Anaesthesia of the collapsed patient Flashcards
What are the top tips for success of anaesthesia of the collapsed patient?
- Reduce stress and anxiety - even thought he animal may seem subdued
- Endotracheal intubation (laryngoscopy, suction)
- Close monitoring
- Titrate/calculate drug doses depending on case
- Careful monitoring (colour, SPO2%, capnography, RR and effort, ABP, ECG, temp)
- Pain relief
- Enrich oxygen supply >35% FiO2%
- Judicious IVFT
Is general anesthesia or heavy sedation safer?
General anesthesia as it ensures a secured airway (ET tube and oxygen), monitoring and control
A young bulldog (with known BOAS stage 3) presents to the practice on a hot summer day, he collapsed after walking into garden. The dog is panting and gasping for breath. The pulse is regular and rapid 132 bpm. The mucous membranes are mauve/pink. CRT is 2.5 seconds. Based on this limited history, where is the problem in the tree of life?
* Mitochondrial function
* Heart rate
* Microcirculatory flow
* Haemoglobin saturation
Haemoglobin saturation
What are the different types of hypoxia?
- Hypoxic hypoxia
◦ Not enough oxygen available to lungs
◦ Low FiO2, hypoventilation, pulmonary disease, BOAS, PDA, fibrosis - Anaemic hypoxia
◦ Reduced haemoglobin content
◦ IMHA, haemorrhage - Circulatory hypoxia
◦ Cardiovascular impairement
◦ Hypovolaemic, septic shock, PTE, DCM and systolic failure - Histotoxic hypoxia
◦ Cells can’t use the oxygen
◦ Mitochondrial problem, cyanide
What is the difference between hypoxia and hypoxaemia?
Hypoxia is low oxygen levels in thetissuesand hypoxemia is low oxygen levels in theblood. Hypoxia is often caused by hypoxemia but not always. You can be hypoxic but not hypoxemic and vice versa.
How can you diagnose hypoxaemia?
- Pulse oximeter, & or blood gas analyser
- Visual observation of mucous membrane colour (not very accurate)
What oxygen saturation and arterial partial pressure of oxygen should prompt oxygen supplementation?
Rule of thumb oxygen saturation below 93% and an arterial partial pressure of oxygen below 70 mmHg should prompt oxygen supplementation
Why is supplying oxygen by flow by not ideal?
- This modestly enriches the FiO2, but only 25-40% if high oxygen flow rates are used (2 to 3 L/min)
- Often not well tolerated by all patients
- Can further contribute to anxiety
What is the downside of supplying oxygen with a mask?
- Rebreathing of carbon dioxide can occur with tightly fitting masks, and periodically switching out the mask is recommended
What are the pros and cons of oxygen cages?
- Physical separation of the clinical team from the patient
- Reduces anxiety
- Good for small patients
- Able to perform nebulization without close handling
- Disadvantage is this approach may ‘miss’ changes
- Expensive
What FiO2 will 1 or 2 nasal lines provide?
- 1 line achieves FiO2 30-50%
- 2 lines achieve FiO2 30-70%
What drug classes should you not use in the premedication/sedation of collapsed patients? What should you use instead?
Avoid
◦ NSAIDs
◦ Alpha 2 agonists
◦ Acepromazine
Use
Opioids (methadone, fentanyl and lidocaine)
What would you use to induce anaesthesia in collapsed patients?
- Propofol or alfaxalone (low end of dose range)
- Propofol or alfaxalone then benzodiazepine then more propofol or alfaxalone
◦ (ie co-induction, theory is it might reduce total dose of propofol or alfaxalone…..) - Ketamine and benzodiazepine
How should you deal with hypotension during anaesthesia?
Defined as BP values of systolic <80–90 mm Hg, mean <60–70 mm Hg, and diastolic <40 mm Hg
- Switch down the volatile agent and consider PIVA – see if this works
- Try an IV bolus of crystalloid (5-20ml/Kg) occasionally colloids are used – see if this works
- If the animal is bradycardic too? Administer anticholinergic (atropine/glycopyrrolate)
- Can then consider an inotrope or vasoconstrictor
- Don’t forget hypothermia/ hypoglycaemia and electrolyte imbalances too
