Electrolytes Flashcards
(26 cards)
Hormones that mediate physiological adjustments in fluid and electrolyte balance
ADH
aldosterone
Naturestic hormone
Medical term for low sodium
Hyponatraemia
Normal serum na conc
135-145 mol/L
What is the plasma osmolarity usally mantained at
280-290 mOsmol/kg
How does adh/vasopressin
Senses low blood volume
ADH/vasopressin secreted by posterior lobe of pit gland
Travels to blood in kidney
Promotes reabs of water from Dct and cd into blood (conc urine produced)
RAAS function
Activated due to low or falling renal perfusion detected by juxtaglomerular app eg significant blood loss, dehydration cardiac failure.
Low renal perfusion causes release of renin➡️ag ➡️ag1
Ag1➡️ag2
Ag2:
Vasoconstriction (increased bp)
Stimulated adh release
Stimulates aldosterone from adrenal gland (promotes na reabsorption from nephron )
These changes promote retention of na in blood , increasing circulating volume and improved renal perfusion to kidneys and other organs.
What plasma osmolarity Is ADH released at
280mosmol/kg
What plasma osmolarity is theist stimulated
290 mosmol/ kg
Hyponatrameia blood serum ranges
Mild 125-135 mmol/L
Moderate 115-125 mmol/L
Severe less than 115 mmol/L
Rate of onset of hyponatramia
Acute - less than 48hrs
Chronic -48 hrs or more
Psuedohyponatraemia
Mesureded conc is low although actual volume is ok. May be due high serum proteins or lipid Levels
What to do if hyponatraemic pt presents with neurological symptoms
Need to maintenance for acute bc of risk of brain damage
Hyponatraemia symptoms
130-135 - a lot of patients may be asymptomatic . Mild ,may develop over time n
If the hyp is chronic there was be subtle absnormalities such as gait disturbances , decreased bone strength and muscle weaknesses , this may contribute to increased risk of falls and fractures.
120-130++ naseua , geenaksied weakness, c fusion and disoreination
<120 (rapid changes , more serious ) confusing and disorientation may worsen and be disabling.
Neurological signs such as seixures (risk! Medical emergency )
<110 impaired consciousness M neurological signs , seizures
Risk of severe mental impairment and death
Hyponatraemia acc with a decreased extracelluar volume
Meds (thiazide diuretics )
Primary adrenal insifficany
Severe v and d (GI na loss)
Sweating (eg severe exercise ) and extensive skin burns (extensive transdermal na loss)
Third space losses - sepsis , bowel obstruction l pancreastis , muscle trauma
Hyponatraemia ass with increased extracelluar volume
Congestive heart failure
Kidney and liver disease
Hyponatraemia ass with normal ec vol
Syndrome if inappropriate antidiuretic hormone (SIADH)
Endocrine disorders - secondary adrenal insufficiency , hypothyroidism
High water low solute intake eg primary poly dipsia - caused by defect in the central thirst regulation , reduced below ADH threshold so encourages to drink despite there being a low plasma osmolarity.
SIADH
Syndrome of inappropriate release of ADH
excessive, uncontrollable release of ADH
Produces state of water xs without Marjorie na retention
SIADH causes
Malignancy - tumours can produce ADH
CNS DISORDERS eg meningitidis
Pulmonary disease eg pneumonia
AIDS/HIV
NON SPECIFIC eg pains , meds. Naseua , stress
SIADH diagnosis
Exclusion - confirmed in 2 nd care
Most common drugs ass w Hyponatraemia
SSRIS eg citaplipram
Diuretics - thiazide diuretics , thiazide like diuretics ( inhibit na reabsorption) take tan days or yrs to present. Also loop Suivre ti s eg furosemide (more common if taken with other drugs like ace inhibitors )
Antipsychotics - haloperidol and phenothiazine’s
Carbamazepine (more freq in elderly)
Drugs less commonly associated with Hyponatraemia
Drugs that increase the action of ADH - opioids , ace inhibitors , ag2ra, PPIS, anticonvulsants, MDMA
Drugs that cause a loss in ADH inhibition eg NSAIDS
Oxytcoin , desmopressin
Others drugs used I. Hyponatraemia
Demeclocylcine
Tolvaptan
Demeclocycline hydrochloride
Directly blocks the tubular effects on ADH
Treats Hyponatraemia caused by inappropriate renal effect of ADH
Shouldn’t be used in severe renal impairmenent
Tolvaptan
Vasopressin v2 receptor antagonist
Treatment of Hn secondary to SIADH
rapid correction of hn during treatment with Tolvaptan therapy can cause osomotic demylentisiom
