3. Mechanism:
Major targets are GABAA receptor gated
Cl-channel.(Many inhalation
anesthetics, barbiturates, benzodiazepines and
propofol)
NMDA receptors are type of glutamate
receptor.(N2O,Ketamine)
4. Inducing agents:
Drugs which on i.v. injection produce loss of
consciousness in approximately 11 seconds.
Used because of rapidity of onset of action.
Then maintain by inhalational agents.
Supplemented with analgesics and muscle relaxants.
5. Thiopentone sodium:
An ultra-short-acting barbiturate used
commonly in the induction phase.
Injected i.v. (3-5mg/kg) produces unconsciousness in
15-20 seconds.
Consciousness regained in 6-10 min.
Disposal mainly by hepatic metabolism (elimination
t1/2 is 7-12hrs).
6. Poor analgesic effect.
Weak muscle relaxant.
Respiratory depression is transient and severe in large
doses.
Does not sensitizes the heart to adrenaline, cardiac
arrhythmia are rare.
Indications:- Minor surgery that are less painful.
7. Adverse effects:
Laryngospasm-relived by atropine premedication.
Fall in BP.
Shivering and delirium.
Acute intermittent porphyria-C/I.
Other uses:
Rapid control of convulsions.
Narco analysis.
8. Methohexitone sodium:
short-acting and has a rapid onset of
action.
Three times more potent and similar in
its effects to thiopentone sod.
Has a quicker and briefer action(5-8 min).
Indication:-For oral surgery and dentistry.
A/E:-Excitement during induction and recovery
period.
9. Propofol-Milk of amnesia
Short-acting for both induction as well as
maintenance.
An oily liquid employed as a 1% emulsion.
Unconsciousness occurs 15-45 sec and lasts 5-10 min.
Propofol is highly protein-bound and is metabolized
by conjugation in the liver.
Intermittent injection or continuous infusion used for
total i.v. anesthesia when supplemented by fentanyl.
Most suited for out patient surgery.
10. Adverse effect:
Fall in BP and bradycardia.
Pain on injection.
Dystonia and myoclonic movements are common.
Propofol has reportedly induced priapism in some
individuals.
Other uses:
In sub-anesthetic doses, it is the drug of choice for
sedating intubated patients in ICU.
11. Etomidate:
Short-acting induction anesthesia.
Has a briefer duration of action (4-8 min) than
thiopentone.
Etomidate is highly protein bound and metabolised by
hepatic and plasma esterases to inactive products.
Onset of action: 30–60 seconds.
Peak effect: 1 minute.
Indications:
As sedative, for short procedures such as reduction of
dislocated joints and cardioversion.
12. Slower acting drugs:
Benzodiazepines:
Used for induction, maintenance and supplementing
anesthesia as well as for conscious sedation.
In larger doses injected i.v. produce sedation, amnesia
and unconsciousness in 5-10mins.
If no anesthetic or opioid is given, the patient becomes
responsive in 1hr. But, amnesia for 2-3hrs.
Poor analgesics.
Opioid or N2O is added, if the procedure is painful.
Indication-in endoscopies, cardiac
catheterization, angiographies, regional anesthesia
,fracture setting.
13. Action is rapidly reversed by flumazenil 0.5-2mg i.v.
Diazepam:
0.2-0.5mg/kg , slow undiluted injection in a running i.v.
This technique reduces burning sensation in vein and
incidence of thrombophlebitis.
Lorazepam:
Potent, slower-acting, less irritating than diazepam.
Amnesia is more profound. (Dose : 0.04 mg/kg)
Midazolam:
Water-soluble, shorter acting drug used for sedation of
intubated patients. (Dose : 1-2.5mg i.v.)
In other critical care anesthesia as 0.02-0.1mg/kg/hr
continuous i.v. infusion.
14. Ketamine:
Related to phencyclidine-dissociative anesthesia.
DA-characterised by profound
analgesia, immobility, amnesia, feeling of dissociation
from ones own body.
Site of action-Cortical and sub cortical areas.
Act by inhibiting NMDA receptors.
Dose of 1-3mg/kg i.v. produces the above effects within
a minute & recovery after 10-15 mins, but remains
amnesic for 1-2hr.
Metabolized in the liver and has an
elimination t1/2 3-4hrs.
15. Indications:
Head and neck surgeries, asthmatics, Short
surgeries, Burn dressings.
Combined with diazepam used in
angiographies, catheterization, and trauma surgeries.
Adverse effects:
-Heart rate, Cardiac output, BP increased.
-Delirium, hallucination, involuntary movements
during recovery.
Contraindication:
-HT,IHD.
-Increased ICP.
16. Fentanyl:
Short-acting, opioid analgesic related to pethidine.
Has rapid onset and short duration of action about
30-50 min.
Strong agonist at the μ-opioid receptors.
Used to supplement anesthetics in balanced
anesthesia.
Also used in neurolept analgesia in combination with
droperidol.
17. Indications:
Combined with BDZs, used for
endoscopic, angiographic, cardiac catheterization, burn
dressing and other minor procedures.
used most often in operating rooms and intensive care
units.
Adverse effects:
Nausea, vomiting and itching often
occurs during recovery.
Marked respiratory depression.
Slight fall in BP.
18. Dexmedetomidine:
An α2 agonist with sedative and analgesic
effect.
Has a half life of 2-3hrs.
Metabolized in liver and excreted mainly as inactive
urine metabolites.
Adverse effects:-Hypotension and bradycardia.
20. Balanced anesthesia:
Modern anesthesia involves a combination of i.v.(for
induction) and inhalational anesthesia(for
maintenance). Sometimes volatile(sevoflurane) is
used for induction.
Muscle relaxant-facilitate intubation.
Local anesthetics-tissue infiltration, peripheral nerve
block.
Potent opioid analgesic & CV drugs(β blocker, ca
channel blocker)used to control autonomic responses
to noxious surgical stimuli.
21. Conscious sedation:
This technique refers to drug induction alleviation of
anxiety & pain in combination with an altered level of
consciousness associated with the use of smallest
doses of sedative medication.
Pt.retains ability to maintain patent airway &
responsive to verbal comments.
Drugs-diazepam,midazolam,propofol.
22. Neuroleptanalgesia
Method of i.v. anesthesia which combines the use of
neuroleptic drug with an opioid analgesic.
Subject is conscious & able to co-operate during
surgery.
most favoured combination- droperidol + fentanyl
After administering nitrous oxide with oxygen
neuroleptanalgesia can be converted to
neuroleptanesthesia.
C/I - patients receiving MAO inhibitors, abuse drugs
or alcohol, with Parkinson disease.