Fluid and Electrolytes: Acids and Bases Tuesday, July 14, 2009 9:42 PM
• Fluid and Electrolytes Acids and Bases • Julie Mann, RN, ACNP • Some New Terms ○ Total body water Sum of all the water or fluids within all of the body comparments in the pt. makes up 60% of body weight. ○ Intracellular fluid (ICF) Within cells 2/3 of total body water. ○ Extracellular fluid (ECF) Outside of cells 1/3 of total body water. Additionally there is sweat, urine. ○ Interstitial Fluid Fills the space around the cells and outside of blood vessels. ○ Intravascular Fluid Fluid in the blood vessels (plasma) • Osmolarity and Osmotic pressure ○ Osmolality: concentration of a solute per kilogram of water Primary electrolyte is sodium. ○ Osmolarity concentration of solute per liter of a solution. Creates osmotic pressure. ○ Osmotic Pressure: the pulling power of a solution for water. ○ Isotonic Solution: physiologically equivalent to blood plasma (no osmotic diff, no shifting of fluids occurs) and other body fluids, stay in ECF space. e.g. Normal Saline, ringers, lactated ringers. Replacing water. ○ Hypotonic: less concentrated solution Pull water out of vessels into cells. Increased cell water and decreased vascular fluid. e.g. given if cells are dehydrated, renal failure. D5 (5% dextrose) half normal saline, D5 water (5% dextrose with water), drives water into cells. Contraindicated for fragile neural cells, we don't like swelling brains (cerebral edema). Have to be monitored. ○ Hypertonic: A more concentrated solution Given for drastically low sodium level or hypoglycemic given D50 (50% dextrose), D10 (10% dextrose) newborn with diabetic mother. Have to be monitored.
e.g. high percentage saline ○ Hypotonic: A more dilute solution • Oncotic Pressure ○ Oncotic pressure (colloid oncotic pressure): the pulling force exerted by colloids in a solution Albumin - most important colloid for maintaining oncotic pressure, helps maintain adequate vascular pressure. Sits in vessels and pulls fluid into blood vessels. Administered for patients with third space fluid, draws fluid back into vascular system so we can pee it out. • Capillary filtration ○ Capillary hydrostatic pressure Pushing the water out of the capillary Fluid moves out of capillaries into tissues. ○ Capillary oncotic pressure Pulling water into the capillary ○ In artery CHP greater than COP fluid moves into tissues, in vein COP greater than CHP fluid moves into vessels. • Chemical Regulation of fluid balance ○ ADH (antidiuretic hormone) acts on distal tubules of the kidneys Secreted by posterior pituitary, regs water balance by acting on distal tubules of the kidneys Increase in BP, rise in osmolality, kidneys get rid of more water (neg feedback loops) Blood volume low, cause renal tubules to not get rid of water. ○ Aldosterone Secreted from adrenal gland causes kidneys to secrete K+ instead of Na+ Water follows sodium, helps body hang onto extra water (neg feedback loop) ○ Glucocorticoids Cortisol, promote renal retention of Na+ and H2O ○ Atrial natriuetic peptide (ANP) and Brain natriuretic peptide (BNP) released with high blood volume or blood pressure causing vasodilation, trigger aldosterone and ADH to be released. Found in either atria or ventricles released into body when atria or ventricle is stretched. There is a blood test for BNP ○ Thirst Mechanism
When as much as 1 milliosmol/liter decrease in amount of water needed. Triggers aldosterone and ADH. Depressed in elderly. More likely to experience dehydration. • Alterations in Water balance ○ Dehydration More body water loss than taken in ○ Overhydration More body water taken in than loss. • Alterations in Water Balance ○ Isotonic Alterations Amount gained/loss is proportion to electrolytes gain/loss Isotonic Fluid Loss Lose fluid and electrolytes at same rate - wound, excessive diaphoresis. Isotonic Fluid Excess Gain fluid and electrolytes at same rate - over hydrate with isotonic solution. • Alterations in Water Balance ○ Hypotonic Alterations Osmolality of serum is less than should be (normal). Low sodium level. Water and not enough electrolytes. Water Excess --> water toxicity Drinks too much fluid, hard to develop b/c body has several compensatory mechanisms. Neurological condition to drink large amounts of fluid, marathon runners drinking only water. Confusion, convulsions, muscle twitching, headaches. ○ Hypertonic Alterations Osmolality is elevated above normal, more sodium than water. Water Deficit Dehydration from pure water loss. Body can't concentrate urine, ie. lose large volumes of fluid through kidneys, (diabetes) --> hypovolemia (low blood volume)
Alterations in Sodium • Sodium ○ Helps conduct neural impulses, helps reg K+, found in all body fluids, neurological responses. ○ nml: 135 to 145 mEq/L (each lab has own normals)
Hyponatremia below 135 Causes Renal disease Diuretics GI losses Skin Losses Wound drainage ○ Hypernatremia above 145 Causes Decreased water intake Watery diarrhea Fever Hyperventilation Burns Increased sodium dietary intake • What happens to people? ○ hyponatremia • behavioral changes lethargy confusion • depressed reflexes • seizures • coma ○ hypernatremia • thirst • fever • dry mucous membranes • restlessness • Alterations in Potassium ○ Potassium, even small changes are poorly tolerated. • Functions: maintains action potentials of muscles, assists in controlling the cardiac rates/rhythms, conducts nerve impulses. ○ nml: 3.5 to 5 mEq/L ○ Mechanisms of regulation renal regulation Kidneys maintain balance by excreting or reabsorbing in glomerulus (mostly). Extra- and intra cellular shifts Temporary shift into RBC (hemoglobin), liver muscles, bone ○
Hypokalemia Low intake in diet, excessive loss of K+ usually in gut (suctioning), nausea/vomiting, sweating profusely, diabetes encephalitis. ○ Hyperkalemia Excessive intake of potassium, usually body tolerates well unless a lot given quickly, renal failure, potassium sparing diuretics. • What happens to the person ○ Hypokalemia Mild losses asymptomatic Well tolerated Acute Losses cause Skeletal Muscle Weakness Loss of smooth muscle tone Cardiac dysrhythmias Lethargy/Fatigue Inability to concentrate ○ Hyperkalemia Slow onset usually well tolderated Mild Restless ness Intesting cramping Diarrhea Severe: (see slide) • Alterations in Calcium and Phosphorus and Magnesium ○ Vitamin D regulation Calcitriol - form of vit D makes Ca and Phosphorus available for bone mineralization. Helps absorb Ca in intestine. Activates parathyroid hormone. ○ Parathyroid hormone regulation Helps increase blood calcium levels by transporting Ca out of bones. Aid reabsorption in kidneys Raise serum Ca levels and lowers Phosphorus levels b/c they have an inverse relationship with one another. • Alterations in Calcium ○ Muscle contractions, clotting abil, neurological conduction, rigidity to teeth/bones. ○ Normal level 8.5-10.5 mg/dl ○ Hypocalcemia ○
Causes Hypoparathyroidism Hypomagnesemia Alkalosis Multiple blood transfusions Malabsorptive states Renal disease ○ Hypercalcemia Causes Hyperparathyroidism Hypophosphatemia Hyperthyroidism Vitamin D intoxication Steroid therapy Immobility Lithium therapy • Alterations in Calcium ○ hypocalcemia Paresthesias (muscle pain) skeletal muscle cramps abdominal spasms and cramps hyperactive reflexes Hypotension bone pain, deformities, factures ○ hypercalcemia Polyuria (a lot of peeing), polydipsia (very thirsty) anorexia, n/v, constipation Ataxia (uncoordinated muscle movements) osteoporosis lethargy stupor, coma HTN - may be due to inabil of muscle cells to relax fully. • Alterations in Phosphorus (Phosphate) ○ Inverse relationship with Ca, essential for muscular function, important for RBC function, cellular metabolism, role in formation of teeth/bones. ○ Normal level: 2.5 to 4.5 mg/dl ○ Hypophosphatemia From decreased absorption of Vit D, intestinal loss, less skin absorption, diabetic ketoacidosis, alcoholic, poor dietary intake. ○ Hyperphosphatemia
From renal insufficiency, low blood calcium, chemotherapy, parathyroid gland is understimilated, prolonged Vit D exposure, antacids, salicylates, excessive intake of phos supplements, massive transfusions of blood. Alterations in Phosphorus Manifestations Hypophosphatemia ○ Intention tremor ○ Ataxia, Paresthesias ○ Seizures ○ muscle weakness ○ bone pain ○ Osteomalacia (softening of bone) ○ bleeding disorders ○ impaired WBC fxn Hyperphosphatemia ○ paresthesias ○ Tetany (rigidity to muscles) ○ hypotension ○ cardiac arrhythmias Alteration in Magnesium ○ Usually a function of dietary intake, role in enzymatic process in body, helps power Na/K pump (convert ATP to ADP), transmits electrical impulses across nervous system and MSK, necessary to release parathyroid hormone. ○ Normal level: 1.8 to 3.0 mg/dl ○ Hypomagnesia Chronic alcoholism (most common) Decreased dietary intake Decreased absorption d/t GI pathology Increased GI losses Increased Renal excretion Burns ○ Hypermagnesia Untreated diabetic ketoacidosis Adrenal insufficiency Mg++ treatment in preeclampsia (pregnancy induced HTN) Lithium ingestion Volume Depletion Alteration in Magnesium Manifestations hypomagnesia ○ personality change
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nystagmus tetany tachycardia hypertension cardiac arrhythmias ○ + Babinski, Chvostek, and Trousseau signs hypermagnesia ○ Lethargy ○ Hyporeflexia ○ Confusion ○ Coma ○ Hypotension ○ Cardiac arrhythmias ○ cardiac arrest Acid Base Disturbances Acid-Base Balance ○ Must be regulated in a narrow range to function normally ○ Lungs, kidneys, and bone regulate the balance ○ Hydrogen ions maintain membrane integrity and speed enzymatic reactions ○ Bicarbonate is maintained as well. ○ pH represents a power of hydrogen ○ pH < 7.4 is acidic, > 7.4 alkaline Buffers ○ Absorb excess H+ and OH○ Prevent significant change in pH ○ Exist as acid base pairs ○ Carbonic Acid Buffering (bicarb) [main system] Lungs and kidneys Changing rate of ventilation (blow off extra CO2 or retain) Retain bicarb or excrete extra in pee. ○ Protein Buffering (hemoglobin) CO2 loaded onto hemoglobin ○ Renal Buffering (phosphate) Secreting H ions in urine and reabsorbing bicarb in renal tubules. Acid Base Disorders ○ Metabolic versus Respiratory ○ ○ ○ ○ ○
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Metabolic - produce and alteration in bicarb (hydrogen and CO2 associates and disassociates to be moves through system), Respiration - alteration in partial pressure of CO2, increase or decrease in ventilation ○ Acidotic versus Alkalotic pH level • Metabolic Acidosis ○ Decrease HCO3- with decrease pH ○ Causes Diabetic Ketoacidosis, kidney failure, aggressive suctioning of the GI tract ○ Compensation in increased resp. rate (blow off CO2) Kussmaul type respiration. ○ Treatment Treat underlying cause, replace fluid/electrolyte volume. Supplemental sodium bicarb if severe (IV) • Metabolic Alkalosis ○ Increased pH due to primary excess of HCO3○ Causes Increase in intake of alkalotic solution (IV, oral [antacids]), vomiting, binge purge. ○ Compensation Decrease respiratory rate and depth Kidneys bring down pH by excreting more HCO3 in urine (basic urine). ○ Treatment With fluid replacements. • Acid Base Imbalances ○ Metabolic Acidosis Early: HA (head ache) lethargy Severe: Coma Death Compensatory Mechanism Kussmaul respirations ○ Metabolic alkalosis Weakness Muscle cramps
Hyperactive reflexes Tetany Shallow, slow respirations Confusion Convulsions Atrial tachycardia • Respiratory Acidosis ○ impaired alveolar ventilation and increase in PCO2 along with decrease in pH ○ Causes Respiratory disorder (pneumonia, pulmonary edema, respiratory distress syndrome, damage muscles of chest wall, extremely obese (limited movement of chest wall), ○ Compensation Conserve and generate bicarb in body Kidneys excrete H+. ○ Treatment Improve ventilation status (mechanical ventilator). • Respiratory Alkalosis ○ decrease in PCO2 producing an elevated pH and increase in HCO3○ Causes Anxiety attack (psychogenic hypoventilation), hypoxia caused by some form of lung disease, problem with stimilation to ventilate, problem with respiratory center of brain, mechanical vent w/ incorrect vent settings. ○ Compensation Eliminated bicarb in kidneys, conserve H+ ○ Treatment Underlying cause, supplemental oxygenation, change ventilation settings, anxiety - reassurance. • More Acid-Base Imbalances ○ Respiratory Acidosis First: Breathlessness Restlessness Apprehension Then: Lethargy Disorientation Muscle twitching
Tremors Convulsions Coma ○ Respiratory Alkalosis Dizziness Confusion Tingling of extremities Convulsions Coma Deep rapid respirations are the primary symptom • Serum lab values (will be posted on Moodle)