4. STAGES OF GENERAL ANESTHESIA:
I. STAGE OF ANALGESIA:
Starts from beginning of anesthetic inhalation and lasts up
to loss of consciousness.
Patient remains conscious , can hear and see.
Amnesia develops at the end of this stage.
Reflexes and Respiration is normal.
II. STAGE OF DELIRIUM:
From loss of consciousness to beginning of regular
Respiration.
Patient may shout ,struggle.
Heart rate and BP increases.
5. III.SURGICAL ANAESTHESIA:
Extends from onset of regular respiration to cessation of Breathing.
It may be distinguished into 4 planes
PLANE 1:Roving eye balls.This plane ends when eyes become
fixed.
PLANE 2:Loss of corneal and laryngeal reflexes.
PLANE 3:Pupil starts dilating and light reflex is lost.
PLANE 4:Intercostal paralysis ,shallow abdominal respiration ,
dilated pupil.
IV.MEDULLARY PARALYSIS:
Cessation of breathing to failure of circulation and death.
7. inhalational anesthetics:
1.)volatile liquids:
A. ETHER:(Diethyl ether)
It is a highly volatile liquid,
produces irritating vapours and are inflammable and explosive.
Advantages:
It can be used without any complicated apparatus.
Potent anaesthetic and good analgesic.
Disadvantages:
Slow induction and recovery.
Cardiac arrest and convulsion in children.
Cross placental barrier.
8. B. HALOTHANE:
Flourinated volatile liquid with sweet odour.
supplied in amber coloured bottle
Advantages:
Potent anaesthetic
Non-inflammable and non-irritant
Rapid induction and recovery
Disadvantages:
Requires special apparatus
Hypotension and arrhythmia
Poor analgesic and muscle relaxation.
9. C. ENFLURANE:
Non-inflammable with mild sweet odour
Similar to halothane in action
Disadvantages:
Induces Seizures in deep anaesthesia and therefore not
used now.
Renal toxicity.
D. ISOFLURANE:
Isomer of enflurane and have similar properties but
slightly more potent
10. 2.)GAS:
NITROUS OXIDE: LAUGHING GAS
Colourless odourless inorganic gas with sweet taste
Advantages:
Non-irritating and non-inflammable
Rapid induction and recovery
Very potent analgesic
No nausea and vomiting
Non-toxic to liver,kidney and brain
Disadvantages:
Not potent alone(supplementation)
Hypoxia
11. INTRAVENOUS ANAESTHETICS:
1.)INDUCING AGENTS:
A. THIOPENTONE SODIUM
Ultra short acting barbiturate
Highly soluble in water yielding a very alkaline solution ,which must be freshly
prepared before injection.
Advantages:
Induction and recovery is rapid
Disadvantages:
Poor analgesic ,Weak muscle relaxant
Uses:
Thiopentone sodium is commonly used inducing agent.
It can be employed as the sole anesthetic for short operations that are not
painful.
12. B. PROPOFOL:
Oily liquid employed as 1% emulsion.
Advantages:
Induction and recovery is rapid
Lacks airway irritancy
Disadvantages:
Fall in BP,Bradycardia
It is not approved for use in children;
prolonged sedation,severe metabolic effects and heart failure
even in adults.
Uses:
It is the drug of choice for sedating intubating patients in ICU.
Patient acceptability is good.
13. Benzodiazepines:
Diazepam :
In addition to preanaesthetic medication ,BZD are now frequently
used for inducing , maintaining and supplementing anesthesia as
well as for conscious sedation .
Relatively large doses are injected i.v produce sedation , amnesia
and then unconscious in 5-10 min .
14. 2.) SLOWER ACTING DRUGS:
DISSOCIATIVE ANAESTHESIA:
KETAMINE:
Is a Dissociative Anaesthetic as it produces a cataleptic state in which the
patient appear to be awake but is detached from the environment and is
unresponsive to pain.
Unique drug ,because, it has Hypnotic, Analgesic and Amnesic efects
No other drug has these 3 features.
Advantages:
Respiration is not depressed.
Disadvantages:
Heart rate , BP,Cardiac output increases.
Uses:
Used for operations on the head and neck.
15. OPIOID ANALGESIC:
FENTANYL:
High Potent opioid analgesic(mu receptor agonist)
Short duration of action
Rapid onset of action
Disadvantages:
Respiratory depression
Uses:
Used as supplement anaesthetics in Balanced Anaesthesia.
Ideal for children and un-cooperative patients.
16. ALPHA -2 AGONIST :
DEXMEDETOMIDINE and CLONIDINE:
Action of central alpha-2 adrenergic receptor has been known to
cause sedation and analgesia
Clonidine causes anaesthesia
Disadvantages:
Respiratory depression.
Hypotension ,dry mouth,bradycardia
Uses:
Critically ill/ventilated patients in ICU.
