Monday, August 5, 2013

Three things I learned: Top 10 mistakes to avoid in you dyspnoeic patients

Pericardial effusion in a feline patient.
Loyal SAT readers will know that I am a massive fan of webinars…you can sit in your pyjamas drinking cups of tea and soak up excellent information without struggling to find a car park (of course I do enjoy getting out from time to time, don’t want to be giving the wrong idea).

Dr Justine Lee presented a fantastic webinar on the common mistakes veterinarians tend to make in the management of dyspnoeic patients. The webinar was a promo for Vet Girl On the Run  a US-based tech-savvy CVE provider that produces podcasts and webinars that one can subscribe to.

Dr Lee is a board-certified emergency and critical care specialist, widely published in the scientific literature but an author in her own right. You can read more about her here

The webinar covered everything from TFAST (see below) to acute lung injury (ALI), acute respiratory distress syndrome (ARDS), breed predispositions and when to give blood vs oxygen.

I learned a lot, but if I had to pick three nuggets of wisdom this would be them:

  • I knew about FAST ultrasound (not dodgy ultrasound but Focused Assessment with Sonography for Trauma)…I just hadn’t heard of TFAST (add Thoracic to the acronym). One uses ultrasound to look for effusion at four sites. It’s likely more sensitive than thoracic radiographs in many cases and possibly less stressful for the patient. For effusions to cause dyspnoea you need about 20mg/kg of effusion fluid, which is easily picked up using TFAST. (It’s also a useful way of differentiating cardiomegaly from pericardial effusion).
  • Dr Lee was very adamant that vets over-radiograph dyspnoeic cats and really it doesn’t help that much prior to a chest tap. Her argument was very persuasive…she talked us through various thoracic radiographs in dyspnoeic cats and she was right…rarely did they yield a diagnosis or reveal something totally unexpected. Instead, she is an enthusiastic advocate of TFAST + bilateral thoracocentesis (and gave practical hints to this end). [The one exception is Siamese cats, esp those who smell like cigarette smoke, as they often have asthma or chronic disease which can make the lungs very friable and may lead to a post-tap pneumothorax].
  • Interestingly, although we are taught to aim for the 7th to 9th intercostal space, (if you go beyond the 9th you might find yourself aspirating liver), she is not a rib counter. Rather, she palpates to the end of the xiphoid and draws an imaginary line vertical from here…which takes her to around the 8th intercostal space. A nice shortcut when you have a dyspnoeic patient on your hands. She is guided by the history – if trauma and she suspects air she taps at the dorsal third of the chest, if fluid is suspected she taps ventrally.
  • Interestingly she said the most painful part of thoracocentesis is withdrawing the needle from the pleural space, so she tries to redirect it as gently as possible.
  • [I’m going to sneak in an extra thing I learned here: Northern breed dogs like huskies are predisposed to pneumothorax secondary to spontaneous bullae].
  • It’s easy to make assumptions when assessing the dyspnoeic patient but important to keep an open mind. For example, dyspnoeic small breed dogs with a heart murmur tend to have CHF - but if their HR is less than 150bpm its less ikely to be cardiac (e.g. congestive heart failure) in origin and more likely to be primary respiratory.
  • It can be hard to definitively diagnose ALI/ARDS but it is seen in animals with prolonged hypotension, aspiration of stomach contents, sepsis, trauma, pancreatitis, neurogenic pulmonary oedema, cirrhosis, toxic inhalation, animals which have undergone lung resection or multiple transfusions. There are no pathognomic findings but it tends to be acute on onset, not referable to CHF or left atrial hypertension, associated with severe hypoxaemia and visible as bilateral alveolar infiltrates on radiographs.

So that is more than three. 

I love listening to a speaker who has years of practical experience behind her. The talk was peppered with clinical examples (some hair-raising, but all helpful) and Justine and her associate Dr Garret Pachtinger were happy to answer a lot of questions on the topic.

(And one more thing I learned. Dr Lee is a keen toxicologist and discussed a number of her cases, and mentioned that albuterol inhalers are fine when used appropriately but when your dog chews on your cat’s puffer, the resulting albuterol overdose can lead to massive tachycardia, bronchodilation and hypokalaemia which can be life threatening).

If you missed the webinar there is another being held on Monday August 26 7-9pm, which in US EDT is the same as 9-11am in Australian EST.  The new topic is "Top 10 mistakes to avoid in your emergency patients" and you can register here. This is a complimentary webinar so if you'd like to try out this style of learning its worth setting the time aside.

UPDATE: If you want a more in depth review of respiratory physiology you might also want to enrol in the CVE's TimeOnline respiratory physiology course which starts today. The notes look excellent and there is good video and text support material.