Fluid BalanceFluid Compartments 60% adult body weight composed of water Decreases with ageTwo compartmentsIntracellular 66% (inside the cell)Extracellular 33%Interstitial fluid (between cells)Vascular compartment (blood in veins and arteries and lymph in the lymphatic system) Water moves passively between compartments by:1. Osmosis Movement of particles across a semi-permeable membrane from greater to lesser concentration, to balance solute-to-solvent content2. Sodium-potassium pump3. Protein shifts and other ion shiftsTonicity Isotonic: concentration of solutes/solvent is equal Hypotonic: concentration of solutes is lower than the solvent (fluid is dilute) Hypertonic: concentration of solutes is higher than the solvent (fluid is more concentrated) Regulates fluid balance Thirst mechanism ($ with age) Kidneys (output - urination) Aldosterone from the adrenal glands promotes sodium retention (and water) Atrial natriuetic peptide/brain natriuetic peptide (ANP/BNP) causes more sodium to be released, and more water built up Antidiuretic hormone (ADH) from the posterior pituitary, prevents diuresis, prevents urination (WATER REGULATION)Osmolarity measures concentration of solutes (particles, like Na, K, glucose) in a solution Serum osmolality levels (assessed fluid status)Normal range: adults 285-300 mOsm/kgUrine osmolality levelsNormal range: > 850 mOsm/kg Specific Gravity: 1.005 -1.030Values become more dilute with age Osmolality easy calculation: 2x the sodium (Na) levelHematocrit: the % of red blood cells (RBCs) in total blood volume Normal hematocrit Men: 41.5 - 50.4%Women: 35.9 - 44.6% Hemodilution (fluid overload), and dehydration affect hematocrit level in opposite directionsCritical values>55% dehydration, viscous (thick) blood<35% fluid overload, dilute bloodSodium- extracellular- 135-145- Hypo <135 (fluid overload)- Hyper > 145 (dehydration)Blood Urea Nitrogen (BUN): measures end-product of protein metabolism, evaluatesrenal function Regulated by Kidneys and liver Diet-protein intakeHydration statusDrugs Blood level: 10-20mg/dl adultIncreases with age Elevates with DEHYDRATION and renal failure CREATININE: Directly reflects kidney function! More to come for urinary/renal lectureHypovolemic- dehydration-from vomiting, diarrhea, sweating, NG drainage, diuretics-mild- loss of 1-2L (2% body weight)-moderate- loss of 3-5 (5%)-severe- loss of 5-10 (8%)Third spacing excess fluid in the body leaves the vascular space  gets into the tissues causes swelling (edema)o Extremitieso Sacrumo Periorbital areasHAPPENS IN POST- OPEx: ascites, joint spaces, pleural, pericardialSo patients have fluid overload in the interstitial space but are dehydrated in the vascular space causing s/s of dehydration.****NORMAL FLUID INTAKE1500-2000 ml/day!800 ml from foodOrthostatic hypotension- 20mmhg drop in systolic bp within 3 mintues of standing upNursing interventions for fluid volume deficito Encourage oral intake (what if they are NPO?)o Administer Intravenous fluidso Monitor I&O (15 ml urine per kidney per hour)o Monitor weight (same time DAILY)o Monitor osmolality, electrolytes, especially sodium, BUN, hematocrit (know what normal values are!!)o AVOID dark drinks- cola, caffine#1. Isotonic solutions (fluid/electrolytes are equal) Normal Saline (0.9% NS) or Lactated Ringers (LR)  Amounts of electrolytes (solutes) and water are close to plasma (blood) levels Caution: lactated ringers can alter acid-base balanceo do not use in alkalosis state o do not use for liver failure- can’t process lactateo Considered a volume expander; stays in vascular space (EXTRACELLULAR SPACE, INTRAVASCULAR) Use: Mild to severe DEHYDRATION#2. Hypotonic solutions (FEWER SOLUTES) 5% Dextrose in water (D5W) 45% normal saline (0.45 NS)o Used for fluid losses SEVERE INTRACELLULAR DEHYDRATION- burns, bleeding, vomitingo PUSHES FLUID BACK INTO CELLS!o Fluid, no electrolytesDextrose is metabolized and water is leftElectrolyte status can become diluted#3. Hypertonic Solutions (MORE SOLUTES) Usually any solution with Dextrose added will become hypertonic o D5 0.45 NACLo D5 0.22 NSo D5 0.9 NS Adds both water and electrolytes Extra solutes pull fluid from extracellular space back into the intracellular space Good for postoperative swelling  Good for patients with mild to moderate fluid overload Must know examples of each of these IV solutionsSodium Normal levels are: 136-145 Major extracellular cation Responsible for WATER BALANCE, electrolyte balance, and acid-base balanceo osmolarity o intravascular osmotic pressure Kidneys will maintain sodium balances by excreting sodium if we take in too much *unless we have diseased kidneys Aldosterone directly regulates sodium Sodium and potassium are inversely proportional …as one goes up the other goes downHyponatremia Very common in elderly Plasma volume Na+ $ 135mEq/L Excessive sodium loss through fluid losses such as GI losses, third spacing, burns Not enough aldosterone from the adrenal glands (Addison’s disease) Kidney disease (sodium is diluted due to fluid overload) N/V/D Weak, lethargy, seizuresRestoring Fluid Restrictiono 1500ml per 24 hours High sodium foods IV replacement (slow replacement) Medication: inhibit antidiuretic hormone (ADH)Hypernatremia Na $ 145 mEq/L Sodium retention or fluid losses will raise the serum sodium levelo Lots of urine outputo Diarrheao Burns- fluid loss from skin Excessive aldosterone secretionInterventionso Fluid replacemento Encourage fluidso Low sodium foodso IV fluids (slow infusion)HypotonicD5W0.45 Normal saline (NS)o Medications DiureticsLasixPotassium Normal values: 3.5 - 5.5 meq/L Major INTRAcellular cation Maintains acid-base balance in the body  Very important in regulating membrane potentials in neuromuscular tissue and the heart!Hypokalemia Increase cell excitabilityo Neural: fatigue, decreased reflexes, paresthesia, irritability to seizuresand comao Cardiac: cardiac problems such as fibrillation, ECG changes, decreased muscle contractiono Muscular: muscle weakness and crampso GI: anorexia, nauseao Sagging ST segment, flat T waves Potassium supplements (TAKE WITH FOOD)o IV 10 – 20 mEq in 50-100ml fluid over 1 hr max rate Never push the medication Must be diluted on a intravenous pump device, not by gravity