Unit 2- Inhalant Anesthetics Flashcards
Dissociative Anesthesia
Analgesia and sleep, different levels of the CNS are dissociated from one another
Dissociative Agents
Ketamine and tiletamine
Dissociative Anesthetics
Induce sedation, immobility, amnesia, and analgesia, reflexes are maintained, good somatic analgesia and poor visceral analgesia, poor muscle relaxation, affects fetus
Dissociatives Pharmacologic Effects
Increased cerebral blood flow and intracranial pressure, cardiac depression or paradoxical stimulation in healthy animals, apnea in cats
Cyclohexlyamine Effects
Described in humans, altered perception without hallucination, detachment and depersonalization, addictive, memory loss, hyperthermia, convulsions, and death
Cyclohexamine Influcences
Blank stare, confusion, chemical odor, cyclic behavior
Ketamine
Used for induction and maintenance of general anesthesia, used with sedative and muscle relaxant, for cats, dogs, small ruminants, swine, horses, and cattle
Ketamine Unique Properties
Hypnotic, analgesic, amnesic
Ketamine MOA
Interrupts connection between cortex and limbic system, stimulates opioid receptors, stimulates catecholamine release
NMDAR
N-methyl-D-aspartate receptors involved in excitatory glutaminergic neurotransmission, antagonized by ketamine
Ketamine NMDAR Antagonist
Affects NMDA receptors on GABA interneurons resulting in high GABA and low glutamate levels, affects many other targets as well
Ketamine Use
For minor procedures in cat, tranquilizer with opioids to induce anesthesia, constant rate infusion for analgesia
Ketamine Combination in Horse
Xylazine used as muscle relaxant prior to ketamine
Ketamine Combination in Small Animal
Xylazine, diazepam, midazolam, or dexmedetomidine used to prevent seizures and provide muscle relaxation
Ketamine Combination in Ruminants
Diazepam or xylazine used to provide muscle relaxation
Ketamine Adverse Effects
Seizures in horses and dogs, salivation and trancelike state in cats, and corneal ulceration
Ketamine Contraindications
Animals with corneal injury, animals with head trauma or tumors
Telazol
Tiletamine and zolazepam, short term anesthesia in uncooperative dogs and feral cats
Telazol Combination Horses
With xylazine and butorphanol
Telazol Combination Pigs
Xylazine and ketamine
Telazol Combination Ruminants
Alone or with xylazine
Telazol Adverse Effects
Muscle tremor, paddling, whining, and tachycardia in dogs, hyperthermia
Telazol Contraindications
Corneal ulcer or head trauma
Inhalant Anesthetics MOA
Unknown, likely not a single receptor
Inhalant Site of Action
Brain and spinal cord
Inhalant Administration
Administered by specialized equipment, through a mask connected to a vaporizer and delivery system
Inhalant Anesthesia Safety
Depth of anesthesia can be altered more rapidly, safer for liver and kidney problems, breathing 100% oxygen, intubated
Inhalant Anesthesia Disadvantages
Slower induction, requires special machine, safety issues
Inhalant Uptake
From the lungs, uptaken more rapidly with higher concentration
Inhalant Distribution
Determined by regional blood flow to CNS and other tissues
Inhalant Elimination
By the lungs
Inhalant Metabolism
Minimal hepatic
Vapor Pressure
Tendency of a liquid to enter the gaseous state, temp and anesthetic dependent
Volatile Agents
Higher vapor pressure, delivered from a precision vaporizer: isoflurane, sevoflurane, desflurane, halothane, diethyl ether
Nonvolatile Agents
Low vapor pressure, delivered from a non-precision vaporizer: Methoxyflurane
Blood:Gas Partition Coefficient
Measure of solubility of an anesthetic in blood as compared to air
Low Blood:Gas Partition Coefficient
Agent more soluble in alveolar gas than blood, faster induction and recovery
High Blood:Gas Partition Coefficient
Agent more soluble in blood than alveolar gas, slower expected induction and recovery
Minimum Alveolar Concentration
Measure of potency of a drug used to determine vaporizer setting, higher potency= lower MAC
Halogenated Compounds
Inhibit signals through GABA receptors, NMDA receptors, M and N receptors, and serotonin receptors: Enflurane, Isoflurane, Desflurane, and Sevoflurane
Halogenated Compounds Pharmacologic Effects
Reversible CNS depression, hypothermia, safe for epileptics, cardiac depression, ventilation depression
Halogenated Compounds Adverse Effects
Increase intracranial pressure, decrease blood flow and renal flow, hypoventilation, carbon dioxide retention and acidosis
Isoflurane and Sevoflurane
High vapor pressure, good for induction, stable at room temp, low blood:gas partition coefficient
Isoflurane
More potent than sevoflurane
Sevoflurane
Faster induction and recovery than iso, high controllability of depth of anesthesia, higher anesthetic index, more expensive
Isoflurane Pharmacologic Effects
Maintains cerebral blood flow, fewest cardiac effects, eliminated through lungs, good muscle relaxation, little analgesia
Sevoflurane Pharmacologic Effects
Maintains cerebral blood flow, minimal cardiac depression, eliminated through lungs, minimal hepatic metabolism, good muscle relaxation, little analgesia
Desflurane
Similar to iso, precision vaporizer, lowest blood: gas partition coefficient, rapid induction and recovery, least potent inhalant, eliminated by lungs
Halothane
Not commonly used besides pigs
Nitrous Oxide
Used by human medicine, sometimes used at room temp
Doxapram
Respiratory stimulant for shortening recovery after anesthesia
Doxapram Use
In neonate puppies and kittens after C-section, IV or sublingual
