year 5 passmed metabolic medicine Flashcards
AKI what is most serious complication - electrolyte abnormality
high K
how do beta blockers cause hyperkalaemia
*beta-blockers interfere with potassium transport into cells and can potentially cause hyperkalaemia in renal failure patients - remember beta-agonists, e.g. Salbutamol, are sometimes used as emergency treatment
how are heparins thought to induce hyperkalaemia
both unfractionated and low-molecular weight heparin can cause hyperkalaemia. This is thought to be caused by inhibition of aldosterone secretion
renal tubular acidosis causes what kind of abg finding
hyperchloraemic metabolic acidosis (normal anion gap).
when the body loses bicarbonate (HCO3-) and retains chloride (Cl-) to maintain a normal anion gap. This happens because the kidneys are unable to excrete protons in the urine
explain how SIADH works
SIADH - excessive release of (ADH) - leads to water retention, volume expansion, and dilutional hyponatraemia
ADH is produced by the hypothalamus and stored in the posterior pituitary gland.
It regulates water balance by increasing water reabsorption in the collecting ducts of the kidneys, thereby decreasing the volume of urine produced
In SIADH, there is an inappropriate and continuous release of ADH that is not inhibited by normal physiological mechanisms, such as adequate or excess body fluid levels
As a result, the kidneys reabsorb more water, leading to decreased urine output, and expansion of extracellular fluid volume.
Importantly, this increase in body fluid volume does not lead to the expected signs of fluid overload, such as oedema or hypertension, because the excess fluid is uniformly distributed throughout all body fluid compartments.
However, as water is retained in the body, the concentration of electrolytes in the blood, particularly sodium, becomes diluted, leading to hyponatraemia.
leading to a high Urine osmolality (>100 mOsm/kg) in relation to serum osmolality, as the kidneys should normally dilute urine in the setting of low serum osmolality.
Urine sodium concentration: Urine sodium concentration is typically high (>40 mmol/L) due to the action of ADH on the renal tubules.
why do you not see signs of fluid overload in SIADH
The increase in body fluid volume does not lead to the expected signs of fluid overload, such as oedema or hypertension, because the excess fluid is uniformly distributed throughout all body fluid compartments.
hypercalcaemia mx
intially with IV fluids
and then add Iv bisphosphonates - if fluids fail
severe hypocalcaemia (e.g. carpopedal spasm, tetany, seizures or prolonged QT interval) what mx
IV calcium gluconate
regardless of SIADH if sodium is under 120 what should you do
Hypertonic saline is usually indicated in patients with acute, severe, symptomatic hyponatraemia (< 120 mmol/L)
eg 3% NaCl solution
treatment of hypernatraemia
Start a slow infusion of 0.9% sodium chloride solution
how does acute pancreatitis cause low calcium
Pancreatic damage: When the pancreas is damaged, pancreatic lipase releases free fatty acids.
Calcium binding: The free fatty acids bind to calcium salts in the pancreas, forming calcium soaps.
Calcium deposition: The calcium soaps deposit in the retroperitoneum, reducing the availability of calcium.
two things causes euvolaemic hyponatraemia
SIADH (urine osmolality > 500 mmol/kg)
hypothyroidism
how can acute pancreatitis cause hypocalcaemia (3)
acute pancreatitis can cause hypocalcemia through several mechanisms, including calcium precipitation within pancreatic tissues, the impaired release of parathyroid hormone (PTH), and the binding of calcium to fatty acids released during lipolysis.
renal tubular acidosis causes
low potassium
what is renal tubular acidosis
Renal tubular acidosis (RTA) occurs when the kidneys do not remove acids from the blood into the urine as they should. The acid level in the blood then becomes too high, a condition called acidosis. Some acid in the blood is normal, but too much acid can disturb many bodily functions.
There are three main types of RTA.
Type 1 RTA, or distal RTA, occurs when there is a problem at the end or distal part of the tubules.
Type 2 RTA, or proximal RTA, occurs when there is a problem in the beginning or proximal part of the tubules.
Type 4 RTA, or hyperkalemic RTA, occurs when the tubules are unable to remove enough potassium, which also interferes with the kidney’s ability to remove acid from the blood.
