Altered Fluid, Electrolyte and Acid-Base Balance
Fluid, Electrolytes and Acid-Base Balance
Water and electrolyte intake and output are regulated through hormonal and neural interactions
Most metabolic processes in the body result in the production of acid
Acid is removed through the lungs (CO2) and kidney (acid/base balanc)***EXAM QUESTION!!!
Distribution of Ions
Chlorine usually follows Na+
Think of electrolyte imbalance if you see:
Interstitial fluid (ISF) (OUTSIDE CELL)
- high Na, Cl, Ca - cognition changes
- low K, Mg, P - breathing problems
- med HCO3 -diarrhea/vomiting
-massive burns/ blood loss
Intracellular Fluid (ICF) (INSIDE CELL) -arrhytmias
- high K -muscle cramps
- low Ca, Na, HCO3, Cl Caution: Diuretics and BP meds can create
- mod P, Mg an electrolyte imbalance
3 Na out to ECF/ 2 K in, which goes against the concentration gradient (since Na+/K ATPase requires
energy) makes sense why the fluid INSIDE the cell has higher K.
(Potassium is pumped inside AGAINST the concentration gradient. 2 inside-- when if there was no
energy it would want to leak out due to the concentration gradient).
Sodium-Potassium Pump Altered Sodium Balance
- Aldosterone is used for sodium balance. It helps reabsorb Na + water (while excreting K+).
Hyponatremia - Decreased levels of sodium in the blood (less than 135mEq/L)
- Can be caused by excessive Sweating, Vomiting/Diarrhea, cirrhosis
(i.e. a long distance runner). Need to intake electrolytes/sodium because if you just drink water, you will
only dilute the salt even more. ** limit intake of water
Muscle effects: (↑depolarization)
Muscle twitching & weakness
Reduced extracellular circulating volume leads to:
Tachycardia (↑ HR reflex tachycardia)
Oliguria: Reduced urine output – body tries to retain Na+
Anuria: absent urine output – body tries to retain Na+
Altered Neuronal FX leads to (this is due to the fact that there can be cerebral edema,
increasing intercranial pressure) brain swelling causes most of the symptoms!
Nausea + vomiting Seizures
* means one of the first signs
Hypovolemic hyponatremia- Total body water (TBW) decreases; total body sodium (Na )
decreases to a greater extent. The extracellular fluid (ECF) volume is decreased.
Hypervolemic hyponatremia-Total body sodium increases, and TBW increases to a greater
extent. The ECF is increased markedly, with the presence of edema.
Hypernatremia-Increased levels of sodium in the blood (over 145mEq/L)
- Caused by excess sodium intake or loss of body water.
- Think about DEHYDRATION SYMPTOMS
Altered cell metabolism causes:
Fluid shifts cause:
Thirst- need water to dilute (↓ concentration)
Hypertension (↑ Na linked to HTN)
Tachycardia Altered Potassium Balance
- cannot wait on this test- CRITICAL VALUES!
-has an 80% filtration rate through the kidney (aldosterone= hormone regulator)
-Any time there is sodium- potassium membrane disturbance, it will lead to muscle cramps +
- Potassium is needed for cardiac function and skeletal/smooth muscle contraction
Hypokalemia- Potassium levels of less than 3.5mEq/L in the blood
- Caused by diuretics, severe vomiting and diarrhea
Lower potassium levels in the extracellular space will cause hyperpolarization of the resting membrane potential.
This hyperpolarization is caused by the effect of the altered potassium gradient on resting membrane potential. As a
result, a greater than normal stimulus is required for depolarization of the membrane in order to initiate an action
- In the heart, hypokalemia causes hyperpolarization in the myocytes' resting membrane potential. The more
negative membrane potentials in the atrium may cause arrhythmias because of more complete recovery from
sodium-channel inactivation, making the triggering of an action potential more likely. In addition, the reduced
extracellular potassium (paradoxically) inhibits the activity potassium current and delays ventricular
repolarization. This delayed repolarization may promote reentrant arrhythmias.
Dizziness (↓BP causes this)
Cardiac Arrhythmias- life threatening
Muscle Weakness +Leg Cramps, which cause:
Anorexia (loss of appetite)
Polyuria + poorly concentrated urine
Hyperkalemia- Potassium levels of more than 5.0mEq/L in the blood
- Is Iatogenic, due to drugs or renal failure (not excreting enough), trauma
- is a precursor to MI
- Increased extracellular potassium levels result in depolarization of the membrane potentials of cells. This
depolarization opens some voltage-gated sodium channels, but not enough to generate an action potential. After a
short while, the open sodium channels inactivate and become refractory, increasing the threshold needed to generate
an action potential. This leads to the impairment of neuromuscular, cardiac, and gastrointestinal organ systems. Of
most concern is the impairment of cardiac conduction which can result in ventricular fibrillation or asystole.
Altered membrane potential causes:
flaccid paralysis – loss of muscle tone (because of effect on Na channels)
Edema Altered Chloride Balance -follows sodium
Hypochloremia- When blood levels are less than 98mEq/L
- Usually occurs as a result of hyponatremia, hypokalemia and metabolic alkalosis
- Caused by vomiting, diarrhea, diuretics
Metabolic Alkalosis Reasoning: Due to volume depletions, the chloride level decreases. Hence, the
kidneys retain the bi-carbonate and sodium ions for balancing the incurred loss. As a result, bicarbonate
accumulates in the ECF, thereby raising the pH level leading to hypochloremic metabolic alkalosis.
** this explains the shallow, depressed breathing
Weakness And Twitching
Shallow Depressed Breathing (metabolic alkalosis)
Hyperchloremia- When blood levels are more than 108mEq/L
- Caused by dehydration, kidney failure, brain trauma
- Associated With Metabolic Acidosis
Metabolic Acidosis Reasoning: a decrease in plasma bicarbonate concentration, and in an increase in
plasma chloride concentration. Acidosis is associated with ↑ Breathing.
Deep Rapid Breathing (acidosis)
Diminished Cognitive Ability
Cardiac Arrest Altered Calcium Balance
- Release of calcium is controlled by the parathyroid gland, important for vit D absorption and muscle
contraction and enzymes
- There is evidence that the parathydroid gland effects mood- so its no surprise that hyper/ hypo cause
irritability and depression. The key difference is that Hypo = anxiety, whereas Hyper= psychotic
effects, like confusion/delirium.
- Calcium is involved in muscle contraction. When there is low Ca in the blood, the system is actually
more excitable; thus, leading to twitches, cramps, tenany, etc. (Decreased Ca increases the likelihood
of an action potential = twitches. However, Increased Ca causes weakness because muscles are LESS
LIKELY to depolarize.).
- Cardiac Arrhythmia is associated with hypo/hyper, as you need balance for proper contraction
Hypocalcemia- Calcium blood levels of less than 8.5mg/dL
- Caused by Vit D deficiency, menopause (loss of estrogen), osteoporosis, heparin/glucagon, thyroid,
burns, kidney failure
Hypotension- due to ↓ Blood volume
Mood changes (Anxiety, Irritability, depression)
Tetany- involuntary contraction of muscles
Laryngospasm- ↑ contraction in the voice box (life threatening)
Seizure- due to ↑excitability in the brain
Hypercalcemia- Calcium blood levels of more than 10.5mg/dL
- Caused by excessive bone break down, thyroid disease, intake of Ca
Mood changes (Delirium/ Confusion, irritability) (also due to ↓ firing of muscles)
Nausea And Vomiting (due to ↑ Gastric sections)
Headaches (made worse by vomiting)
Muscle Effects: (due to ↓ firing of muscles)
Constipation- due to decreased muscle contractions in GI/ dehydration
Cardiac Arrhythmia Altered Magnesium Balance
- Magnesium is needed for almost all biochemical mechanisms: DNA and Protein synthesis,
oxidative phosphorylation, mitochondrial respiration.
- Magneisum is an effective Calcium Channel Blocker (CCB), and it can block cardiac K+
- Is a known cause of hypotension and cardiac dysfunction.
- Preeclampsia needs mg infusions
- Magnesium’s role in the balance of sodium and potassium is that of an intermediary.
Potassium is unable to cross the cell membrane on its own, and requires magnesium to
unlock the door for its entrance. Once the cell membrane is open, the cell can absorb all of
the potassium it needs for a proper balance. (thus, low mg means less K absorption and more
- There are concurrent effects between Mg and Ca, K, Na
Hypomagnesemia- Blood levels less than 1.5mEq/L
-Caused by malnutrition, malabsportion syndromes, burns, alcoholism
- lack of Mg depolarizes the heart!
Hypotension (due to ↓BV)
Occurs With Hypocalcemia (because ↑ elimination of Ca) And Hypokalemia (because it
↑elimination of K+)
Muscle Effects : (due to increased depolarization, muscle excitation)
Hypermagnesemia- Blood levels more than 2.5mEq/L
- linked with renal failure/dialysis, or excessive intake
Muscle effects: (due to ↓ depolarizations of muscles)
Decreased sodium movement causes:
Bradycardia (because its an effective CCB and blocks K channels in the heart) Altered Phosphate Balance
- has a relationship with calcium
Phosphate is the most abundant intracellular anion and is essential for membrane structure, energy
storage, and transport in all cells. In particular, phosphate is necessary to produce ATP, which provides
energy for nearly all cell functions. Phosphate is an essential component of DNA and RNA. Phosphate is
also necessary in red blood cells for production of 2,3-diphosphoglycerate (2,3-DPG), which facilitates
release of oxygen from hemoglobin.
- Approximately 85% of the body's phosphorus is in bone as hydroxyapatite, while most of the remainder
(15%) is present in soft tissue.
Hypophosphatemia- Blood levels less than 2.5mg/dL