Name of Blog: Blog #9

Answer the following for a Blog Summary:

• How does the sensitivity for blockade by a LA compare regarding the following types of fibres:

(a) myelinated fibres with unmyelinated fibres; and 

(b) pressure/touch nerves with the dorsal nerves that transmit pain impulses?

 

a.) Smaller myelinated fibres are easier blocked than larger and unmyelinated fibres.

b.) Fibres in the middle of a thick nerve bundle is blocked slower than those at the outside of the bundle.

 

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

Heart	Class 1 antiarrhythmic drugs. Ex. Lidocaine acts as a class 1 antiarrhythmic drug which blocks the sodium channels in the heart with the goal of blocking the propagation of an action potential & prolonging the refractory period).
Skeletal muscle	LA’s have a very weak blocking action, thus not used for any clinical applications.
Cocaine	↑ mood, and Cocaine influences central catecholamine mediated neurotransmission (inh. NA re-uptake).

 

• What is the basis for the selection of a LA?

Depending on the desired effect and the type of procedure/ clinical application.

• Why are LA solutions sometimes saturated with CO2?

All inhaled anesthetics can produce some carbon monoxide (CO) from their interaction with strong bases in dry carbon dioxide absorbers. CO binds to hemoglobin with high affinity, reducing oxygen delivery to tissues. Desflurane produces the most CO, and intraoperative formation of CO has been reported. CO production can be avoided simply by using fresh carbon dioxide absorbent and by preventing its complete desiccation.

• Which of the LA are typically used for surface anaesthesia?

Cocaine is used in procedures requiring high surface activity & vasoconstriction, eg. ear,nose and eye surgery.