Sodium and Water Balance
By the end of the week, students will be able to:
Body Fluid Compartments and Principles of IV Fluid Replacement
- Identify the major body fluid compartments and the membrane barriers between the body fluid compartments
- Compare the volume and composition of the major body fluid compartments
- Evaluate the mechanisms and processes that act to maintain the differences in composition between body fluid compartments
a. Examine the properties of the barriers that impede net movement of water and solute between body fluid compartment
b. Examine the properties of the barriers that allow net movement of water and solute between body fluid compartments
c. Assess the driving forces for movement of water and solute across the barriers, and review the Starling forces
- Evaluate basic principles of intravenous fluid replacement
a. Examine the composition of IV solutions commonly employed in the treatment of disturbances in body fluid volume
b. Analyze how water and solute from a given IV fluid will partition into the body fluid compartments
c. Deduce appropriate IV fluid therapy based on volume status and serum electrolyte values
Renal Sodium Handling
- Evaluate renal sodium handling, and identify the fraction of filtered sodium reabsorbed in the different nephron segments
- Examine the cellular mechanisms involved in renal tubule sodium transport, and discuss the driving forces necessary for function of the various renal sodium transport processes, including the WNK system
- Evaluate neurohumoral regulation of renal sodium handling, discuss which cellular processes are regulated, and explain the mechanism(s) by which these processes are regulated
a. Analyze how changes in renal sympathetic nervous system activity regulate glomerular filtration and renal tubule sodium transport processes
b. Examine activation of the renin-angiotensin-aldosterone system (RAAS), and assess the effects of RAAS on glomerular filtration and renal tubule sodium transport processes
c. Examine generation and release of natriuretic peptides, and explain the effects of natriuretic peptides on renal tubule sodium transport processes
Renal Water Handling and Urinary Concentration and Dilution
- Identify the most frequent causes of alterations in water balance
- Evaluate renal tubule water handling, and identify the fraction of filtered water reabsorbed in the different nephron segments
- Examine the cellular transport mechanisms involved in renal tubule water transport
- Assess the neurohumoral regulation of renal water handling
a. Evaluate the role of thirst
b. Evaluate mechanisms for release of antidiuretic hormone (ADH), and discuss the cellular mechanisms responsible for the effects of ADH on water transport
- Diagram renal mechanisms responsible for forming a concentrated or dilute urine, and assess the role of counter current multiplier in these processes
- Appraise the role of urea in the formation of a concentrated urine
a. Describe renal urea handling
b. Explain how renal urea transporters are regulated by ADH
Volume Regulation
- Appraise the major routes of gain and loss for sodium and for water
- Diagram the most frequent causes of alteration in sodium and water balance
- Examine the concept of effective circulating volume, and explain the difference(s) between effective circulating volume and extracellular fluid volume
- Identify the receptors responsible for sensing the effective circulating volume, and assess the role of these sensors in volume regulation
- Examine the relationship between total body sodium and effective circulating volume
a. Compare the difference between total body sodium and the sodium concentration in body fluid compartments
b. Evaluate the relationship between alterations in plasma sodium concentration and sodium balance
c. Evaluate the relationship between alterations in plasma sodium concentration and water balance
d. Examine how renal sodium excretion is determined by the effective circulating volume
- Evaluate the mechanisms of edema formation and discuss the role of renal sodium retention in edema formation
- Examine the pharmacology of diuretics
a. Identify the sites of action of furosemide, thiazide diuretics, spironolactone, and triamterene/amiloride, and compare the mechanisms by which these pharmaceutical agents affect diuresis
b. Evaluate the use of diuretics in the treatment of generalized edema
c. Evaluate the use of diuretics in other pathophysiological conditions (hypertension, renal failure, hypercalcemia or hypercalciuria
