Drug Summaries:





Adverse effects



  • Alpha-2 agonist
  • Sedative
  • Analgesic
  • Muscle relaxant
  • Reversible
  • Sedative effects last longer than analgesic effect
  • Bradycardia
  • Emesis
  • Salivation
  • Vasoconstriction followed by hypotension
  • Hypoventilation
  • Thermoregulation – matches env. Temp
  • Bradydysrhythmias or ventricular arrhythmias – potentially fatal
  • Catastrophic if cardiac dz is present



  • Dissociative anesthetic
  • Wide safety margin
  • Wide dose range
  • Safe agent – minimal CV and respiratory effects
  • 1-2 minute of onset
  • Preserves cranial and airway reflexes
  • Must be combined with a muscle relaxant
  • Lubricate eyes to avoid dry cornea
  • Does not provide good relief from  visceral pain
  • Muscle rigidity and involuntary movement
  • Convulsions
  • Prolonged recovery (especially if topping off)
  • Ataxia
  • Excitement/bizarre behavior, vocalization


  • Benzodiazepines
  • Mild sedatives
  • Centrally mediated muscle relaxation
  • Anticonvulsant
  • Synergistic effects with other drugs
  • No respiratory or CV effects at clinical doses
  • Can cause excitement if used on its own
  • Long ½ life = 21-37 hours


If something worries you = ASK FOR HELP

-       Don’t panic…

  • Xylazine – heart rate can easily drop to 30
  • Individual variability in metabolic rate / drug metabolism

-       Ask the surgeons to stop what they are doing

-       Reassess the patient without surgical stimulation

  • Check equipment – eg absent heart beat may be due to esophageal stethoscope moving cranially

-       Decide to administer more anesthetic drugs

  • Better to give lower top up and repeat if needed

-       Wait for drugs to take effect – at least 2 minutes

-       Consider Other drugs – eg Atropine


-       Emergency Situations

-       1st step – is it actually an emergency? 

-       Airway, Breathing, Circulation

-       Emergencies that you are most likely to see

  • Cardiac arrest – most likely (esp with Xylazine)
  • Respiratory arrest

-       Emergency action

  • Can you ventilate patient?
    • ET tube + manual ventilation with AMBU bag (avoid hyper/over inflation)
    • Is the heart beating?
      • Cardiac massage – 80-100bpm
      • Can you feel a pulse?
        • Carotid, femoral
        • Drugs:  Epinephrine, atropine, lidocaine
        • IV Fluid bolus = 90ml/kg over 15 minutes (dog)


Additional clinical notes:

-       If monitor every 5-10 minutes – will be able to spot any changes and will be able to intervene before a dog moves

  • BE CONSISTENT If you want to detect changes
  • Expect reaction when traction on ovarian pedicle (tachycardia, patient movement)
    • If on light plane, will wake up when start pulling ovarian and require top-ups

-       “Topping Up”

  • Ketamine:  Give fractions of induction does (eg Ketamine at 2mg/kg)
    • Repeated top-up doses can cause prolonged recovery
    • Max dose for anesthesia = 20-30mg/kg → We’re only using 5mg/kg
    • Xylazine:  Give 1/10 the initial dose
      • May supply 10-15 minutes additional relaxation and analgesia
      • Be aware of cardiovascular effects – BRADYCARDIA (reflex vagal response to vasoconstriction and hypertension and decreased sympathetic outflow from CNS)

-       Recovery will be prolonged à esp with lots of top ups

  • Ketamine may cause hallucinations, ataxia
  • Can use ace for dysphoria, but not in geriatric patients due to risk of hypotension

-       Likely problems to be encountered

  • Dogs with pre-existing conditions:  cardiac abnormalities, renal insufficiency, respiratory disease, emaciation, parasites
    • These should be assessed during our THOROUGH PHYSICAL EXAMS
    • Lightening of anesthetic plane → patient moving on surgery table
    • Regurgitation/vomit – why we intubate
      • May need to flush esophagus
      • Bradycardia – likely due to Xylazine
        • After 2 hours, bradycardia not likely related to xylazine anymore – probably OK to treat with Atropine
        • Poor quality recovery
          • Hypothermia!!!!!