Water Balance and Body Fluid Compartments

1. Homeostasis A Water balance and body fluid compartments Year 2 Unit I

2. Learning objectives • Sources of Body Water Gain and Loss • Indicate the relative fluid volume and solute composition of the fluid compartments of the body. • Calculate the fluid volume of body fluids compartments • List the factors that determine body water content including age, body mass, and body fat. • List and know the main the mechanisms which maintains fluids and electrolyte balance and control of plasma osmolality • Define and calculate plasma osmolality • Explain the mechanism of water moment between fluid compartments • Understand the concept of osmotic equilibrium and be able to calculate plasma osmolarity and body fluid volume following the infusion of iv fluids (for example saline) 9/23/2017

3. Water Balance Water gain Water loss Food and drink 2.2 L/day Insensiblewater loss0.9 L/day Skin Lungs 1.5 L/day Urine Metabolism 0.3 L/day 0.1 L/day Feces 2.5 L/day Totals 2.5 L/day Intake 2.2 L/day Metabolic production0.3 L/day Output2.5 L/day + – = 0

4. Balance Concept Fluid and electrolyte balances are necessary, in the long-term, to maintain life. Fluid Loss = Fluid Intake Electrolyte Loss = Electrolyte Intake Fluid Intake: regulated by thirst mechanism, habits Electrolyte intake: governed by dietary habits Fluid Output:regulated mainly by kidneys Electrolyte output: regulated mainly by kidneys

5. Fluid Balance (ml/day) – 70 kg adult Fluid intake and out put after the ingestion of high salt diet Normal High Salt Diet Intake (ml/day)Fluids ingested 2100 From metabolism 200 2300 4100 200 4300 Output (ml/day) Insensible - skin 350 Insensible – lungs 350 Sweat 100 Feces 100 Urine 1400 2300 350 350 100 100 3400 4300

6. Fluid Balance (ml/day) – 70 kg adult Fluid intake and out put after heavy exercise Heavy Exercise Normal Intake (ml/day) Fluids ingested 2100 From metabolism 200 200 2300 Output (ml/day) Insensible - skin 350 350 Insensible - lungs 350 650 Sweat 100 5000 Feces 100 100 Urine 1400 2300 6400 6600 500 6600

7. Distribution and calculation of body fluids compartments 1.TBW is 60%of body weight 2.40% of body wieght is ICF 3. 20 of body weight % is ECF 2. 2/3 of TBW is ICF 3. 1/3 is of TBW is ECF 70 kg adult male

8. ECF compartments • Interstitial fluid compartment : bathing the cells and constitute about 75 % of ECF (11 L) • Plasma and lymph (intravascular vascular fluid compartment) approximately 25 % of ECF 3 L • Transcellular fluid compartment Small amount of interstitial found in special compartments including CSF, plural fluid , synovial fluid, pericardial fluid (1)

9. Major cations and anions of Intra cellular and extracellular fluids

10. Non electrolytes of the plasma

11. The fluid compartments and electrolyte composition of an adult human weighing 70 kg.

12. Total Body Water in Relation to Body Weight: Effects of Gender, Body Build and Age Body Build TBW (%) TBW (%) TBW (%) Adult Male Adult Female Infant Normal 60 50 70 Lean 70 60 80 Obese < 50 <42 <60 Increasing obesity decreases TBW % Increasing age decreases TBW %

13. Measuring Body Fluid Volumes: Indicator Dilution Principle Measuring Body Fluid Volumes: Indicator Dilution Principle Indicator Mass A= Volume A x Concentration A A Indicator Mass A = Indicator Mass B Volume B = Indicator Mass B / Concentration B Indicator Mass B= Volume B x Concentration B

14. Indicator Dilution Principle Volume (B) = Indicator Mass (B) Concentration (B) = Q (amt. injected) C (after equilibrium) • Valid if: • Indicator disperses only in compartment measured • Indicator disperses evenly in compartment • Indicator not metabolized or excreted (or • correction must be made for excretion/metabolism)

15. Distribution and calculation of body fluids compartments 1.TBW is 60%of body weight 2.40% of body wieght is ICF 3. 20 of body weight % is ECF 2. 2/3 of TBW is ICF 3. 1/3 is of TBW is ECF 70 kg adult male

16. TPRBlem ake QuestionTake You want to measure total body water in a patient.You inject 10 ml of a solution of antipyrine with a concentration of 150 mg/ml i.v. After equilibrium, the concentration of antipyrine in the blood is 0.03 mg/ml. What is the total body water of this patient, assuming no excretion ? Amount antipyrine injected (Q) = 10 ml x 150 mg/ml = 1500 mg Q / C (after equilibrium) Total body water volume = = 1500 mg / (.03 mg/ml) = 50,000 ml = 50 liters

17. Calculations of various fluid volumes

19. Blood volume Blood pressure Volume receptors in atria andcarotid and aortic baroreceptors trigger homeostatic reflexes Cardiovascularsystem Behavior Kidneys Cardiac output,vasoconstriction Thirst causeswater intake ECF and ICFvolume KEY Stimulus Receptor Effector Conserve H2Oto minimizefurther volumeloss Tissue response Bloodpressure Systemic response (a) Fluid and Electrolyte Homeostasis

20. Response to water deprivation

21. Endocrine and neuronal regulation of fluid and electrolytes balance Osmoreceptor–antidiuretic hormone (ADH) feedback mechanism for regulating extracellular fluid osmolarity. Figure 28-9

22. Control of water balance : ADH ADH synthesis in the magnocellular neurons of hypothalamus, release by the posterior pituitary, and action on the kidneys

23. Renin Angiotensin Aldosterone system and fluids and electrolytes balance