Term
Where is potassium excreted?
How does the Na/K pump regulate potassium levels? |
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Definition
90% by the kidneys - Hyperkalemia the most common electrolyte disorder in CKD
Whenever the Na/K pump is activated (Insulin, catecholamines), K moves into the cell
Metabolic acidosis prompts Hyperkalemia |
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Term
| What is the normal range for Potassium? |
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Definition
Normal K - 3.5 to 5
Severe hypokalemia < 2.5
Severe hyperkalemia > 7 |
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Term
| What are causes of hypokalemia? |
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Definition
- Poor diet, renal loss due to aldosterone or loop diuretics
- Low magnesium - impairs Na/K pump and increases K wasting
- Insulin and catecholamines shifts into cells
- Metabolic alkalosis |
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Term
| What agents result in drug-induced hypokalemia? |
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Definition
- Albuterol and insulin shift K into cells
- Aminoglycoside antibiotics increase excretion
- SPS & sorbitol = K binder |
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Term
| What are signs and symptoms of hypokalemia? |
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Definition
- cramping and weakness until severe
- Severe levels < 2.5 - ECG changes, arrhythmia
- Early Tx - correct underlying hypomagnesemia, increase intake of K rich foods (fruit, meat), salt substitutes |
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Term
| When is oral therapy used to treat hypokalemia? |
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Definition
When asymptomatic and K < 3.5.
KCl most common therapy - all cause GI upset |
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Term
| When should IV potassium supplements be used? |
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Definition
In severe symptomatic hypokalemia, oral supplements not tolerated.
Causes pain at infusion site - avoid prep in D5W, as insulin lowers K
Need to monitor ECG for hyperkalemia |
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Term
| How are potassium supplements dosed in renal insufficiency? |
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Definition
| Reduce doses by 50% in renal insufficiency |
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Term
| How is hyperkalemia diagnosed? |
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Definition
K >5, severe at >7.
- frequently asymptomatic, see cramping, ECG changes, arrhythmia in severe cases |
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Term
| What causes hyperkalemia? |
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Definition
- Unresponsive to aldosterone, increased intake
- Decreased excretion in CKD**, meds that increase K (AceI, Ksparing, NSAIDs)
- Adrenal insufficiency - anything that decreases aldosterone or response to aldosterone
- Metabolic acidosis shifts K out of cells, as does DM and BBs |
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Term
| How is hyperkalemia treated? |
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Definition
- Symptomatic - IV calcium, then other Tx. Has no effect on K levels, reverses ECG changes
- Asymptomatic - Shift K into cells w/ drugs, increased elimination
- Increased uptake of K into cells: Insulin, Dextrose, Sodium bicarb in acidosis patients, albuterol
- Increased loss: furosemide, Kayexalate |
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Term
| What is the normal range for magnesium levels? |
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Definition
| Normal: 1.7 - 2.4, distributed between bone and muscle). Affects hormone regulation |
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Term
| What causes hypomagnesemia? |
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Definition
- Reduced intake
- Reduced absorption
- Increased loss - GI or drug induced
- Internal redistribution - like K, insulin pushes Mg into cells |
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Term
What causes high magnesium levels?
What are the S/S and Tx? |
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Definition
Mg > 2.4
Seen in stage 4/5 CKD, elderly, and Tx w/ magnesium salts
Eventually compromises heart and vasculature
Reduce Mg intake, antagonize w/ Calcium, force loss w/ furosemide |
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Term
What is the normal value for calcium?
Why is it important to normalize a measured calcium value? |
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Definition
Normal: 8.5 - 10.5
Calcium is bound to albumin, so if albumin is low, calcium is falsly low. Normal Albumin: 4.0 g/dl |
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Term
| How do you correct for a low albumin in a calcium reading? |
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Definition
Corrected serum calcium = measured serum calcium + {0.8*(4.0 - measured albumin)}
Where 4.0 is the normal albumin level and 0.8 is a constant |
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Term
| What causes hypercalcemia? |
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Definition
Metabolic acidosis - decreases calcium binding to albumin
Hyperparathyroidism - increased PTH removes Ca from bones and incr serum Ca
Medication induced hypercalcemia |
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Term
| How is calcium homeostasis maintained? |
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Definition
In the presence of high calcium, calcitonin lowers serum calcium by depositing onto bones. A high phosphorus level lowers calcium, inhibits active Vit D
In the presence of low calcium, PTH removes Ca from bones and activated Vit D |
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Term
What are S/S of hypercalcemia?
How is it treated? |
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Definition
Ca > 10.5, severe > 13. Treat at > 12
Fatigue, weakness, etc
- Increase renal loss by 0.9% saline, loop diuretics, bisphosphonates used in osteoporosis
- Last line - Mithramycin/gallium nitrate, for unresponsive. Can't use in renal patients
- Do not use calcitonin w/ saline
- Prednisone for neoplasms patients. Do not use IV phosphate |
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Term
| What are the S/S of hypocalcemia? |
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Definition
Ca < 8.5
Cramps, can be chronic: depression, memory loss
Many S/S: Dental, neurological, bone |
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Term
| What causes hypocalcemia? |
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Definition
Removal of the parathyroid gland
Vit D deficiency, Mg deficiency
Drug induced, CKD |
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Term
| How is hypocalcemia treated? |
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Definition
Is albumin lower than 4? Correct calcium level. Still low?
Is Mg low? PTH? Vit D? - fix these contributing factors.
Symptomatic - IV CaCl, not - oral calcium |
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Term
| What is the normal range for phosphorus? |
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Definition
Normal - 2.5 to 4.5
Severe > 7 |
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Term
What causes high phosphorus levels?
What are S/S? |
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Definition
Renal failure - High Phos = low Ca --> PTH tries to correct, gets high
Hypo-PTH
Medication induced, Rhabdo
- Eventual deposition of calcium crystals, causes tissue ischemia in arteries, joints etc.
Severe: hypocalcemia, tetany |
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Term
| How are high phosphorus levels treated? |
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Definition
Symptomatic: IV CaCl, dialysis
Asymptomatic: Phosphorus binders - Renvela, etc |
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Term
| What are low phosphate levels and how is it treated? |
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Definition
- Phos < 2.5, severe < 1 due to incr excretion, decr absorption and redistribution (insulin)
- Symptomatic: IV phos, watch levels closely. mild - oral supplement |
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