General Anesthetics Drugs used to induce a state of unconsciousness with the overall aim of ensuring hypnosis, amnesia , analgesia, immobility, skeletal muscle relaxation, and loss of control of reflexes of the autonomic nervous system. Features of ideal anesthetic
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Drugs used to induce a state of unconsciousness with the overall aim of ensuring hypnosis, amnesia, analgesia, immobility, skeletal muscle relaxation, and loss of control of reflexes of the autonomic nervous system.
1. Rapid and smooth induction and recovery.
2. Wide safety margin.
Minimal side effects.
Use of more than one agent to obtain ideal anesthesia.
I. Muscle relaxants
II. Pre-anesthetic medications.
Suppress muscle tone.
Atracurium, Vecuronium, Succinylcholine.
- Loss of pain sensation.
- The patient is conscious and conversational.
- Increased, irregular blood pressure.
- Increased respiratory rate.
- Surgical anesthesia.
- Regular respiration & relaxation of sk. muscles.
- Eye reflexes decrease until the pupil is fixed.
- Medullary paralysis.
- Severe depression of vasomotor and respiratory centers.
- Death may occur.
Time elapsed between onset of administration of anesthetic and development of effective surgical anesthesia.
Time during which the patient is surgically anesthetized.
The time from discontinuation of anesthetic drug until consciousness is regained.
(Blood : gas partition coefficient )
Methoxyflurane 12 Slow
Halothane 2.3 Slow
Enflurane 1.8 Medium
Isoflurane 1.4 Medium
Sevoflurane 0.69 Rapid
Desflurane 0.42 poor & Rapid
Nitrous Oxide 0.47 Rapid
Nitrous oxide >100
- metabolic rate.
- ICP (due to cerebral vasodilatation) # in head injuries.
- Dose - dependent EEG changes (Enflurane).
- Sensitize heart to catecholamines (Halothane)
- All respiratory depressants.
- Decrease hepatic flow.
- Hepatotoxicity (Only halothane ).
- All are skeletal muscle relaxants to varying degree.
- Cardiac output
- No sensitization of the heart to catecholamines
- Potent coronary vasodilator.
- H R
Pungent (not for pediatrics).
- H R
- Little effect on HR
due to low blood solubility.
Bone marrow depression- leukopenia
Abortion - Congenital anomalies
2. Pernicious anemia.
1. Ultra short acting barbiturates.
Rapid onset of action 1 min (high lipid solubility)
Ultra short duration of action 15 - 20 min
Metabolized slowly by the liver.
1. Chronic obstructive lung disease.
3. Hypersensitive patients.
4. Severe hypotension (hypovolemic & shock patient).
1. Induction of general anesthesia.
2. Alone in minor procedure (endoscopy).
3. Balanced anesthesia (midazolam).
4. Pre-anesthetic medication (diazepam)
- Ultra-short acting hypnotic (non barbiturates).
- No analgesic activity.
- Decreases ICP.
Induction of Anesthesia
- Hypnotic (non barbiturates).
- No analgesia.
- Decreases ICP.
1. Hypotension (PVR).
2. Excitation (involuntary movements).
3. Pain at site of injection.
5. Clinical infections due to bacterial contamination.
- Rapid onset of action (slower than thiopental)
- Metabolized in the liver to active metabolite (Norketamine).
1. BP & cardiac output (central sympathetic activity)
2. Increases plasma catecholamine levels.
4. Potent bronchodilator (asthmatics).
- Short duration of action.
- Potent analgesia.
- No muscle relaxation
1. Head injuries.
3. Bronchial asthma.
4. Chronic obstructive lung diseases.
5. Hypovolemic shock (Large dose only).
relaxation BUT no loss of consciousness.
co-operation of the patient.
Neuroleptanesthesia : a combination of (Fentanyl + Droperidol + nitrous oxide).