HLSC Acids and Bases

Osmosis

– movement of water across a
semi-permeable membrane
• Solution/water(solvent) moves
from an area of low solute (ion)
concentration to an area of high
solute concentration

Tonicity

osmotic pressure of two solutions separated by a
semipermeable membrane

Isotonic

equal solute concentrations
– causes no fluid shifts

Hypertonic

higher solute concentrations
– causing fluids to shift out

Hypotonic

lower solute concentrations
– causing fluids to shift in

Capillary hydrostatic pressure

Outward push from blood vessel

Capillary oncotic pressure

Inward pull to the blood vessel

Interstitial hydrostatic pressure

The push out of interstitial space into vessel

Interstitial oncotic pressure

The pull into the interstitial space from the vessel
– Usually minimal due to low [protein] present in tissues

Edema

– Excess fluid in the interstitial space
– ↑ capillary hydrostatic pressure,
↑capillary pressure, ↓ plasma
oncotic pressure, lymphatic
channel obstruction

Hypervolemia

– Excess fluid in the intravascular
space

Water intoxication

Excess fluid in the intracellular
space

Sodium

• Normal range 135-145 mEq/L
• Most significant cation and prevalent
electrolyte of extracellular fluid
• Controls serum osmolality and water balance
• Plays a role in acid-base balance
• Facilitates muscles and nerve impulses
• Dietary intake main source
• Excreted through the kidneys and
gastrointestinal tract

Hypernatremia

• Sodium > 145 mEq/L
• Serum osmolarity increases
• Results in fluid shifts

Causes of Hypernatremia

Deficient water or excessive sodium

Diagnosis of Electrolyte Imbalances

H&P , blood chemistry, and urine
analysis

Treatment of Electrolyte Imbalances

Identify and manage underlying cause, supplementation 

Hyponatremia

• Sodium < 135 mEq/L
• Serum osmolarity decreases

Chloride

• Normal range 98-108 mEq/L
• Mineral electrolyte
• Major extracellular anion
• Found in gastric secretions, pancreatic juices,
bile, and cerebrospinal fluid
• Plays a role in acid-base balance
• Dietary intake main source
• Excreted through the kidneys

Hyperchloremia

Chloride > 108 mEq/L

Hypochloremia

Chloride < 98 mEq/L

Potassium

• Normal range 3.5-5 mEq/L
• The primary intracellular cation
• Plays a role in electrical conduction, acid-
base balance, and metabolism
• Dietary intake main source
• Excreted through the kidneys and
gastrointestinal tract

Hyperkalemia

Potassium > 5 mEq/L

Hypokalemia

Potassium < 3.5 mEq/L

Calcium

• Normal range 4-5 mEq/L
• Mostly found in the bone and
teeth
• Plays a role in blood clotting,
hormone secretion, receptor
functions, nerve transmission,
and muscular contraction
• Has inverse relationship with
phosphorus
– When increased, phosphorus
decreased
• Has synergistic relationship with
magnesium
– Both increased together

Hypercalcemia

Calcium > 5 mEq/L

Hypocalcemia

Calcium < 4 mEq/L

Causes of Hypocalcemia

– Excessive losses:
• hypoparathyroidism, renal failure, hyperphosphatemia, alkalosis, pancreatitis, laxatives, diarrhea, and other medications
– Deficient intake:
• decreased dietary intake, alcoholism, absorption
disorders, and hypoalbuminemia

Phosphorus

Normal range 2.5-4.5 mg/dL
• Mostly found in the bones and small amounts are in the bloodstream
• Plays a role in bone and tooth
mineralization, cellular metabolism, acid-base balance, and cell membrane formation
• Dietary intake main source
• Excreted through the kidneys

Hyperphosphatemia

Phosphorus > 4.5 mg/dL

Causes of Hyperphosphatemia

Deficient excretion:
• renal failure, hypoparathyroidism, adrenal insufficiency, hypothyroidism, and laxatives
– Excessive intake or
cellular exchange:
• cellular damage, hypocalcemia, and acidosis

Hypophosphatemia

Phosphorus < 2.5 mg/dL

Causes of Hypophosphatemia

– Excessive excretion or cellular exchange:
• renal failure, hyperparathyroidism, and alkalosis
– Deficient intake:
• malabsorption, vitamin D deficiency, magnesium and aluminum antacids, alcoholism, and decreased dietary intake

Magnesium

• Normal range 1.8-2.5 mEq/L
• An intracellular cation
• Mostly stored in the bone and
muscle
• Plays a role in muscle and nerve function, cardiac rhythm, immune function, bone strength, blood glucose management, blood
pressure, energy metabolism, and protein synthesis
• Dietary intake main source
• Excreted through the kidneys

Hypermagnesemia

Magnesium > 2.5 mEq/L

Causes of  Hypermagnesemia

Causes of Hyponatremia 

• Deficient sodium
– Diuretic use
– Gastrointestinal losses
– Excessive sweating
– Insufficient aldosterone
levels
– Adrenal insufficiency
– Dietary sodium
restrictions
• Excessive water
– Hypotonic intravenous
saline (0.45% saline)
– Hyperglycemia
– Excessive water ingestion
– Renal failure
– Syndrome of inappropriate antidiuretic hormone
– Heart failure

Causes of Hyperchloremia

– Increased chloride intake or
exchange:
• hypernatremia, hypertonic intravenous
solution, metabolic acidosis, and hyperkalemia
– Decreased chloride excretion:
• hyperparathyroidism, hyperaldosteronism,
and renal failure

Causes of Hypochloremia

– Decreased chloride intake or exchange:
• hyponatremia, 5% dextrose in water intravenous
solution, water intoxication, and hypokalemia
– Increased chloride excretion:
• diuretics, vomiting, metabolic alkalosis, and other gastrointestinal losses

Causes of Hyperkalemia

– Deficient excretion:
• renal failure, Addison’s disease, certain medications, and Gordon’s syndrome
– Excessive intake:
• oral potassium supplements, salt substitutes, and rapid intravenous administration of diluted potassium
– Increased release from cells:
• acidosis, blood transfusions, and burns or any other cellular injuries

Causes of Hypokalemia

– Excessive loss:
• vomiting, diarrhea, nasogastric suctioning, fistulas, laxatives, potassium-losing diuretics, Cushing’s syndrome, and corticosteroids
– Deficient intake:
• malnutrition, extreme dieting, and alcoholism

– Increased shift into the cell:
• alkalosis and insulin excess

Causes of Hypercalcemia

– Increased intake or release:
• calcium antacids, calcium supplements, cancer,
immobilization, corticosteroids, vitamin D deficiency, and hypophosphatemia
– Deficient excretion:
• renal failure, thiazide diuretics, and hyperparathyroidism

pH Normal Level

7.35-7.45, remember 7.4

PaCO2 Normal Level

35-45

PO2 Normal Level

80-100

HCO3 Normal Level

22-26

Buffers

• Chemicals that combine with an acid or base to change pH
• Immediate reaction to counteract pH variations until compensation is initiated

Respiratory Regulation

Alters carbon dioxide excretion
• Speeding up respirations will
excrete more carbon dioxide
– decreasing acidity
• Slowing down respirations
will excrete less carbon dioxide
– increasing acidity
• Uses chemoreceptors
• Responds quickly, but is short-lived

Renal Regulation

• Alters the excretion or
retention of hydrogen or bicarbonate
• More effective by
permanently removing hydrogen
• Responds slowly, but longer
lasting

Respiratory Acidosis

• Results from carbon dioxide retention
– which increases carbonic acid

Metabolic Acidosis

• Results from a deficiency of bicarbonate or an
excess of hydrogen

Metabolic Alkalosis

Results from excess bicarbonate, deficient
acid or both

Respiratory Alkalosis

• Results from excess exhalation of carbon dioxide
– which leads to carbonic acid deficits

Mixed Disorders

• Respiratory and metabolic disorders
resulting in an acidotic or alkalotic state
• Both the respiratory and renal systems
demonstrate an imbalance of acid or base