pneumocephalus

some of our surgeons request that we use high flow oxygen for our pneumocephalic pt's as well. this is a controversial practice. there are a few studies out there, here's a link to the most recent:

http://thejns.org/doi/abs/10.3171/JNS/2008/108/5/0926?cookieSet=1&journalCode=jns

this study makes it sound like it works (and it very well may) but look at their population size. ;-)

i like it but I bet it is hard to find participants for this study. It is kind of a rarity I have only seen one case since I have been in Neuro ICU. I guess it is controversal treatment. In our unit it is controversial too. I guess something that the oxygen is lighter then room air which oxygen takes over that spot and then the oxygen reabsorbs. It still confuses me a little but I got the general concept.

kent

This is peripheral to what you're discussing, but years ago, pneumoencephalograms were sometimes done: CSF was removed and oxygen introduced in order to provide contrast for x-rays. I remember that from school but never actually saw one done. They were pretty much abandoned when CT scans and MRIs were developed. I actually did a short Google search of the term to see if there was any information that addressed labman's question, but I didn't find anything.

I did take care of quite a few patients who had myelograms done, "back in the day" and know how bad the headache can be from losing just a small amount of CSF; I can't imagine how hideous a pneumoencephalogram must have been. We kept our myelogram patients flat and pushed fluids for 24 hours but occasionally one would think it was cute to "cheat" and sneak up to the bathroom; they very often lived to regret it.

it's not as rare as you think... i'd say that approx 50% of our crani for tumor pt's experience this post-op.

and this is coming from one of the top ranked neurosurg programs (sadly) lol

Well I have worked in our Neuro ICU for around 5-6 months and this is the first time they have found a patient (or atleast one I have taken care of have this) unless they failed to tell me in report or they let the patient reabsorb the pneumo.

We diagnose this at least once an hour in our ER, and rarely use oxygen. The patients are usually happy with a couple of Percocet, and come back regularly.

we see it here and there, in fact, my pt. last week had quite a bit of air. 100% Fio2 x24hrs..blow it out..

Hey Neuro RNs

I have a ming boggling question for you. It really has me going for a loop. When a patient on our unit has a pneumocephalus on our unit some of the neurosurgeons order patient to lie flat and to be on 100% non rebreather oxygen mask.

My question is I just do not get the pathophysiology of this at all or how it decreases pneumocephalus. Someone please help me.

kent

Whether or not it works is questionable, but the principle is simple. The air in the head is just that: air. That means that it's ~80% nitrogen, 20% oxygen (ignoring the minor components). At normal atmospheric pressure, that means the partial pressure of oxygen (ppO2) in the air-filled intracranial space is 0.20 and the ppN2 is 0.80. By Henry's law, the partial pressure of gases dissolved in a liquid (in this case blood) is a function of the gradient of partial pressure of the gas in contact with the liquid and that already dissolved in the liquid. Thus, if a liquid contains a ppN2 of 0.80 and it is in contact with air, the liquid will not absorb any more nitrogen, because it has reached equilibrium. If, however, the ppN2 in the liquid is 0.00, and it is in contact with air (ppN2=0.80), then the gradient favors the absorption of that gas into the liquid.

Bottom line: less nitrogen in the inspired air --> less nitrogen dissolved in the blood --> greater concentration gradient of nitrogen between the air inside the head and the blood --> greater absorption of the nitrogen inside the head into the blood, thus clearing the volume of gas faster from the intracranial space.

Any certified scuba diver should know Henry's law backwards and forwards, as it is highly relevant in diving physiology.

One time we had a patient from outside hospital with pneumocephalus and they put a drain in his head to drain out the air. lol.