1. General Anesthesia

2. G A
Drug induced absence of perception of all sensation allowing surgery or other painful procedure to be carried out

3. Triad of General anaesthesia
Hypnosis
Analgesia
Muscle relaxation

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.
3- Antagonise the action of the excitatory
neurotransmitter glutamic acid on the
N-methyl-aspartate (NMDA) receptor.

5. 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 Anesthesia*
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 Anesthesia
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 anesthesia to make it more safe and pleasant.
To relieve anxiety – benzodiazepines.
To prevent allergic reactions – antihistaminics.
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 anesthetics.
To prevent bradycardia and secretion.

9. Phases of Anesthesia Induction: putting the patient to sleep
Maintenance: keeping the patient asleep
Recovery: waking the patient up

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

11. (halothane isoflurane, desflurane, sevoflurane)
General Anesthetics
Parenteral
Inhalational
Gas
Volatile liquids*
Barbiturates
(nitrous oxide)
(halothane isoflurane, desflurane, sevoflurane)
Enflurane
(thiopental)
Opioids
(fentanyl)
Benzodiazepines
(midazolam)
(etomidate, propofol)
ketamin

12. Inhaled Anesthetics Easily vaporized liquid halogenated hydrocarbons
Administered as gases
(gas)

13. 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 anesthetic; fast induction & recovery

14. Properties of Inhaled anesthetics
Enflurane
Rapid induction and recovery
Used for maintenance of anesthesia
Less potent than halothen
-good muscle relaxation
less sanitization to the myocardium
Metabolize into fluoride ion
Decrease BP

15. Parenteral Anesthetics (IV)
Most commonly used drugs to induce
anesthesia
Barbiturates (Thiopental* & Methohexital)
Benzodiazepines (Midazolam)
Opioids (Morphine & Fentanyl)
Propofol*
Etomidate
Ketamin

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

17. 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.

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

19. Xylazine
It is used in veterinary medicine for many diagnostic and surgical procedures.
It is α2 sympathomimetic agent, it act by activation of central α2 receptors which will cause reduction or depression in release of dopamine and norepinphrine.

20. 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.

21. Methodology recovery Duration of anesthesia Duration of analgesia
onset
agents
Ketamine
only
Ketamine&
xylazine

22. Thank you