types of drug used in anaesthesia

1. General Anaesthesia
Uttara Joshi

2. General Anaesthesia
produce• General anaesthetics are the drugs that
reversible loss of all sensation & consciousness.
Classification:
1. Inhalational
A. Gas: N2O, Xenon
B. Liquids: Ether, Halothane, En/Iso/Des/Sevo-flurane
2. Intravenous
A. Inducing agents: Thiopentone sodium, Propofol,
Methohexitone, Etomidate
B. Slow acting
 Dissociative anesthesia: Ketamine
 Benzodiazepines: Diazepam, Lorazepam, Midazolam
 Opioid analgesics: Fentanyl

3. Points to be covered
 Halothane*,
 Cyclopropane*,
 Diethyl ether*,
 Methohexital sodium,
 Thiopecal sodium,
 Trichloroethylene .

4. Induction, Maintenance & Recovery
• Induction is defined as the period of time from
administration of anaesthetic to the development of
effective surgical anaesthesia in the patient.
• Maintenance provides a sustained surgical anaesthesia.
• Recovery is the time from discontinuation of administration
of anaesthesia until consciousness and protective
physiologic reflexes are regained.
Balanced Anesthesia
• All components of anesthesia is achieved by using
combination (e.g: low dose opioids + volatile GA + N2O)
Minimum Alveolar Concentration (MAC)
• Lowest concentration of the inhalational anesthetic in
alveoli needed to produce immobility in response to painful
stimulus.

5. Stages of anaesthesia
1. Stage I—Analgesia: Loss of pain sensation results from
interference with sensory transmission. The patient progresses
from conscious and observes analgesia. Amnesia and reduced
awareness of pain occur as Stage II is approached.
2. Stage II—Excitement: The patient experiences delirium and
possibly combative behaviour. A rapid acting agent, such as
propofol, is given intravenously before inhalation anaesthesia is
administered.
3. Stage III—Surgical anaesthesia: There is gradual loss of muscle
tone and reflexes as the CNS is further depressed. Regular
respiration and relaxation of skeletal muscles with eventual loss
of spontaneous movement occur in this stage. This is the ideal
stage of anaesthesia for surgery. Continuous careful monitoring
is required to prevent undesired progression into Stage IV.
4. Stage IV—Medullary paralysis: Severe depression of the
respiratory and vasomotor centres occur during this stage.
Death can rapidly ensue unless measures are taken to maintain
circulation and respiration.

6. Mechanism of action of General Anaethetics
• Inhalational anaesthetics, barbiturates,
benzodiazepines & propofol potentiate the action of
inhibitory transmitter GABA to open Cl¯ channels.
• Action of glycine (another inhibitory transmitter
which also activates Cl¯ channels) in the spinal cord
and medulla is augmented by barbiturates, propofol
& many inhalational anaesthetics.
• Ketamine selectively inhibits the excitatory NMDA
type of glutamate receptor.
• Certain fluorinated anaesthetics and barbiturates
inhibit the neuronal cation channel gated by
nicotinic cholinergic receptor.

8. Inhalational Anaesthetics
Nitrous oxide (N2O)
• It is cheap & commonly used anaesthetic.
• It is low potency anaesthetic but good analgesic.
• It has fast onset & recovery.
• It is given as 70% N2O + 25-30% O2 + 0.2-2% other potent
anaesthetic (Halothane)
• It has little effect on respiration, heart & BP.
Uses: Maintain surgical anaesthesia, obstetric practice,
emergency management of injuries, refractory pain, etc
Adverse Effects: It interacts & degrades Vit B12.
Contraindications: Pneumothorax, air embolus, obstructive
middle ear, etc.

9. Halothane
• It is a volatile liquid with sweet odour, non-irritating &
non-explosive.
• It is potent anaesthetic but poor analgesic.
• It dilates bronchi so preferred in asthma patient.
• For induction 2-4% & for maintenance 0.5-1% is delivered
by using special vapouriser.
Adverse effects:
• Hepatitis
• Hyperthermia
• Hangover
• Shivering
Contraindication:
• Jaundice
• Raised CSF pressure

10. Intravenous anaesthetics
Inducing agents
• Produce anaesthesia within 20 sec.
• Reduce dose of other anaesthetics
• Supplemented with analgesics & muscle relaxant
Thiopentone sodium.
• It is ultrashort acting thiobarbiturate administered i.v.
• Single dose induces hypnosis & anaesthesia without analgesia
• When administerd i.v. it quickly enters CNS & depresses function
within minutes. Injected i.v. (3-5mg/kg) as 2.5% solution.
• Redistributed to skeletal muscles & adipose tissue serves as
reservoir.
Uses: Inducing agent, Control of convulsion, Protect from cerebral
ischemia
Adverse effects: Laryngospasm, shivering & delirium during recovery
Contraindications: Hypersensitivity to barbiturates, Hypotension

11. Cyclopropane
Cyclopropane is a colorless gas with a petroleum-like
odor. It is shipped as a liquid at 4-6 atms. It is easily
ignited. The vapors are heavier than air. Contact with
the liquid may cause frostbite. It can asphyxiate by the
displacement of air and has a narcotic effect in high
concentration (formerly used as an anesthetic gas).
Under prolonged exposure to fire or intense heat the
containers may rupture violently and rocket.

12. Cyclopropane is a cycloalkane composed of three
carbon atoms to form a ring. It has a role as an
inhalation anaesthetic. It is a cycloalkane and a
member of cyclopropanes.

13. Diethyl ether
Diethyl ether, or simply ether, is an organic compound in the
ether class with the formula
sometimes abbreviated as Et
(see Pseudoelement symbols). It is a colorless, highly
volatile, sweet-smelling ("Ethereal odour"), extremely
flammable liquid. It is commonly used as a solvent in
laboratories and as a starting fluid for some engines. It was
formerly used as a general anesthetic, until non-flammable
drugs were developed, such as halothane. It has been used as
a recreational drug to cause intoxication. It is a structural
isomer of butanol.

14. Formula: (C2H5)2O

15. Benzodiazepines
• Pre-anaesthetic medication
• Used for inducing, maintaining & supplementing
anaesthesia
Opioids
• Fentanyl is short acting potent opioid related to
Pethidine
• Used for neuroleptic analgesia(intense analgesia)
during endoscopies, angiographies, burn-dressings
Adverse effects: Nausea, Vomiting, Muscle dystonia

17. Methohexital
Methohexital or methohexitone is a drug
which is a barbiturate derivative. It is
classified as short-acting, and has a rapid
onset of action. It is similar in its effects to
sodium thiopental, a drug with which it
competed in the market for anaesthetics

18. Methohexital

19. Trichloroethylene
Trichloroethylene (TCE) is a nonflammable, colorless
liquid with a somewhat sweet odor and a sweet, burning
taste. It is used mainly as a solvent to remove grease
from metal parts, but it is also an ingredient in
adhesives, paint removers, typewriter correction fluids,
and spot removers.
however, TCE was still in use as an anesthetic in Africa.

20. Formula: C2HCl3

21. Pre-anaesthetic medications
• Medicines used before anaesthesia to make it
more pleasant & safe. They are given for:
Relief of anxiety & apprehension
Amnesia
Potentiate & supplement analgesic action
Decrease secretion & vagal stimulation
Antiemetic effect
Decrease acidity & volume of gastric juice
e.g: opioids, sedative anti-anxiety drugs,
anticholinergics, antacids, antiemetics, etc.

22. LOCAL ANAESTHESIA (LA)
• Local anaesthetics are the drugs that blocks the
generation & conduction of nerve impulse without
affecting consciousness.
• The generation & transmission of nociception
(pain) can be prevented by blocking voltage gated
Na+ channel in afferent neuron.
• They can act on any part of the nervous system &
on every type of nerve.
• Advantages of
consciousness,
LA
function
over GA: Unaltered
of vital organ is
unaffected, safe for patients, useful for minor &
major operations.

24. THANK YOU