W3: Anaesthesia rotation

Me monitoring a patient situated in the MRI chamber behind me. I am listening for heart rate via an esophageal stethoscope, while keeping an eye on the monitors for SPO2, EtCO2, BP etc

Most people have told me that anaesthesia was a relatively chilled week, but somehow I felt like it was pretty exhausting, maybe it was because I was churning out some content for the Cambridge Vet School’s Instagram page everyday for a week as well (@camvetschool by the way, if you wanted to check it out!) So I am quite relieved that I don’t have to do it anymore! Although I did enjoy seeing the audience engagement increased each time I posted something. Anywho on more pressing matters, here is a review of the anaesthesia rotation :)!

Overall thoughts and reflections

The first day was pretty chaotic (as with most first days) as we were still figuring out the routine of things. The thing with anaesthesia is that you arrive at Small Animal Theatre with your theatre scrubs and scrub shoes and then change into them with your name tag and put your scrub hat on to meet with the anaesthesia team for your induction/ briefing. (Oh, remember to bring water and snacks into the changing room too #essentials) There is a board with all the cases of the day with timings and people in charge of them and you sign up to a case each. When your case has been admitted, you change out of blue scrubs into your grey scrub top and normal clothes to go to wards/ reception etc to do a pre-assessment of your patient. You get really good at changing in and out of clothes real quick by the end of the week (I wore stretchy but formal-looking leggings to give myself some comfort, lol!) After you assess your patient, you come up with an anaesthetic plan with risk factors, considerations and your choice of sedatives, analgesic, anaesthetic agents etc. Then you discuss with the anaesthetist in charge about your plan, put in an IV catheter if needed, induce, intubate and start monitoring your patient’s vital parameters as required (useful to bring a fob watch and stethoscope with you!) Throughout the procedure you are monitoring your patient, with attention to their SPO2 , EtCO2 levels, blood pressure, heart and respiratory rate, temperature and to make adjustments to the anaesthetic agent or analgesia if needed.

What I found most stressful was during the critical moments of inducing your patient, as you need to ensure that they are at an adequate plane of anaesthesia to intubate ASAP in order to get oxygen (and/or medical air) into your patient. While monitoring your patient, you may get quizzed (which is also super awful but necessary evil- especially when you know you literally read it the night before, but I swear the stress just makes your brain go mush and delays your ability to recall facts..) so you are basically trying to do multiple things at once and I was pretty overwhelmed the first few times round (probably still am tbh).

What to revise to make the best out of your rotation

  • principles of anaesthesia – multimodal analgesia, the concept of targeting different levels of nociceptive pathways for analgesia, considerations for an obese patient, young patient etc
  • clinical exam for pre-anaesthetic assessment
  • anaesthetic machine check list
  • mechanism of action and common functions, effect duration of common sedatives, anaesthetic agents, analgesic drugs, for example:
    • alpha-2 agonists causes vasoconstriction -> leads to hypertension -> causing a compensatory bradycardia in patient (so you would expect to see some bradycardia in patient)
      • are sedatives but also have analgesic effects, can be antagonised by atipamezole (which works quite quickly in an animal, within ~5 minutes! I was v surprised)
      • takes about 10 minutes if given via IM in the animal to take effect,
      • duration: dose dependent -> NOAH resource
    • acepromazine ACP has loads of effects and mechanism of action
      • phenothiazine- main action central dopamine antagonist
      • a1- antagonism
      • anxiolytic
      • antiarrhythmic
      • antihistamine
      • duration: 6-8 hours
    • everything in the little clinical anaesthesia booklet
  • Minimum alveolar concentration MAC – the concentration of vapour in the alveoli of lungs that is needed to prevent movement (motor response) in 50% of subjects in response to surgical (pain) stimulus
    • MAC is used to compare strengths/ potency of anaesthetic vapours
    • Isoflurane – 1.3% in dog, and 1.6% in cat
      • Since it takes 1.3% of isoflurane to anaesthetise 50% of subjects, using it at 2-2.6% would theoretically anaesthetise 100% of subjects (and 2% is what I have commonly observed in past procedures done)
    • Sevoflurane – 2.4% in both species

Some things I learnt on rotation

  • anaesthesia considerations for obese pets
    • respiratory considerations- as increased intrathoracic fat (and intraabdominal fat) causes animal to be more prone to diaphragmatic splinting, respiratory depression
    • vet times article for more info
  • anaesthesia considerations for brachycephalic obstructive airway syndrome (BOAS) dogs
    • short nose breed dogs have a shortened skull and excess soft tissue relative to skull, resulting in compression of the nasal passage and excess pharyngeal tissue -> increased airway resistance, a.k.a. they cannot breath properly so a lot of care must be taken into account when placing them under general anaesthesia
    • potential risks in a BOAS dog
      • They are prone to airway obstruction during the perianaesthetic period hence need extensive monitoring and should not be left alone – in an acute emergency case of obstruction, first thing to do is to pull their tongue forwards to raise the larynx, which buys you some time to think about what to do next, and in severe cases you may need to re-intubate the dog
      • Regurgitation risk – 40-60% of BOAS dogs, can be caused by oesophageal diverticula, hiatal hernia.  A chronic increase in thoracic airway pressure also draws the stomach into  the chest, causing gastroesophageal reflux.
        • How to combat this – Fast BOAS dogs 3-6 hours prior to surgery
        • Prophylactic omeprazole, metoclopramide as regurgitation and cause gastric reflux of stomach acids that can harm the oesophageal lining
        • Keep HEAD RAISED, especially during induction
        • Intubate ASAP once pre-med and induced, inflate cuff ASAP to prevent possible regurgitation that can lead to aspiration pneumonia
        • If regurgitation has occured -> suction to remove the contents, or use a swab to remove as much as possible, you can even use a urinary catheter attached to a syringe to ‘suction’ it out
      • VIN article for more info
  • dental block seminar – purpose is to reduce systemic analgesia needed and provide a stable anaesthetic for patient during dental extraction procedures
    • types of dental nerve blocks
      • 1. mandibular – desensitizes the lower jaw including canine teeth, done extraoral (insert needle where the dip/notch lies on ventral ramus) or intraorally. When we did this, we put the needle in the appropriate area first before attaching the syringe containing lidocaine.
        • concerns: if done bilaterally, animal may lose awareness of jaw position and may clamp jaw down and traumatise tongue in the process, so better to do unilateral block or provide extra monitoring if unable to do unilateral.
      • 2. mental – desensitizes rostral mandible, incisor tooth
        • insert needle/ thread catheter through to the mental foramen
      • 3. infraorbital – desensitizes incisors, canine and first 3 molars (but depending on the dog’s facial conformation, may not provide sufficient coverage for the canine tooth root)
        • insert needle into infraorbital canal via infraorbital foramen
      • 4. maxillary – desensitizes branches of the maxillary nerve, upper rows of teeth and hard palate
        • 2 methods
          • a) thread a green catheter via infraorbital foramen to reach the nerve bundles located caudally
          • b) using lateral canthus of eye as a guide, follow to narrowest part of zygomatic arch and feed needle on the ventral aspect of the zygomatic arch to the nerve bundle area
      • 5. palatine – rarely done in small animal surgeries, more in equine
    • local anaesthetic agents – Na channel blockers
      • lidocaine
        • 5 minute onset time, duration of action: 1-2 hours
        • antiarrhythmic- effective for ventricular tachycardia tx but can be pro-arrhythmic in other heart conditions besides VT
      • bupivacaine
        • 20 minute onset time, duration of action: 6-8 hours
        • do not use IV! can cause myocardial toxicity, can cause arrhythmias
    • nb: if there is an area of infection like pus due to a tooth root abscess etc, the local anaesthetic (LA) would be less effective as infection increases acidity of the region. LA efficacy depends on the pH and pKa of the region.
  • non-rebreathing and rebreathing system review
    • vin article
    • useful to draw the breathing circuit out to help understand how it works
  • Westie WHWT breeds are prone to pulmonary fibrosis a.k.a. Westie lung, so although may not be picked up during lung auscultation exam, may see an abnormally high end tidal CO2 because of subclinical pulmonary fibrosis.

That is all from me for now! Stay tune for (hopefully) some vlogs coming up on the youtube channel 🙂 Oh! And I recently got a KO-FI link, so if you find the content on this blog useful, and would like to support to buy me a cup of coffee (no pressure!) You can do so here:

Buy Me a Coffee at ko-fi.com

3 thoughts on “W3: Anaesthesia rotation

    1. Hey Bella, thanks so much! Yes it is a big change but a great one indeed, I love doing more practical things and applying the knowledge we’ve learnt 🙂 having some case responsibility is a bit stressful but is all part of the learning process. What year of study are you in?

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