9: Electrolytes Flashcards
How do you work out osmolality?
2 (Na + K) + glucose + BUN
What causes the osmolal gap?
Unmeasured solutes
What is the usual osmolal gap?
10mOsm/kg
Which electrolyte has the highest conc in the ECF?
Na as freely permeates
What % of body weight is circulating blood volume?
6-8%
What % of blood is venous and what % is arterial?
70% venous, 30% arterial
WHich volumes must be maintained during hypovolaemia?
ICF and circulating volume
Which two pressures affect Na and protein distribution?
Osmotic and oncotic
WHich receptor does ADH act on to cause vasoconstriction?
V1
How does the V1 receptor cause vasoconstriction?
Increasing intracellular Ca
Which receptor does ADH act on to cause antidiuretic effect?
V2
What % of water does ADH allow resorption of?
90% rather than 80%
What is a primary cause of nephrogenic diabetes insipidus?
Congenital receptor problem
What is a secondary cause of nephrogenic diabetes insipidus?
Hypercalcaemia or endotoxins
What are some examples of things that cause receptor interference in nephrogenic DI?
Toxins e.g. E Coli, drugs e.g. GCs, metabolic e.g. hypoK, hyperCa, tubular injury/loss e.g. pyelonephritis
Which breed can inherit Fanconi syndrome?
Basenjis
What can cause acquired Fanconi syndrome?
Gentamycin and ethylene glycol
WHat are clinical signs of Fanconi syndrome?
PUPD, weight loss, poor coat, weakness, dehydration
How does Fanconi syndrome affect urine?
Glucosuria and aminoaciduria and phosphaturia
What does Fanconi syndrome cause impaired absorption of?
Na, K, HCO3,
What does Fanconi syndrome cause hypo- of?
Hypophosphataemia
How does congestive heart failure cause a viscious circle?
Reduced renal perfusion activates RAS, so high ADH and angiotensin II, so cardiac remodelling and fibrosis so volume overload and condition worsens
What happens if ECF tonicity is too high?
Brain cells produce idiogenic osmoles to maintain intracellular osmolality
What happens if you correct hyperNa too quickly?
Osmotic brain swelling
