Neuraxial Anesthesia I Exam I Flashcards
(175 cards)
1
Q
What are the 4 types of central neuraxial anesthesia?
A
- Spinal Anesthesia
- Epidural Anesthesia
- CSE (combined spinal and epidural)
- Caudal anesthesia
2
Q
What type of neuraxial anesthesia do we normally not use (except for sometimes in children)
A
- Caudal anesthesia
3
Q
What are the clinical indications of neuraxial anesthesia? (4)
A
- Surgical procedures involving the lower abdomen, perineum, and lower extremities
- Orthopaedic surgery
- Vascular surgery on the legs
- Thoracic surgery in adjunct to GETA
4
Q
What are the 2 most common types of orthopaedic surgery that we use spinal anesthesia for?
A
- Knee replacement
- Hip arthroplasty
5
Q
Why do we use neuraxial anesthesia as an adjunct to general anesthesia in thoracic surgeries?
A
- To optimize post op pain management so the patient can better breathe, cough, and ambulate.
6
Q
What 6 major things does neuraxial anesthesia reduce as opposed to GETA? (6)
A
- Reduces post op ileus
- Reduces thromboembolic events
- Reduces PONV
- Reduces Respiratory complications
- Reduces bleeding
- Reduces narcotic use
7
Q
What are the other benefits of using neuraxial anesthesia over GETA? (7)
A
- Better/greater mental alertness
- Less urinary retention
- Patient is quicker to eat, void, and ambulate
- The avoidance of unexpected overnight admission from complications of general anesthesia
- Quicker PACU discharge times
- Preemptive anesthesia
- Blunts the stress response from surgery
8
Q
What factors in the OR can induce PONV? (5)
A
- Opioid use
- Being female
- Volatile gases
- Neostigmine
- Longer surgery times
9
Q
Why do patients with spinal anesthesia sometimes have more urinary retention?
A
- Due to bladder distension
- However, it is still less urinary retention than patients who recieved GETA.
10
Q
What is the difference between relative contraindication and **absolute **contrainidation when discussing neuraxial anesthesia?
A
- Relative means it depends on the situation. You can do the procedure, but it depends because it will be extra work and you may not get the block.
- An absolute contraindication means the patient has a condition that absolutely prevents them from recieving neuraxial anesthesia.
11
Q
What are the relative contraindications in neuraxial anesthesia? (4)
A
- Deformities of the spinal column such as spinal stenosis, kyphoscoliosis, scoliosis, and ankylosing spondylitis.
- Pre-existing diseases of the spinal cord such as multiple sclerosis and post polio syndrome. Neuraxial anestheasia could exacerbate a progressive, degenerating spinal disease.
- Chronic headache/ backache
- The inability to perform SAB or epidural after 3 attempts.
12
Q
What are the absolute contraindications in neuraxial anesthesia? (13)
A
- Patient refusial
- Evidence of dermal site infection
- Coagulopathy/ risk of epidural hematoma
- Platelets < 100,000
- INR > 1.5
- PT, a PTT, or bleeding time that is 2x the normal amount
- Known coagulation disorder
- Taking anticoagulants
- Severe or critical valvular heart disease, specifically aortic stenosis. AS < 1.0cm^2 and MS < 1.0cm^2
- HSS - idiopathic hypertrophic subaortic stenosis
- Operation > duration of LA (EX: cannot use SAB for a long case because it has a short duration of action)
- increased ICP
- Severe CHF with an EF < 30-40% and preload dependence.
13
Q
A CRNA/RRNA must find someone else to obtain the SAB or epidural after they have attempted ___ times without successfully getting the block.
A
- 3 times
14
Q
What time of approach will you need to use with neuraxial anesthesia for patients with scoliosis?
A
- A side approach versus a medial apprach to get to the subarachnoid or epidural space.
15
Q
What is informed consent for anesthesia?
A
- Makes the patient aware of potential complications that could happen due to anesthesia.
16
Q
What is the normal range for INR?
A
- 0.8 - 1.1
17
Q
What i the normal range for aPTT?
A
- 25-32 seconds
18
Q
What is the normal range for bleeding time?
A
3-7 minutes
19
Q
What is the normal range for platelet count?
A
150,000 - 300,000
20
Q
- What is the acronym for the intrinsic pathway?
- What does this mean?
- What anticoagulant is used on this pathway?
- What bleeding test is used for this pathway?
A
- If you cant buy the intrinsic pathway for $12, you can buy it for $11.98
- 12 > 11 > 9 > 8 > final common pathway
- Heparin
- aPTT and ACT
21
Q
- What is the acronym for the extrinsic pathway?
- What does this mean?
A
- For 37 cents you can buy the extrinsic pathway.
- 3 > 7 > final common pathway
- Coumadin
- PT and INR
22
Q
- What is the acronym for the final common pathway?
- What does this mean?
A
- The final common pathway can be purchased at the five and dime for 1 or 2 dollars on the 13th of the month.
- 5 > 10 > 1 > 2 > 13
23
Q
What does bleeding time look at?
A
platelet function
24
Q
What is the death spiral?
A
- Seen with aortic stenosis
- Hypotension causes myocardial ischemia
- Which then causes ischemic contractile dysfunction
- Which then causes decreased cardiac output
- Which then causes wordening hypotension
- Which then causes increased ischemia and death
25
What are the clinical manifestations of aortic stenosis based on? (3)
* Angina
* Syncope
* Heart failure
26
If a patient has angina with aortic stenosis, what is their likelihood of survival?
5 years
27
If a patient has syncope with aortic stenosis, what is their likelihood of survival?
3 years
28
If a patient has heart failure with aortic stenosis, what is their likelihood of survival?
2 years
29
What hemodynamic instability is not good with aortic stenosis?
* Hypotension
30
For spinal anesthesia:
* Onset
* Spread
* Nature of block
* Motor block
* Hypotension
* Onset: rapid
* Spread: higher than expected and may extend extracranially because it travels with the CSF in the subarchnoid space.
* Nature of block: dense (numbness all over)
* Motor block: dense ( shouldn't be able to move legs)
* Hypotension: likely
31
For epidural anesthesia:
* Onset
* Spread
* Nature of block
* Motor block
* Hypotension
* Onset: slow
* Spread: as expected anc can be controlled with volume of LA
* Nature of block: segmental (EX: numbness L4-T10)
* Motor block: minimal (could potentially still walk due to minimal blockade)
* Hypotension: less than spinal
32
For spinal anesthesia:
* Onset in minutes
* Duration
* Placement level
* Difficulty of placement
* Dosing of LA
* Concentration of LA
* LA toxicity
* Gravity influence
* Manipulation of dermatome spread after dosing
* Onset in minutes: quick, within 5 minutes
* Duration: limited and fixed based on duration of action of each LA.
* Placement level: L4 - L5, L5-S1, L3-L4
* Difficulty of placement: no
* Dosing of LA: dose based in mg
* Concentration of LA: concentrated and fixed
* LA toxicity: no
* Gravity influence: yes based on baracity
* Manipulation of dermatome spread after dosing: Yes (1st 5 minutes) position changes baracity (iso, hyper, and hypo), dose
33
For epidural anesthesia:
* Onset in minutes
* Duration
* Placement level
* Difficulty of placement
* Dosing of LA
* Concentration of LA
* LA toxicity
* Gravity influence
* Manipulation of dermatome spread after dosing
* Onset in minutes: slow (10-15 minutes)
* Duration: unlimited
* Placement level: any level
* Difficulty of placement: more skill required
* Dosing of LA: volume based in mL
* Concentration of LA: varies
* LA toxicity: yes
* Gravity influence: yes based on position
* Manipulation of dermatome spread after dosing: Incremental dermatome spread based on volume 1-2 mL per segment
34
What must you do immediately after giving a spinal anesthetic and why?
* Have a nurse in front of them in case they fall and lay them on their back because the onset of action is rapid.
35
How do you know if your SAB is in the right spot?
They start feeling numb very quickly
36
* What are the 2 main indicators on the monitor that let you know your spinal anesthesia is working?
* Why is this?
* Hypotension
* Bradycardia
* Due to sympathectomy of cardioaccelerator nerves T1 - T4
37
What are the cardioaccelerator nerves in the spine?
T1 - T4
38
* What is a wet tap when doing an epidural?
* What fluid will you see?
* What does this cause?
* When your large needle for your epidural unitentially went directly through the dura matter and into the subarachnoid space.
* You will see CSF
* Gives the patient a severe/chronic headache.
39
What type of patients does a wet tap usually happen in when doing an epidural?
* Skinny patients
40
What is the most amount of volume of LA you would use for a spinal anesthetic?
* No more 3 - 4 mL
41
Is the concentration of LA lower or higher in your epidrual anesthesia versus spinal anesthesia?
* lower concentration in epidural but has more volume of fluid (EX: 0. 0125mg in 10mL)
42
What causes local anesthesia systemic toxicity (LAST)?
* Systemic absorption of your LA into the blood stream.
* Innadvertantly putting LA into the veins.
43
Why does last happen very rarely in spinal anesthesia?
* Because there aren't alot of veins in the subarachnoid space for you to hit with your needle.
44
Whay is LAST more common in epidural anesthesia?
* Because there are alot more veins to potentially hit with your needle in the epidural space.
45
What is baracity
* It refers to the density of the LA compared to the CSF in the subarachnoid space during a spinal block.
46
Why do we not care about baracity with epidural anesthesia?
Because there is no CSF in the epidural space
47
* What are the 2 main things located in the epdirural space?
* What 1 thing is not located here?
* engorged veins and fats
* Contains no CSF
48
* What is the main component of the subarchnoid space for spinal anesthesia?
* What is the impirtance of this?
* CSF
* Your LA will travel the entire distance the CSF covers, the spinal cord and brain.
49
* In terms of baracity for spinal anesthesia, what does hyperbaric mean?
* How should you position your patient?
* The LA will sink
* If you want your LA to go higher than your injection site, you would trendelenburg the bed so the drug travels up the spinal cord.
50
* In terms of baracity for spinal anesthesia, what does hypobaric mean?
* The LA will rise
51
* In terms of baracity for spinal anesthesia, what does isobaric mean?
* The LA will stay at the position of the injection site.
52
What do we test first, within the first 5 minutes, on a patient recieving spinal anesthesia?
sensory function
53
What 3 neurons travel together to the brain up the afferent pathway?
* sensory
* pain
* temperature
54
* When giving epidural anesthesia, what is the test dose method?
* What is this method used to prevent?
* Get the full volume that you need for your epidural anesthesia drawn up in your syringe > give the LA in incremential dosing of 3-4mLs, once you have injected the incremental dose, aspirate it back out into the syringe to make sure you havent traveled to a vein > then push another incremental dose back into the patient.
* Used to prevent LAST which is more common in epdirual anesthesia.
55
How many total vertebra do we have?
* 33
56
How many cervical vertebra do we have?
* 7
57
How many thoracic vertebra do we have?
* 12
58
How many lumbar vertebra do we have?
5
59
How many sacral vertebra do we have?
5 (fused together)
60
How many coccyx vertebra do we have?
4 (fused together)
61
Describe the curvature of scoliosis
* S-shaped spine
62
Describe the curvature of kyphosis
* Pronounced posterior curvature of thoracic spine that gives you a hunchback look
63
Describe the curvature of lordosis
* Pronounced anterior curvature of the lumbar spine.
64
Each vertebra except ___ is divivded into 2 main body parts; the ___ and the ___
* C1
* Anterior segment
* Posterior segment
65
What is another name for the anterior segment?
* The body
66
What is another name for the posterior segment?
the vertebral arch
67
What 2 structures link the anterior and posterior segments of the vertebra?
* Lamina
* Pedicle
68
* What do the lamina and pedicle form?
* What 3 things does this space house?
* The vertebral foraman which is the crucial space within each vertebra.
* The vertebral foramen houses the spinal cord, nerve roots, and the epidural space.
69
In the spinal cord, what is the function of the epdirural space?
* Used as a protective cushioning around the spinal cord.
70
Label the picture
71
Label the picture
72
Label the picture
73
What part of the spine is our landmark for neuraxial anesthesia to let us know we are midline?
* The spinous process
74
Where are the transverse processes located on the vertebra?
To the right and left lateral sides
75
Where is the spinous process located on the vertebra?
on the posterior side of the vertebra.
76
What is the purpose of having muscles attach to and connect the transverse and spinous processes?
To help stabalize the spine
77
What is the difference between the cervical and thoracic spinous processes compared to the lumbar spinous processes?
* Cervical spinous processes have a large tilt downwards in the caudal direction.
* Thoracic spinous procecesses have a slightly less tilt dowbwards than the cervical.
* Lumbar spinous processes stick out directly posterior/perpendicular.
78
What type of approch do cervical and thoracic epidural anesthesia require due to the nature of their spinous processes?
A cephalad approach (meaning the needle points upwards) because the spinous spocesses are pointing downwards.
79
Why is is easier to do spinals and epidurals in the lumbar space?
Because those vertebra stick out directly posterior/perpendicular which makes it much easier to reach the spaces around the spinal cord such.
80
What are intevertebral disks?
Soft pads between each vertebra that act as shock absorbers
81
What are intervertebral foramina?
The openings between the vertebrae where spinal nerves exit the spine
82
What forms the anterior side of the intervebral foramina?
* Vertebral body
* Intervetebral disc
83
What forms the posterior side of the intervertebral foramina?
* the facet joints on the posterior side of the spine
84
What are the 3 major impacts of disc degeneration?
* When the discs where down over time, the intervertebral foramina becomes smaller.
* The narrowing of the intervertebral foramina can press on the spinal nerves potentially causing pain, numbness, or weakness.
* These patients have a much harder time curving their back forward (which is needed for neuraxial anesthesia) because it is painful.
85
What are the 2 parts that form each facet joint in each vertebra?
* The inferior articular process of the top (superior vertebra)
* The superior articular process of the bottom (inferior vertebra)
86
What are the functions of the facet joints? (2)
* To help guide and limit spines movement
* To keep the back's motions controlled.
87
What happens if a facet joint gets injured?
It can press on the nearby spinal nerves
88
What are the symptoms if a facet koint gets injured?
The compression of the spinal nerves in the area can cause pain and muscle spasms in the area of skin served by that nerve (dermatome)
89
What is the term for bending your spinal cord/vertebrae forward?
Flexion
90
What is the term for bending your spinal cord/vertebrae backwards?
extension
91
Label the landmarks
92
What is the landmark for L4?
Superior aspect of the iliac crest
93
What is the landmark for S2?
Posterior superior iliac spine
94
What is tuffiers line?
* A horizontal line that runs across the top edges of the hip bones (iliac crests) and meets at the L4 vertebra midline.
95
What is another name for tuffiers line?
Intercristal line (this is an older term)
96
What does tuffiers line help identify?
the correct spaces between vertebrae for inserting spinal anesthesia needles.
97
What space is above tuffiers line?
The space between L3 and L4
98
What space is below tuffiers line?
The space between L4 and L5
99
In infants up to 1 year, tuffiers line (intercristall line) corresponds with what area on the spine?
The L5 to S1 intervertebral space
100
What is the landmark for C7?
Vertebra prominens
101
What is the landmark for T3?
Spinous process of the scapula
102
What is the landmark for T7?
Inferior angle of the scapula
103
What is the landmark for L1?
Lowest rib
104
Where is the safest site for a subarachnoid block?
* Tuffiers line (the midline space between the superior aspects of the iliac crests)
* The interspinous space between L4 and L5
105
Describe the sacrum
A triangular shaped section of 5 fused vertebrae
106
In the sacrum, the lamina of S5 is ___ and bridged only by ___.
* incomplete
* ligaments
107
* Where is the sacral hiatus located?
* What does it align with?
* What ligament covers it?
* What is it an access point for?
* Located at the base of the sacrum.
* Aligns with the S5 vertebra
* Is covered by the sacrococcygeal ligament
* Acts as an acess point to caudal anesthesia.
108
* What is the only sacral bone that is not fused?
* What is it bridged by?
* S5
* The Sacrococcygeal ligament bridges S4 to S5.
109
* What is the sacral cornua?
* Where is it located?
* What is the function?
* What is it a landmark for?
* Projections of the articular processes in the sacrum
* They are horns or bony protuberances that guard the area of the sacral hiatus.
* Is a landmark for caudal anesthesia.
110
* What is the landmark for caudal anesthesia?
* What is the access point for caudal anesthesia?
* Sacral cornua
* Sacral hiatus
111
Label the sacrum
112
When is caudal anesthesia typically used?
For pediatric patients
113
* Is caudal anesthesia epidural or spinal?
* Why?
* Epidural
* Because there is no CSF in this space. S5 where your sacral hiatus is located is epidural/potential space.
114
* Where does the intrathecal space end in the spinal column?
* What fluid also ends here and doesn't go any further?
* S1-S2
* CSF
115
The epidural space is a ___ space.
potential
116
Where does the spinal cord start?
* Medulla oblongata
* Rostral origin
117
* What is the conus medullaris?
* Where does it end in adults?
* Where does it end in infants?
* The inferior portion of the spinal cord that tapers off at the end.
* Adults = Between L1 and L2 vertebrae
* Infants = at L3
118
Where does the spinal cord end?
L1-L2
119
* What is the Cauda Equina?
* What does it consist of?
* A bundle of spinal nerves extending from the conus medullaris to the dural sac.
* It consists of nerves roots from L2 to S5 vertebrae and the coccygeal nerve.
120
What does cauda equina mean?
* Hair of the horse
* represents what all the nerve endings look like in this area of the spinal column.
121
How many nerve endings does each vertebra have?
2: a right and a left
122
* Where does the subarachnoid space end?
* What level in adults?
* What level in infants?
* At the dural sac
* S1-S2 in adults
* S3 in infants
123
Does the CSF go beyond S2?
no
124
* What is the filum Terminale?
* What is it a continuation of?
* Where is it located?
* What is the function?
* A structure that continues downward from the end of the spinal cord.
* Is a continution of the pia mater.
* Extends from the conus medularis to the coccyx (tailbone)
* Main function is to anchor the spinal cord to the coccyx.
125
What is another name for the coccyx?
tailbone
126
Where is the internal filum terminale located?
Begins at the conus medullaris, extending to the dural sac.
127
Where is the external filum terminale located?
* Starts at the dural sac and extends into the sacrum.
128
* How many anterior spinal arteries are there?
* How many posterior spinal arteries are there?
* 1
* 2
129
* Where does the anterior spinal artery originate from?
* Does is supply the motor or sensory portion of the spinal cord?
* How much of the spinal cord does it supply?
* Originates from the vertebral artery
* Supplies the front motor portion of the spinal cord.
* Supplies the anterior 2/3rds of the spinal cord.
130
* Where do the 2 posterior spinal arteries emerge and originate from?
* Do they supply the motor or sensory portion of the spinal cord?
* Emerge from the cranial vault and originate from the vertebral artery.
* Supplies the posterior sensory portion of the spinal cord.
131
The central area of the spinal cord, supplied only by the anterior spinal artery, is predominately a ___ area.
* motor area
132
* Which spinal artery is more vulnerable to ischemia?
* Why?
* The anterior spinal artery (motor)
* Because it is a single artery, it doesn't have as many protective links.
133
What is anterior spinal artery syndrome?
* Also known as anterior cord syndrome.
* A condition resulting from interuption of blood flow through the anterior spinal artery, which causes loss of motor function and loss of pain and temperature sensation below the level of the lesion. Proprioception and vibration sensation are preserved.
134
What are the causes of anterior spinal artery syndrome? (4)
* Low blood pressure/ prfound hypotension.
* mechanical blockage
* blood vessel disease (vasculopathy) Triple A
* bleeding/hemorrhage.
135
Where does the anterior spinal artery recieve additional connections (anastimotic links) from?
the intercostal and iliac arteries, althoug these are variable for the anterior spine.
136
* What is the artery of Adamkiewicz?
* Where is it located?
* Damage to this artery will cause what?
* A crucial connection that supplies blood to the lower 2/3rds of the spinal cord.
* Arises from the aorta between the T9 to L2 regions.
* Damage to this artery will cause anterior spinal artery syndrome.
137
How do the posterior spinal arteries protect themselves from ischemia?
There are 2 of them and they have many different connections called collateral anastomotic links that help protect the sensory part of the spinal cord from ischemia.
138
Where do the anastomotic links for the posterior spinal arteries originate from?
The subclavian arteries and intercostal arteries.
139
What type of anesthesia is typically used for aortic surgeries?
General anesthesia
140
Where is the supraspinous ligament?
Runs along the posterior side of the body and connects the tips of the spinous processes from the upper back to the lower back.
141
Where is the interspinous ligament?
Located between the spinous processes and provides stability by joining adjacent vertebrae
142
Where is the ligamentum flavum?
* These form the sidewalls of the space outside the spinal cord (epidural space.
* They are thicker in the lower spine.
143
What does piercing the ligamentum flavum indicate?
indicates entry into the epidural space during procedures.
144
Where is the posterior longitudinal ligament?
Runs along the backside of the vertebral bodies, inside the spinal column
145
Where is the anterior longitudinal ligament?
* Runs along the front side of the vertebral bodies, and runs the length of the spinal column.
* Also connects to the outer fibers of the intervertebral discs, helping to bind the vertebrae together.
146
Label the ligaments
147
What are the layers you traverse during a midline approach for a spinal block?
* Skin
* Subcutaneous fat
* Supraspinous ligament
* Interspinous ligament
* ligamentum flavum
* dura mater
* subdural space
* Arachnoid mater
* subarachnoid space
148
What are the layers you traverse during a paramedian approach for a spinal block?
* Skin
* Subcutaneous fat
* ligamentum flavum
* dura mater
* subdural space
* Arachnoid mater
* subarachnoid space
149
What are the layers you traverse during a midline epidural?
* Skin
* Subcutaneous fat
* Supraspinous ligament
* Interspinous ligament
* ligamentum flavum
* Epidural space
150
Why would you use a paramedian approach for spinal anesthesia?
When the interspinous ligament is calcified or the patient cannot flex their spine (EX: kyphoscoliosis)
151
What are the 3 ways a patient can be positioned for a paramedian spinal approach?
* sitting
* lying on their side
* lying face down
152
What is the procedure for doing a paramedian spinal approach?
* Insert the needle 15 degrees off the spine's midline.
* Position the needle 1cm to the side (lateral) and 1 cm below (inferior) the space ebwteen the vertebrae (interspace)
153
What is your landmark to know you are midline for spinal or epidural anesthesia?
spinous process
154
Label the structures
155
Label the structures
156
What is the order of the 3 meningial layers from outer to inner?
* Dura mater - outer
* Arachnoid mater - middle
* Pia mater - inner
157
What does the pia mater directly cover?
Directly covers the spinal cord.
158
* Where does spinal anesthesia stop?
* Where does epidural anesthesia stop?
* The subarachnoid space
* The epidural space
159
What are the contents of the subarachnoid space?
CSF
160
What are the contents of the epidural space?
* small epidural veins veins
* fatty tissue
* air
* nerves
* lymphatics
161
Where is the epidural space?
Superficial to the dura mater
162
Where is subdural space?
A potential space between the dura mater and the arachnoid mater.
163
Where is the subarachnoid space?
Between the arachnoid mater and the pia mater.
164
What is the purpose of the CSF in the subarachnoid space?
It cushions and protects the spinal cord.
165
How do we know that the spinal anesthesia is in the wrong place?
* Patient still has motor movement
* Sensation is still there
* We don't see the drop in HR and BP
166
What is the other term for spinal anesthesia?
intrathecal anesthesia
167
What is the most important thing in the epidural space for our LA?
* The fatty tissue
* If the LA is lipid soluble then it will hang around a little longer
168
What are the boundaries of the epidural space? (5)
* Cranial border: at the top, near the base of the skull at the foramen magnum.
* Caudal border: at the bottom, near the sacrococcygeal ligament which is connected to the coccyx.
* Anterior border: in front, lined by the posterior longitudinal ligament along the vertebrae.
* Lateral borders: on the sides, marked by the bony projections of the vertebrae called vertebral pedicles.
* Posterior border: at the back, framed by the ligamentum flavum and the bony plates of the vertebrae called the vertebral lamina.
169
What is the thing we are most concerned about in the epidural space?
the epidural veins
170
Where are the veins located in the epidural space?
on the lateral sides
171
How are drugs absorbed in the epidural space?
fatty tissue in this area can absorb and decrease the availability of certain drugs such as bupivicaine.
172
In the epidural space, which LA is absorbed more than lidocaine, fentanyl, and morphine?
Bupivicaine
173
What is another name for the epidural veins?
Batson's plexus
174
Describe the structure of the veins in Batson's plexus? (3)
* Valveless and form a plexus draining blood from the cord and its linings
* Density of veins increases laterally
* Become engorged under conditions such as obesity or pregnancy, increasing the risk during needle procedures in this area.
175
What is the significance of knowing that the veins are on the lateral sides of the epidural space?
If you hit a vein you are not midline. Pull the needle and reinsert midline.
