinflating the cuff is another cause of tracheal necrosis.

    Never be complacent

    What we think happened was the patient was repositioned during the dental procedure and the endotracheal tube was twisted in the process, causing either ischaemic compromise to a portion of the trachea or direct damage to the trachea.

    Thankfully, “Clicky” made a full recovery, but this case certainly highlights that we must never be complacent when it comes to handling our anesthesia cases.

    Low incidence does not mean no incidence, and individualised anaesthetic plans – along with in-depth training for the anaesthetist (who most often are veterinary technicians and nurses) – will help reduce the chances of adverse events occurring.

    Clicky's x-ray
    Clicky’s x-ray
  • Mentor tip: CSF taps

    Mentor tip: CSF taps

    I remember my first CSF tap; my hands were shaking – not ideal when you are advancing a needle towards the spinal cord.

    If you go a couple of millimetres too far, the needle goes into the spinal cord and it could cause the patient to go into respiratory arrest.

    Some things I am happy to try on my own after researching, but this was not one of them.

    Subjective versus objective

    I remember being told you should feel a “pop” when you are entering the right place, but what does feeling a “pop” actually feel like or mean? This subjectiveness is what made CSF taps so stressful for me.

    The advantage I had was that my mentor was there, and removed the subjective “pop” and replaced it with an objective “see fluid”. My mentor knew the risks, but understood the importance of emergency vets knowing how to do CSF taps, as an early diagnosis of meningitis can save a patient’s life.

    Mentor’s method

    What my mentor did was create a way of teaching CSF taps that minimised risks – by teaching to look to see if you actually “see fluid”.

    He said to advance the needle 1mm at a time, then stop and look down the hub and the barrel of the needle, and check for CSF. If you’re in the right spot it comes out within a second or two.

    This method may take longer, as you are advancing the needle much more slowly, but it makes the whole process safer as you could objectively know when you are in the right spot.

    Experience

    If you are a mentor, then you are very experienced. However, it is this experience that means we can lose perspective and forget how difficult some of the things we do actually are.

    So, if you are faced with a situation where you have to teach a mentee something with high risks, rather than avoiding teaching it and doing it yourself all the time, consider ways of reducing the risks while teaching it, or teach it in a way that has additional steps that are more objective and make it safer for first-timers.

    What high-risk procedure or task have you been taught to perform by a good mentor?

  • Festive threats to four-legged family members

    Festive threats to four-legged family members

    Now well into December, and getting ever closer to Christmas, there will be an abundance of “goodies” around the house that are not so good for the four-legged family members.

    Image: © Freeimages/s22k.
    Jordan advises colleagues to ensure clients keep an eye on their pets during the festivities. Image: © Freeimages/s22k.

    Most owners are aware of the dangers of chocolate and so are likely to rush down to the vet on Boxing Day when their Labrador has broken into the tin of Heroes – but what other festive dangers are there that owners are not so clued up on?

    Pudding

    The festive favourite Christmas pudding, while enjoyable for us, can be lethal for pets. It is the raisins, currants and sultanas that may lurk within that are poisonous.

    While the mechanism of toxicity is poorly understood, we know it can cause acute kidney failure in dogs.

    The treatment protocol for poisoning by raisins, etc, is similar to general suspected poisoning with an unknown agent: give an emetic (to make the animal vomit), an adsorbent (for example, activated charcoal) and supportive care (IV fluids) to protect the kidneys for a few days.

    Antifreeze

    Ethylene glycol, more commonly known as antifreeze, is extremely toxic to pets, with consumption of tiny amounts resulting in crystal formation in the kidneys, and so acute renal failure. Antifreeze smells and tastes sweet, so pets are often attracted to it. For this reason, it is best for owners to ensure it is kept in a secure container, well away from pets.

    Early symptoms include neurological signs, such as wobbliness, twitching, seizures and depression. As the poisoning progresses, the animal will have cardiac and respiratory signs, such as increased heart and respiratory rate. It’s vitally important owners look out for these signs if their pets have had any possible access to antifreeze (for example, if they’ve got into the garage or if a cat has been missing for a few days and potentially been locked in someone’s shed).

    The antidote for ethylene glycol poisoning is ethanol, because it replaces ethylene glycol as a substrate for the enzyme that breaks it down into toxic products. More specifically, lab-grade ethanol is best.

    Sweetener

    Xylitol is a sugar-free sweeter that is used in chewing gum, cakes and sweets, particularly diabetic foods. Xylitol causes insulin release in the body, resulting in hypoglycaemia and, later, liver damage.

    Symptoms include vomiting and signs of hypoglycaemia: lethargy, weakness, collapse and, if it progresses, seizures and coma. Unlike ethylene glycol, there isn’t a specific antidote, but supportive care, including fluids and liver protectants, is vital. The prognosis for xylitol toxicity is good if the animal’s hypoglycaemia is corrected quickly, so it is essential for owners that suspect this to contact their vet immediately. If you’re trying to determine whether xylitol is in a product, it is often listed as a food additive, code E967.

    Decorations?

    And don’t forget the potential foreign body too – if the cat has been playing with the tinsel and managed to swallow some or the dog has ingested a few tasty looking baubles.

    Enjoy the festive season, but advise owners to keep an eye on their pets this Christmas.

  • The wrong end of the telephone

    The wrong end of the telephone

    Pepsi3
    Jordan and Pepsi in happier times.

    A couple of weeks ago, I received the phone call I’ve been dreading since moving away to university.

    My horse had had an accident in the field, hurt her leg, and the vet was on the way. That’s all the information I received until the next call, with the vet on the other end.

    “Communication within the tarsal joint… leg swinging… don’t think the long bone is actually fractured but significant damage to tendons at the back… rapid respiratory rate.”

    As soon as I knew which way the conversation was going, I barely heard the rest.

    My girl, who I’d had for 10 years. My girl, who’d been passed from pillar to post before we gave her the stable long-term home she’d never had. My girl, who had taught me to ride by being an infuriatingly awkward cow at the best of times.

    My girl, who, when in the mood, was unbeatable and with whom I achieved a national title. My girl, who was the only one I trusted not to hurt me after my four-week stint in hospital when another horse landed on me. My 21-year-old girl, who’d been steadily getting stiffer from arthritis over the last few months. My girl, who, when I last rode about a week before this incident, was 10 times better than she’d been in a long time.

    pepsi2
    “My girl, who, when in the mood, was unbeatable and with whom I achieved a national title.”

    My girl was about to be shot…

    All the vet language stopped making sense, the clinician rationale went out the window. I just needed to know one thing, vet to vet student: is this fair? Could it wait five hours for me to tear down the M6 to say a final goodbye or would even that be an unnecessary amount of suffering?

    I think I already knew the answer.

    I felt utterly helpless and beyond reason for the following days, but as the shock wore off I was able to consider things retrospectively.

    Having spoken to the family that were with her at the time, I’ve gathered a bit more information and been able to convince myself it was the right and only decision.

    pepsi1
    RIP Pepsi.

    I’ve seen many animals have to be euthanised, for varying reasons. Some cases were more upsetting than others, but, for the most part, I’ve been able to detach myself from it – always telling myself it was for the best, in the animals’ interest for welfare reasons, and that there were no alternatives.

    They say clients will only take in a small proportion of bad news. Now I know what that means. All the vet talk just went straight over my head, and the only thing I really got was that there was only one way it was going. This has outlined the importance of clear and concise communication when delivering bad news to my own clients in the future.

    In communication skills classes, we’re told to encourage owners to bring someone with them who can write down key points and ensure they understand before proceeding. Now I appreciate the value of this so much more, having been the receiver instead of the bearer of bad news.

    While the pain is still raw, I think I can take something from this to help me be more empathetic and ensure I communicate effectively in the future.

    You can steal all the ham sandwiches you want now, Pepsi.

     

    pepsi4