Ketamine

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Ketamine is an N-methyl-D-aspartate (NMDA) receptor antagonist, used as a tranquilizer, antiemetic and analgesia agent for treatment of neuropathic pain syndrome[1], or as a premedicant prior to general anesthesia.

At high, fully anesthetic level doses, ketamine has also been found to bind to opioid μ receptors and sigma receptors and induce a state of dissociative anesthesia[2].

Ketamine has a rapid pharmacological action characterised by profound analgesia, mild cardiac stimulation, normal pharyngeal-laryngeal reflexes, mild respiratory depression and markedly increased intraocular pressure[3].

This drug causes complex reactions in the brain depressing certain areas and stimulating others, which enables it to anesthetize and cause seizures in overdose[4].

It increases the release of dopamine and noradrenaline which are excitatory and increase the release or serotonin, which is a depressant. It produces paralysis with some muscle rigidity, good analgesia, complete amnesia. Many reflexes are retained; swallowing, coughing, pedal, corneal, laryngeal, however the animal does not blink and the cornea should be kept lubricated during long operations.

Ketamine can be used in isolation or in combination with other drugs such as xylazine, acepromazine, diazepam or medetomidine[5].

Ketamine also allows for reduced requirements for halothane, isoflurane[6] or sevoflurane[7].

It may have a role in "resetting" of the central nervous system in maladaptive pain states.

Ketamine can be used for routine surgical procedures when administered in combination with diazepam, medetomidine, propofol[8] or xylazine for desexing[9].

As a sole agent, it can be given for minor procedures such as catheterisation associated with urolithiasis.

This drug is contraindicated in canine patients with glaucoma, seizures or chronic renal disease.

Recommended dose ate is 10 - 20 mg/kg, given subcutaneously, intramuscularly, epidurally[10] or intravenously as a constant rate infusion at 0.5 - 1.0 μg/minute[11].

References

  1. Rojas AC et al (2012) The effects of subarachnoid administration of preservative-free S(+)-ketamine on spinal cord and meninges in dogs. Anesth Analg 114(2):450-455
  2. Chohan AS (2010) Anesthetic considerations in orthopedic patients with or without trauma. Top Companion Anim Med 25(2):107-119
  3. Kovalcuka L et al (2013) The effects of ketamine hydrochloride and diazepam on the intraocular pressure and pupil diameter of the dog's eye. Vet Ophthalmol 16(1):29-34
  4. Haskins SC et al (1985) Ketamine in dogs. Am J Vet Res 46:1855–1860
  5. Ko JC et al (2013) Influence of ketamine on the cardiopulmonary effects of intramuscular administration of dexmedetomidine-buprenorphine with subsequent reversal with atipamezole in dogs. J Am Vet Med Assoc 242(3):339-345
  6. Aguado D et al (2011) Reduction of the minimum alveolar concentration of isoflurane in dogs using a constant rate of infusion of lidocaine-ketamine in combination with either morphine or fentanyl. Vet J 189(1):63-66
  7. Love L et al (2011) The effect of ketamine on the MACBAR of sevoflurane in dogs. Vet Anaesth Analg 38(4):292-300
  8. Mannarino R et al (2012) Minimum infusion rate and hemodynamic effects of propofol, propofol-lidocaine and propofol-lidocaine-ketamine in dogs. Vet Anaesth Analg 39(2):160-173
  9. Baba MA et al (2012) Pinhole castration technique: An alternative to orchiectomy in stray dogs. Anim Reprod Sci Dec 8
  10. DeRossi R et al (2011) Evaluation of thoracic epidural analgesia induced by lidocaine, ketamine, or both administered via a lumbosacral approach in dogs. Am J Vet Res 72(12):1580-1585
  11. Bednarski R et al (2011) AAHA anesthesia guidelines for dogs and cats. J Am Anim Hosp Assoc 47(6):377-385