sodium and water balance

Question 1

what is the effective circulating volume affected by ?

Answer 1

volume
cardiac output
vascular resistance

Question 2

what electrolyte is the major determinant of ECV ?

Answer 2

sodium
excess sodium is associated with higher ECV

Question 3

what are the classic signs associated with ECV ?

Answer 3

orthostatic hypotension

Question 4

what are the physiologic effects associated with low ECV ?

Answer 4

sympathetic nervous system
renin angiotensin aldosterone system
bn7bes sodium

Question 5

what are the three classic pathologic conditions associated with low ECV and what are the associated TBW levels ?

Answer 5

volume depletion - nausea vomiting and diarrhoea , low ECV , but decreased total body water

heart failure - low ECV , increased TBW
cirrhosis - low ECV , increased TBW

Question 6

how does ADH work ?

Answer 6

vasopressin works by causing retention of free water

Question 7

what are the triggers for ADH release ?

Answer 7

increased plasma osmolality
hypovolemia
low blood pressure
low ECV
byuroo7 el collecting duct and starts inserting aquaporin 2 channels , concentrates the urine and brings water back to the blood stream

Question 8

what are the ADH levels in excess water vs in restricted water ?

Answer 8

excess water has low ADH
restricted water will lead to increased ADH

Question 9

what effect does sodium have on ECV ?

Answer 9

restricted sodium is associated with a lower ECV
excess sodium is associated with a higher ECV

Question 10

what effect does the ECV have on the SNS and the RAAS system ?

Answer 10

when ECV is low SNS and RAAs are activated
when ECV is high (expanded) they are inhibited

Question 11

what is a lack of water balance vs a lack of sodium balance reflected by ?

Answer 11

a lack of water balance is reflected by hypo or hypernatremia
a lack of sodium balance is reflected by hypo or hypervolemia

Question 12

GI losses ?

Answer 12

volume loss which means there is more ADH
more commonly associated with hyponatremia

Question 13

what are the levels of ADH in heart failure ?

Answer 13

always high

Question 14

what is SIADH ?

Answer 14

associated with excessive ADH release
too much ADH is associated with more water retention and hence the hyponatremia

Question 15

what are the key findings associated with SIADH ?

Answer 15

hyponatremia
normal volume status
concentrated urine ( due to high ADH )