• Is a temporary state consisting of
unconsciousness, loss of memory, lack of pain,
and muscle relaxation.
• A patient under the effects of anesthesia is said
to be anesthetized.
• Types of Anesthesia
• Local anesthesia
• General anesthesia
Pre-Anesthetic Medication :
• Drugs administered before an anesthetic to decrease
anxiety and to obtain:
Emergence from anesthesia.
These drugs are
• Sedative hypnotic ::
• To subside worry and tension e.g Diazepam .
• For smooth induction and decrease post operative pain
• To reduce bronchial secretion e.g Atropine .
• To prevent nausea and vomiting e.g Promathiazine .
•A drug that brings about a
reversible loss of sensation along
with the loss of consciousness .
General Anaesthesia (GA)
• A variety of drugs are given
to the patient that have
different effects with the
overall aim of ensuring
Stage I: Analgesia
decreased awareness of pain . Consciousness may be
impaired but not lost..
Stage II: Disinhibition
Excitatory stage, uncontrolled movement, irregular
Goal is to move through this stage as rapidly as possible.
Stage III: Surgical anesthesia
return of regular respiration.
Loss of blink reflex, regular respiration . Surgical
procedures can be performed at this stage.
Stage IV: Medullary Depression
This is the stage between respiratory arrest and death due
to circulatory collapse..
Stages Of General Anesthesia
MAC(minimum alveolar concentration)
•A measure of potency of
Pharmacokinetics of Inhaled
1. Amount that reaches the brain
Indicated by oil:gas ratio (lipid solubility)
2. Solubility of gas into blood
The lower the blood:gas ratio, the more anesthetics will arrive at
Rate of Entry into the Brain: Influence of Blood
and Lipid Solubility
General Actions of Inhaled Anesthetics
• Depressed respiration and response to CO2.
• Depression of renal blood flow and urine output.
• High enough concentrations will relax skeletal muscle.
• Cardiovascular System
• Generalized reduction in arterial pressure and peripheral vascular
• Isoflurane maintains CO and coronary function better than other
• Central Nervous System
• Increased cerebral blood flow and decreased cerebral metabolism.
• Rapid induction and
• No adverse effects on
• Good analgesia
• Diffusion hypoxia
• Post operative nausea
• Ineffective anesthetic
• Inadequate muscle
• Non irritating
• Safe for children
• Can be given in
• Weak analgesia and
• CVS and respiratory
•Malignant hyperthermia (MH) is a
state of skeletal muscle induced in
susceptible individuals by
inhalational anesthetics and/or
succinylcholine (and maybe by
stress or exercise).
•Signs: tachycardia, hyperthermia,
muscle rigidity, sweating, arrhythmia.
•May be fatal.
•Treated with Dantrolene.
• Rapid inhalation and
• CNS excitation
• May cause seizures
• Most exert their actions by potentiating
• GABAergic actions may be similar to
those of volatile anesthetics, but act at
different sites on receptor.
• Most decrease cerebral metabolism and intracranial
• Most cause respiratory depression.
• May cause apnea after induction of anesthesia.
•They cause cardiovascular
• Short acting
• Can be used in
• Very good analgesic
• Post operative
• Increase cerebral
• Rapid and smooth
onset and recovery
• Reduce intracranial
• Poor analgesic
• Excreted through
• DEFINITION: Local anaesthesia is drug-induced
reversible local blockade of nerve conduction in a specific
part of the body that does not alter consciousness.
Prosperities of ideal LA
• Reversible action.
• No allergic reaction.
• No systemic toxicity.
• Rapid onset of action.
• Sufficient duration of action.
• Stable in solutions.
• Not interfere with healing of tissue.
• Have a vasoconstrictor action or compatible with VC.
• Not expensive
Bier block (IV
Six Placement Sites
Esters vs Amides
• The ester linkage is more easily broken so the ester drugs
are less stable in solution and cannot be stored for as
long as amides.
• Amide anaesthetics are also heat-stable.
• The metabolism of most esters results in the production of
para-aminobenzoate (PABA) which is associated with
• Amides, in contrast, very rarely cause allergic
phenomena. For these reasons amides are now more
commonly used than esters.
The mechanism of action of local
• Disruption of ion
channel function via
specific binding to
holding them in an
• Disruption of ion
channel function by the
incorporation of local
into the cell membrane
• Small nerve fibres are more sensitive than large nerve
• Myelinated fibres are blocked before non-myelinated
fibres of the same diameter.
• Thus the loss of nerve function proceeds as loss of pain,
temperature, touch, proprioception, and then skeletal
muscle tone. This is why people may still feel touch but
not pain when using local anaesthesia.
Absorption and distribution
• Some of the drug will be absorbed into the systemic
circulation: how much will depend on the vascularity of the
area to which the drug has been applied.
• The distribution of the drug is influenced by the degree of
tissue and plasma protein binding of the drug. the more
protein bound the agent, the longer the duration of action
as free drug is more slowly made available for
Metabolism and excretion
• Esters (except cocaine) are broken down rapidly by
plasma esterases to inactive compounds and
consequently have a short half life. Cocaine is hydrolysed
in the liver. Ester metabolite excretion is renal.
• Amides are metabolised hepatically by amidases. This is
a slower process, hence their half-life is longer and they
can accumulate if given in repeated doses or by infusion.
• Local anesthesia.
• Ventricular arrhythmia.
• Decrease haemodynamic response to tracheal intubation
also decrease cough.
• Treatment of epileptic fits.
Advantages of local anaesthesia
• Non inflammable.
• Excellent muscle relaxant effect.
• During local anesthesia the patient remains conscious.
• It requires less skilled nursing care as compared to other
anesthesia like general anesthesia.
• Maintains his own airway.
• Less pulmonary complication.s
• Aspiration of gastric contents unlikely.
• Less nausea and vomiting.
• Contracted bowel so helpful in abdominal and pelvic
• Postoperative analgesia.
• There is reduction surgical stress.
• Earlier discharge for outpatients.
Advantage of using adrenaline:
•Epinephrine vasoconstricts arteries reducing bleeding and also
delays the resorption of lidocaine, almost doubling the duration of
•Bupivacaine has caused several deaths when the epidural
anaesthetic has been administered intravenously accidentally.
• CNS: excitation followed by
dépression (drowsiness to
unconsciousness and death due to
• Cardiovascular System: bradycardia,
heart block, vasodilation
• Allergic reactions: allergic dermatitis
to anaphylaxis (rare, but occur most
often by ester-type drugs).
• Accidental rapid
• Rapid absorption, such
as from a very vascular
site ie mucous
• Overdose .
Factors reducing toxicity:
• Decide on the concentration of the local anaesthetic that
is required for the block to be performed. Calculate the
total volume of drug that is allowed according to the table