Fluid and Electrolyte Balance

What are the two major fluid components of the body?

• Intracellular fluid (inside the cells)

• Extracellular fluid (outside the cells like in blood)

That does selectively permeable mean for cell membranes?

Water can travel freely by simple diffusion, but not all substances can pass

What are electrolytes?

Minerals like sodium, potassium, calcium, magnesium, etc that circulate in the blood, stool, and urine and are essential for nerve transmission and muscle contraction

Why do electrolyte imbalances affect an ECG?

Because the heart is a muscle and depends on electrolytes for proper electrical activity

What situations can cause electrolyte imbalances?

• GI losses (vomiting, diarrhea, suctioning)

• Kidney issues

• Burns

• Wounds

• Exit route for electrolytes

What are the main roles of sodium?

To regulate water inside and outside the cells and help to regulate nerve impulses

What is a normal sodium level?

135-145 mEq/L

What happens to cells when sodium is high in the ECF?

The shrink because sodium is higher outside the cells and pull the fluid with it

What happens to cells when sodium is low in the ECF?

The cells swell because sodium is higher inside the cell and water follows

What is hypernatremia?

High sodium level

What are signs of hypernatremia?

High sodium in the blood means water leaves the brain and neurons shrink/fire abnormally

• Agitation

• Restlessness

• Altered LOC

• Nausea/Vomiting (LATE SIGN)

• Increased muscle tone (LATE SIGN)

Water is kept in the body (ECF specifically) because it follows the high salt

• Increased BP

• Edema

• Decreased urine output

• Flushed skin

• Fever (Fluid stays in, less sweating and body cant cool itself)

Salt makes you dry and thirsty (dehydrated)

• Thirst

• Swollen, dry tongue (LATE SIGN)

What is hyponatremia?

Low sodium levels

What are the signs of hyponatremia?

Cells (especially ones in the brain) swell and mess up neuronal firing

• Altered LOC

• Seizures

• Increased ICP

• Headache

Less fluid in the ECF

• Orthographic hypotension

• Dizziness

• High urine osmolality (kidneys holding onto little sodium with low fluid)

• Low serum osmolality (not enough stuff in blood)

Swollen GI cells

• Diarrhea

• More bowel sounds

Neurons cannot depolarize normally

• Weak/cramping muscles

• Fatigue

What is the normal chloride level?

95-105 mEq/L

What are the main roles of chloride?

Maintains acid-base balance (negative, so goes down when acid is lost to maintain neutral charge) and aids digestion (makes HCl which is the stomach acid that helps breakdown food)

How are chloride levels maintained?

By it being kept, dumped, or reabsorbed by the kidneys, sweat glands, or GI tract

How do chloride levels relate to sodium?

Loss of sodium usually means a loss of chloride so symptoms mirror a sodium imbalance (chloride is negative and passively follows positive sodium)

Where is potassium mainly found?

Inside the cells

What is potassiums role?

Muscle contractions and nerve impulses

What is the normal potassium level?

3.5-5 mEq/L

What is the sodium-potassium relationship?

Low sodium means high potassium and visa versa because the like to swap in the cell (so when sodium gets pushed into the cell potassium gets pushed out and visa versa)

What is hyperkalemia?

High potassium

What cause hyperkalemia?

• Tissue damage like burns or rhabdomyolysis (cells burst and release their potassium)

• Addison’s disease (A lack of aldosterone which normally would tell the kidneys to reabsorb sodium and get rid of potassium)

• Renal failure (kidneys are the main way of getting rid of potassium)

• Potassium-sparing diuretics

• Ace Inhibitors (These lower aldosterone)

• NSAIDs (Decrease kidney perfusion and aldosterone)

What are the signs of hyperkalemia?

Too much potassium, cells cant repolarize normally (partially depolarized all the time)

• Early muscle twitches (muscles trying to adjust to the potassium)

• Muscle weakness (then muscles get tired from being overexcited)

• Deceased contractility

• Reputation failure (breathing muscles stop working as well)

• Rhythm changes (heart muscles are overexcited, then tired.. can cause asystole)

Usually high potassium is because kidneys are failing or aldosterone is low so you will also see:

• Urinary output low

What is hypokalemia?

Low potassium in the ECF

What causes hypokalemia?

• Loop diuretics (more sodium that reaches the distal tubules and swaps out some for potassium in the blood, aka more potassium leaves in urine)

• Corticosteroids (act like aldosterone, tell kidneys to reabsorb sodium and dump potassium)

• Too much insulin (makes potassium shift into the cells by activating Na/K pump)

• Cushing’s syndrome (too much cortisol which an aldosterone like effect)

• Starvation (not eating enough potassium and insulin spikes)

• Vomiting (GI content has a lot of our potassium)

• Suctioning (GI content has a lot of our potassium)

What are the signs of hypokalemia?

Potassium controls resting membrane potential of nerves and muscles, with too little, nerves cannot fire properly

• Lethargic

• Low shallow respirations

• Lethal dysrhythmias

• Leg cramps

• Limp muscles

• Low BP and HR

The kidneys become resistant to ADH because of the low potassium

• Lots of urine is made

What is the critical potassium giving safety rule?

NEVER IV push potassium you could give them instant hyperkalemia and mess with their heart

What are the main roles of calcium?

• Bone and teeth health

• Muscle contraction (after a nerve impulse arrives, calcium inside the muscle cell makes the contraction happen)

• Nerve conduction (calcium controls neurotransmitter release)

• Clotting (a required cofactor in it clotting cascade)

What regulates calcium levels?

• Vitamin D (helps absorb calcium from food and move it into blood)

• PTH (pulls calcium form the bones, increases reabsorption, and activates vit D)

• Calcitonin (lowers blood calcium by putting calcium in bones)

What is the normal calcium level?

8.5-10.5 mg/dL

What is hypercalcemia?

High calcium in the ECF

What causes hypercalcemia?

• Overactive parathyroid (pulls calcium out of bones)

• Increased vitamin D Or supplements (more calcium enters the blood as it increases calcium absorption)

• Bone cancer (breaks down bones and puts calcium in the blood)

• Thiazides (meds that decrease calcium excretion by kidneys)

• Lithium (affects parathyroid function, increase calcium)

What are signs of hypercalcemia?

• Weak muscles (calcium interferes with normal muscle contraction in high quantities as the cannot contract and relax well)

• ECG changes (cells repolarize faster so there is a shorter QT interval)

• Absent reflexes (calcium helps nerves fire at regular levels if there is too much though it raises the threshold for them to fire)

• Kidney stones (too much calcium in the urine that groups together)

What is hypocalcemia?

Low calcium levels in the ECF

What causes hypocalcemia?

• Low PTH (PTH normally raises blood calcium by pulling form bones, less PTH means less calcium)

• Low intake

• Low vitamin D (Vitamin D helps absorb calcium so when its low you can’t absorb it as well)

• CKD (Kidneys normally help activate vitamin D and regulate calcium)

Certain medications

• Bisphosphonates (move calcium into bones)

• Aminoglycosides (increase calcium loss)

• Anticonvulsants (affect vitamin D metabolism)

What are signs of hypocalcemia?

Calcium normally helps stabilize nerve membranes so when it is low nerves become hyper excitable and contract uncontrollably

• Convulsion

• Reflexes hyperactive

• Arrhythmias

• Muscle spasms

• Positive Trousseau’s sign (hand flexion when BP cuff is inflated)

• Positive Chvostek’s sign (Facial twitch when tapping the cheek)

• Tingling/numbness

Where is magnesium mainly found?

Inside the cell

What is magnesium’s role?

• Helps Na/K pump (needed for ATP to function)

• Regulates BP (plays a role in vasodilation)

• Competes with calcium to relax muscles (when magnesium binds instead of calcium, muscles relax instead of contracting)

What is the normal magnesium levels?

1.5-2.5 mg/dL

What is hypermagnesemia?

High magnesium in the ECF

What causes hypermagnesemia?

• Renal failure (kidneys normally excrete excess magnesium)

• Overcorrection (when you are trying to treat hypomagnesemia)

What are signs of hypermagnesemia?

Magnesium normally promotes muscle relaxation so if there is too much they relax a lot

• Lethargy

• Absent reflexes

• Impaired breathing

High magnesium slows cardiac conduction

• Hypotension

• Arrhythmias

• ECG changes

Causes vasodilation (extreme relaxing of vascular system)

• Red hot face

Decrease in bowel motility

• GI issues

CNS depression

• Confusion

What is hypomagnesemia?

Low magnesium in the ECF

What causes hypomagnesemia?

• Poor intake

• Malabsorption (If you have Gi issues like Crohn’s or Celiac and cannot absorb it all)

• PPIs (Proton Pump Inhibitors which can in long term use decrease magnesium absorption in the gut)

• Alcoholism (Leads to poor nutritional intake and Gi malabsorption)

• Other electrolyte imbalances (Closely linked with potassium and calcium)

What are signs of hypomagnesemia?

Magnesium normally is a calming electrolyte so without it muscles cannot relax as much and nerves are not stable

• Trousseau’s/Chvostek’s (because of muscle irritation)

• Weakness (muscles cannot relax and get tired)

• Increased reflexes

• Torsafes de pointes (a dangerous ventricular arrhythmia that can lead to cardiac death)

• Low calcium and potassium (linked with low mag)

• Hypertension (mag normally helps blood vessels relax, without this BP can go up)

What is the main roles of phasphate?

• Bone and teeth building (Phosphate combines with calcium to form hydroxyapatite which is the main mineral in bones and teeth)

• Energy storage (A major part of ATP)

What influences phosphate absorption?

Vitamin D (increases absorption of both phosphate and calcium by increasing the production of transport proteins to move them into the bloodstream)

What is the normal phosphate level?

2.5-4.5 mg/dL

What is hyperphosphatemia?

High phosphate in the ECF

What causes hyperphosphatemia?

• Phosphate laxatives (some bowel preps have a lot of phosphate in them)

• Increased vitamin D (Too much vitamin D makes too much phosphate be taken up)

• Muscle damage (Phosphate is stored inside muscle cells so when they are broken down a lot is released into the bloodstream)

• Hypoparathyroidism (Normally PTH helps the kidneys excrete phosphate but with it being low, kidneys hold onto it)

What are the signs of hyperphosphatemia?

Similar to hypocalcemia:

• Convulsions

• Hyperactive reflexes

• Arrhythmias

• Muscles spasms

• Pruritus

• Chvostek’s/Trousseau’s

What is hypophosphatemia?

Low phosphate in the ECF

What causes hypophophatemia?

• Aluminum antacids (Aluminum binds phosphate in the gut and prevents absorption or phosphate)

• Starvation (Not enough phosphate from diet)

• Refeeding syndrome (After prolonged starvation, giving a sudden high carb meal can cause insulin to spike which drives phosphate into cells)

• Overactive parathyroid (PTH causes the kidneys to excrete more phosphate so when it is hyperactive, the kidneys get rid of too much)

• Low vitamin D (Vitamin D is needed for phosphate absorption in the gut so if it is low, absorption decreases)

What are the signs of hypophosphatemia?

• Bone pain/fractures (phosphate is needed for bone strength)

• Osteomalacia (Softening of bones due to poor mineralization)

• Neuro changes (A key component of ATP so neurons cannot function without the energy)

• RBC destruction (ATP is needed for RBCs so without it, they are fragile and can hemolyze)

What is an isotonic fluid?

A fluid that has the same concentration of solutes as the inside of your cells meaning it wont cause water to move in or out of them

What is a hypertonic solution?

A solution with a higher concentration of solutes and lower water content to the cells, causing water to move out of the cells into the ECF

What is a hypotonic solution?

A solution with a lower concentration of solutes and high water content to the cells, causing water to move into the cells from the ECF

What fluid is given if there is a fluid volume deficit?

Isotonic solution

What should always be done before hanging IV fluids?

Chart that a CNS assessment was performed

Why must swelling be assessed before charting?

Because you need to determine the underlying cause of the swelling

What is a subtle early sign of dehydration in children?

Puffy eyes or a sunken fontanel

What vital sign should always be taken in pediatrics?

An apical pulse

What should you check when in doubt about patient status?

Oxygen levels

What is pharmacodynamics?

What drugs to do the body

What is pharmacokinetics?

What the body does to the drug (absorption, distribution, metabolism, elimination)

What electrolyte imbalances increases risk of metabolic alkalosis?

Hypokalemia

Why are inhaled meds usually not enough to affect electrolytes unless used chronically?

Systemic absorption is minimal unless used long term