Anesthetic Pre-medications - Sedatives Flashcards
(29 cards)
what is the purpose of anesthesia
to numb pain and/or induce inconsiousness
how does anesthesia work
blocks nerve signals at the level of the CNS (general anesthesia)
block nerve signals at thevel of PNS at a specific location (local anesthesia)
what are the main steps in anesthesia protocol
- Premedication: to reduce anxiety and pain before anesthesia
- Induction: to rapidly and smoothly produce state of unconiusness - IV
- Maintenance: keep patient unconscious - inhaled
- Recovery: emergance from general anesthetic
what are different types of premeducations
- sedatives/anxiolytics/neuroleptics
- analgesics
- muscle relaxants
- anticholinergics
role of sedatives as premedication
- inhibit irritabiliy and excitement
- cause some degree of sleepiness
role of anxiolytics as premedication
- inhibit apprehension and fear
- does not induce sleepiness/hypnosis
- formerly known as “minor tranquilizers”
role of neuroleptics as premedication
- results in emotional detachment (apathy) and suppress agitation-related movement
- also known as anti-psychotics or “major tranquilizers”
- many have sedation properties too
what are the benefits of using sedative/anxiolitic drugs before surgery as premedication
- easier surgical preperation
- reduces anesthetic dose needed and therefore chance of side-effects
- smoother recovery for patients
3 classes of pre-medications - sedative and anxiolytics
phenothiazines: neuroleptic/sedative
alpha-2 agonists: sedative
benzodiazepines: sedative/anxiolytic
clinical effects of Chlorpromazine - a Phenothiazine
- reduction of fear and anxiety
- sedation
- muscle relaxation
clinical indications of Chlorpromazine - a Phenothiazine
- reduction of agitation before surgery
- *also main use to treat schizophrenia
Phenothiazine’s mechanism of action
- block dopamine D2 receptors in the brain
- D2 blockade causes sedation, reduced agitation
- also blocj peripheral a1 receptors - side effects
side effects of Phenothiazine’s
- have to do with peripheral a1 receptor blockade
- vasodilation and hypotension
how do phenothiazines (chlorpromazine) cause hypotension
- when they bind to a1 they block NE from binding to carry out vasoconstriction
clinical effects of Dexmedetomidine - an Alpha2 agonist
- sedation/hypnosis (sleepiness)
- analgesia (pain relief)
- muscle relaxation
clinical indications of dexmedetomidine - an Alpha2 agonist
- for seation in adults prior to and/or during surgical procedures
Alpha2 agonists mechanism of action
- selective for a2 receptors
- in presynaptic neurons cause K+ channels to open and Ca2+ channel suppression (inhibitory)
- leads to membrane hyperpolarization and inhibits NT release
Inhibiting NT release by dexmedetomidine binding a2 receptors leads to…
- sedation (instead of wakefulness)
- analgesia (instead of pain)
- hypotension (instead of SNS outflow)
- muscle relaxation (instead of motor activity)
Dexmedetomidine is a selective a2 agonist if…
injectled SLOWLY and at LOW DOSES
Dexmedetomidine can also stimulate a1 and a2b receptors when…
drug is injected RAPIDLY pr at HIGH DOSES causing transient hypertension
how does dexmedetomidine cause transient hypertension when it binds a1 receptors
- drug binds a1 at BV (SNS) first if injected rapidly causing hypertension
- then binds receptors on brain (CNS) to inhibit SNS outflow - relaxes BV
side effects of dexmedetomidine
- hypotension, bradycardia, heart block
- casued by inhibition of SNS outflow from the CNS via a2a receptor
effects of Alpha2-agonists (e.g. Dexmedetomidine) on HR and BP
HR = decreased
BP = increased if injected rapidly at high dose
BP = decreased if injected slowly at low dose
clinical effects of Midazolam - a Benzodiazapine
- reduce anxiety
- drowsiness/fatigue
- muscle relaxation
- amnesia
- anti-seizure effects
