NMDA Receptor Antagonists Flashcards
What does NMDA stand for
N-Methyl-D-Aspartate
Ketamine is used for..
Induction of anesthesia & dissociative anesthetic (ketamine produces profound anesthesia by dissociating the animal from its surroundings)
Analgesia for acute or chronic pain
Chemical restraint
Central sensitization - reduce wind up pain and hyperalgesia, esp in chronic pain patients
Is ketamine an analgesic?
Yes,
it blocks NMDA receptors in the CNS at the level of the spinal cord - preventing windup!!!
Somatic - can receive pain but not respond
Effective for managing acute, chronic and neuropathic pain
Ketamine:
Controlled?
Yes, ketamine is a controlled drug
Is ketamine reversible??
No reversal agents for ketamine!
Ketamine:
Onset & duration
Onset: 1-5 mins
Duration: 10-30 mins
Routes: IM SQ IV & orally
What parts of the pain pathway does ketamine act on?
Blocks NMDA receptors in the CNS at the level of the spinal cord
-Preventing windup
Modulation = spinal cord
Effects of ketamine
Dissociative anesthetic (dose needed to block pain receptors is much less than needed to induce anesthesia (used in CRI)
Analgesic
Prevents windup - Modulation
Good somatic (skin & limbs)
Mild muscle rigidity
What does increasing the dose of ketamine do?
Increasing the dose increases the length of anesthesia - not depth
Where is ketamine metabolized and secreted?
In the liver and secreted in the urine
CAUTION: in hepatic & renal patients
What is ketamine often combined with?
Diazepam for induction agent
TITRATE
CAUTIONS with ketamine:
No reversal
Increases CO, HR, CVP (central venous pressure)
Increases intracranial pressure
Better tone to blood vessels
Highly protein bound
(Decrease dose in liver dysfunction, tachycardia, bronchodilation, apneutic breathing, increase muscle tone)
CNS - seizures, head trauma (ICP, IOP)
Kidney dz cats
Mod organ dysfunction
Hallucinations
What does ketamine do to CNS? and what might state might our patient be in?
Catalepsy (unresponsive, muscle rigidity)
Intact reflex’s: more challenging to determine anesthetic depth - central dilated eyes & stay open, normal/increased muscle tone amnesia, nystagmus, hallucinations
Trance like state; appears awake but immobile and unaware of surroundings
What does ketamine do to the cardiovascular system?
Increases HR, CO, and BP
Decreased isotropy
Is ketamine safe in seizure and head trauma patients?
No
Amantadine
Antiviral properties
Chronic Pain management
Oral
Duration: 24 hrs
Effects of Amantadine
Neuropathic pain relief
Central sensitization reduction (windup)
What is Amantadine used for?
Chronic pain
Osteoarthritis
Cancer
Adjunct w NSAIDS or opioids
General effects of NMDA receptor antagonists
Analgesia
Dissociative anesthesia
Central sensitization
Adjunctive use for enhanced pain control or sedation
General side effects of NMDA receptors
Increases HR, Intracranial pressure and muscle rigidity
CAUTION in animals w heart dz, head trauma or seizure patients
Reversal agents of NMDA receptor antagonists
NMDA antagonists don’t have specific reversal agents 😢
BUT may be combined w drugs to mitigate side effects
ex. Benzodiazepines for muscle relaxation
Does ketamine provide good analgesia
No - not analgesic!
