Fluid and Electrolyte balance Tom Grant and Marc Heymann

List and explain four factors that regulate the excretion of potassium from the renal tubules?  Plasma potassium concentration  Aldosterone  Tubular flow rate  H+ concentration

A tree falls on bird watching amateur Matt Newman, crushing his calf muscle and pinning him down. It takes the paramedics 5hrs to reach him. They were on their lunch break, and enjoying copious amounts of grapes. 1) What is the name given to this condition (breakdown of muscle following crush injury)? Rhabdomyolysis 2) Why should the paramedics refrain from immediately lifting the tree and free the leg ? (2) There would be large amounts of potassium freed, which can cause arrhythmias. 3) Hamish Auld, junior and reckless paramedic (who is dreadful at surfing), unknowingly puts the patient in mortal danger by lifting the tree up. What treatment should be given to Matt instantly and why? (2) Calcium gluconate IV It decreases excitability of myocardial cells and protects the heart (potassium is the major determinant of resting membrane potential) (You could also give insulin, which facilitates uptake of potassium into cells from the blood) BONUS question: What level of blood potassium requires immediate attention? >7mmol/L

Water follows which of the following electrolytes?  Potassium  Urea  Chloride  Sodium  Calcium

An angry yet stunning woman, Priyanca Patel, enters your clinic with polyuria, polydypsia and dilute urine. The doctor laughs and says ‘urine trouble’. You order a water deprivation test. 1) After giving the patient ADH, they start to produce more concentrated urine. What condition does this point towards? Central diabetes insipidus 2) What is the name given to synthetic ADH administered in this test? Desmopressin Although not relevant, Priyanca also has explosive diarrhoea

What is the main cation and anion in the blood?  Sodium and Chloride  Urea and Sleugugide  Sodium and Phosphate  Phosphate and Chloride  Sodium and Bicarbonate

Where is most water absorbed within the nephron?  Thin descending loop of henle  Proximal convoluted tubule  Thick ascending loop of henle  Collecting ducts  Thin ascending loop of henle

What is most important for the reabsorption of sodium in the kidneys?  Facilitated diffusion via GLUT2  Active transport via SGLT1  Facilitated diffusion via GLUT4  Active transport via SGLT2  Active transport via CFTR

Where does ADH have its biggest effect (on aquaporin 2)  Proximal convoluted tubule  Thin descending loop of Henle  Thin ascending loop of Henle  Thick ascending loop of Henle  Collecting ducts

What is the mechanism of action of ADH on aquaporins?  Increase cGMP, activate PKC, aquaporin synthesis and vesicle translocation  Increase cAMP, activate PKA, aquaporin synthesis and vesicle translocation  Decrease cGMP, activate PKC, aquaporin synthesis and vesicle translocation  Decrease cAMP, activate PKA, aquaporin synthesis and vesicle translocation  Binds to and agonises H2 receptors in the stomach

What is the main purpose of the counter current mechanism?  Concentration of urine  Absorption of phosphate  Increasing insertion of AQP2 into collecting duct  Regulating the pH of urine via phosphate buffering  Responds to low flow in lumen by causing dilation of afferent arteriole

1) There are 2 mechanisms by which GFR is autoregulated in the nephron. What are these? (2) Myogenic response Tubuloglomerular feedback 2) A lovely bachelorette Dacil Robadobalo spent a long time in the public hot tub at a busy bathhouse (naked), and has become completely dehydrated. She is now hypovolaemic, and has hypotension. This is exacerbated by her explosive diarrhoea (you have to feel bad for the other people in the hot tub). What is the response of the JGA? (4) Hypovolaemia -> decreased GFR Decreased flow of salt (NaCl) to macula densa cells in DCT Macula densa cells stimulates renin production in granular cells RAAS system is activated to increased blood pressure (including action of ADH and aldosterone) Adenosine is not released (so there is dilation of the afferent arteriole, leading to increased GFR)

Do you know your RAAS? It is as important as recycling.

Fill this table in?