Test 1- Induction meds Flashcards
Induction of anesthesia
Transition from a (semi-) conscious state to unconsciousness
Dangerous and stressful event
Priorities:
o Establish patent airways, give oxygen o Maintain cardiovascular function
o Maintain anesthesia
Induction happens almost invariably via administration of a short acting anesthetic iv
Injectable anesthetics
Dissociative anesthetics
o Ketamine, tiletamine, phencyclidine
Propofol
Barbiturates
o Thiopental, pentobarbital Imidazole derivates:
o Etomidate, metomidate
Neurosteroids: alphaxalone, alphadolone
Ketamine
Old but relatively safe anesthetic
Onset is slower than that of thiopental
Has an active metabolite
Eliminated slower from cats than from dogs Dysphoria may be present during recovery
Ketamine: CV effects
Direct negative inotropic effect
Causes catecholamine release (sympathomimetic effect) therefore indirectly increases HR and contractility
Danger: if the catecholamine stores are depleted (very sick patient) or under anesthesia (catecholamine release inhibited) negative inotropic effect may dominate!
Ketamine: respiratory effects
Minimal respiratory depression!
Apneustic breathing (breath hold at full inspiration)
FRC of the lungs is higher than with other agents
Bronchodilation (useful in asthma)
Upper airway reflexes may work (gagging) but do
not function well
Intracerebral pressure (ICP)
The body compensates via squeezing out CSF and blood volumes from the skull
If the critical volume is reached pressure goes up and the brain herniates
There is hardly any perfusion in that state and the prognosis is grave
The anesthetist can manipulate IC blood volume therefore can control ICP!
Factors increasing cerebral blood volume
Hypercapnia, hypoxia Hypertension
Effect of drugs!
Ketamine: CNS effects
Cerebral vasodilation: intracerebral volume and pressure increase (ICP)!
May worsen cerebral perfusion and cause brain herniation in patients with elevated ICP
Cerebral metabolic O2 consumption increases
May be seizurogenic but may also be used to
treat epileptic seizures
Indications of ketamine
Hypovolemic shock
Asthma
Most risk patients may tolerate it in small doses
Useful for chemical immobilization of
aggressive animals
Contraindications of ketamine
Brain trauma or tumor
Perforating eye injury
HCM and most other heart diseases
Epilepsy
Telazol
Contains tiletamine (similar to ketamine) and zolazepam (benzodiazepine)
Effect is similar to diazepam-ketamine, but Telazol is longer acting
Formulated as powder to be diluted as needed
Useful for aggressive small animals or wild animals
Propofol
Fast onset short duration
Fast metabolism in the liver
No accumulation
Smooth induction and
recovery
Ideal for TIVA
The basic formulation does
not contain preservative Give only IV
Propofol: CV effects
Vasodilation (hypotension) Negative inotropy (mild effect)
No reflex tachycardia
Propofol: respiratory effects
Respiratory rate decreases
Apnea possible (depending on dose and
speed of administration)
Tidal volume decreases
Does not inhibit laryngeal movement (intubation may be difficult)
Propofol: CNS effects
Cerebral vasoconstriction
Intracerebral blood volume and ICP decreases!
Cerebral metabolic O2 consumption decreases
Has antiepileptic effect and may be used to terminate status epilepticus
May cause muscle twitches
