LA, GA Flashcards
When pt is having inhaled GA, develops hypertention, tachycardia, hyperthermia, severe muscle rigidity and acidosis. What happen to pt? How to manage?
- Malignant hyperthermia
- Treat with dantrolene (to reduce release of Calcium) + supportive measurement
IV GA is used for:
- Induction (faster onset of action)
Most IV GA lacks of analgesic properties , can be combined with inhaled or local anesthetics for short procedures
Pt with intracranial bleeding, need for RSI, what induction agent to use?
- Barbiturate
Or - Propofol
Or - Etomidate
Not to use ketamine
What is the MOA of thiopental (e.g. of barbiturate)?
- Binds to GABAa receptors and facilitates actions of GABA by increasing the duration of GABA gated chloride channel opening
- Also works on AMPA receptor to depress glutamate mediated excitation
- Non synaptic membrane effects
Benzodiazepine is used for
- Pre anaesthetic medication and adjuvants during procedure under LA , due to their effects on sedation, anxiolytic and amnestic properties
How to accerate the recovery from large dose of benzodiazepam be given to elderly esp?
- Benzodiazepine antagonist ( flumazenil) can be given
- Need to closely monitor and multiple dosing as flumazenil has short duration of action (<90min)
Ketamine, MOA
NMDA Receptor antagonist producing disassociative anesthesia
Effects of ketamine
- Catatonia
- Amnesia
- Analgesia
No Loss of consciousness
Ketamine can be used for elderly pt or those with cardiogenic or septic shock due to:
Ketamine stimulate cardiovascular system through the cental sympathetic nervous system, and inhibiting reuptake of NorA ( does not reduce BP)
Disavdvantage of ketamine:
- Increase cerebral blood flow, o2 consumption and ICP
- Decrease RR
- A/W post OP disorientation, illusion and dream
- Higher risk for drug abuse ( chemically r/t phencyclidine (PCP)
Instead of GA, the alternative anaesthesia mothods:
- Balanced anesthsia (IV induction, inhaled, LA , muscle relaxants and cardiovascular drugs)
- Monitored anesthesia care: ( midazolam, propofol infusion for mod to deep sedation , opioid or ketamine)
- Conscious sedation: smaller doses of sedatives with mild altered LOC. ( midazolam, propofol, and opioid analgesics)
LA effects:
- Analgesics and paralysis can be achieved using specific pathways
ADE of LA
- Localized prolonged anesthesia or parasthesia due to infection via injection site, excessive fluid pressure in confined cavity, and severing of nerves and support tissues during injection
- Systemic reaction: depressed CNS effect, allergic reaction, vasovagal episode and cyanosis due to LA toxicity
LA is usually injected around nerves, what is derermined by Asborption and distribution?
- Off set of action and systemic toxicity
(Not onset of action)
MOA of LA:
- Binds to receptors near the intracellular end of Na channels
- Voltage and time dependent blockage (effect is more marked in rapidly firing fibers)
- Reduce depolarization
- Prolonged repolarization
- Anti inflammatory effects
- Effects on other channels [leads to ADE)
