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