Published Nov 4, 2002
OK, Here goes....
1) You are doing a carotid artery endarterectomy. You have the choice of regional vs gerneral anesthesia. Which one has the better outcome?
2) You are going to give mannitol prior to dural opening. Does your patient have a space occupying lesion or aneurysm/SAH?
These were on my neuro test today.
OK, I'm going to guess just for kicks.
1. I'd say general. I would think with the patient asleep, I'd be better able to control the blood pressure. Like someone said here long ago, the sympathetic nervous system is the best catecholamine.
2. Although my experience with neuro is limited, I'd say a space occupying lesion. My rationale here, is that if the pressure inside the cranial vault is elevated due to the space occupying lesion, the surgeon is going to want to decrease ICP before opening the dura to keep brain protrusion to a minimum.
Well, does anyone have the right answers?
1) Studies fail to show a difference in outcomes. Awake patients are able to communicate (really not communicate) cerebral ischemia when the carotid is clamped. This gives the team a sensitive indicator of brain function. Shunting can be done if collateral circ is insufficent. general anesthesia provides a quiet field, and some element of protection of the brain due to the decreased CMRO2. You are right about the sympathetic discharge. However, this population is usually very sick with co-existing diseases and may benifit from the sns stimulation. On the otherhand, MI risk, perioperativly, for this population is reported to be 8-35%, so reduction of SNS discharge may be benificial. Beta-blockers are your friend here.
2) Nice job Dad!!
Follow up question. But why not mannitol prior to dural opening with aneuysms/SAH?
I don't know anything about giving manitol in surgery but. I rareley consider ICP problems in SAH. almost always consider Increased ICP in subdurals especially day two or three when they blossom.
I guess it depends what vessel the SAH would be in. I assume they are in surgery to be clipped. still. I cant rememeber the last time I had an SAH with volitile ICP.
Per our neurosurgeons, they want mannitol almost anytime the dura is opened to allow for improved access. A "slack brain" (I love that term). The differentiation about when to give it is with a bleed, decompressing the brain to early just allows more blood to enter and irritate the brain. There is some element of tamponade going on. Basically they want you to wait until the last minute to shrink the brain were as with a SOL B-dad was right, protrusion out of the surgical opening is frowned upon.
I think this Q&A is a splendid Idea.
I have to laugh at that term "Slack Brain" makes sense though. I was just sitting in another boring class and thought about this issue some more.
of course I am talking about ICU mangment of a patient rather than interoperatively although some of the same issues could spill into the OR.
Subarachnoid Hemorages (SAH) are given a score. one score the hunt and hess I belive scores their neuro status like a GCS would, only more specific. the second the Fisher score (1-4) reflects the size of the bleed or how much blood is in the brain. so when your in the OR you can ask the Neuro sugeon what the patients fisher score was. and that would tell you how much blood we are talking about. Why? I don't know. maybe I will when I get in there. but, patients with higher Fisher scores maybe more likely to vasospasm than patients with lower Fisher scores. Especially if you are in the OR day 4,5,6,7 or greater.
OK, Next question. you are doing a posterior spinal fusion and the SSEP tech says the amplitude has decreased and the latency has increased. What are the possible causes and list 5 interventions to correct the problem.
Sounds like a valley question,
Decreased amplitude and increased latency would suggest damage is occurring in the neural pathway being monitored. Other possibilities
Body temp changes
changes in PaCO2
changes in PaO2
As a side note, we never utilize SSEP monitoring, do you?
I don't know from valley but I'm looking for 5 things you can influence to bring them back to normal. Yes, we monitor them on most fusions above the lumbar region.
Next question. This is a favorite of one of our clinical instuctors.
How does ephedrine work, at the receptor level?
Five things other then correcting the problems above? Sorry, as I said none of the surgeons here utilize it. So the only way I know anything about it is from valley.
SSEPS can be improved by reducing the distraction on the nerves, Lightening your anesthetic, improving blood pressure, increasing O2 carrying capacity and correcting those abnormalities smiling ru mentioned.
Ephedrine is a noncatacholamine that causes the release of norepi at the nerve receptor. it is resistant to metabolism by COMT and MAO increaseing its duration of action. What else?
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