W10 Electrolyte imbalance (MAH) Flashcards
Electrolytes
What are the significant electolytes?
What do they do?
- Electrolytes are substances that, when dissolved in a solution, create electrically charged particles called ions
- Electrolytes are essential for basic life functioning, such as maintaining electrical neutrality in cells and generating and conducting action potentials in the nerves and muscles
- Significant electrolytes include sodium, potassium, chloride, magnesium, calcium, phosphate, and bicarbonates. Electrolytes come from our food and fluids
- Electrolytes help move nutrients into body’s cells and help move waste out of the body’s cells
- Electrolytes maintain a healthy water balance, and help stabilise the body’s acid/base (pH) level.
What are the key electrolytes?
what are their roles?
- K+ play a vital role in muscle contraction and nerve cell function
- Na+ are primarily responsible for maintaining fluid balance and transmitting nerve impulses
- Cl- help balance fluid levels
- Mg2+ are involved in various enzymatic reactions and play a role in muscle and nerve function too
- Ca2+ are essential for muscle contraction, blood clotting, and maintaining bone health
- PO43- contribute to energy metabolism and DNA synthesis
Maintaining the balance of electrolytes in our body is crucial for overall health:
- proper diet and hydration
- Imbalance:
» dehydration
» muscle cramps
» irregular heartbeat
» seizures
Diagnostic tests: Electrolytes and Anion Gap
What are the Typical reference ranges for commonly requested tests?
- Serum Sodium 133 – 146 mmol/L
- Serum Potassium 3.5 – 5.3 mmol/L
- Serum Urea 2.5 – 7.8 mmol/L
- Serum Chloride 95 – 108 mmol/L
- Serum Bicarbonate 22 – 29 mmol/L
- Serum Phosphate 0.8 – 1.5 mmol/L
- Serum Magnesium 0.7 – 1.0 mmol/L
- Serum Albumin 35 – 50 g/L
- Serum Total Protein 60 – 80 g/L
- Serum Osmolality 275 – 295 mmol/kg
NB: ranges may differ between laboratories.
* Population samples
* Average +/- 2 s.d
* 95% confidence
* 5% of normal can reside outside of this
Sodium homeostasis:
What are the normal ranges?
Whay are the functions
- 135 to 145 mmol/L
- Main extracellular ion – [Na] is higher OUTSIDE of the cell
- Maintains fluid balance – NA attracts water
- Plays a major role in the action potential of nerves and muscle cells – ↑ [Na] equals ↑
neuromuscular excitability
Regulation:
* RAAS causes NA retention – ↑ [Na]
* Natriuretic hormones causes [Na] excretion – ↓
[Na]
Sodium Normal range: 135 to 145 mmol/L
Tests?
Test:
* routine lab test for non-specific health complaints
* Monitoring at risk patients:
* i.v. fluids
* Risk of developing dehydration
* Hypertension
* heart failure
* Liver disease
* Kidney disease
* Osmolality of blood / urine
* If altered then investigate [urine sodium]
Interesting facts about sodium: (for info)
Can ↑ plasma Na:
* Recent trauma, surgery, or shock because
blood flow to the kidneys is decreased.
* Lithium and anabolic steroids
* Corticosteroids, laxatives, cough
medicines and oral contraceptives
Can ↓ plasma Na:
* Drugs such as diuretics, sulphonylureas,
ACE inhibitors, heparin, ibuprofen
(NSAIDs), carbamazepine, tricyclic
antidepressants, and vasopressin
What are the causes of hyponatremia? (low plasma [Na])
What are the signs and symptoms?
Caused by either losing more sodium than water, orgaining more water than sodium
* Low dietary sodium intake
* Primary polydipsia
* Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
* Diuretics
* Vomiting
* Diarrhoea
* Congestive heart failure
* Renal disease
* Liver disease
S/S
* Neuro: seizures and coma
* Headaches, tired, weakness, nausea, vomiting
* Respiratory arrest
What are the causes of hypernatremia? (high plasma [Na])
What are the signs and symptoms?
CAUSE:
* Unreplaced fluid loss via the skin
(extensive burns, fever, exercise, and exposure to high temperatures)
* Unreplaced fluid loss via gastrointestinal tract (excessive vomiting, or diarrhoea)
* Osmotic diuresis
* Hypertonic saline administration
* Hypertonic tube feeding
* Diabetes
* OTC meds with lots of salt
* Inhalation of salt water
S/S
* Dehydration
* Tachycardia
* Agitation and restlessness
* Disorientation
* Weakness
* Irritability
* Stupor > unconscious
* Coma
Potassium:
Functions?
Regulation?
- Major ICF cation (98% is intracellular)
- Potassium plays a key role in maintaining cell
function - Almost all cells possess an Na+-K+-ATPase, which pumps Na+ out of the cell and K+ into the cell and leads to a K+ gradient across the cell membrane
- Regulates heart and muscle contractions –maintains membrane potential
Regulation:
* Internal and external mechanisms
* Insulin and Beta 2 agonists shift K into cells
* Aldosterone alters uptake into cells and thus
urinary K levels
* Stimulation of alpha adrenoreceptors releases K from cells especially in the liver
Interesting facts about potassium: (for info)
The way that your blood is taken and handled can affect the potassium concentration in your blood sample
* clenched or pumped fist = ↑K
* If blood cells are damaged during sample collection they can burst and release potassium into the blood
* Some collection tubes contain potassium salts as a preservative
* Potassium can also be elevated if the specimen takes a long time to travel from your GP surgery
Hypokalaemia – too little K in ECF
Causes? (2)
S/S?
CAUSE:
1. External balance shift - increase in potassium
excretion in the kidneys
* Hyperaldosteronism
* Any disease which increases aldosterone e.g. Heart Failure, cirrhosis
* use of loop / thiazide diuretics
2. Internal balance shift where potassium moves into the cells, from the interstitium and blood
* Hypo-osmolality – water dragged into cells and
take K with it
* metabolic alkalosis – H must leave cells and
exchanged for K
* beta agonists promote the activity of the sodium-potassium ATPase
Signs and symptoms
* Abnormal heart rhythms (arrhythmias: flat T waves, ST depression)
* Muscle twitches
* Muscle cramps
* Severe muscle weakness, leading to paralysis
* Low blood pressure (hypotension)
* Bradycardia
* Lightheadedness or faintness
* Excessive urination (polyuria)
* Excessive thirst (polydipsia)
* Decreased GI motility»_space;>obstruction
Hyperkalaemia - too much K in ECF
Causes?
S/S?
- Advanced kidney disease
- A diet high in potassium
- Metabolic acidosis
- Tissue breakdown – crush injuries
- Medications: renin inhibitors, ACE inhibitors, angiotensin II receptor antagonists, selective aldosterone blockers, and potassium-sparing diuretics
Signs and symptoms
* Abnormal heart rhythms tight and contracted (arrhythmias: peaked T waves, ST elevations)
* …can lead to v-fib
* Low blood pressure (hypotension)
* Bradycardia
* Decreased urine output
* Profound muscle weakness
»>respiratory failure
* Increased GI motility»_space;>diarrhoea
Calcium
functions?
- Essential for muscle contraction, enzyme activity nerve function, blood clotting, cell division, healthy teeth and bones
- Helps to release neurotransmitters and hormones
- Absorbed through the intestines under the influence of activated vitamin D
- The amount of calcium in the blood is controlled by the combined actions of parathyroid hormone (PTH) and 1, 25-dihydroxyvitamin D (Vitamin D).
- Calcium is tested to help diagnosis and monitor a range of conditions relating to the bones, heart, nerves, and kidneys
- Other tests: phosphate, PTH, Vitamin D and
magnesium - Urine calcium may be requested if individuals have symptoms of kidney stones
Interesting facts about Calcium (for info)
- About 99% of calcium is found in the
bones - Blood and urine calcium measurements cannot be used to assess how much calcium is in the
bones. A test similar to an X-ray, called a bone density or ‘Dexa’ scan, is needed for this purpose.
