Electrolyte Disorders Flashcards
What is a U&E test?
Blood test for urea and electrolytes when assessing renal function.
What is measured in U&E test?
- Sodium - Potassium - (Chloride) - (Bicarbonate) - Urea - Creatinine Water is estimated
What are common causes of electrolyte imbalance?
- Kidney disease - Illnesses with symptoms that cause fluid loss/dehydration (e.g. vomiting, diarrhoea, sweating) - Intestinal/digestive issues - Hormone imbalance - Medications like antibiotics, diuretics and those used to treat cancer and heart disease - Haemorrhage
In terms of body functioning, what 6 electrolytes are the most important?
- Sodium - Potassium - Chloride - Bicarbonate - Calcium - Phosphate
How does excretion of ions usually occur?
- Excretion of ions occurs mainly through the kidneys, with lesser amounts lost in sweat and in faeces. - Excessive sweating may cause a significant loss, especially of sodium and chloride. - Severe vomiting or diarrhoea will cause a loss of chloride and bicarbonate ions.
What 2 components make up the ECF?
Plasma + Interstitial Fluid
What is the typical volume of sodium inside and outside cell?
ECF: 140 mmol/L
ICF: 10 mmol/L
What is the typical ECF volume? ICF volume?
The major division is into Intracellular Fluid (ICF: about 23 litres) and Extracellular Fluid (ECF: about 19 litres) based on which side of the cell membrane the fluid lies.
What is the major cation of ECF?
Sodium - is responsible for one-half of the osmotic pressure gradient that exists between the interior of cells and their surrounding environment
How is sodium excreted?
Mainly by the kidneys:
- Sodium is freely filtered through the glomerular capillaries of the kidneys
- Much of the filtered sodium is reabsorbed in the proximal convoluted tubule
- Some remains in the filtrate and urine, and is normally excreted
How does decreasing blood volume affect the conc of any solute?
This will raise the conc of any solute
![](https://s3.amazonaws.com/brainscape-prod/system/cm/326/084/574/a_image_thumb.png?1604490532)
After a huge water loss (e.g. dehydration), how does this affect ECF and ICF?
Water lost first from ECF (this is where most of the water is) and there is a redistribution
![](https://s3.amazonaws.com/brainscape-prod/system/cm/326/084/675/a_image_thumb.png?1604490634)
Sodium and potassium body distribution:
![](https://s3.amazonaws.com/brainscape-prod/system/cm/326/084/734/a_image_thumb.png?1604490671)
What is an isotonic solution?
In an isotonic solution—iso means the same—the extracellular fluid has the same osmolarity as the cell, and there will be no net movement of water into or out of the cell.
How does a loss of isotonic fluid from the body affect sodium?
- Loss is from ECF
- No change in [Na]
- No fluid redistribution
![](https://s3.amazonaws.com/brainscape-prod/system/cm/326/084/816/a_image_thumb.png?1604490824)
What is a hypotonic solution?
If the extracellular fluid has lower osmolarity than the fluid inside the cell, it’s said to be hypotonic—hypo means less than—to the cell, and the net flow of water will be into the cell.
What is the effect of a loss of hypotonic fluid?
- Greater loss from ICF than ECF
- Small increase in [Na]
- Fluid redistribution between ECF and ICF
![](https://s3.amazonaws.com/brainscape-prod/system/cm/326/084/976/a_image_thumb.png?1604490935)
What is the effect of a gain of isotonic fluid e.g. saline drip
- Gain is to ECF
- No change in [Na]
- No fluid redistribution
![](https://s3.amazonaws.com/brainscape-prod/system/cm/326/085/005/a_image_thumb.png?1604491025)
How does a gain of isotonic fluid (e.g. saline drip) affect blood pressure?
Increases blood pressure
What is the effect of a gain of hypotonic fluid e.g. water, dextrose?
- Greater gain to ICF than ECF
- Small decrease in [Na]
- Fluid redistribution between ECF and ICF
![](https://s3.amazonaws.com/brainscape-prod/system/cm/326/086/155/a_image_thumb.png?1604491109)
What is hyponatraemia? What is it usually associated with?
- A lower-than-normal concentration of sodium
- Usually associated with excess water accumulation in the body, which dilutes the sodium
- Also due to loss of sodium from the body
What can cause a loss of sodium?
- A decreased intake of the ion coupled with its continual excretion in the urine.
- Several conditions, including excessive sweating, vomiting, or diarrhea; the use of diuretics; excessive production of urine, which can occur in diabetes; and acidosis, either metabolic acidosis or diabetic ketoacidosis.
What can cause a relative decrease in blood sodium?
An imbalance of sodium in one of the body’s other fluid compartments, like IF, or from a dilution of sodium due to water retention related to edema or congestive heart failure.
At the cellular level, what is the effect of hyponatraemia?
- Increased entry of water into cells by osmosis, because the concentration of solutes within the cell exceeds the concentration of solutes in the now-diluted ECF
- The excess water causes swelling of the cells; the swelling of red blood cells—decreasing their oxygen-carrying efficiency and making them potentially too large to fit through capillaries—along with the swelling of neurons in the brain can result in brain damage or even death.
What is hypernatraemia? What can it result from?
- Hypernatremia is an abnormal increase of blood sodium.
- It can result from water loss from the blood, resulting in the hemoconcentration of all blood constituents.
- Hormonal imbalances involving ADH and aldosterone may also result in higher-than-normal sodium values.