2. CNS
• In one word : DEPRESSION
• At high levels, LA will produce tonic-clonic convulsions
• Procaine, Lidocaine etc produce ANTICONVULSANT properties.
3. • This drugs are used for management of grand mal & petit mal seizures
• The depressant action of LA raise the seizure threshold by decreasing the
excitability of cortical neurons in epileptic patients
4. PRECONVULSIVE SIGNS &
SYMPTOMS
• Numbness of the tongue & circumoral regions
• If excitation or sedation occurs in the first 5 or 10 minutes after administration of
LA, it should consider as a warning that convulsive activity could be possible.
• Shivering, slurred speech, muscular twitching, visual/auditory disturbances,
dizziness, drowsiness, disorientation & tremor.
5. CONVULSIVE PHASE
• Duration of seizures is related to blood level of LA & inversely related to
arterial pCO2 levels.
• Seizures last less than or equal to one minute.
• In seizure,
1) cerebral blood flow &
2) cerebral metabolism increase
8. RESPIRATORY SYSTEM
• DUAL EFFECTS :
1. Non-overdose levels : Direct relaxant action on bronchial smooth muscle
2. Overdose levels :
9. CVS
• Direct action on myocardium & peripheral vasculature.
• Increased LA blood levels result in decreased myocardial depolarization
• Decrease in myocardial excitation, decrease in conduction rate & decrease in
the force of contraction
• Produces hypotension ( direct relaxation effect on vascular smooth muscle )
10. LOCAL TISSUE TOXICITY
• Skeletal muscle will heal within 2 weeks of being injected with local
anaesthetic.
• Longer acting LA produces more damage to skeletal muscle than shorter
acting LA.
11. TOXICITY OF LOCAL ANAESTHESIA
1- Causes
2- Factors reducing toxicity.
12. CAUSES
• Accidental rapid intravenous injection.
• Rapid absorption, such as from a very vascular site i.e mucous membranes.
• Overdose
13. FACTORS REDUCING TOXICITY
• Decide on the concentration of the local anaesthetic that is required for the block to
be performed. Calculation of the total volume of drug should be done.
• Use the least toxic drug available.
• Use lower doses in frail patients or at the extremes of ages.
• Always inject the drug slowly (around 1ml /minute) and aspirate regularly looking
for blood to indicate an accidental intravenous injection
14. • If Injection of a test dose of 2-3ml of local anaesthetic containing adrenaline is accidentally
given intravenously it will often (but not always) cause significant tachycardia.
• Add adrenaline (epinephrine) to reduce the speed of absorption. The addition of adrenaline
will reduce the maximum blood concentration by about 50%. Usually adrenaline is added in
a concentration of 1:200,000, with a maximum dose of 200 micrograms.
• Make sure that the patient is monitored closely by the anaesthetist or a trained nurse during
the administration of the local anaesthetic and following the surgery.
15. ADVANTAGES OF LOCAL
ANAESTHESIA
• During local anesthesia the patient remains conscious
• Maintains his own airway.
• Excellent muscle relaxant effect.
• Requires less skilled nursing care as compared to other anesthesia like general
anesthesia.
• Non inflammable.
16. • Less pulmonary complications
• Aspiration of gastric contents unlikely.
• Less nausea and vomiting.
• Contracted bowel so helpful in abdominal and pelvic surgery.
• Postoperative analgesia.
• There is reduction surgical stress.
• Earlier discharge for outpatients.
17. • Suitable for patients who recently ingested food or fluids.
• Local anesthesia is useful for ambulatory patients having minor procedures.
• Ideal for procedures in which it is desirable to have the patient awake and
cooperative.
• Less bleeding.
• Expenses are less.
18. DISADVANTAGES OF LOCAL
ANAESTHESIA
• There are individual variations in response to local anesthetic drugs.
• Rapid absorption of the drug into the bloodstream can cause severe,
potentially fatal reactions.
• Apprehension may be increased by the patient's ability to see and hear.
• Some patients prefer to be unconscious and unaware.
19. • Direct damage of nerve.
• Post-dural headache from CSF leak.
• Hypotension and bradycardia through blockade of the sympathetic nervous
system.
• Not suitable for extremes of ages.
• Multiple needle pricks may be needed.
