Anaesthetics Flashcards
What are the 2 forms of anaesthetic and what is their given route?
General and Local
- General is given IV or inhaled (Volatile)
- Local is injected regionally
What is conscious sedation?
use of small amounts of anaesthetic for benzodiazapines to produce a sleepy like effect where you maintain verbal contact but feel comfortable
What is anaesthesia and what do is cause?
-combination of analgesia, hypnosis, depression of spinal reflexes and muscle relaxation including insensibility and immobility
What are the range of effects on the CNS produced during general anaesthesia?
-Guedel’s signs
stage 1) analgesia and consciousness
stage 2) unconscious breathing erratic but delirium could occur leading to an excitement phase paradoxical excitement
stage 3) surgical anaesthesia, with 4 levels describing increasing depth until breathing weak
stage 4) respiratory paralysis and death
What is potency?
potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity
What is MAC?
minimum alveolar concentration
-concentration of alveolar at which 50% of subjects fail to move to surgical stimulus
NOTE - at elm, conc of alveolar = conc in spinal cord
What factors affect induction and recovery?
SOLUBILITY (partition coefficients)
- blood:gas partition (solubility in the blood)
- oil:gas partition (solubility in lipid (fat tissue))
What does oil:gas partition determine?
the potency and slow accumulation due to partition in to the fat therefore HIGH POTENCY = HIGH SOLUBILITY IN FAT
What factors affect MAC?
- age (high in infants, lower in elderly)
- hyperthermia (increased - opposite for hypothermia)
- pregnancy (increased)
- alcoholism (increased)
- central stimulants (increased)
- other anaesthetics and sedatives (decreased)
- opioids (decreased)
What affect does nitrous oxide have on the delivery of inhalation anaesthetics?
reduces the MAC value as it has anaesthetic effect so increased delivery with reduced dosing
What is the target for most anaesthetics?
GABA A receptors
What is GABA?
major inhibitory transmitter
What is GABA A receptor?
LGIC (cl- conductance=]
What do anaesthetics tend to do and what are the exceptions and what do they do?
with the exception of Xe, N2O and ketamine, all other anaethestics potentiate GABA A mediated Cl- conductance to depress CNS activity
-anxiolysis *inhibits anxiety)
-sedation
-anaesthesia
the other ones work on NMDA receptors- antagonists
What do anaesthetics modulate?
the balance between excitation (glutamate) and inhibition (GABA)
What systems and structures in the brain do anaesthetics target?
- reticular formation depressed with connectivity lost between the 3 systems
- thalamus transmits and modifies sensory information
- hippocampus depressed (memory)
- brainstem depressed (resp and some CVS)
- spinal cord depresses dorsal horn (analgesia) and motor neuronal activity (MAC)
What are the names of intravenous anaesthetics (general anaesthetic)?
PKB
- Propofol
- Ketamine
- Barbiturates
just note that ketamine is the slowest acting
What is the MOA of propofol, ketamine and barbiturates?
P and B
-potentiate GABA receptors upsetting the balance between glutamate and GABA in the brain
K
-NMDA receptor antagonist
What are the uses of propofol, ketamine and barbiturates?
given for induction phase in anaesthesia and puts patients to sleep in preparation for surgery
What are the side effects of general anaesthesia?
- post-operative nausea and vomiting
- hypotension
- post operative confusion and delirium
- chest infection
What are the names of volatile anaesthetics?
HIND
Halothane
Isoflurane
Nitrous Oxide
Desflurane
What is the MOA of Halothane, Isoflurane, Nitrous Oxide, Desflurane
N20 - NMDA receptor antagonist
H/I/D - potentiate GABA receptors
What are the uses of Halothane, Isoflurane, Nitrous Oxide, Desflurane?
can be used alongside nitrous oxide to reduce the MAC so reduced dosing is required
What are the symptoms of Halothane, Isoflurane, Nitrous Oxide, Desflurane?
- post-operative nausea and vomiting
- hypotension
- post operative confusion and delirium
- chest infection
What are the names of local anaesthetics?
Where are they injected into in upper extremities, lower extremities and in labour?
Please Refrain Bill’s Lips - CAINE
Procaine
Ropivacaine
Bupivacaine
Lidocaine
in upper extremity’s injected into inter scalene, supra clavicular, infraclavicular or axillary nerve
in lower extremity’s either femoral, sciatic, popliteal or saphenous
in labour can be extradural/intrathecal
What is the MOA of Procaine, Ropivacaine, Bupivacaine, Lidocaine
All are lipid soluble
B - blocks small myelinated nerves (VG Na+ channels) causing a nociceptive and sympathetic block
B is the most potent and last longest
P is esterase metabolised so shorter lasting but not much in it
B?L?R - amides so last longer
What does adrenaline do to local anaesthetics and why?
increases the duration because causes vasoconstriction so there is less distribution
What are the uses of Procaine, Ropivacaine, Bupivacaine, Lidocaine ?
dentistry, obstetrics, regional surgery, post operative and pain management
What are the side effects of Procaine, Ropivacaine, Bupivacaine, Lidocaine ?
cardiovascular toxicity
