Term
| Is the interior of a cell (when polarized) neutral, positively charged, or negatively charged? Why? |
|
Definition
| Slightly negative because the Na/K ATPase system exchanges 3 Na+ out of cell for every 2 K+ into cell. |
|
|
Term
| What is action potential? |
|
Definition
| A large change in membrane potential from a resting value of about -70 mV to peak of about +35 mV and back to -70 mV again. |
|
|
Term
| How is an action potential generated? |
|
Definition
| If depolarization exceeds a threshold level (abvoe -55 mV), voltage gated sodium channels are activated and large amounts of sodium enter the cell |
|
|
Term
| Why does the membrane potential increase to 35 mV? |
|
Definition
| The large influx of sodium cations |
|
|
Term
| What happens as action potential reaches its peak? |
|
Definition
| Sodium channels close and potassium channels open--> potassium exits cell (cell is repolarizing) |
|
|
Term
| How to local anesthetics work? |
|
Definition
| Bind directly to voltage-gated sodium channels and block the entrance of sodium into cell. |
|
|
Term
| Does the blocking of voltage gated sodium channels alter resting membrane potential? |
|
Definition
|
|
Term
| What is sensitivity to local anesthetic blockade determined by? |
|
Definition
Axonal diameter
degree of myelination
conduction velocity
relative location in nerve bundle |
|
|
Term
| What is the structure of local anesthetics? |
|
Definition
benzene ring (lipophilic) + teriary amine (hydrophilic) separated by:
ester = ester LA's OR...
amide= amide LA's |
|
|
Term
|
Definition
|
|
Term
| How are Local anesthetics metabolized? |
|
Definition
Esters: pseudocholinesterase
Amides: Liver |
|
|
Term
| What happens if you give an ester in the subarachnoid space? |
|
Definition
| It will last longer because there are no esterases in the CSF. |
|
|
Term
| Who would you want to be careful giving an amide LA to? |
|
Definition
| Anyone with hepatic dysfunction (cirrhosis) or decreased blood flow to liver (CHF, Vasopressors) |
|
|
Term
| What can prilocaine cause? |
|
Definition
| methemoglobinemia d/t metabolite--> O-toluidine |
|
|
Term
| What is pharmacological treatment for methemoglobinemia? |
|
Definition
methylene blue 1-2 mg/kg IV over 5 mins.
Converts Fe3+ to Fe2+ |
|
|
Term
| What can prilocaine cause? |
|
Definition
| methemoglobinemia d/t metabolite--> O-toluidine |
|
|
Term
| What is pharmacological treatment for methemoglobinemia? |
|
Definition
methylene blue 1-2 mg/kg IV over 5 mins.
Converts Fe3+ to Fe2+ |
|
|
Term
| Who would you want to be careful giving an amide LA to? |
|
Definition
| Anyone with hepatic dysfunction (cirrhosis) or decreased blood flow to liver (CHF, Vasopressors) |
|
|
Term
| How does lipid solubility relate to potency and duration of action. |
|
Definition
It is directly proportional to potency. The more lipophilic the more readily it will cross nerve membrane--> less molecules required for blockade= enhanced potency.
Lipid solubility is also directly proportional to duration of action. The more lipid soluble, the less likely the LA is going to be cleared by blood flow |
|
|
Term
| How does protein binding relate to duration of action? |
|
Definition
| local anesthetics bind to alpha-1 acid glycoprotein (and albumin to a lesser extent) which prolongs their elimination |
|
|
Term
|
Definition
| It is the pH at which the non-ionized and ionized form of drug is in equilibrium |
|
|
Term
A) is the non-ionized form lipid or water soluble?
B) what about the ionized form?
C) Do we want more non-ionized or more ionized? |
|
Definition
A) Lipid
B) Water
C) Non-ionized |
|
|
Term
| True or False. A local anesthetic with a high amount of ionized drug will have a quicker onset than one with a high amount of non-ionized drug? |
|
Definition
| FALSE. The non-ionized form has a quicker onset due to its lipid solubility and ability to penetrate cell wall |
|
|
Term
| What happens if you inject a local anesthetic in an environment that is more basic then the pKa of that drug? |
|
Definition
| You will have more non-ionized portion of the drug and it will have a fast onset |
|
|
Term
| What is the most cardiotoxic local anesthetic? |
|
Definition
| bupivicaine- blocks cardiac Na+ channels and dissociates very slowly |
|
|
Term
| When should you NEVER combine local anesthetic with epinephrine? |
|
Definition
| If doing a peripheral nerve block on a penis or on digits (fingers, toes) |
|
|
Term
| Name the structures you will penetrate when doing an epidural from posterior to anterior |
|
Definition
1. Skin
2. Sub Q tissue
3. supraspinous ligament
4. intraspinous ligament
5. ligamentum flavun (crunch)
6. epidural space |
|
|
Term
A) If doing a spinal, what structures exist anterior to the epidural space?
B) Where is CSF? |
|
Definition
A) spinal meninges- dura mater, arachnoid mater, pia mater
B) Between arachnoid and pia mater |
|
|
Term
When doing an epidural, once you have threaded the catheter what MUST you do?
why? |
|
Definition
TEST DOSE- 3 mL of 1.5% lidocaine (45mg) with 1:200,000 epinephrine (15 mcg)
to make sure you are not in a blood vessel (if you are you will see increase in HR and BP by ~20-30%) and to make sure you are not in the subarachnoid space (if you are the pt will exhibit signs of spinal-- numb from belly button down FAST, but not enough to elicit "high" spinal) |
|
|
Term
| How many vertebrae are there? |
|
Definition
| 33 total- 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal |
|
|
Term
| You have 7 cervical vertebrae but how many cervical nerve roots are there? |
|
Definition
|
|
Term
| What are the CV effects of epidural/spinal anesthesia? |
|
Definition
Decreased heart rate if block up to level T1-T4 (cardioaccelerator fibers)
Vasodilation (dec. CO d/t VENOUS dilation and dec. preload)
Should see compensatory tachycardia after BP drops, unless cardioaccelerator fibers blocked |
|
|
Term
| What is the order of blockade with Local anesthetics? |
|
Definition
| sympathetic, temperature, pain, touch, pressure, motor, vibration, proprioception |
|
|
