LOCAL ANAESTHETICS Flashcards
Give 3 features of local anaesthetics
- Reversible blockers
- Affect restricted area
- Patient is fully conscious
What are the 6 methods of administrating LA?
- Topical
- Infiltration
- Nerve block
- Epidural
- Spinal regional
What is the effect of administering LA more proximally?
Affects a greater number of axons and has a bigger effect. The closer to the CNS you are, the more axons are effected
Explain how topical anaesthetic works
The anaesthetic is placed on the skin or gums and diffuses through the surface. The diffusion is slow and it only affects a small area. They block nerve endings in the skin and can be used for burns and itching
Explain how infiltration anaesthetic works
The LA is injected into the skin/ tissue in a circle and takes out all the nerves within the circle. This allows for better coverage and knocks out more axons. LA can be injected into an open wound
Explain how nerve block anaesthetic works
More proximal to CNS and so takes out more axons. An injection of a local anaesthetic to numb the nerves supplying a particular part of the body, such as the hand, arm or leg
Explain how epidural anaesthetic works
The epidural space is a fluid-filled space that LA can be injected into. It is used during labour and it is close to the spinal cord and so can take out lots of axons. Injected at L3-L4 region
Explain spinal anaesthesia
Go into a fluid filled space and goes into a spinal cord. Can knock out sensation in both legs. Still restricted but area covered is a large area
This is the same as regional
LA effect on cardiovascular system (2)
- Heart - heart rate slows down because there are fewer contractions
- Blood vessels - dilation and lower blood pressure because smooth muscle does not work as well
LA effect on other excitable tissues
- High does can result in convulsions or tremors
- CNS - affects brain neurones
Side effects (2)
- hypersensitivity reactions due to effects of what the LA dissolves into
- Inaccurate use can result in very high doses
Drugs given alongside LA
- Vasoconstrictors like adrenaline
4 qualities of a good LA
- Reversibly block voltage gated Na+ channels
- Low toxicity
- block in nociceptive neurones
- Time that they are in effect for is appropriate
