The document provides an overview of general anesthetics, including their definition, classification, mode of action, stages of anesthesia, and various drugs used. It highlights the characteristics of general anesthetics, such as inducing unconsciousness and muscle relaxation, while detailing specific drugs, their uses, contraindications, dosages, and potential adverse effects. Key examples include inhalational anesthetics like halothane and nitrous oxide, and intravenous options like thiopental sodium.

1. GENERAL ANAESTHETIC
By-: KARTIK TIWARI

2. ● Outline-:
● General introduction
● Classification of general anaesthetic
● Mode of action
● Stages of anaesthesia
● Drugs
- Uses
- Contradiction
- Dosage
- Adverse effect

3. ★ General introduction
● Definition-:General anaesthetic is defined as the chemical
agent which causes reversible loss of sensation or
unconscious the whole body.
● General anaesthetic is used to unconscious the whole body.
● It act on Central nervous system (CNS) and peripheral parts
of the body.
● The characteristics of general anaesthetic are:
1. Unconsciousness
2. Amnesia
3. immobilisation and muscle relaxant.

4. ★ Classification of general anaesthetic
General anaesthetic
Inhalant Injectable
Gaseous Voletile liquids Fast acting drugs Slow acting drugs
Benzodiazepines Opioid
analgesic
Dissociative
anaesthetic
Nitrous oxide Ether
Halothane
Isoflurane
Desflurane
Sevoflurane
Thiopentone sod.
Methohexitone
sod.
Propofol
Etomidate
Diazepam
Lorazepam
Midazolam
Ketamine
Fentanyl

5. ● N2O and ketamine do not affect GABA or glycine gated Cl¯ channels.
Rather they selectively inhibit the excitatory NMDA type of glutamate
receptor. This receptor gates mainly Ca2+ selective cation channels in
the neurones, inhibition of which appears to be the primary mechanism
of anaesthetic action of keta-mine as well as N2O. The volatile
anaesthetics have little action on this receptor.
● Mode of action
● Inhalational anaes-thetics, barbiturates, benzodiazepines and propofol
potentiate the action of inhibitory transmitter GABA to open Cl¯
channels.

6. ★ Stages of anaesthesia
Modern anesthetics act very rapidly and achieve deep anesthesia quickly.
With older and more slowly acting anesthetics, the progressively greater
depth of central depression associated with increasing dose or time of
exposure is traditionally described as stages of anesthesia.
A. Stage 1: Analgesia
In stage 1, the patient has decreased awareness of pain, sometimes
with amnesia. Consciousness may be impaired but is not lost.
B. Stage 2: Disinhibition
In stage 2, the patient appears to be delirious and excited. Amnesia
occurs, reflexes are enhanced, and respiration is typically irregular;
retching and incontinence may occur.

7. C. Stage 3: Surgical Anesthesia
In stage 3, the patient is unconscious and has no pain reflexes;
respiration is very regular, and blood pressure is maintained.
D. Stage 4: Medullary Depression
In stage 4, the patient develops severe respiratory and cardiovascular
depression that requires mechanical and pharmacologic support.
★ Drugs
Halothane
Form - Volatile liquid
● Uses:
Induction and maintenance of anaesthesia

8. ● Contraindications:
History of unexplained jaundice or pyrexia following previous exposure to
halothane; family history of malignant hyperthermia; raised cerebrospinal
fluid pressure; porphyria
● Precautions:
Anaesthetic history should be carefully taken to determine previous
exposure and revious reactions to halothane (at least 3 months should be
allowed to elapse between each re-exposure); avoid for dental procedures
in patients under 18 years unless treated in hospital (high risk of
arrhythmias); pregnancy and breastfeeding
● Dosage:
Induction, using specifically calibrated vaporizer, gradually increase inspired
gas concentration to 2–4% (ADULT ) or 1.5–2% (CHILD ) in oxygen or
nitrous oxide–oxygen
Maintenance, ADULT and CHILD 0.5–2%

9. ● Adverse effects:
arrhythmias; bradycardia; respiratory depression; hepatic damage
Nitrous oxide
Form - Inhalation gas
● Uses:
Maintenance of anaesthesia in combination with other anaesthetic agents
(halothane, ether, or ketamine) and muscle relaxants; analgesia for
obstetric practice, for emergency management of injuries, during
postoperative physiotherapy and for refractory pain in terminal illness
● Contraindications:
Demonstrable collection of air in pleural, pericardial or peritoneal space;
intestinal obstruction; occlusion of middle ear; arterial air embolism;
decompression sickness; chronic obstructive airway disease, emphysema

10. ● Dosage:
Anaesthesia, Adult and Child nitrous oxide mixed with 25–30% oxygen
Analgesia, 50% nitrous oxide mixed with 50% oxygen
● Adverse effects:
nausea and vomiting; after prolonged administration megaloblastic
anaemia, depressed white cell formation; peripheral neuropathy
Thiopental sodium
Thiopental is a representative intravenous anaesthetic. Various drugs can
serve as alternatives Injection (Powder for solution for injection), thiopental
sodium, 0.5-g and 1-g ampoules.
● Uses:
Induction of anaesthesia prior to administration of inhalational anaesthetic;
anaesthesia of short duration
● Contraindications:
Inability to maintain airway; hypersensitivity to barbiturates;

11. ● Dosage:
Induction, by intravenous injection as a 2.5% (25 mg/ml) solution over
10–15 seconds, Adult 100–150 mg (reduced in elderly or debilitated
patients), followed by a further 100–150 mg if necessary according to
response after 60 seconds; or up to 4 mg/kg; Child 2–7 mg/kg repeated if
necessary according to response after 60 seconds.
Form - Volatile liquid
● Uses:
Induction and maintenance of anaesthesia (administered from many types
of vaporizers)
● Contraindications:
severe liver disease; diabetes mellitus; impaired kidney function; raised
cerebrospinal fluid pressure.
Ether, anaesthetic

12. ● Dosage:
Induction, Adult and Child , up to 15% in inspired gases
Maintenance of light anaesthesia, Adult and Child 3–5% in air (with or
without muscle relaxants); up to 10% for deep anaesthesia
● Adverse effects:
transient postoperative effects include impairment of liver function and
leukocytosis; nausea and vomiting; capillary bleeding.