Fluid Balance Fluid Compartments 60% adult body weight composed of water Decreases with age Two compartments Intracellular 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: Osmosis Movement of particles across a semi-permeable membrane from greater to lesser concentration, to balance solute-to-solvent content Sodium-potassium pump Protein shifts and other ion shifts Tonicity 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/kg Urine osmolality levels Normal range: > 850 mOsm/kg Specific Gravity: 1.005 -1.030 Values become more dilute with age Osmolality easy calculation: 2x the sodium (Na) level Hematocrit: the % of red blood cells (RBCs) in total blood volumeNormal hematocrit Men: 41.5 - 50.4% Women: 35.9 - 44.6% Hemodilution (fluid overload), and dehydration affect hematocrit level in opposite directions Critical values >55% dehydration, viscous (thick) blood <35% fluid overload, dilute blood Sodium- extracellular 135-145 Hypo <135 (fluid overload) Hyper > 145 (dehydration) Blood Urea Nitrogen (BUN): measures end-product of protein metabolism, evaluates renal function Regulated by Kidneys and liver Diet-protein intake Hydration status Drugs Blood level: 10-20mg/dl adult Increases with age Elevates with DEHYDRATION and renal failure CREATININE: Directly reflects kidney function! More to come for urinary/renal lecture Hypovolemic- 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) Extremities Sacrum Periorbital areas HAPPENS IN POST- OP Ex: ascites, joint spaces, pleural, pericardial So patients have fluid overload in the interstitial space but are dehydrated in the vascular space causing s/s of dehydration. ****NORMAL FLUID INTAKE 1500-2000 ml/day! 800 ml from foodOrthostatic hypotension- 20mmhg drop in systolic bp within 3 mintues of standing up Nursing interventions for fluid volume deficit Encourage oral intake (what if they are NPO?) Administer Intravenous fluids Monitor I&O (15 ml urine per kidney per hour) Monitor weight (same time DAILY) Monitor osmolality, electrolytes, especially sodium, BUN, hematocrit (know what normal values are!!) 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 balance do not use in alkalosis state do not use for liver failure- cant process lactate 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) Used for fluid losses SEVERE INTRACELLULAR DEHYDRATION- burns, bleeding, vomiting PUSHES FLUID BACK INTO CELLS! Fluid, no electrolytes Dextrose is metabolized and water is left Electrolyte status can become diluted #3. Hypertonic Solutions (MORE SOLUTES) Usually any solution with Dextrose added will become hypertonic D5 0.45 NACL D5 0.22 NS 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 solutions Sodium Normal levels are: 136-145Major extracellular cation Responsible for WATER BALANCE, electrolyte balance, and acid-base balance osmolarity 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 down Hyponatremia 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 (Addisons disease) Kidney disease (sodium is diluted due to fluid overload) N/V/D Weak, lethargy, seizures Restoring Fluid Restriction 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 level Lots of urine output Diarrhea Burns- fluid loss from skin Excessive aldosterone secretion Interventions Fluid replacement Encourage fluids Low sodium foods IV fluids (slow infusion) Hypotonic D5W 0.45 Normal saline (NS) Medications Diuretics Lasix Potassium Normal values: 3.5 - 5.5 meq/LMajor INTRAcellular cation Maintains acid-base balance in the body Very important in regulating membrane potentials in neuromuscular tissue and the heart! Hypokalemia Increase cell excitability Neural: fatigue, decreased reflexes, paresthesia, irritability to seizures and coma Cardiac: cardiac problems such as fibrillation, ECG changes, decreased muscle contraction Muscular: muscle weakness and cramps GI: anorexia, nausea Sagging ST segment, flat T waves Potassium supplements (TAKE WITH FOOD) 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 Phlebitis, Vesicant medication Hyperkalemia Interventions Dietary restriction Increase urine output Diuretics Hydration Medications Sodium polystyrene sulfonate (Kayexalate) K+ ion