1. How does the sensitivity blockade by LA compare regarding the following types of fibers: 

• Myelinated fibers with unmyelinated fibers:

Unmyelinated fibers are more sensitive to the effects of local anesthetics, because there are easier to block than myelinated fibers. 

• Pressure/ touch nerves with the dorsal nerves that transmit pain impulses?

Sensory fibers have a high firing rate and relatively long action potential duration. As type A delta and C fibers participate in high frequency pain transmission, this characteristic may favor blockade of these fibers earlier and with lower concentrations of local anesthetics. 

 

2. Make a list of the effects of LA on other tissues

CNS: local anesthetics are capable of producing a spectrum of central effects, including: light-headedness, sedation, restlessness, nystagmus, and tonic-clonic convulsions. Severe convulsions may be followed by coma with respiratory and cardiovascular depression. 

Cardiovascular: with the exception of cocaine, all LA's are vasodilators. Patients with pre-existing cardiovascular disease may develop heart block and other disturbances of cardiac electrical function at high plasma levels of local anesthetics. Cardiovascular toxicity can occur. 

 

3. What is the basis of the selection of a LA?

The duration of the procedure, the type of procedure, the target site of the procedure. 

 

4. Why are LA solutions sometimes saturated with CO2?

CO2 acts as a buffer for the local anesthetic and reduces the pain of the injection and it increases the onset rate of action of the anesthetic. 

 

5. Which of the LA are typically used for surface anesthesia? 

Cocaine, Benzocaine and Oxybuprocaine.