Fluid and electrolytes help

  1. Good afternoon,

    Needed some help with fluid and electrolytes. I unserstand the lab values, but trying to really understand WHY you see the symptoms you do, and how they are connected to other electrolytes.

    My main question is the relationship between Hyperkalemia and its symptoms..so..
    Hyperkalemia causes:
    Respiratory weakness
    Lower limb weakness
    tall T wave
    Decreased BP, irregular pulse (tachy to compensate?)

    So, K is the main Intracellular ion, and is exchanged for sodium in the sodium potassium pump, which creates action potentials.

    So, if you have too much Potassium OUTSIDE the cell, there is too much Sodium INSIDE the cell? Is that why there is muscle weakness and decreased BP, because there isn't enough action to get the cells firing normally?

    I probably need to review the sodium-potassium pump
    And hwart contractility as well, AP was a long time ago.
  2. 5 Comments

  3. by   Noctor_Durse
    Hi, ok so with too much potassium outside of the cell that will change the Potassium equilibrium potential (look this concept up). When this equilibrium potential not working properly it changes the ECF millivoltage/electrochemical gradient. Potassium is not flowing down its gradient as fast as it should because there is more K+ on the other side of the cell membrane thus the action potential is slowed this causes: Respiratory weakness Lower limb weakness tall T wave, irregular pulse.

    someone correct me if i'm wrong.

  4. by   Middleburg08
    Thank you for the reply, really appreciate it.

    Is that why you would also see muscle weakness and slower hwart rate in hypokalemia as well? Because the action potential is changed?
  5. by   Noctor_Durse
    For K+, the normal equilibrium potential is -85 mV or so, but the resting potential is -70 mV. That means there's a tendency for K+ to try and leave the cell at rest, because doing so would reduce the concentration gradient across the cell membrane. The K+ would continue to leave until the resting potential = the K+ equilibrium potential, at which point the force generated by the concentration gradient would equal that generated by the electrostatic attraction between the positive potassium ion and the negative cell interior. This doesn't happen, however, because the cell membrane isn't perfectly permeable to K+, and because the Na/K pump is constantly pumping in 2K+ for every 3Na+, but all in all it gets pretty close.

    In the hypokalemic state, you increase the concentration gradient between the inside and outside of the cell. There was already little K+ outside to begin with relative to the inside of the cell, and hypokalemia makes that worse. That increases the equilibrium potential (i.e., pushes it further negative), because now you need more electrostatic charge to resist an increased concentration gradient. Conversely, in the hyperkalemic state, you decrease the concentration gradient. That means that there's less driving force for K+ to get out of the cell, and you need less electrostatic charge to resist the concentration gradient. Therefore, the equilibrium potential is decreased (i.e., closer to 0 than -85 mV).

    So here's the kicker: after the AP upstroke (i.e., repolarization), Na+ channels close, more K+ channels open, and the cell potential is again being driven by the K+ equilibrium potential. The more negative the K+ equilibrium potential, the greater the energy available for repolarization, and the faster you're going to depolarize.

    Hypokalemia: more negative K+ equilibrium -> more force pushing K+ out of the cell -> faster repolarization

    Hyperkalemia: less negative K+ equilibrium -> less force pushing K+ out of the cell -> slower repolarization
  6. by   Esme12
    There are 6 major electrolytes. Sodium, potassium, calcium, chloride, magnesium and phosphorus. It is primarily potassium, calcium and sodium that will cause problems when they are out of whack.


    When there is a sodium imbalance quite often there will be changes in mental status - confusion, delirium, etc. Often seen with traumatic brain injury where diabetes insipidus (pathological voiding of large amounts of dilute urine) and its opposite SIADH (syndrome of inappropriate antidiuretic hormone - minimal urine output but very concentrated) may occur. Sodium imbalances are also seen with dehydration in some patients (elderly, burn victims, many others) and the blood levels will go up. Very rarely, sodium levels in the blood will go down because of consuming large quantities of fluids.

    The other main electrolyte imbalance seen is when potassium is out of whack, and its most serious consequence is cardiac problems that can be life-threatening (you will see T wave changes: depression with hypokalemia, elevation with hyperkalemia, among other changes in the EKG like QRS interval changes).

    For these 2 main electrolyte imbalances remember: Sodium equals mentation, and Potassium equals cardiac.

    Sodium does affect fluid. In fact, they say sodium always follows water. There are a lot of people with edema related hypernatremia; and a lot of dehydration related to sodium and chloride losses. Potassium tends to affect the heart and in the clinical area you will see dramatic instances of people with hypokalemia and hyperkalemia. Calcium affects the muscles and is not as commonly seen clinically because it is detected because of lab testing.

    Sodium - body water balance
    Potassium - contraction of skeletal and smooth muscle and nerve impulse conduction
    Calcium - formation and structure of bones and teeth, cell structure and function, cell membrane permeability and impulse transmission, the contraction of all muscle types and is necessary in the blood clotting process
    Chloride - important in the digestive acids; closely linked to sodium
    Magnesium - affects nerve and muscle action by affecting calcium usage, activates enzymes involved in carbohydrate and protein metabolism, helps in the transport of sodium and potassium across cell membranes, and influences the levels of sodium, potassium, calcium and some body hormones (parathyroid hormone)
    Phosphorus - formation and structure of bones and teeth, this electrolyte is needed in the following activities: utilization of B vitamins, acid base homeostasis, bone formation, nerve and muscle activity, cell division, the transmission of hereditary traits, metabolism of carbohydrates, proteins and fats

    Check out these threads
    Really need help with electrolytes and fluids

    Fluid/Electrolytes-Helpful Study Materials
  7. by   Middleburg08
    Thank you as well Esme! And Noctor_Durse! Was I on the right track at least with my thought process for hyperkalemia?

    And with personality changes like in sodium imbalances, are those caused because sodium & water are connected, so if there isn't enough water/too much sodium in the intravascular space then the ECF takes from the cells and vice versa, too much fluid in the vascular space forces it out and causes cellular swelling?