What is local anesthesia defined as?
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A loss of sensation in a circumscribed area of the body caused by depression of excitation in nerve endings or inhibition of the conduction process in peripheral nerves.
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What is local anesthesia defined as?
A loss of sensation in a circumscribed area of the body caused by depression of excitation in nerve endings or inhibition of the conduction process in peripheral nerves.
What is an important feature of local anesthesia?
It produces loss of sensation without inducing a loss of consciousness.
Is the effect of local anesthesia reversible?
Yes, it is reversible.
Does local anesthesia cause structural damage to neurons?
No, it does not cause structural damage to neurons.
What position should the subject be in for an intradermal injection?
Seated in a chair with arms (not on a stool).
Why is Lidocaine the most widely used local anaesthetic drug?
It acts more rapidly, is more stable than most other local anaesthetics, and is effectively absorbed from mucous membranes.
Where should the intradermal injections be administered on the body?
On the forearm, at positions well spaced over the forearm.
What concentrations of Lidocaine are used for surface anaesthesia?
2 to 4%
What is an indication that the intradermal injection was administered correctly?
A blister should be raised.
What is the maximum concentration of Lidocaine solutions for uses other than surface anaesthesia?
1%
What is the duration of action of Lidocaine when used with adrenaline?
About 90 minutes
What should you do if no blister is raised after an intradermal injection?
Repeat the injection at a different site, as the initial injection was probably too deep.
Why are vasoconstrictors like adrenaline added to local anaesthetics?
To diminish local blood flow, slow the rate of absorption of the local anaesthetic, and prolong its local effect.
Why is care necessary when using adrenaline?
Because, in excess, it may produce ischaemic necrosis.
At what angle should the needle be inserted for an intradermal injection?
At a very horizontal angle, between 10-15 degrees.
Does a single application of a topical lidocaine preparation generally cause systemic side effects?
No, it does not generally cause systemic side effects.
What is the final concentration of adrenaline used with local anaesthetics to prolong their action?
1 in 200,000
Why should adrenaline not be added to injections used in digits and appendages?
Because it may produce ischaemic necrosis.
What are the main causes of toxic effects after the administration of local anaesthetics?
What effect do most local anaesthetics, except cocaine, have on blood vessels?
They cause dilation of blood vessels.
What should be done when administering adrenaline to elderly or debilitated persons?
Reduce the dose.
What systems are mainly involved in the systemic toxicity of local anaesthetics?
The central nervous and cardiovascular systems.
How should adrenaline be administered in cases of severe renal or liver disease?
Avoid or reduce the dose.
What are the central nervous system (CNS) effects of local anaesthetic toxicity?
What precaution should be taken when using adrenaline in the 3rd trimester of pregnancy?
Avoid its use.
Why should reduced doses of local anaesthetics be given in some cases?
To avoid accumulation of the drug and subsequent toxicity.
What equipment should be available when administering adrenaline?
Resuscitative equipment.
How does injection into inflamed or infected tissues affect the absorption of local anaesthetics?
It increases absorption into the blood, leading to higher plasma concentrations and potential toxicity.
What are the contraindications for using adrenaline?
Hypovolaemia, sino-atrial disorders, all grades of atrioventricular block, severe myocardial depression, respiratory depression, acute porphyria.
Why should solutions containing adrenaline not be used for anaesthesia in appendages?
Because it may produce ischaemic necrosis.
What are some central nervous system effects of local anesthetics at lower concentrations?
Dizziness, blurred vision, nausea, and vomiting.
What are some central nervous system effects of local anesthetics at higher concentrations?
Muscle twitching, tremors, and convulsions.
What are severe central nervous system effects of local anesthetics?
Respiratory failure, unconsciousness, and coma.
What are some cardiovascular effects of local anesthetics?
Myocardial depression and bradycardia, peripheral vasodilatation, hypotension, arrhythmias, and cardiac arrest.
How does lidocaine work as a local anesthetic?
Lidocaine blocks fast voltage-gated sodium channels in the cell membrane of neurons, preventing depolarization and inhibiting the generation and propagation of nerve impulses.
Which neurons are primarily affected by lidocaine at lower blood concentrations?
Sensory neurons.
What happens when lidocaine is present at higher blood concentrations?
The effects become generalized.
