Serum Electrolytes &
Arterial blood gases
Dr. Mohammed K. El-Habil
MSC. Pharmacology
2014
Electrolytes
 Solutes that form ions (electrical
charge)
 Cation (+)
 Anion (-)
 Major body electrolytes:
 Na+, K+, Ca++, Mg++
 Cl-, HCO3-, HPO4--, SO4-
Electrolyte Distribution
 Major ICF ions
 K+
 HPO4--
 Major ECF ions
 NA+
 CL-, HCO3-
Electrolyte Normal Values
Sodium
Potassium
Phosphrus
Chloride
Calcium
Urea
Creatinine
Magnesium:
CO2
Bicarbonate
135 – 145 mEq/L
3.5 – 5 mEq/L
1.8-2.3 mEq/L
98 – 106 mEq/L
9 – 11 mEq/L
20 – 40 mEq/L
0.7 – 1.2 mEq/L
1.5 – 3 mEq/L
22 – 26 mEq/L
24-30 mEq/L
Hypernatremia
Na+ is more than 135 – 145 mEq/L
Manifestations
Thirst, lethargy, agitation, seizures, and
coma, shrinking of brain.
Similar to :
Central or nephrogenic diabetes
insipidus (DI).
In treatment, reduce Na+ levels
gradually to avoid cerebral edema
Hyponatremia
Results from loss of sodium-containing
fluids
Sweat, diarrhea, emesis,..etc.
Or from water excess
Inefficient kidneys
Drowning, excessive intake
Manifestations
Confusion, nausea, vomiting, seizures, Brain
edema and coma
Hyperkalemia
 Serum Potassium greater than 5.5
mEq/L
- More dangerous than hypokalemia
because cardiac arrest is frequently
associated with high serum K+ levels
Hyperkalemia
Manifestations
Weak or paralyzed skeletal muscles
Ventricular fibrillation or cardiac block
Abdominal cramping or diarrhea
Hypokalemia
Low serum potassium caused by
Abnormal losses of K+ via the kidneys
or gastrointestinal tract
 Drugs: Diuretics
Magnesium deficiency
Metabolic alkalosis enhance H-K
pumping & entrance of K intracellular .
Hypokalemia
Manifestations
Most serious are cardiac arrhythemias
Skeletal muscle weakness
Weakness of respiratory muscles
Decreased gastrointestinal motility
Calcium
Obtained from ingested foods
More than 99% combined with
phosphorus and concentrated in
skeletal system
Inverse relationship with phosphorus
Otherwise…
Calcium
Balance controlled by
Parathyroid hormone
Calcitonin
Vitamin D/Intake
Bone used as reservoir
Hypercalcemia
High serum calcium levels more than
9 – 11 mEq/L caused by
Hyperparathyroidism (two thirds of
cases)
Malignancy (parathyroid tumor)
Vitamin D overdose
Prolonged mobilization
Hypercalcemia
Manifestations
Decreased memory
Confusion
Disorientation
Fatigue
Constipation
Treatment
Excretion of Ca with loop diuretic
Hydration with isotonic saline
infusion
Synthetic calcitonin
Hypocalcemia
Low serum Ca levels caused by
Decreased production of PTH
Acute pancreatitis
Multiple blood transfusions
Alkalosis
Decreased intake
Hypocalcemia
Manifestations
Weakness/Tetany
Positive Trousseau’s or
Chvostek’s sign
Laryngeal stridor
Dysphagia
Tingling around the
mouth or in the extremities
Treatment
Treat cause
Oral or IV calcium supplements
Not IM to avoid local reactions
Treat pain and anxiety to prevent
hyperventilation-induced respiratory
alkalosis
Phosphate
Primary anion in ICF
Essential to function of muscle, red
blood cells, and nervous system
Deposited with calcium for bone and
tooth structure
Hyperphosphatemia
High serum PO43 (more than1.8-2.3
mEq/L) caused by:
Acute or chronic renal failure
Chemotherapy
Excessive ingestion of phosphate or
vitamin D
Manifestations
Calcified deposition: joints, arteries,
skin, kidneys, and corneas
Neuromuscular irritability and tetany
Hypophosphatemia
Low serum PO43 caused by
Malnourishment/malabsorption
Alcohol withdrawal
Use of phosphate-binding antacids
During parenteral nutrition with
inadequate replacement
Hypophosphatemia
Manifestations
CNS depression
Confusion
Muscle weakness and pain
Dysrhythmias
Cardiomyopathy
Magnesium
50% to 60% contained in bone
Coenzyme in metabolism of protein
and
carbohydrates
Factors that regulate calcium balance appear to
influence magnesium balance.
Acts directly on myoneural junction
Important for normal cardiac function
Hypermagnesemia
High serum Mg more than 1.5 – 3 mEq/L caused
by
When renal insufficiency or failure is present
Manifestations
Lethargy or drowsiness
Nausea/vomiting
Impaired reflexes***
Respiratory and cardiac arrest
Hypomagnesemia
Manifestations
Confusion
Hyperactive deep tendon reflexes
Tremors
Seizures
Cardiac dysrhythmias
Electrolytes
Electrolytes
Renal Function
Arterial blood gases
Interpretation of ABGs
Diagnosis in six steps
Evaluate pH
Analyze PaCO2
Analyze HCO3
Determine if Balanced or Unbalanced
Determine if CO2 or HCO3 matches
the alteration
Decide if the body is attempting to
compensate
Interpretation of ABG
1.
2.
3.
4.
5.
pH over balance
PaCO2 = “respiratory” balance
HC03- = “metabolic” balance
If all three normal = balanced
Match direction. e.g., if pH and PaCO2 are
both acidotic, then primary respiratory
acidosis
6. Together, CO2 & HCO3 act as metabolic &
respiratory buffer like:
7. H2O + CO2 ˭ ˭ ˭ H2CO3 ˭ ˭ ˭ HCO3 + H
Metabolic Acid-base Disorders:
Some Clinical Causes
METABOLIC ACIDOSIS
↓HCO3- & ↓ pH
- lactic acidosis; ketoacidosis; drug poisonings (e.g., aspirin, ethylene
glycol, methanol)
diarrhea; some kidney problems (e.g., renal tubular acidosis,
interstitial nephritis)
METABOLIC ALKALOSIS
↑ HCO3- & ↑ pH
contraction alkalosis, diuretics, corticosteroids, gastric suctioning, vomiting
hyperaldosterone state (e.g., Cushing’s syndrome, Bartter’s syndrome,
severe K+ depletion)
Respiratory Acid-base Disorders:
Some Clinical Causes
RESPIRATORY ACIDOSIS
↑PaCO2 & ↓ pH
Central nervous system depression (e.g., drug overdose)
Chest bellows dysfunction (e.g., Guillain-Barré syndrome,
myasthenia gravis)
Disease of lungs and/or upper airway (e.g., chronic obstructive lung
disease, severe asthma attack, severe pulmonary edema)
RESPIRATORY ALKALOSIS
↓PaCO2 & ↑ pH
Hypoxemia (includes altitude)
Anxiety
Sepsis
Any acute pulmonary insult (e.g., pneumonia, mild asthma attack, early
pulmonary edema, pulmonary embolism)
Acid-Base Disorders
Acid-Base Disorders
Interpretation of ABGs
pH 7.26
Normal (7.35-7.45)
PaCO2 67 mm Hg (35-45)
PaO2 47 mm Hg
(80-100)
HCO3 26 mEq/L
(22-26)
What is this?
 Respiratory acidosis
Interpretation of ABGs
pH 7.18
PaCO2 38 mm Hg
PaO2 70 mm Hg
HCO3 15 mEq/L
What is this?
 Metabolic acidosi