Term
In "resting state" the nerve cell is polarized:
Excess ___ charges on the interior of cell
Excess ___ charges on the extracellular surface
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Definition
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Term
| In resting state, the cell membranes permeability to Na+ is low. K+ is more freely permeable. This is maintained by the the Na/K pump and creates a net ___ charge on the interior of the cell |
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Definition
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Term
| Describe the mechanism of action of local anesthetics |
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Definition
Local anesthetics produce their effects by blocking Na channels. They bind directly to intracellular voltage dependent Na channels thus blocking the large Na influx associated with membrane depolarization.
This does not alter the resting membrane potential. |
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Term
| Name 4 characteristics that determine nerve sensitivity to blockade |
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Definition
Axonal diameter
Degree of myelination
Conduction velocity
Relative location in nerve bundle |
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Term
| The lipophilic portion of local anesthetic structure |
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Definition
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Term
| The hydrophilic portion of local anesthetic structure |
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Definition
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Term
| The lipophilic and hydrophilic portions of a local anesthetic are separated by a chain that contains either an ___ or ___ linkage |
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Definition
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Term
| Local anesthetics are ___(strong/weak) ___(acids/bases) carrying a slightliy ___(postive/negative) charge at physiologic pH |
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Definition
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Term
| How are ester local anesthetics metabolized primarily? |
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Definition
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Term
| This byproduct of some ester local anesthetics has a high incidence of allergic reactions |
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Definition
| PABA (para-aminobenzoic acid) |
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Term
| Why do esters that are injected intrathecally rely on their absorption into the blood stream to be metabolized? |
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Definition
| CSF lacks esterase enzymes |
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Term
| How are amide local anesthetics metabolized? |
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Definition
the liver
**decreases in liver function or blood flow will decrease the rate of metabolism |
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Term
| Compare normal hemoglobin to methemoglobin |
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Definition
| Normal hemoglobin has iron in the ferrous state (Fe2+), Methemoglobin has iron in the ferric state (Fe3+) and its oxygen carrying capability is poor |
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Term
| What local anesthetics are responsible for methemoglobinemia? |
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Definition
| Methemoglobinemia is caused by metabolites of prilocaine and to a lesser extent by topical benzocaine |
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Term
| Name the treatment for methemoglobinemia |
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Definition
methylene blue: 1-2 mg/kg of 1% solution over 5 minutes
**This reduces Fe3+ to Fe2+ |
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Term
| How does lipid solubility of local anesthetics correlate with their potency and duration of action? |
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Definition
| The greater the lipid solubilty, the more potent it is and the longer the duration of action |
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Term
| How does the protein affinity of a local anesthetic affect its duration of action? |
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Definition
| Binding to proteins prolongs their elimination |
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Term
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Definition
| pKa is the pH at which the specific drug is 50% ionized and 50% unionized |
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Term
Novocaine/procaine:
Max dose?
Duration?
Duration with epi? |
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Definition
Novocaine/procaine:
Max dose: 12 mg/kg
Duration: 30-60 min
Duration with epi: 30-90 min |
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Term
Nesacaine/chloroprocaine:
Max dose?
Duration?
Max dose with epi?
Duration with epi? |
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Definition
Nesacaine/chloroprocaine:
Max dose: 12 mg/kg
Duration: 30-60 min
Max dose with epi: 14 mg/kg
Duration with epi: 30-90 min |
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Term
Pontocaine/tetracaine:
Max dose?
Duration? |
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Definition
Pontocaine/tetracaine:
Max dose: 3 mg/kg
Duration: 90 min - 6hrs
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Term
Cocaine:
Max dose?
Duration?
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Definition
Cocaine:
Max dose: 3 mg/kg
Duration: 30-60 min |
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Term
Xylocaine/lidocaine:
Max dose?
Duration?
Max dose with epi?
Duration with epi? |
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Definition
Lidocaine/xylocaine:
Max dose: 4 mg/kg (3-5)
Duration: 30-120 min
Max dose with epi: 7 mg/kg
Duration with epi: 120-360 min |
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Term
Carbocaine/mepivacaine:
Max dose?
Duration?
Max dose with epi?
Duration with epi? |
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Definition
Mepivicaine/carbocaine:
Max dose: 4 mg/kg
Duration: 45-90 min
Max dose with epi: 7 mg/kg
Duration with epi: 120-360 min |
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Term
Ropivicaine:
Max dose?
Duration? |
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Definition
Ropivicaine:
Max dose: 3 mg/kg
Duration: 90-240 min |
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Term
Marcaine/bupivacaine:
Max dose?
Duration?
Max dose with epi?
Duration with epi? |
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Definition
Marcaine/bupivacaine:
Max dose: 2.5 mg/kg
Duration: 120-240 min
Max dose with epi: 3.2 mg/kg
Duration with epi: 180-420 min |
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Term
Duranest/etidocaine:
Max dose?
Duration?
Max dose with epi?
Duration with epi? |
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Definition
Duranest/etidocaine:
Max dose: 6 mg/kg
Duration: 120-180 min
Max dose with epi: 8 mg/kg
Duration with epi: 180-420 min |
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Term
A Bier block involves injection of local anesthetic _____ (route).
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Definition
Intravenously
**Used for procedures of the hand and forearm |
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Term
| With a Bier block, a patient may complain of "tourniquet pain" if the surgery extends past how long? |
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Definition
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Term
| Name some symptoms of local anesthetic toxicity |
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Definition
Circumoral and tongue numbness
Lightheadedness and tinnitus
Visual disturbances
Muscle twitching
Unconsciousness
Convulsions
Coma
Respiratory arrest
CV collapse
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Term
| Describe the treatment of local anesthetic toxicity |
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Definition
- Oxygen to raise the seizure threshold
- Ett if needed
- Hyperventilate to ↓ delivery of local anesthetic to brain
- Drugs: Benzos, barbs
- Supportive treatment of CV collapse
- Lipid rescue protocol (20% intralipid)
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Term
| Which local anesthetic is the most cardiotoxic? |
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Definition
bupivicaine
**blocks cardiac sodium channels and dissociates very slowly |
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Term
| Name some sites for peripheral nerve blocks |
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Definition
Digits
Ankles
Brachial plexus
Lower extremities
Penile
**Do not use epi with digits or penile blocks |
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Term
| Name the structures you will go through when placing an epidural from posterior to anterior |
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Definition
Skin
Subcutaneous tissue
Supraspinous ligament
Intraspinous ligament
Ligamentum flavum
Epidural space
Spinal meninges: Dura mater, arachnoid mater, pia mater
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Term
| Describe the "Hanging Drop" method of epidural placement |
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Definition
- Drop of fluid at the hub of the needle
- Insert in slow increments
- When fluid gets "sucked in" you are in the epidural space
- **primarily recommended for thoracic epidural
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Term
| Describe the LOR technique for epidural placement |
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Definition
- Touhy syringe with a few mL's of air or saline
- Slowly advance either with constant pressure or tapping on plunger until there is a "loss of resistance" which signifies you are in the epidural space
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Term
When giving an epidural test dose of 3 ml of 1.5% lidocaine with epi 1/200k, what happens if the catheter is intravascular?
If the catheter is subarachnoid? |
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Definition
Intravascular - increase in HR & BP by 20%
Subarachnoid - show S/S of spinal |
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Term
| Name the drugs (with concentration) that we use for epidural |
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Definition
Chloroprocaine 2-3%
Lidocaine 1-2%
Mepivicaine 1-2%
Bupivacaine 0.25-0.75%
Ropivacaine 0.1-0.5% |
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Term
| Caudal epidurals involve entering the epidural space through the ____ ____ and penetration of the ____ _____. |
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Definition
sacral hiatus
sacrococcygeal ligament |
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Term
| Spinals are injection of local anesthetic into the _____ space |
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Definition
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Term
Break down the vertebrae by regions
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Definition
7 cervical
12 thoracic
5 lumbar
5 sacral
4 coccygeal |
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Term
| Name the drugs used for spinals |
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Definition
Bupivacaine 0.75%
Lidocaine 5%
Tetracaine 0.5-1%
Procaine 10%
**each drug has different characteristics
**sensory vs motor blockade |
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Term
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Definition
| The density of the drug as compared to CSF |
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Term
| The superior iliac crest is a key landmark for which vertebrae? |
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Definition
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Term
| The nipple line is a key landmark for which vertebra? |
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Definition
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Term
| The xiphoid process is a key landmark for which vertebra? |
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Definition
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Term
| The umbilicus is a key landmark for which verterbra? |
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Definition
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Term
| Name some absolute contraindications to local and regional anesthesia |
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Definition
Patient refusal
Severe uncorrected coagulopathies
Severe AS
Hypovolemic shock
Increased ICP
Infection at site
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Term
| Name some relative contraindications to local and regional anesthesia |
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Definition
Sepsis
Uncooperative patient
Pre-existing neuro deficits
Severe spinal deformity
Stenotic valve lesions |
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Term
| Which contraindications to local and regional anesthesia are considered controversial? |
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Definition
Prior back surgery
Communication issues
Complicated surgery |
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Term
| Name some physiologic effects of spinal anesthesia and epidurals |
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Definition
- CV effects (mainly due to SNS blockade)
- Vasodilation
- Decreased venous return
- Decreased BP/CO
- Decreased HR (cardioaccelerator fibers T1-4)
- Pulm effects: Blockade of intercostals
- Nausea caused by hypotension
- Hypothermia due to vasodilation
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Term
| In regards to order of blockade, a local's effect on spinal nerves depends on: |
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Definition
Diameter
Speed
Myelination
Location in bundle |
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Term
| List the order of blockade |
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Definition
S-T-P-T-P-M-V-P
Sympathetic, temp, pain, touch, pressure, motor, vibration, proprioception |
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Term
| Name some possible complications of spinals and epidurals |
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Definition
Hypotension
N/V
Post-dural puncture headache
High spinal |
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