ICP management for dummies
So you get a page that the ICPs are high. What do you do?
Step 1: Do not panic. If you panic, everyone panics.
Step 2: See the patient. Evaluate. Think. Are they sitting upright, talking to you, stating they feel great with the ICP monitor reading some absurd number? It might be wrong. Re-zero, troubleshoot, scan if you need to. Alternatively, some people live at ICPs of 50-70 - think of all the pseduotumor patients. Just because the number is high does not necessarily mean something bad is happening; the reason why elevated ICPs are bad is because of concern for decreased cerebral perfusion. If someone is neurologically intact, then they are clearly perfusing their brain. You can sit on high-grade SAH patients with ICPs in the 60s as long as they are awake and talking to you and without deficit; However, if someone is posturing with a blown pupil, then something probably has to be done about it.
Step 3: ABC - Airway, breathing, circulation first, always. Are they intubated? Do they need to be? Are they hemodynamically stable? If they are not protecting their airway, secure the airway first. If they are unstably hypotensive, push fluids/pressors/blood as appropriate - because if you send an unstable patient to CT and they code in the scanner, you're retarded
Step 4: ICP algorithm
- First thing, get the head of bed up, ensure neck is not excessively extended, or worse, flexed. This sounds really small but ensuring great venous drainage can buy you a lot of ICP lowering benefit. The only thing that should stop you from doing this is (very) unstable T/L spine fractures - which is why you should radiographically clear spines on any TBI as soon as possible, in anticipation of this occurring in the future, so you're not hurridly looking for total spine scans when your patient is herniating. I was once told by a team that they could not sit up a patient with very elevated ICPs because of straight-leg precautions after angio. Weigh the risk of groin hematoma vs rapid death from herniation, realize why this is absurd, and get the head of bed up. In the very least, you can do reverse-T.
- Second thing, assuming they are intubated, which people with ICP monitors often are, increase resp rate. Learn how to work your hospital ventilators so you know how to do this. This move does not buy you long-term ICP relief, but it gets you a rapid lowering that buys you time to think and plan your next moves. Reiteration: this is not a viable option for ICP management in any time-course longer than a few hours. You will get rebound effects, and after a while you will get worsening of ischemia from lower oxygen delivery to brain. A second thought: look at the rest of the parameters of your vent while you're there - if the PEEP is absurdly high, consider lowering it to improve venous drainage. Preventing herniation takes precedence over ARDSnet protocols or whatever else. Get an ABG to confirm no CO2 retention but don't wait for the results before you change the rate.
- Third, hyperosmolar therapy. Mannitol vs hypertonic saline. They both have rebound effects - the brain parenchymal osms will reset, and then you will get rebound edema. This happens much faster with mannitol than with hypertonic saline; mannitol buys you a few hours, with hypertonics you get about 24-48 hours. This is why we only use mannitol when we are about to crash someone to the OR for decompression, or if you can't get your serum osms up with hypertonic saline alone for whatever reason. Otherwise, I will always use 3% first. FYI a 250cc bag of 3% pushed at max speed delivers the same salt load as a 25cc bolus of 23% saline and you don't have to deal with an ICU team getting antsy about central lines. FYI#2 never allow central line placement to delay OR in someone who needs it stat; if its really needed, anesthesia can do it under the drapes while you operate. How much hypertonics can you give? I start getting nervous when Na>160 and Osm>320. At that point, if its not working, its not working and you should try something else.
NB: problematically, if the BBB is compromised, the hypertonics will go directly into that tissue and draw fluid in and actually worsen edema. This isn't a problem if your ICP issues are from a traumatic acute subdural, but it is a big problem if they are from a big ischemic stroke -- all the mannitol will go into the bad side and swell and crush the good side even more.
- Fourth, sedation. I like boluses of propofol, which is often rapid and very effective at lowering ICPs, as long as blood pressures will tolerate. From subjective experience, propofol has more ICP lowering effect than other things, like versed or precedex, but I have no objective evidence to support that. Pushing sedation of whatever agent of your choice is a fast and effective way of both lowering ICPs and (theoretically) of lowering cerebral oxygen demand. This is titratable - you can go from a few propofol boluses to get someone through a procedure or an event, all the way to sedating someone into burst suppression for recalcitrant ICP issues. If you're going to burst suppress, pentobarb >> extremely high dose propofol (i.e. 200mcg/kg/hr).
- Fifth, paralytics. When all else fails, you can put people on drips of non-depolarizing paralytics; this is especially helpful for people who are bucking the vent or shivering etc and you think this movement is contributing to ICP elevation. NB: most people prefer cis drips for this because of its predictable pharmacokinetics, whereas for roc or vec, the elimination is non-linear is if you put people on a drip of roc or vec for several days, it can take them > 24-48 hours to wake up and start moving, *even if* their train of fours show 4/4 twitches, so give people generous amount of time before you start brain death testing. You can have up to 80% residual neuromuscular blockade and have 4/4 twitches. Needless to say, do not remove your ICP monitor until they wake up, because you won't have an exam to follow.
Side notes:
- figure in early whether or not people will be surgical candidates. In people who are not surgical candidate, I would use exclusively salt, sedation, and paralytics and only use hyperventilation transiently to get someone through an ICP spike; I wouldn't use mannitol unless I couldn't get their osms high enough with Na alone.
- in people with EVDs, draining off CSF (or lowering the drain) can be an excellent option to temporarily lower ICPs, especially if there is a hydrocephalus component. If you get a dramatic ICP response to the drainage of a relatively small amount of CSF, that tells worlds about the ventricular compliance and about where you may be sitting on the pressure-volume curve.
Sunday, August 28, 2016
Thursday, August 18, 2016
Open lumbar spine surgery - Part I
Types of tables:
- Jackson with OSI frame: standard setup that we use - has table with the rails and the pads for chest, hips, thighs. can adjust level of rods at each end so you get extra T or reverse-T - if you're doing say an L5-S1 fusion and the sacral slope is really steep, you can get feet up so you're working horizontally, etc etc. When putting people on OSI, put chest pad on upper chest- not directly against chin, not too low for women. Some people think you should straighten knees relative to hips so you avoid hypothetical risk of fusing people in hip flexion position, however in real life this is rarely a problem.
- Jackson table with Wilson frame: forced flexion over the arc. Gets you better access to the disc, which is useful if you're doing a discectomy, however can give you a false sense of security about how much decompression you have achieved. Like you feel nerve roots, you think they are decompressed because they are in forced flexion, but then when back goes straight everything closes off and then you're not decompressed anymore. Also as a note - if you're gonna use a Wilson frame, better to do Jackson table because its' lower - Wilson frame is high, unless you're really tall you're gonna be on 4 steps.
- Jackson table w Axis frame - can bend in half. Most useful for XLIF/DLIF when you position patient laterally, really opens up space between iliac crest and and ribs.
- Jackson flattop - useful vs standard table because its radiolucent and also no giant pedicle in the middle- so if you're doing an ALIF you have an easier time getting C-arm under table.
Arm positioning :
- up for middle T/L - make sure no hyperextension of arms back or too anterior, keep elbows soft, 90 degrees; protect against axillary nerve injury
- down/wrapped for C and upper T
Setting up the room:
- head towards anesthesia, scrub nurse at legs, surgeon on each side of back.
- assuming the pathology doesn't have laterality, choose the side of patient that doesn't have the base of the C-arm on it, so you're not moving your steps/foot pedals around every time the C-arm moves.
- when you move c-arm out of the way, move it towards anesthesia/patient head - because your scrub nurse is by patient's legs and you don't want the c-arm between you
General principles
- Look at CT scan before every case; look at anatomy - planning on lami, make sure there is actually lamina at every level. Some people have big facets, and there may be no lamina to take at a given level, or some atypical scoliosis, such that you have to drill at an angle. if you meant to do a lami, without a fusion, and you violate the facet capsule or worse drill facet when you didn't mean to, then you're hosed because you've destabilized that level.
- determine pedicle sizes on scan, pick out screw size and length beforehand, write them on the board
Process:
- localize level first with c-arm.
- mark incision
- prep and drape wide
- 15 blade through skin
- buzz through fat with impunity
- put finger in and feel for the spinous processes - directly above spinous process is fascia. every time. every time. that's where it is. lateral to spinous process will be bumps for paraspinous muscle.
- take cobb and scrape last bit of fat off fascia. In everyone except super old frail people with terrible fascia, you can scrape and you will not accidentally break through as long as you're not jabbing aggressively
- cut on either side of spinous process. Take cobb, put raytech on it, and scrape down along spinous process. you should be sub-periosteal. if you are not, you will be in muscle - it will bleed like crazy and the patient will have a lot more postop pain. alternative to cobb is bovie down bone (but be careful directly lateral to lamina- there lie nerve roots). problem with bovie is it will cause paraspinal muscles to tighten and fight you - option to ask anesthesia for short-acting muscle relaxant. if someone has pacemaker or otherwise can't tolerate electrocautery, then you have to do the bipolar and cut thing which sucks.
- your cobb will then land on lamina. scrape ROSTRAL and LATERAL - next you will land on a valley of bone which is the superior aspect of pars, between the superior facet and the lamina. then scrape your cobb more rostral and more lateral - you will go over a bump, this is the facet capsule, and then you will land on the transverse process. If you're only doing a lami, you don't need to see TP but if you're doing a fusion you will need to expose a lot of the TP.
- THE PEDICLE IS ROSTRAL TO THE SPINOUS PROCESS. once you find the spinous process, you have to go rostral to find pedicle. this is especially true in thoracic spine - if you try to take shortcuts and aren't thoughtful, and you go for the pedicle directly next to the spinous process, you will put the screw in the wrong level.
- the anatomy is as such: from rostral to caudal superior facet, TP/pedicle, lamina, inferior facet, with the pars representing the bridge of bone connecting superior to inferior facet
NB
- if you're doing a lami, you cannot drill all the way lateral - if you take pars, you destabilize
- you cannot bovie with impunity directly lateral to the spinous process/lamina - that's where the nerve roots come out. (if patient jumps and they are not paralyzed, its because your electrocautery hit a nerve root). this is why we don't paralyze spine cases.
- there is often a large artery next to pars - if it starts bleeding like crazy, don't dive after it with electrocautery, as you might hit nerve roots.
- if someone has giant, super hypertrophied facets, you might need to drill off the inferior aspect of facet to access entry point for pedicle screw - be careful - you can only drill approx 1/3 of facet joint before you destabilize
Thoughts on cervical decompression
- if most of someone's compression is coming from disk, you can do ACDF
- if there is a hypertrophied ligamentum flavum or facet arthropathy, you can get a lot more decompression of spinal cord if you come from the back
Types of tables:
- Jackson with OSI frame: standard setup that we use - has table with the rails and the pads for chest, hips, thighs. can adjust level of rods at each end so you get extra T or reverse-T - if you're doing say an L5-S1 fusion and the sacral slope is really steep, you can get feet up so you're working horizontally, etc etc. When putting people on OSI, put chest pad on upper chest- not directly against chin, not too low for women. Some people think you should straighten knees relative to hips so you avoid hypothetical risk of fusing people in hip flexion position, however in real life this is rarely a problem.
- Jackson table with Wilson frame: forced flexion over the arc. Gets you better access to the disc, which is useful if you're doing a discectomy, however can give you a false sense of security about how much decompression you have achieved. Like you feel nerve roots, you think they are decompressed because they are in forced flexion, but then when back goes straight everything closes off and then you're not decompressed anymore. Also as a note - if you're gonna use a Wilson frame, better to do Jackson table because its' lower - Wilson frame is high, unless you're really tall you're gonna be on 4 steps.
- Jackson table w Axis frame - can bend in half. Most useful for XLIF/DLIF when you position patient laterally, really opens up space between iliac crest and and ribs.
- Jackson flattop - useful vs standard table because its radiolucent and also no giant pedicle in the middle- so if you're doing an ALIF you have an easier time getting C-arm under table.
Arm positioning :
- up for middle T/L - make sure no hyperextension of arms back or too anterior, keep elbows soft, 90 degrees; protect against axillary nerve injury
- down/wrapped for C and upper T
Setting up the room:
- head towards anesthesia, scrub nurse at legs, surgeon on each side of back.
- assuming the pathology doesn't have laterality, choose the side of patient that doesn't have the base of the C-arm on it, so you're not moving your steps/foot pedals around every time the C-arm moves.
- when you move c-arm out of the way, move it towards anesthesia/patient head - because your scrub nurse is by patient's legs and you don't want the c-arm between you
General principles
- Look at CT scan before every case; look at anatomy - planning on lami, make sure there is actually lamina at every level. Some people have big facets, and there may be no lamina to take at a given level, or some atypical scoliosis, such that you have to drill at an angle. if you meant to do a lami, without a fusion, and you violate the facet capsule or worse drill facet when you didn't mean to, then you're hosed because you've destabilized that level.
- determine pedicle sizes on scan, pick out screw size and length beforehand, write them on the board
Process:
- localize level first with c-arm.
- mark incision
- prep and drape wide
- 15 blade through skin
- buzz through fat with impunity
- put finger in and feel for the spinous processes - directly above spinous process is fascia. every time. every time. that's where it is. lateral to spinous process will be bumps for paraspinous muscle.
- take cobb and scrape last bit of fat off fascia. In everyone except super old frail people with terrible fascia, you can scrape and you will not accidentally break through as long as you're not jabbing aggressively
- cut on either side of spinous process. Take cobb, put raytech on it, and scrape down along spinous process. you should be sub-periosteal. if you are not, you will be in muscle - it will bleed like crazy and the patient will have a lot more postop pain. alternative to cobb is bovie down bone (but be careful directly lateral to lamina- there lie nerve roots). problem with bovie is it will cause paraspinal muscles to tighten and fight you - option to ask anesthesia for short-acting muscle relaxant. if someone has pacemaker or otherwise can't tolerate electrocautery, then you have to do the bipolar and cut thing which sucks.
- your cobb will then land on lamina. scrape ROSTRAL and LATERAL - next you will land on a valley of bone which is the superior aspect of pars, between the superior facet and the lamina. then scrape your cobb more rostral and more lateral - you will go over a bump, this is the facet capsule, and then you will land on the transverse process. If you're only doing a lami, you don't need to see TP but if you're doing a fusion you will need to expose a lot of the TP.
- THE PEDICLE IS ROSTRAL TO THE SPINOUS PROCESS. once you find the spinous process, you have to go rostral to find pedicle. this is especially true in thoracic spine - if you try to take shortcuts and aren't thoughtful, and you go for the pedicle directly next to the spinous process, you will put the screw in the wrong level.
- the anatomy is as such: from rostral to caudal superior facet, TP/pedicle, lamina, inferior facet, with the pars representing the bridge of bone connecting superior to inferior facet
NB
- if you're doing a lami, you cannot drill all the way lateral - if you take pars, you destabilize
- you cannot bovie with impunity directly lateral to the spinous process/lamina - that's where the nerve roots come out. (if patient jumps and they are not paralyzed, its because your electrocautery hit a nerve root). this is why we don't paralyze spine cases.
- there is often a large artery next to pars - if it starts bleeding like crazy, don't dive after it with electrocautery, as you might hit nerve roots.
- if someone has giant, super hypertrophied facets, you might need to drill off the inferior aspect of facet to access entry point for pedicle screw - be careful - you can only drill approx 1/3 of facet joint before you destabilize
Thoughts on cervical decompression
- if most of someone's compression is coming from disk, you can do ACDF
- if there is a hypertrophied ligamentum flavum or facet arthropathy, you can get a lot more decompression of spinal cord if you come from the back
Wednesday, August 17, 2016
Cranioplasty
- just like for a decompressive hemicrani - when you're making a giant trauma flap incision, you have to think about positioning such that you can reach the back of the head/most posterior aspect of incision. If someone has excellent neck mobility, you can just put them flat and turn head all the way over. If someone doesn't have good neck mobility (ie. c-collar, really old, arthritis, contractures) then you put a bump under the shoulder to get you access to back of head. similar principle for shunt - shoulder bump to straighten out neck for optimal tunneling.
- putting someone on a horse-shoe means that you can reach more posterior around their head more easily - think about your hand/wrist position relative to head vs them being flat on a table, and having the table block you
- shave around the incision area only
- cover eyes well with tegaderm, and then again with the 1000 drape, put drape as low across brow as you can to get the biggest field, but make sure to shield eyes - chlorhexadine is very caustic to corneas
- stuff xeroform into the ears only if you intend to use a chlorhexadine prep - it is ototoxic. if you are painting betadine or using alcohol only this step is skiappable
- prep and drape wide - you will have to tunnel a drain out of your flap
- feel bone edges under incision - if you have bone under incision you can cut all the way down. if you do not, you have to be careful - go thru skin with knife and then carefully bovie/dissect because its scalp - dura - brain. you will definitely not have any bone over the squamous temporal bone, because if you did a good decompression originally, you put a burr hole right at the pterion/over root of zygoma, and you kerrison'd all the way flush to the floor of the middle fossa for good temporal lobe decompression.
- for temporalis muscle, carefully dissect it off the dura - if you don't dissect between temporalis muscle and scalp, you can have a better chance of not causing a frontalis palsy. this is also a good place to find the bone edge and begin to develop the plane between periostium and dura.
- if you are lucky, there will be a good plane between periostium and dura, and you can follow that plane all the way around - you are not done until you see all bone edges. Put screws into the bone flap, push it flush all the way against anterior aspect of bone. if temporalis muscle is large and healthy, you can just close (fascia on fascia) anterior temporalis muscle against posterior. If its kind of bad looking, consider putting in a mesh over the cranial defect where temporal bone used to be, to buttress it and prevent a hollowing defect later on.
- if you are not lucky, the whole thing will be scarred down and socked in and you just have to create a plane - find the bone, do not violate dura.
- leave a subgaleal drain, use hemovac (same width of drain all the way around vs JP which is a wider drain; HMV hurts less coming out, creates a smaller hole to close when removed). Always leave drain because it will bleed a lot and you will not be able to use aggressive electrocautery because otherwise it won't heal well.
- tunnel your drain before you close, tunnel it outside of your flap becusae it will heal better. do not sew in drain until you finish closing, otherwise you'll shift the position of the drain in head and where you tunnel it out may not be as sterile as the rest of your field so do that last.
- close galea with 3-0 vicryl with C-23 needle
- close skin with either absorbable sutures or staples - for healthy people who will heal well, choose absorbable - it looks nicer, plus you don't have to hurt people 2 weeks later when you take them out. If there is any question about whether someone will heal an incision though, use staples - you can hypothetically leave staples in forever. also they are faster.
- if you are struggling to close, either because scalp is really scarred or tight, consider nylon sutures with horizontal mattress- you can use it to pull the scalp incrementally closer together
- just like for a decompressive hemicrani - when you're making a giant trauma flap incision, you have to think about positioning such that you can reach the back of the head/most posterior aspect of incision. If someone has excellent neck mobility, you can just put them flat and turn head all the way over. If someone doesn't have good neck mobility (ie. c-collar, really old, arthritis, contractures) then you put a bump under the shoulder to get you access to back of head. similar principle for shunt - shoulder bump to straighten out neck for optimal tunneling.
- putting someone on a horse-shoe means that you can reach more posterior around their head more easily - think about your hand/wrist position relative to head vs them being flat on a table, and having the table block you
- shave around the incision area only
- cover eyes well with tegaderm, and then again with the 1000 drape, put drape as low across brow as you can to get the biggest field, but make sure to shield eyes - chlorhexadine is very caustic to corneas
- stuff xeroform into the ears only if you intend to use a chlorhexadine prep - it is ototoxic. if you are painting betadine or using alcohol only this step is skiappable
- prep and drape wide - you will have to tunnel a drain out of your flap
- feel bone edges under incision - if you have bone under incision you can cut all the way down. if you do not, you have to be careful - go thru skin with knife and then carefully bovie/dissect because its scalp - dura - brain. you will definitely not have any bone over the squamous temporal bone, because if you did a good decompression originally, you put a burr hole right at the pterion/over root of zygoma, and you kerrison'd all the way flush to the floor of the middle fossa for good temporal lobe decompression.
- for temporalis muscle, carefully dissect it off the dura - if you don't dissect between temporalis muscle and scalp, you can have a better chance of not causing a frontalis palsy. this is also a good place to find the bone edge and begin to develop the plane between periostium and dura.
- if you are lucky, there will be a good plane between periostium and dura, and you can follow that plane all the way around - you are not done until you see all bone edges. Put screws into the bone flap, push it flush all the way against anterior aspect of bone. if temporalis muscle is large and healthy, you can just close (fascia on fascia) anterior temporalis muscle against posterior. If its kind of bad looking, consider putting in a mesh over the cranial defect where temporal bone used to be, to buttress it and prevent a hollowing defect later on.
- if you are not lucky, the whole thing will be scarred down and socked in and you just have to create a plane - find the bone, do not violate dura.
- leave a subgaleal drain, use hemovac (same width of drain all the way around vs JP which is a wider drain; HMV hurts less coming out, creates a smaller hole to close when removed). Always leave drain because it will bleed a lot and you will not be able to use aggressive electrocautery because otherwise it won't heal well.
- tunnel your drain before you close, tunnel it outside of your flap becusae it will heal better. do not sew in drain until you finish closing, otherwise you'll shift the position of the drain in head and where you tunnel it out may not be as sterile as the rest of your field so do that last.
- close galea with 3-0 vicryl with C-23 needle
- close skin with either absorbable sutures or staples - for healthy people who will heal well, choose absorbable - it looks nicer, plus you don't have to hurt people 2 weeks later when you take them out. If there is any question about whether someone will heal an incision though, use staples - you can hypothetically leave staples in forever. also they are faster.
- if you are struggling to close, either because scalp is really scarred or tight, consider nylon sutures with horizontal mattress- you can use it to pull the scalp incrementally closer together
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