General anesthesia induced by inhalation or
intravenous injection of various anesthetic drugs
it renders patients analgesic, amnesic, and
unconscious, and provides muscle relaxation
These desired effects are not produced safely by
a single anesthetic
A combination of drugs is necessary to produce
all of these desired effects sought with
Balanced anesthesia approach to meet the patient
It involve the induction of anesthesia with a
combination of drugs.
It take each drug’s beneficial effects while minimizing
each agent’s adverse effects.
A state of light anesthesia not deep enough to permit
Diazepam slowly intravenous
Thiopental sodium rectally
The depth of anesthesia has been
divided into four sequential stages:
Stage 1: Analgesia (induction )
Stage 3:Surgical anesthesia
Stage 4: Medullary paralysis
Lippincott’s pharmacology 4th edition
Analeptic drugs (drugs stimulate medullary
centers ) e.g. doxapram IV infusion
Mechanism of action
No specific receptor has been identified
The focus is now on interactions of the inhaled anesthetics with
proteins comprising ion channels. E.g., the general anesthetics
increase the sensitivity of the GABAA receptors to the
neurotransmitter, GABA. →↓Postsynaptic neuronal excitability
Other receptors are also affected by volatile anesthetics; e.g., the
activity of the inhibitory glycine receptors in the spinal motor
neurons is increased.
In addition, the inhalation anesthetics block the excitatory
postsynaptic current of the nicotinic receptors.
Weak anesthetic (Low potency)
Has rapid induction and recovery
Good analgesic and sedative properties
No skeletal muscle relaxant properties
Exposure to nitrous oxide for long periods cause
vitamin B 12 deficiency and megaloplastic anemia
Uses -Minor operation
-combined with other anesthetics to enhance
Is the prototype to which newer inhalation
anesthetics have been compared
General anesthetic with rapid induction and rapid
Has moderate analgesic and skeletal muscle
Non-irritant to respiratory tract &produce
• Hypotension, bradycardia and cardiac arrhythmias.
• Post operative nausea and vomiting
• Respiratory depression and hypoventilation.
• Hepatotoxicity (halothan hepatitis) rarely .
• Malignant hyperthermia may occur with halothane
Halothane drug interaction
Halothane sensitizes the myocardium to the effects
of sympathomimetics. These agents may Produce
serious cardiac arrhythmias in the presence of
Halothane adverse effects
Relatively rapid induction and recovery
Produces good analgesia, skeletal muscle relaxation
No sensitization of heart to catecholamines.
At high concentration produces CNS stimulation
Similar to enflurane but it is irritating to the airway and can
cause laryngospasm and excessive secretions
Similar to enflurane but it produces concentration-
rapid uptake without irritating the airway during Induction
it may prove to be nephrotoxic.
They have rapid induction and recovery
No analgesic and no skeletal muscle relaxation
Ultrashort acting barbiturates
•Short duration of action
•Repeated injection lead to prolongation of its duration of action
Ultrashort- acting barbiturates
induction of anesthesia
anesthersia short operative procedures
Bronchospasm in asthmatics
Necrosis and ulceration if injected around the vein
Arterial spasm, thrombosis and gangrene if injected into the artery
No cardiovascular and respiratory depression
Induction of anesthesia
Permit anesthesia for short operative procedures
an intravenous sedative/hypnotic used in the induction
or maintenance of anesthesia.
Rapid onset of anesthesia and very fast recovery
Benzodiazepines are sedative hypnotic drugs
Diazepam, lorazepam and Midazolam
Characters of anesthesia:
produces rapid induction and short duration.
unconsciousness’ with amnesia
Administered by intravenous and intramuscular
Produces “dissociative” anesthesia
Slow onset and recovery is associated with dysphoria
It stimulates the central sympathetic outflow
may increase Blood pressure, heart rate
Increase intracranial pressure and intraocular pressure
Contraindicated in hypertension and psychic disturbances
Morphine, meperidine , and fentanyl
Employed as supplements during general anesthesia
Very large doses of opioids may be infused to obtain
Opioids can cause hypotension, respiratory depression
,Muscle rigidity and post anesthetic nausea and
Drugs given before administration of anesthesia in
Provide amnesia for the preoperative period
Relieve of preoperative pain if it present.
Reduce the requirement for an anesthetic agent.
Minimize undesirable side effects associated with
some of these agents (Salivation, bradycardia,
coughing, vomiting) = produce vagolytic effect.
Reduce the volume and acidity of gastric contents.
Preanesthetic medication usually require the use
of two or three drugs together
Drugs that reduce gastric acidity
The most commonly used
classes of Drugs
Sedative hypnotics and anti-anxiety drugs
e.g. diazepam IM
(sedation, amnesia and reduce anxiety)
e.g. meperdine IM
(Reduce pain , reduce the amount of general anesthetic
e.g. atropine, scopolamine IM
(Decrease salivation and bronchial secretion, protect
against bradycardia and hypotension)
Drugs that reduce gastric acidity
e.g. ranitidine and antacids