WEEK 2 - Fluid Electrolyte Balance Flashcards
What are some functions of calcium? (x5)
- Normal coagulation
- Nerve conduction
- Bone density
- Contraction/relaxation of muscles
- Hormone secretion - insulin
Where is calcium found and in what proportions?
99% in bone
1% in plasa
Normal TOTAL calcium concentration?
2.1-2.6 mmol/L
Changes in which protein effect calcium levels?
Serum albumin
Describe the effects of acid-base balance of calcium?
- In metabolic and respiratory acidosis = increased serum Ca and decreased binding capacity to albumin
- In metabolic and respiratory alkalosis = decreased serum Ca and increased binding capacity to albumin
What are some causes of hypocalcaemia? (x6)
- Hypoalbuminaemia
- PTH deficiency
- Chronic renal failure
- Vitamin D deficiency
- Excess loss eg. rhabdomyolysis
- Drugs
What are some signs and symptoms of hypocalcaemia?
- Irritability, confusion, depression and psychosis
- Prolonged QT interval on ECG
- Hypotension that is not responsive to IVF/vasopressors
- Hyperreflexia
- Parasthesias, intestinal cramps
- Tetany
What is Chvostek’s sign and what does it indicate?
Contractions of facial muscles in response to a light tap over the facial nerve in front of the ear - indicates hypocalcaemia
What is Trousseau’s sign and what does it indicate?
Carpal spasm induced by inflating a BP cuff above systolic pressure for a few mins, hand goes back to normal once cuff is removed - indicates hypocalcaemia
How to treat mild hypocalcaemia?
- Vitamin D preparations
- Oral Ca
- Increase dietary intake of Ca
How to treat severe hypocalcaemia?
- Parenteral Ca infusion VIA A CENTRAL LINE ONLY
- Pulmonary and cardiovascular support
Causes of hypercalcaemia?
- Increased intestinal absorption
- Excessive skeletal calcium release
- Inadequate Ca excretion
False highs of calcium may be caused by? (x2)
- Hyperalbuminaemia
- Haemoconcentration
What are some signs and symptoms of hypercalcaemia?
- Bone destruction
- Lethargy and muscle weakness in the lower extremities
- Impaired kidney function and renal calculi
- ECG abnormalities - short QT interval, prolonged PR interval, wide QRS, flattened/inverted T waves, arrhythmias
Treatment for hypercalcaemia?
- HYDRATION - dilute serum Ca and promote urinary excretion of Ca
- IV isotonic saline = 6L/24hrs
- Loop diuretics
- Bisphosphonates to decrease bone reabsorption
- Calcitonin to decrease bone resorption and increase urinary excretion
- Dialysis for renal failure
How is phosphorus related to calcium?
Has an inverse relationship with calcium
Where is P found?
- 1% in blood
- 10% in muscle
- 85% combined with calcium in bones and teeth
How is P absorbed and excreted?
- Absorbed via vitamin D
- Excreted via renal clearance (67%) and in faeces (33%)
Role of P in acid-base balance?
Binds with H2 in urine to buffer - acidification of urine
What are some causes of hyperphosphataemia?
- Renal insufficiency
- Increased cell breakdown or cellular injury
- Endocrine diseases
- Cancer
- Acidosis
- Excessive P intake
What are the signs and symptoms of hyperphosphataemia?
Usually asymptomatic!
- BUT S&S related to drop in Ca (inverse relationship) = tetany, seizures, delirium, tingling, cramps
- Sharp flexion of the wrist and extension of the feet
Treatment of hyperphosphataemia?
- Wait 4-8 hours before testing levels if pt is on glucose-based fluids
- Limit intake of P
- Diuretics
- Monitor Ca, uric acid and phosphate levels
- Dialysis if severe
Does low serum P = hypophosphataemia?
NOP
Low P does not necessarily mean total body depletion since only 1% of P is in blood
Causes of hypophosphataemia?
- Hypoventilation due to: alkalosis, sepsis, anxiety, pain, heatstroke
- DKA, decreased P absorption, vitamin . deficiency
Treatment of mild hypophosphataemia?
Increase dietary intake of P, oral supplements
Treatment of severe hypophosphataemia?
IV KPO4 or NaPO4 in dilute concentrations
Nursing care for a pt with hypophosphataemia?
- Monitor vitals
- Monitor pts on TPN (TPN = increase P)
- Monitor for drug interactions
Where is Mg absorbed and stored?
- Absorbed in the ileum
- Stored in bones
Normal serum levels of Mg?
1.5-2.5 mEq/L
Functions of Mg?
- AP conduction, vasodilation and CV regulation, bone metabolism, regulation of [Ca]
- Activation of cofactors of enzymes
- Activation of B enzymes
- Cofactor in DNA and protein synthesis
- Transporter in Na/K pump
Drop in Mg = similar drop in which electrolytes?
P
Ca
K
Na
Causes of hypomagnesemia?
- Chronic alcoholism
- Excessive gastric/intestinal drainage
- Decreased protein intake
- Renal tubular disease, nephrotoxic drugs
- Acidosis
Signs and symptoms of hypomagnesemia?
- CNS, CVS, GI and neuromuscular irritability
- Positive Chvostek’s and Trousseau’s signs
Treatment of hypomagnesemia?
Mg replacement - oral or IV
Causes of hypermagnesemia?
- Renal failure
- Untreated DKA
- Excessive intake of antacids
Signs and symptoms of hypermagnesemia?
- Flushing, increased perspiration
- Muscle weakness
- Nausea, vomiting
- Hypotension
- Dysrrhythmias
Functions of Cl?
- Works with Na to maintain osmotic pressure (CSF = NaCl)
- Stomach acid (HCl)
Where is chloride found?
- 80% in ECF
- Minimal found in the ICF, found in specialised cells (eg. nerves)
How is Cl removed from the body?
90% excreted in urine, 10% in faeces and sweat
Causes of hyperchloraemia?
- Decrease in intravascular fluid
- Dehydration
- DKA
- Bicarbonate deficiency
- Hypernatraemia
- Shock
- Starvation
Signs and symptoms of hyperchloraemia?
- Hyperventilation
- Decreased CO
- Compensation for decreased fluid balance
Treatment for hyperchloraemia?
- Correct fluid balance
- Increased blood pH
- Replace bicarbonate
Causes of hypochloraemia?
Any drop in Na, K, other cation to which Cl can bind
Signs and symptoms of hypochloraemia?
Hypoventilation, tetany, muscle cramping, confusion
Treatment for hypochloraemia?
High Na diet, assess K, Na, Cl, Ca, pH and bicarb levels, emesis control, IVF
What is a buffer/buffering pair?
Buffer - any chemical that can bind to excessive OH- or H+ without a significant change in pH
Buffering pair - a weak acid and its conjugate base
How goes the carbonic acid-bicarbonate pair work?
Increase in bicarb = acidosis
When the amount of carbonic acid also decreases = ratio of 20:1 is restored = pH is restored – pH adjustment via compensation
Which body systems use the carbonic acid-bicarbonate pair?
Lungs - compensates by increasing or decreasing ventilation
Kidneys - compensates by producing acidic or alkaline urine
What are the 4 forms of acid base imbalance?
- Respiratory acidosis
- Respiratory alkalosis
- Metabolic acidosis
- Metabolic alkalosis
What is respiratory acidosis?
Elevation of PCO2 due to hypoventilation
What is respiratory alkalosis?
Depression of PCO2 due to hyperventilation
What is metabolic acidosis?
Depression of HCO3- or an increase in non-carbonic acids
What is metabolic alkalosis?
Elevation of HCO3- or a decrease in non-carbonic acids
What are ABGs used for?
- To determine oxygenation
- To determine acid-base balance
Is HCO3- acidic or basic? What about H2CO3?
Why are they important?
HCO3- = basic H2CO3 = acidic
These two make up a conjugate pair used as a buffer
What characteristics of ABGs define COMPENSATED acidosis/alkalosis?
NORMAL pH +
ABNORMAL HCO3- and ABNORMAL PaCO2
pH is normal has the body has had time to restore it via compensatory measures
What characteristics of ABGs define UNCOMPENSATED acidosis/alkalosis?
ABNORMAL pH, HCO3- and PaCO2
There has not been enough time for the body to activate compensatory measures for abnormal pH
Explain pH balance in respiratory acidosis
pH becomes acidic as the lungs retain CO2
The kidneys counteract and balance this by retaining HCO3-
Explain pH balance in respiratory alkalosis
pH becomes basic as the lungs expire too much CO2
The kidneys counteract and balance this by increasing their excretion of HCO3-
Explain pH balance in metabolic acidosis
pH becomes acidic as the kidneys excrete too much HCO3-
The lungs counteract and balance this by expiring more CO2
Explain pH balance in metabolic alkalosis
pH becomes basic as the kidneys retain too much HCO3-
The lungs counteract and balance this by retaining CO2
