5.2 Regulation of Body Fluid Compartments ECF ICF.pptx

The Body Fluid Compartments: Extracellular and Intracellular Fluids; Edema Lecture Outline I. Fluid Intake and Output are Balanced During Steady-State Conditions II. Body Fluid Compartments III. Determination of Volumes of Specific Body Fluid Compartments IV. Clinical Abnormalities of Fluid Volume R...

The Body Fluid Compartments: Extracellular and Intracellular Fluids; Edema Lecture Outline I. Fluid Intake and Output are Balanced During Steady-State Conditions II. Body Fluid Compartments III. Determination of Volumes of Specific Body Fluid Compartments IV. Clinical Abnormalities of Fluid Volume Regulation: Hyponatremia and Hypernatremia V. Edema: Excess Fluid in the Tissues 1 The Body Fluid Compartments: Extracellular and Intracellular Fluids; Edema Objectives I. List the factors involved in daily fluid including insensible and sensible losses II. Identify how body fluids are distributed III. Identify the mechanisms of sodium alterations and consequences IV. List 4 causes of edema 2 References Assigned reading from your text: Hall Chapter 25- Read selected headings 3 Fluid Balance  Fluid and electrolyte balance are necessary to maintain life. Fluid loss = fluid intake Electrolyte loss = electrolyte intake  Intake: • Fluid intake: regulated by thirst mechanism, habits • Electrolyte intake: governed by dietary habits • 2100 ml daily from intake • 200 ml daily from oxidation of carbohydrates Output: Fluid output: regulated mainly by kidneys Electrolyte output: regulated mainly by kidneys • Insensible loss is about 700 ml/day from evaporation (skin, respira • Sweat (100 ml/day), feces (100 ml/day) • Urine volume varies to maintain ECF volume and Na+ concentrati Measuring Body Fluid Volumes: Indicator Dilution Principle eg -inulin used to measure the ECF volume Body Fluid Compartments  Body fluids are: • Distributed across cell membranes : • Determined by osmotic forces (mainly from electrolytes) • Distributed across capillaries : • Determined by hydrostatic and colloid osmotic forces • Intracellular fluid = Total body water - extracellular fluid Interstitial fluid vol. = ECF volume – plasma volume Fluids in potential spaces • e.g. Serous membranes and joint cavities and bursae • Are perfused by adjacent capillaries Effects of Solutions on Cell Volume Isotonic (no change) Hypotonic (cell swells) Hypertonic (cell shrinks) Figure 25-5 Mechanisms of Sodium Alterations Hypernatremia: Na+ conc. • Water loss • Na+ excess Hyponatremia : Na+ conc. • Water excess • Na+ loss Normal plasma [Na+] = 140−145 mmol/L Consequences of Hyponatremia and Hypernatremia • • Water moves in and out of cells. Cells swell (hyponatremia) or shrink (hypernatremia) This has profound effects on the brain. - Neurologic function is altered (confusion, seizures). - Rapid shrinking can tear vessels and cause hemorrhage. - Rapid swelling can cause herniation. Because the skull is rigid, the brain cannot increase its volume by more than 10% without being forced down the neck (herniation). Acute hyponatremia: 1. Acute hyponatremia causes swelling of brain tissues Chronic hyponatremia Brain swelling is attenuated by transport of solutes from the cells Hyponatremia: 2. Stimulates solute transport out of cells 3. Which causes water diffusion out of cells Conditions Causing Edema High capillary hydrostatic pressure • Excess fluid retention by kidneys • Decreased arteriolar resistance (autonomic insufficiency or vasodilator dru • Increased venous pressure (congestive heart failure) Decreased plasma proteins (low oncotic pressure) • Loss of proteins (burns, kidney disease) • Failure to produce proteins (cirrhosis and malnutrition) Increased capillary permeability (histamine reaction or burns) Blockage of lymphatics (cancer, infection) 1. Acute hyponatremia produceswhich of the following? A. B. C. D. Generalized edema No sequelae Swelling of brain tissues Shrinkage of brain tissues 1. A. B. C. D. What isthe primary regulator of fluid volume intake? Sodium Kidneys Thirst mechanism Urine output 11