WEEK 2 - Fluid Electrolyte Balance
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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