Need Pathophysiology help!

ImThatGuy, BSN, RN · Jan 21, 2011

Hi Everyone,
I am a mature student who is having a terrible time understanding fluids and electrolytes in my pathophysiology class that I just started. It would help if our instructor didn't simply read from the text but as I can't change that I am seeking help from all of your experiences.
I have picked up the Easy book for Pathophs. but these chapters are still fuzzy. I do best when I watch You Tube videos that really detail things but I haven't found any good ones for F & E's. Does anyone have any suggestions for me? I did really well in A & P 1 and 2 but feel that I am drowning here. Side note, I have put in 60 hours this week studying for this class. Normally with that amount of time I would have material down real well but not this stuff.
Thank you so much for your help in advance.

60 hours studying? You need to find a new study method. That's insane. As far as helping you understand; I think you need to memorize the role of the electrolytes, their lab values, and sundy information. Once you've got that down approach it from a cause/effect angle.

coast2coast · Jan 22, 2011

Can't tell if you are struggling with basic physiology or clinical data ?

Do you understand osmolarity and diffusion?

What is the difference between the two? http://www.youtube.com/watch?v=AYNwynwaALo&feature=related

What are the major ions in the intracellular space?

What are the major ions in the extracellular space?

How does each type of ion move in and out of a cell?

OP, do you know this stuff already? Or is this what you're struggling with? It's difficult to understand pathophysiology of electrolytes without the normal physiology background ... lab values will make a lot more sense when you get this down. I can answer the questions I posed to you up there, but you should try to do it first (or tell me if I'm way off on what you need ....)

living on faith · Jan 22, 2011

Coast2Coast,

Thank you for trying to help. I am good with Diffusion and Osmosis. However, I don't seem to understand when something says that the "osmolarity is increased or decreased". I understand Cations and Anions and know which is which.

I was a bit fuzzy on Starlings Forces but seem to understand except when they talk about osmolarity. It would be most helpful to have some type of clear understanding about Hyponatremia, Hypovolemia etc. We seem to be discussing signs and symptoms prior to understanding what these things are.

For instance, with Edema one cause is a decrease in Plasma Oncotic Pressure due to lost plasma proteins. Could you explain what that is exactly. I know how important albumin is but need to understand the oncotic pressure of pulling better.

Any and all help would be most appreciated. Also, thank you to I'm That Guy. Yes, I am aware that I need to do "something" different.

ImThatGuy, BSN, RN · Jan 22, 2011

Coast2Coast,
Thank you for trying to help. I am good with Diffusion and Osmosis. However, I don't seem to understand when something says that the "osmolarity is increased or decreased". I understand Cations and Anions and know which is which.
I was a bit fuzzy on Starlings Forces but seem to understand except when they talk about osmolarity. It would be most helpful to have some type of clear understanding about Hyponatremia, Hypovolemia etc. We seem to be discussing signs and symptoms prior to understanding what these things are.
For instance, with Edema one cause is a decrease in Plasma Oncotic Pressure due to lost plasma proteins. Could you explain what that is exactly. I know how important albumin is but need to understand the oncotic pressure of pulling better.
Any and all help would be most appreciated. Also, thank you to I'm That Guy. Yes, I am aware that I need to do "something" different.

Maybe this will help.

I used to teach biology, chemistry, and A&P. This is very fundamental, and there are few statements that aren't completely accurate. More detail would reduce the understanding at this point. They do, however, get the point across and are as "right" as you'll see in nursing school. I talked out loud as I typed this so what you'll read is what I said to the lamp here sitting on my desk.

Ok osmolarity. It refers to to the concentration of substance in a fluid. Chemically, a Solute is the stuff you're dissolving into something, and a Solvent is what it's being dissolved into. This is just the basics, btw. Think of brewing tea: the tea dust is the solute and the water is the solvent.

A decrease in concentration would be less tea in the water or an increase would be more tea in the water. However, you could also say that the concentration decreased as well NOT by taking out tea dust (if you could) but by adding more water and you could increase the concentration not by adding more tea dust but by decreasing the water. Mull that over and see if that makes sense or it may already.

Cations: positively charged...metals....Na, K, Ca, Mg, Li, etc etc etc

Antions: negatively charged...nonmentals...Cl, SO4, PO4, CO3, HCO3, etc.

Hypo is to have less. Hyper is to have more. Hypovolemia would be less volume thus less fluid volume. Hypervolemia would be more fluid volume. Hyponatremia would be less sodium. Hypernatremia would be more sodium. Think of these electrolytes in terms of concentration. If I sucked some plasma out of your body then, assuming your health was good, the sample would be isotonic with iso- meaning "equal." The sodium, water, and other substances would all be in proportionate concentration. If we added more sodium then the sample would be hypernatremic. OR if we removed some water then the sample would be hypernatremic because the concentration is now MORE. Likewise, if I withdrew some sodium then the sample would be hyponatremic in value, BUT if instead I left the sodium alone and added more water it'd be hyponatremic as well because I have manipulated the concentration of solute (sodium) in the solvent (water). Refer to my first paragraph.

If your body was hypovolemic then it'd be due to some problem causing fluid volume depletion such as bleeding, extreme diaphoresis, diuresis, etc.

Water tends to follow molecules. Na is not itself a molecule, but you can assume for a minute that it is. Water always follows sodium. Where you have more sodium you will have more water follow and join it and they'll just sort of be there together.

For the sake of this assume for the moment that the same is true always with albumin (plasma proteins). The albumin is a colloid. Look up the definition of that. It holds fluid within a compartment. The "hold" that it exerts on that fluid is the oncotic pressure. Oncotic pressure or plasma oncotic pressure IS osmotic pressure. Compounds (molecules for the sake of this teaching) have an osmotic pressure on fluids they're dissolved in thus they "hold" fluid in place. There's a scene in the movie shooter with Mark Whalberg where he makes himself an IV and actually refers to osmotic pressure while he's explaining what he's doing. It's all a load of bogus hollywood, but the idea is correct.

That said, when albumin (plasma proteins) leaks out of the capillary then water will follow it and stay there (edema). The same is true of sodium. If that is outside of the vessel (or cell membrane) then water will follow it and stay there. The reverse is also true.

As blood pumps through capillaries the plasma, electrolytes, and albumin is or may be forced out of the membrane, since capillary membranes are thin, and they're forced out because of the pressure exerted by the contraction of the ventricles. This is your hydrostatic pressure. The contraction pushes the blood through the vessels and some fluid as well as electrolyes and albumin is or may be forced through the wall of the capillary by that fluid pressure. It will then leave the intravascular space, but it's not inside a cell so it's not in an intracellular space, but it is in the interstitial space or the space between spaces, lol. So now we have fluid and sodium and albumin outside of the capillary in the interstitial space thanks to the hydrostatic pressure.

This is supposed to happen to offload all the stuff that cells need out of blood. Ideally, on the venous side of the capillary all the waste from the cell and most of the other junk forced out of the capillary via hydrostatic pressure is picked up and carried away by the venous circulation. However, this doesn't always happen, and we see edema or the collection of fluid because it's not being picked back up and recirculated. In a normal healthy individual what isn't picked back up by the venous circulation is picked up by the lymphatic circulation and toted away. Refer to your textbook on that process. Tumors, lymph node removal, infection, obstruction are all factors that may impair the lymphatic system from picking up the fluid and toting it off somewhere.

Ok, so now we've got a bunch of crap in the interstitial space or what I called the space between spaces. Ignoring the lymphatic system for this episode, we know the venous side is supposed to pick the crap back up but isn't.

If we don't have enough protein in the circulation as a whole then we've got problems. Likely the hydrostatic pressure is forcing is out of the arteriole side of the capillary where it remains. In a normal healthy person some will be forced out like I said but you'll have much much more remaining in the general circulation where it's supposed to be. If your protein level is low such as with malnutrition, burns, infection, or other reasons causing protein deficiency then some of what you've got will be forced out and will sit there drawing more fluids because like I said the albumins exert a plasma oncotic pressure and draw and hold fluids (plasma) around them. This means that once the albumin (and sodium will do this too) accumulates in the interstitial spaces that fluid will follow it, sit, and be held there....remembering we're pretending the lymphatic system (our back up cleaner upper) isn't working or just isn't there. If we had normal albumin (protein) levels in the blood, or general circulation, then our concentration in the blood, or intravascular space, would be higher than it would in the interstitial space. That would draw fluid back on on the venous, or venule, side of the capillary, and the fluid would be carried off into the system to go unnoticed. This would occure perpetually and and you'd pick up as much fluid as you leaked out so everything would be fine.

Everything I've mentioned about albumin can be done with sodium too. If you get a greater concentration of sodium then water will follow it and sit there and you'll have more swelling. Eat a lot of salt the GI system will move it to the circulatory system and as the salt in the blood passes by cells it'll draw fluid out of them into the blood raising the amount of fluid in the circulatory system creating higher blood pressure, for example.

Another reason you'll get edema will be like in the inflammation (and allergies) process. The basophils mast cells will release a substance (like histamine) that will cause the capillaries to become more permeable and fluid will leak out causing localized swelling. Once the inflammation (or allergy) subsides then the capillaries reduce their permeability and things go back to normal. The normal healthy person will have the fluid and other material drawn back into general circulation and the lymphatic system will pick up the remainder. Your nose may run because of an allergen which is like the inflammatory process. More fluid is put in the area the allergen was received to water it down and float it off somewhere. Your nose gets drippy so you take an antihistamine to close the capillaries back up no thanks to those mast cells, etc so you stop having fluid leak out and your nose dries back up.

Hope that may have helped. I get off on this stuff because it interests me. Got questions, let me know.

Edit to add: Having digested this (without me reading it again) I may have over-emphasized the idea of albumin being pushed out of the capillary by hydrostatic pressure. You don't have to have that, or sodium, for water (plasma) to escape the intravascular space and go into the interstitial space. Simply not having enough circulating volume of sodium or ablumin, etc would allow plasma to be pushed out through hydrostatic pressure and the small amount in circulation, as with conditions that would cause a deficiency of them, would prevent the oncotic pressure from pulling all of the water back in.

living on faith · Jan 22, 2011

I'mthatguy,

Thank you from the bottom of my heart. I actually think I've got it now. I sure wish I would have asked these questions 60 hours ago. I think I should have had more info regarding the compartments first: ICS vs ECS and then the intravascular and insterstitial fluids. I do understand Starling's forces now and the difference between hydrostactic pressure and oncotic pressure. Now I can move on to understanding the alterations- hyponatremia,etc.

I have a very nice teacher who simply reads from the text which is not the best teaching method for me. I am wondering since you have so much experience in teaching and obviously nursing if you could answer a question- honestly. I am a former teacher who has a BSE and half a masters. I raised my kids and have now returned to an ADN program to obtain my RN license. I did well in both A & P classesn (I had them many years ago but had to retake them because they were so old) and have a 3.9 in my prereqs. I also passed the HESI entrance test with a 93. My question is do you think I will make it through the RN program academically if I am struggling to comprehend patho? I am 44 years old and I am a very hard worker. Persistance is often the key for me for success. I am having one of those weeks though where I have to wonder.

Your help and your thoughts are very much appreciated!

ImThatGuy, BSN, RN · Jan 23, 2011

Ok, let me clear something up. I'm in a BSN program myself so I'm not a nurse. It'll be my second bachelor's. My first B.S. was in general science (bio emphasis), and I got my teaching license through an alternative pathway. I also have part of an M.Ed. (major was school administration). I quit teaching and thus quit that graduate program. I didn't like everything that came with being a teacher. If I told you what I did after I quit teaching and before/during nursing school you'd stop listening to me. :)

My healthcare experience has been as a paramedic which was my side job when I was teaching. I'll note that the very same material you're covering now was covered in paramedic school so there's no difference there. Honestly, I think my medic instructor taught it better too. I also taught elements of this to high schoolers. Additionally, they've covered it in my nursing classes as best they can. It's obvious though they weren't science majors. No disrespect to them. They were just educated differently. They were simply people who studied nursing and had it all thrown on their plate to learn without a lot of background on some of the other processes that make learning it and applying it easier. You'll pick your way through it and get it just like they did.

I think you'll make it through nursing school. The shear number of people that become nurses is too great to assume that your difficulties would hold you back, and that's only my opinion based on observed numbers. You hear a lot about the drop out rates in nursing school, but honestly I don't think they're any worse than most other professional degree programs, i.e. accounting, engineering, etc. The biggest detriment to the kids in my class was not being able to do basic algebra or word problems for drug calculations.

Periodically I'll get on here an answer some questions pertaining to how can I study A&P or something. My answer always relates around that to get it (and know it rather than just passing a test) is to read the book. Honestly, I got my first degree without reading a whole lot, and I can get through many a nursing class without reading a whole lot. However, A&P and Patho are courses where you should read and take a more active approach to it. Don't stop and take notes on it. You're distracting yourself. Read a segment. Think about it. Relate it to what they talked about a couple pages back. Recite it to yourself outloud. Talk your way through it. Apply it to something you know about. It can be time consuming, but I think it's worth it. It's like a hobby to me. I'll periodically pull one of several A&P books I have off the shelf and read over parts of it out of interest. I'm not an expert. I'm not a physiologist. I just like the subject.

I'm actually taking a pathophysiology course now as a part of my program offered by the nursing department. It's a nice refresher, but I wish I were teaching it, lol. My instructor I think understands it, but it's not her forte so she's not connecting the dots very well for some of the other kids in class.

metal_m0nk, BSN, RN · Jan 23, 2011

ImThatGuy offered a great description. The truncated version is that when it comes to understanding the movement or stasis of fluids in the body, a firm understanding of osmosis is key. Osmosis is the common denominator. All other descriptors like hydrostatic pressure and oncotic pressure describe solute or physical effects on the movement of water. So long as you remind yourself that water moves to areas of high solute concentration and areas of low pressure in order to maintain equilibrium, you'll be a step ahead when you move onto the more convoluted explanations of how water is routed and rerouted.

When examining the relationship between hydrostatic and oncotic pressure, consider the following:

1) Hydrostatic pressure and oncotic pressure have a kind of contradictory relationship when it comes to water. When oncotic (molecular) pressure is high, water is attracted. When hydrostatic (physical force) pressure is high, water is repelled.

2) The location of increased hydrostatic pressure in the body usually refers to the vasculature, since it is within the vascular system that physical pressure is regularly exerted on fluids (movement of blood by the pumping of the heart).

The hydrostatic pressure in the interstitial space is usually zero - lower than the hydrostatic pressure in the vasculature. So naturally, based on hydrostatic pressure alone, water will want to move out of the vasculature and into the interstitial spaces to equalize the pressure in both places. But what holds water inside the vasculature despite the higher hydrostatic pressure, is oncotic pressure - all those proteins in the blood (remember, molecules attract water even while pressure repels it). It's a balancing act.

You can figure out which direction water is moving by figuring out the net filtration pressure - which is simply the difference between the repellent hydrostatic pressure exerted on water by the vasculature and the force of attraction exerted on water by oncotic (molecular) forces. If the hydrostatic pressure is greater than the oncotic pressure, repellent forces win out and water is expelled from the vasculature. If oncotic pressure is greater than hydrostatic pressure, attractive forces win out and water is drawn into the vasculature. Make sense?

coast2coast · Jan 23, 2011

Oops, I guess I'm late back to this party ... ImThatGuy and Triquee have given you excellent answers OP. Pathophys is tough, hang in there.