exam 2 Electrolytes & Acid Base Balance

Electrolytes

Substances that carry an electrical charge

Anions

Negative Ions

Cations

Positive ions

Electrolyte functions

- Water balance

- Fluid osmotic pressure

- Normal muscular function

- Normal nerve function

- Activation of enzymes

- Acid base regulation

Cation examples

- Sodium

- Potassium

- Calcium

- Magnesium

- Hydrogen

Anion examples

- Chloride

- Bicarbonate

- Inorganic phosphorus

Extracellular lytes

- Sodium

- Chloride

- Calcium

- Bicarbonate

Intracellular lytes

- Phosphorus

- Potassium

- Magnesium

What causes increases or decreases in electrolytes

- Changes in free water

- Intake

- Translocation

- Excretion/Loss

Translocation

Shifts between intracellular and extracellular fluids

Ways that electrolytes can be excreted or lost

- Renal excretion or retention

- GI loss

- Respiratory system

- Integument

Potentiometry

Uses electrodes to measure ions

Blood analyzer

- Indirect potentiometry measures lytes in total plasma volume

- Inaccurate if triglycerides >1500 mg/dL (Lipemic)

Blood Gas

- Direct potentiometry measures lytes in the aqueous phase only

- More accurate, not affected by lipemia

Important Notes when running blood gases

- Arterial sample preferred

- Run samples quickly and avoid air exposure

Venous samples may be used for:

- Standard chemistries

- Electrolytes

- Venous blood gases

Arterial samples

- Harder to obtain, painful, requires skill

- Provides information about blood gases

- Checks O2 status for critically ill patients

How does lipemia affect electrolytes tests

Lowers measurements in some machines

How does hemolysis affect measurement of intracellular lytes

Increases

How does hemolysis affect measurement of extracellular lytes

Decreases by dilution

Major cation of extracellular fluid

Sodium

Sodium roles

- Maintain osmotic pressure

- Water distribution

- Urine pH

- Acid base balance

- Hydrogen excretion in kidneys

What hormone regulates Na and K balance

Aldosterone

Sodium sample details

- Avoid sodium heparin anticoagulant due to false elevation

- Use lithium heparin for plasma chem

- Hemolysis and lipemia decrease

Hypernatremia

- Water loss (dehydration or eater deprivation)

- Excess sodium ingestion

Primary causes of hyponatremia

- Dilution or water retention

- Sodium loss

Causes of hyponatremia from dilution or water retention

- Water toxicity

- Excessive IV fluids

- CHF

- Edema from low protein (liver failure or glomerular disease)

Causes of hyponatremia from sodium loss

- Vomiting

- Addison's Disease (hypoaldosteronism)

- Use of diuretics

- Kidney injury

Dangers of sodium disturbances

- Vascular damage

- Cerebral dehydration

- Cerebral edema

- Coma

- Seizures

- Death

Major cation of intracellular fluid

Potassium

Potassium role

- Muscle function

- Respiration

- Cardiac function

- Nerve impulses

- Carb metabolism

Potassium sampling details

- Plasma is preferred over serum

- Remove cells asap

Diseases associated with Hyperkalemia

- Addison's disease

- Urinary obstruction

- Renal disease (AKI and end stage CKD)

- Cell lysis (massive trauma, IMHA, necrosis)

- Hyperkalemic periodic paralysis (HYPP)

- Trichuris vulpis infection

- Metabolic acidosis

Diseases associated with hypokalemia

- V/D (loss of GI fluids)

- Diuretic therapy

- Insulin overdose

- Refeeding syndrome

When is potassium disturbance life threatening?

>8.0 mEq/L

Dangers of hyperkalemia

- Decreased cardiac electrical activity (arrythmias, cardiac arrest)

- Neuromuscular weakness (flaccid paralysis)

Dangers of hypokalemia

- Arrythmias (vtach, fibrillation)

- Cardiac arrest

- Hypokalemic myopathy (cervical ventroflexion in CKD cats)

Hyperkalemic periodic paralysis (HYPP)

- Autosomal dominant genetic disorder in horses

- Disruption of sodium ion channels causes hyperkalemia

- Hyperkalemia causes excessive muscle contraction

Hyperkalemic periodic paralysis (HYPP) C/S

- Unpredictable attacks of muscle tremors & weakness

- Collapse

- Sudden death from cardiac arrest or respiratory failure

Hyperkalemic periodic paralysis (HYPP) Lab results

- Elevated K

- Elevated CK (muscle breakdown)

Hyperkalemic periodic paralysis (HYPP) Tx

- Diet (avoid excessive K)

- Avoid rapid diet changes

- Allow regular exercise

Addison's disease

- Hormonal deficiency

- Decreased aldosterone

Addison's disease C/S

- V/D/Anorexia

- Hypotensive and hypoglycemic shock

Addison's Disease lab results

- Na/K ratio <27:1

- Low Blood glucose

Addison's disease Tx

Replace missing hormones

Major anion on extracellular fluid

Chloride

What anion has the same roles as sodium

Chloride

Chloride sampling detail

- Hemolysis and lipemia may dilute

- Separate sample to prevent artificial decrease with prolonged storage

Diseases associated with hyperchloremia

- Metabolic acidosis (body retains Cl- when HCO3 is lost)

- Renal disease

Diseases associated with hypochloremia

- V, anorexia, malnutrition

- Diabetes insipidus

Where is 99% of calcium found?

Bones

Calcium role

- Neuromuscular excitability

- Coagulation and enzyme activation

- Inorganic ion transfer across cell membranes

What measures bound calcium

Total calcium

What measures the active form of calcium

Ionized calcium

What measures total calcium

Standard chemistry panel

What measures ionized calcium (iCa)

Blood gas devices

Calcium samplingdetails

- Contamination with EDTA, citrate, or oxalate will chelate calcium

- Hemolysis and lipemia will decrease

Diseases associated with hypercalcemia

- Hyperparathyroidism

- Neoplasia

- CKD

- Vitamin D toxicity

Diseases associated with hypocalcemia

- Eclampsia or "milk fever" when nursing

- Pancreatitis

- Dietary deficiency in Vitamin D or calcium

- Hypoparathyroidism (parathyroid glands don't produce enough PTH)

- Low albumin (carries Ca)

Dangers of hypercalcemia

- Cardiac arrhythmias and cardiac arrest

- Renal damage & calcinosis

- Reduced neuromuscular excitability, muscle weakness

- Reduced smooth muscle contraction (GI stasis)

Dangers of hypocalcemia

- Tetany and seizures (neuromuscular overexcitability)

- Pain, listlessness, ataxia, twitches, tremors, nervousness

- Cardiac arrhythmias

- GI dysfunction

Eclampsia

Hypocalcemia secondary to nursing

Who is primary affected by eclampsia

Small dogs with large litters

Eclampsia C/S

- Lethargy, anorexia

- Tremors and seizures

Diagnostic used for eclampsia

Ionized calcium

Eclampsia Tx

- Calcium gluconate infusion

- Tums

- Bottle feed nursing puppies

2nd most common intracellular cation

Magnesium

Magnesium role

- Activate enzyme systems

- Production and consumption of acetylcholine

What can falsely increase magnesium

Hemolysis

Hypermagnesemia

- Kidney disease

- Addison's disease

- Cardiovascular collapse (Mg blocks Ca channels)

- Muscle paralysis & weakness (Mg blocks Ca at NMJ)

- Reduced gut mobility

Hypomagnesemia

- Nerve hyperexcitability (tremors, muscle spasms, seizures)

- Cardiac arrhythmias and sudden death

- Affects Ca and K levels

Grass Tetany

Hypomagnesemia in cattle and sheep

Grass tetany C/S

- Excitement

- Tetany or muscle stiffness

- Progresses quickly to death

Grass tetany tx

Calcium magnesium infusion

Grass tetany prevention

Testing or forage, supplementation mineral mix or salt lick

Second most common anion of the extracellular fluid

Bicarbonate

Bicarbonate role

- Buffer against acids

- Aids in transport of CO2 from the tissues for removal from the body

What regulates bicarbonate levels

Kidneys

How can bicarbonate be estimated

CO2 levels

Bicarbonate sampling details

- Arterial blood preferred if measuring o2 levels

- Venous blood preferred if measuring tissue levels of HCO3-

- Lithium heparin plasma

- Chill sample to prevent glycolysis from changing the acid base

Dangers of elevated bicarbonate (metabolic alkalosis)

- Hypoxia in tissues

- Compensatory decreased ventilation (preserves acidic co2)

- Cardiac arrhythmias and arrest

- Tremors, spasms, seizures

Dangers of decreased bicarbonate (metabolic acidosis)

- Reduced cardiac contractility and arrhythmias

- Compensatory hyperventilation (respiratory failure)

- Coma

Where is >80% of inorganic phosphorus found

Bones

Inorganic phosphorus role

- Energy storage, release & transfer ATP

- Carbohydrate metabolism

- Component of phospholipids and nucleic acids

In whole blood where is Inorganic phosphorus found

Plasma

In whole blood where is organic phosphorus found

Erythrocytes

What is inversely related to calcium

Inorganic phosphorus

Causes of Hyperphosphatemia

CKD, vitamin D toxicity, hemolysis

Dangers of Hyperphosphatemia

- Mineralization of tissues (phos binds w/ Ca)

- Causes hypocalcemia

Causes of hypophosphatemia

Refeeding syndrome, DKA, hyperparathyroidism, burns

Dangers of hypophosphatemia

- Hemolysis (due to membrane instability)

- Cardiac arrhythmias

- Altered mentation and seizures

Acid base balance

Steady state of the body's pH

What helps maintain acid base balance

- Buffers

- Respiratory system (immediate)

- Renal system (days)

What decreases pH

Increased hydrogen ions

Normal pH

~7.4 (7.35-7.45)

Acidosis

pH < 7.35

Alkalosis

pH >7.45

Principle of electrical neutrality

# cations = # anions

How is electrical neutrality maintained

Buffers

Anion gap

Difference between total cations and total anions (Na + K) - (Cl + HCO3)