MBBS anesthesiology

1. General Anaesthesia
Dr.T.Saravanan,
Assistant Professor,
Department of Anesthesiology

2. GENERAL ANASTHESIA
• Drug induced absence of perception of all sensation
allowing surgery or other painful procedure to be
carried out

4. Mechanism of action of general
anesthesia
• 1- Old theory the anesthetic agent bind with lipid matrix
of the nerve membrane , this lead to secondary changes
in ion flux and interaction with membrane of the ligand
– gated ion channel.
• 2-Facilitation GABA receptor function.

5. 3-Antagonize the action of the excitatory neurotransmitter glutamic acid
on the N-methyl-aspartate (NMDA) receptor
4-Causes membrane hyper polarization (inhibitory action) by their
activation of potassium channel. 5- anesthetic decease the duration of
opening nicotinic receptor – an action that decrease the excitatory effect
of acetylcholine synapse

6. Classic Stages of
Anaesthesia
• Stage 1: Analgesia decreased awareness of pain, amnesia ,without loss of
consciousness excitation:
• Stage 2 Delirium & excitation, enhanced reflexes, retching, incontinence, irregular
respiration
• Stage 3: Surgical Anaesthesia, unconscious, no pain reflexes, regular respiration, BP is
maintained
• Stage 4: Medullary Depression respiratory & CV depression requiring ventilation &
pharmacologic support.* Seen mainly with Ether. Not all stages are observed with
modern GAs.

7. Pre-anesthetic
medication
It is the use of drugs prior to anaesthesia to make it more safe and pleasant.
To relieve anxiety – benzodiazepines.
To prevent allergic reactions – antihistaminic.
To prevent nausea and vomiting – antiemetics.
To provide analgesia – opioids.
To prevent Bradycardia and secretion – atropine.
The aim is to relieve apprehension and facilitate smooth induction.
To supplement analgesic, amnesic action of anaesthetics.
To prevent bradycardia and secretion.

8. Phases of Anesthesia
• Induction: Putting the patient to sleep
• Maintenance: Keeping the patient asleep
• Recovery: Waking the patient up

9. Anesthesiology
• There are two types of anesthetics :
• Inhalational --- for maintenance
• Intravenous --- for induction and short procedures .

10. (Halothane isoflurane, Desflurane,
Sevoflurane)
• General Anesthetics
• ParenteralInhalational
• GasVolatile liquids*
• Barbiturates(nitrous oxide)(halothane isoflurane, desflurane, sevoflurane)
• Enflurane(thiopental)
• Opioids(fentanyl)
• Benzodiazepines(midazolam)(etomidate, propofol)
• ketamin

11. Properties of Inhaled anesthetics
Nitrous Oxide(N2O)
Laughing gas
Good analgesia
Weak anesthesia
Less effect on respiratory and cardiovascular system.
Rapid onset & recover
Used along w/ other aesthetic;
Fast induction & recovery

12. Properties of Inhaled anesthetics
Enflurane
Rapid induction and recovery
Used for maintenance of anesthesia
Less potent than halothane
Good muscle relaxation
Less sanitization to the myocardium
Metabolize into fluoride ion
Decrease BP

13. Parenteral Anaesthetics (IV)
Most commonly used drugs to induce anaesthesia
Barbiturates (Thiopental & Methohexital)
• Benzodiazepines (Midazolam)
• Opioids (Morphine & Fentanyl)
• Propofol
• Etomidate Ketamine

14. Ketamine
A “dissociative anesthetic” Characterized by:
a)Analgesia, amnesia, eyes open, involuntary limb
movement,.(unconscious appear to be awake)
b)Rapid onset and last for5-10 min.(short acting)

15. Mechanism of action
• It is bind to NMDA (N-methyl-D-aspartate receptor )
and also stimulate the central sympathetic outflow
which cause heart stimulation, increased blood
pressure and cardiac output.

16. Ketamine
Used in children & young adults for short procedures
Side Effects:
1-salivation,
2-hallucinations and vivid dreams(adult)
3- stimulation of sympathetic nervous system cause tachycardia,
increase blood pressure
4- reach to stage two of anesthesia only

17. Pharmacological effects
CNS depression and sedation (30-90 min).Analgesia which last (15-
30 min).
Muscle relaxation.
Emesis
Hypotension and brady cardia
Decreased respiratory rate.
Recovery from effect usually takes 2-4 hr.

18. THANK YOU