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Local Anesthetics Part 2
Terms in this set (28)
IV Regional Anesthesia: Bier Block
50cc of 0.5% lidocaine Plain injected into a hand vein of surgical arm after exsanguinations and tourniquet inflated
-toxicity can occur if tourniquet is deflated <20min after injection of LA
Peripheral Nerve Block
Can block any nerve to prevent the transmission of pain
Examples of Peripheral Nerve Blocks
Femoral nerve block
transverse abdominis plane block(TAP)
Where does the spinal cord extend
Spinal Cord extends from the medulla oblongata to the level of L1 in adults and to L3 in children(this level moves up as we grow)
What is the caudal equina
Below the spinal cord the vertebral canal is filled by the roots of the lumbar and sacral nerves known as the Cauda equina
The meninges are covered by what three layers?
pia mater, arachnoid matter, and dura mater. Pia mater is closely adhered to the spinal cord. The CSF is between the pia and arachnoid mater in the subarachnoid mater in the subarachnoid space, this is where we place local anesthetics and opioids.
Where is the usually needle placement?
the superior aspect of the iliac crest marks approximatly the level of L4. needle placement usually anywhere between L2 and L4
Solution in Epidural space
LA diffuses across the dura to act on nerve roots and spinal cord.
Also diffuses into paravertebral area leading to multiple paravertebral nerve blocks
-set up time about 15-30min before you see sensory anesthesia
-Lidocaine diffuses easily will use in OB crash C/S
Epidural space is a potential space within the spinal canal its boundaries are dura and the ligamentum flavum
Eipdural needles slight curve to end of needle to prevent puncture of dura and CSF leak causing headache.
Zone of Differential Blockade
*2-4 levels below sensory block level
Large dose compared to SAB
-Epinephrine limits systemic absorption also lets you know if you have systemic absorption
*sensory block is the level where pain and touch are blocked
Spinal ANesthesia:Injection of LA in subarachnoid space into CSF
-Action is on superficial layers of spinal cord
-Primary site of action Preganglionic fibers as they leave the spinal cord in the anterior rami
Develop zones of differential anesthesia
*sympathetic block 2 segments cephalic to sensory block
*Motor block averages 2 segments below sensory block
Dose of LA for SAB depends on these factors
-Segment level desired
-Desired duration of anesthesia
Spinal Bupivicaine 0.75% in 8.25% dextrose-How many ccs
for a <5 feet, 5feet to 5ft8in and >5ft8in
What is 10mg of spinal bupivacaine=?
What is the max in ccs of spinal bupivicaine 0.75% you can give?
What does dextrose do to spinal ANesthesia?
makes it heavier than CSF- Plain solution makes it equal with CSF and mixing local, plain solution with sterile nonpreservatitve water makes it lighter than CSF.
Baracity-Determines spread of LA and block height
Position of pt
-sitting, jackknife, trundelenberg
-Dose,volume, and concentration of LA
Sinks to dependent regions of spinal cord
-Heavier than CSF
-Addition of Glucose
-Head down position drug travels toward head
-head up position drug travels to bottom
Floats to non-dependent regions of spinal cord
-Lighter than CSF
-Addition of Distilled water
-head down position drug travels toward feet
-Head up position drug travels to head
stay put diffusing slowly
-Equal to CSF
-Addition of Normal Saline
-Remains at level of injection site
Can we influence block height?
Yes through choice of solution and proper patient positioning. If you place a pt in trundelenburg with hyperbaric solution it can travel up into the thoracic area and cause problems. Like wise if you give hypobaric solution reverse trundelenburg will cause the drug to travel cephalic. Over time in the csf the baracity changes and becomes more isobaric and movement in any direction subsides.
Specific Gravity of LA
Important in determining the spread of drugs in lumbar CSF--specific gravity of CSF=1.003-1.008 @ 37degrees celsius
Level of SAB
Position of Patient
-Supine=hyperbaric tend to settle in dependent areas of spine T4-8
Lateral=Hyperbaric travels to the dependent side
Hypobaric travels to the nondependent side
Complications of Neural Blockade
Occurs because of several different factors
-Failure to reduce standard dose in selected patients
-unusual sensitivity or spread of LA
C/0: dyspnea and have numbness or weakness in upper extremities, nausea with or w/o vomiting, then hypotension
-Treat w O2, reassure pt, treat bradycardia and hypotension
SAB that travels to cervical spinal level=
-severe hypotension,bradycardia and reap insufficiency
-secure airway and ventilate
*IV fluid bolus
*Aggressive use of vasopressors
-epi early if Neo and Ephedrine not effective
*Atropine if severe bradycardia
Order in which Neural block occurs
8mg/kg or 1000mg
3mg/kg or 200mg
plain 4mg/kg w epi 7mg/kg
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