2. GENERAL ANESTHESIA
General anesthesia is a state characterized by
1-Unconsciousness
2-Analgesia
3-Amnesia
4-Skeletal muscle relaxation
5-Loss of Reflexes
3. GENERAL ANESTHESIA
1-Induction:
Time from onset of administration of potent anesthetic to surgical
anesthesia.
2-Maintenance:
Sustained surgical anesthesia
3-Recovery:
Time from discontinuation of administration of anesthesia until
consciousness and protective reflexes are regained.
4. GENERAL ANESTHESIA
Depth of anesthesia:
It is the degree to which CNS is depressed.
It is usual parameter for individualizing anesthesia.
A. Stage I: Analgesia
↓ awareness of pain, with amnesia, consciousness impaired.
B. Stage II: Disinhibition(excitement)
Patient is delirious and excited, amnesia, exaggerated reflexes,
respiration irregular, retching and incontinence.
5. GENERAL ANESTHESIA
C. Stage III: Surgical Anesthesia
Patient is unconscious, loss of reflexes, muscles relaxed, respiration is
regular, B.P is maintained.
Ideal stage of anesthesia for surgery
Continuous careful monitoring is required to prevent progression to
stage 4
D. Stage IV: Medullary Depression
Severe depression of respiratory and vasomotor center.
Death can occur unless measures taken to maintain circulation and
depression
6. CLASSIFICATION OF GENERAL ANESTHETICS
1-Volatile LIQUIDS:
Chloroform
Halothane
Enflurane
Isoflurane
Desflurane
Sevoflurane
2-GASES:
Nitrous oxide
7. CLASSIFICATION OF GENERAL ANESTHETICS
INTRAVENOUS ANESTHETICS:
Barbiturates (Thiopentone)
Benzodiazepines (Midazolam, Diazepam)
Opioid analgesics (Morphine, Fentanyl)
Propofol
Ketamine
Droperidol
10. PROPERTIES OF INHALATIONAL ANESTHETICS
1.MAC :
It is the concen. of inhaled anesthetic needed to eliminate movement in
50% of patients exposed to standardized skin incision.
Smaller the MAC, potent the anesthetic.
2. Blood:Gas partition coefficient:
Relative affinity of an anesthetic for the blood compared to air.
Low ( not soluble in blood)
High (very soluble in blood)
11. PHARMACOLOGICAL EFFECTS OF INHALED
ANESTHETICS
1-CNS:
Vasodilation ↑ cerebral blood flow↑ intracranial pressure.
Enflurane cause seizures, Nitric Oxide cause analgesia and amnesia
2-CVS:
↓BP and cardiac out put
Halothane ↑sensitivity of EPI &NE to heart
Halothane is contraindicated in Pheochromocytoma
12. PHARMACOLOGICAL EFFECTS OF INHALED
ANESTHETICS
3-RESPIRATORY SYSTEM
Respiratory depression and ↑ Paco2.
Bronchodilation
(Maximum bronchodilation with Halothane and Sevoflurane)
↓ mucociliary function in the airway.
13. PHARMACOLOGICAL EFFECTS OF INHALED
ANESTHETICS
4-Kidneys:
↓GFR and urine flow
5-Liver:
Concentration dependent ↓ in portal blood flow
Variation in liver enzymes
6-Uterus:
Relaxation (For intrauterine fetal manipulation or manual extraction of
a retained placenta )
14. ADVERSE EFFECTS OF INHALED ANESTHETICS
1-Cardiac effects:
Halothane Bradycardia, arrhythmias
2- Nephrotoxicity
Metabolites of Enflurane and Sevoflurane Nephrotoxic
3-Hematotoxicity
NO Megaloblastic Anemia (prolong exposure)
4-Hepatotoxicity
Halothane (Trifluoroethanol)
15. ADVERSE EFFECTS OF INHALED ANESTHETICS
5-Malignant hyperthermia:
Exposure to halothane or succinylcholine Uncontrollable ↑ in
skeletal metabolism↑temp. circulatory collapse & death
Cause:
Defect in skeletal muscle ryanodine receptors(RyR1)
Signs/Symptoms:
Muscle rigidity, hyperthermia, tachycardia, hypercapnia,
hyperkalemia, and metabolic acidosis
16. ADVESRSE EFFECTS OF INHALED ANESTHETICS
4-Malignant hyperthermia:
Treatment:
1-Dantrolene
2-Cooloing blankets
3-Maintain respiration
4-Maintain acid base balance
