Sodium Regulation
Normal Range: Sodium levels are maintained between 135-145 mEq/L.
Important Study Focus: Review of the Renin-Angiotensin-Aldosterone System (RAAS) and sodium regulation.
Approach: Start with the left side of the chart, discussing causes first, and then build on the right side as many concepts are oppositional.
Causes of Hypernatremia (>145 mEq/L)
SIADH (Syndrome of Inappropriate Antidiuretic Hormone)
Hypervolemia / Heart Failure
Renal Failure
Diuretics Leading to Sodium Loss
Addison’s Disease
Causes of Hyponatremia (<135 mEq/L)
Diabetes Insipidus (DI)
Increased Sodium Intake
Hypovolemia
Diuretics leading to fluid loss
Dehydration / Excessive Sweating
Clinical Manifestations
Hyponatremia: CNS symptoms including nausea (N/V), confusion, convulsions, headaches (HA), disorientation, agitation, and seizures; dry mucous membranes, increased thirst, flushed skin, elevated body temperature.
Hypernatremia: Similar CNS manifestations and hypervolemia symptoms.
Diagnostic Criteria
Hyponatremia: Na < 135, serum osmolality < 275 mOsm/kg; urine specific gravity > 1.030. Risk of seizures if sodium < 115 mEq/L.
Hypernatremia: Na > 145, serum osmolality > 295 mOsm/kg; urine specific gravity < 1.005.
Treatment for Hyponatremia
Fluid Restriction
Oral Sodium Supplements
Loop Diuretics
IV 3% NS (hypertonic saline)
Fluid Replacement: 0.45% NS (hypotonic) to push water into cells.
Address Underlying Causes.
Calcium Regulation
Normal Range: Calcium levels are maintained between 8.2-10.2 mg/dl.
Regulation Focus: Study the inverse relationship with phosphate (PO4).
Causes of Hypocalcemia (<8.2 mg/dl)
Hypoparathyroidism
Malabsorption issues (Celiac disease, Crohn's disease, alcoholics)
Kidney failure impacting calcium absorption and phosphate elimination.
Alkalosis where increased pH leads to decreased free calcium.
Causes of Hypercalcemia (>10.2 mg/dl)
Hyperparathyroidism
Loss of calcium via diuretics/thiazides
Malignancies
Acidosis where decrease in pH increases free calcium.
Clinical Manifestations
Hypocalcemia: Confusion, irritability, neuromuscular (NM) symptoms like paresthesias, twitching, cramping, tetany, laryngospasm.
Hypercalcemia: Constipation, abdominal cramps, decreased deep tendon reflexes (DTR), hypertension, muscle weakness, increased heart rate.
Diagnostic Criteria
Hypocalcemia: pH > 7.45, calcium < 8.2, PO4 > 4.5 (Trousseau's and Chvostek's signs).
Hypercalcemia: pH < 7.35, calcium > 10.2, PO4 < 2.5.
Treatment for Hypocalcemia
Increased intake of Vitamin D and Calcium supplements.
IV Calcium Chloride (CaCl2).
Treatment for Hypercalcemia
IV Fluids
Loop Diuretics
Bisphosphonates (e.g., Actonel, Fosamax, Reclast).
Phosphate Regulation
Normal Range: Phosphate levels are maintained between 2.5-4.5 mg/dl.
Inverse relationship with calcium: as phosphate increases, calcium decreases and vice versa.
Causes of Hypophosphatemia (<2.5 mg/dl)
Renal Loss/Diuretics
Hyperparathyroidism
Severe Burns
Decreased Dietary Intake (dairy, meats, nuts, seeds).
Causes of Hyperphosphatemia (>4.5 mg/dl)
Renal Disease impacting phosphate elimination.
Hypoparathyroidism.
Clinical Manifestations
Hypophosphatemia: Decreased NM symptoms akin to hypercalcemia including hypertension, increased heart rate.
Hyperphosphatemia: Increased NM symptoms resembling hypocalcemia including decreased heart rate and blood pressure.
Diagnostic Criteria
Hypophosphatemia: PO4 < 2.5, calcium > 10.2.
Hyperphosphatemia: PO4 > 4.5, calcium < 8.2.
Treatment for Hypophosphatemia
Increased Dietary Intake.
Phosphate Supplement (Kphos IV).
Phoslo capsules, particularly with kidney disease.
Treatment for Hyperphosphatemia
If no renal disease, administer IV Normal Saline and Loop Diuretics to dilute and remove phosphate.
Potassium Regulation
Normal Range: Potassium levels are maintained between 3.5-5.0 mEq/L.
Key Balance: 3 Sodium out, 2 Potassium in for neuromuscular (NM) and electrical activity.
Causes of Hypokalemia (<3.5 mEq/L)
Gastrointestinal Loss (vomiting, diarrhea)
Renal Loss (diuretics, particularly thiazides and loops)
Alkalosis
Poor intake
Cushing’s syndrome.
Causes of Hyperkalemia (>5 mEq/L)
Kidney failure (reduction of RAAS and bicarbonate reabsorption)
Drugs increasing potassium (spironolactone, ACE inhibitors)
Acidosis
Increased intake (IV overshoot, crush injuries, burns)
Adrenal insufficiency (Addison’s disease).
Clinical Manifestations
Hypokalemia: Increased blood pressure (hypertension), weakness, hyporeflexia, constipation, abdominal cramping, dysrhythmias, prominent U wave on EKG.
Hyperkalemia: Hyperreflexia, paresthesias, bradycardia, diarrhea, increased bowel sounds.
Diagnostic Criteria
Hypokalemia: K < 3.5 mEq/L, pH > 7.45, EKG changes.
Hyperkalemia: K > 5 mEq/l, pH < 7.35, specific EKG changes (tall peaked T waves, widened QRS).
Treatment for Hypokalemia
Increase dietary potassium intake (apricots, bananas).
Oral Potassium supplements; IV Potassium Chloride (KCl).
Kayexalate; 50% dextrose and regular insulin; bicarbonate; IV calcium gluconate; loop diuretics.
Chloride Regulation
Normal Range: Chloride levels are maintained between 97-107 mEq/L.
Causes of Hypochloremia (<97 mEq/L)
Sweating, vomiting
Alkalosis
Laxative use
Causes of Hyperchloremia (>107 mEq/L)
Dehydration, acidosis (diabetic ketoacidosis, lactic acidosis)
Kidney disease
Salicylate poisoning.
Clinical Manifestations
Hypochloremia: Increased pH leading to CNS symptoms such as tetany, irritability, seizures, twitching.
Hyperchloremia: Decreased pH leading to CNS symptoms such as confusion, lethargy, stupor, tachypnea.
Diagnostic Criteria
Hypochloremia: Cl < 97 mEq/L, Na < 135, Ca < 8.2, pH > 7.45, bicarbonate > 26.
Hyperchloremia: Cl > 107 mEq/L, Na > 145, Ca > 10.2, pH < 7.35, bicarbonate < 22.
Treatment for Hypochloremia
Administering 0.9% NS, Ammonium Chloride, NaCl, KCl, CaCl2.
Treatment for Hyperchloremia
Administer sodium bicarbonate; dilute with 0.45% NS.