Systemic actions of local anesthetics

I like to present some information for students according the systemic actions of local anesthetics.

Local anesthetics are chemicals that reversibly block action potentials in all exitable membranes. The central nervous system and the cardiovasculair system therefore are especially susceptible to their actions. Most of the systemic actions of local are related to their blood or plasma level in the target organ. The higher the level, the greater will be the clinical action. Local anesthetics readily cross the blood-brain barrier. Their pharmacologic action on the Central Nervous system is seen as depression. At low blood levels, there were never noted clinical significance. At higher levels in case of toxic overdose levels, the primary clinical manifestation is a generalized toxic-clonic convulsion. Between these two extremes exist a spectrum of other clinical signs and symptoms such as preconvulsive signs and symptoms of central nervous toxity.

Preconvulsive Signs and symptoms of Central Nervous System Toxity

We can make a difference between the subjective felt symptoms just as numbness of tongue and circumoral region warm, flushed feeling of skin or pleasant dreamlike state.On the otherside according to the objectively observable signs we mention remarkable signs as shurred speech, shivering patients,tremor of muscles of face and distal extremities, muscular twitching, dizziness, visual disturbances, disorientacion tinnitus, generalized lightheadesness.

With a further increase in the blood level of the local anesthetic to above its therapeutic level, adverse reactions may be observed. Because the Central Nervous System is much more susceptible than other systems to the actions of local anesthetics, it is not surprising that the initial clinical signs and symptoms of overdose, toxic situations are in central nervous system. Over high blood levels would produce bilateral numbing of the tongue, as contrasted with the usual unilateral anesthesia seen after dental nerve blocks.

Analgesia

Local anesthetics possess a second action in relation to the Central Nervous System. Administered intravenously, they increase the pain reaction threshold and also produce a degree of analgesia.