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WVC F&E Lecture
WVC F&E Lecture winter 2011
| Question | Answer |
|---|---|
| Isotonic dehydration is an equal loss of water and sodium | there is no fluid shift in either direction. The amount of intracellular and extracellular water remains in balance. This can be caused by a complete fast, vomiting, and diarrhea. |
| Hypertonic dehydration occurs when water loss is greater than sodium loss Blood Na levels may be >145 mmol/l Higher blood Na levels combined with decreased water in the intravascular space increases the osmotic pressure in the bloodstream | which, in turn, pulls more fluid out of the cells. This type of dehydration is usually caused by extended fever with limited oral rehydration. Mortality is more likely to occur from hypertonic than from isotonic dehydration. |
| Hypotonic dehydration occurs when sodium loss is greater than water loss. Blood sodium levels may be less than 135 mmol/l; & osmotic pressure is greater inside the cells, which pulls more fluid out of the intravascular space into the intracellular space. | This type of dehydration occurs with overuse of diuretics, which causes excessive Na & K loss. K depletion affects respiration, increases nausea, if severe enough, may cause respiratory arrest or (CNS) seizures. K depletion may also cause arrhythmias |
| Homeostasis | Body functions within a narrow range of normal; Homeostatic mechanisms regulate body systems; Balance is the key |
| Solvent | the water portion of body fluids |
| Solute | the particles dissolved in the water |
| Viscosity | the thickness of the fluid, the less water the higher the viscosity |
| Permeability | how porous the membrane is that separates two compartments |
| Intracellular | Within the cells |
| Extracellular | Outside the cells |
| Intravascular | in the blood circulation system (plasma) |
| Interstitial | in the tissues between the cells |
| Transcellular – | small amount of fluid in the eyeball, GI spaces and cerebrospinal fluid |
| Equilibrium- | when the pressures on both sides of the membrane are equal |
| Disequilibrium | when the pressures are different from one side of the membrane to the other |
| Filtration – | movement of fluid across a barrier as a result of hydrostatic pressure |
| Diffusion | Free movement of particles (solute) across a permeable membrane Movement of particles in and out of cells via the kinetic energy of molecular motion |
| Osmosis | movement of water (solvent) across a selectively permeable membrane |
| Active Transport | movement of a substance across a barrier against a concentration gradient using energy |
| Osmosis | Process through which only water moves through a selectively permeable membrane; If membrane is impermeable to a solute it cannot cross but water can |
| Osmolarity | is the number of milliosmoles per liter - size measurement |
| Active Transport | A cell uses energy to move a substance across a cell membrane against an uphill gradient. This is sometimes called “pumping” and the mechanism is known as a membrane pump. The sodium-potassium pump is an example. The energy it uses is ATP |
| Osmolality | is the number of milliosmoles per kilogram of solution – weight measure |
| osmolarity of body fluids | is 300 mOsm/L |
| Isotonic | osmotic pressures are equal on both sides of membrane |
| Hypertonic | osmotic pressure is higher on one side > 300 |
| Hypotonic | osmotic pressure is lower on one side < 300 |
| How the Body Balances Fluid | kidneys are the main organ the body uses to help regulate fluid, endocrine system releases hormones in response to changes in fluid & electrolyte balance, kidneys will retain water & sodium or excrete water & sodium. |
| The thirst center of the brain is activated in the case of dehydration | and the sympathetic nervous system compensates |
| Aldosterone | secreted by the adrenal gland in response to decreased sodium level. Water follows sodium, decreases osmolarity. |
| Antidiuretic hormone (ADH) | secreted by the posterior pituitary gland in response to changes in serum osmolarity. Water is retained and returned to circulation. |
| Dehydration | fluid intake is less than the body’s fluid needs |
| Overhydration | fluid intake is greater than the body’s needs |
| What Happens in Dehydration | Body loses fluid, Blood solute osmolarity increases, Serum sodium level rises, Water molecules shift from ICF to ECF, Cells shrink as more fluid shifts into ECF, Patient develops mental status changes & other symptoms of decreased cardiac output |
| Fluid Overload | Can be an actual excess of TBW or a fluid excess in one or more compartments, Can be isotonic, hypotonic or hypertonic, Most problems are the result of vascular fluid volume excess or dilution of blood or electrolytes. |
| What Happens in Fluid Overload | Excess sodium or fluid is retained; Osmolarity is usually decreased; Release of ANP and BNP; Fluid moves out of the intravascular space into the interstitial space; Fluid accumulates in the ECF; Edema develops in the lungs and other tissues |
| Assessing for Overhydration | History, Vital signs, Auscultate breath sounds, Jugular vein distention, Edema, Jugular Vein Distention |
| Electrolytes | Electrolytes work w/ fluids to maintain homeostasis. Electrolytes are substances that, when in solution, separate into electrically charged particles called ions; Anions are electrolytes with negative charge; Cations are electrolytes with positive charge |
| Exciters increase cell action potential. The higher the concentration, the more excitable the cell membrane. | -Potassium –Sodium |
| Anions | Bicarbonate, Chloride, Phosphorus |
| Cations | Calcium, Magnesium, Potassium, Sodium |
| Major Extracellular Electrolytes | Sodium,-Chloride-Calcium-Bicarbonate |
| Major Intracellular Electrolytes | Potassium- Phosphate-Magnesium |
| Stabilizers control over-excitation of the cell membrane. The higher the concentration, the less excitable the cell. Suppress excitation. | -Calcium –Magnesium |
| Basic Metabolic Panel (Sometimes called a Chem-7) | Sodium: 135-145 mEq/L, Potassium: 3.5-5.0 mEq/L, Chloride: 98-106 mEq/L,Glucose: 50-100, fasting, BUN: 10-20 mg/dL, affected by body fluid levels, Creatinine: 0.5 -1.2 mg/dL, CO2: 23 – 30 mEq/L,( not to be confused with arterial blood gas normals) |
| Potassium | Major cation of the ICF, 3.5 to 5 mEq/L, Nerve cell conduction and muscle contraction, Affects depolarization/repolarization of cardiac muscle, Must be replaced daily |
| Hypokalemia | A level below 3.5 mEq/L, Reduces excitability of cells Nerve & muscle less responsive to stimuli; Affects heart, respiration, neuromuscular,GI and kidneys, Influenced by age, meds, chronic disease, diet, diuretics cause lose of K, rapid HR, hypo-refexia |
| Hyperkalemia | Serum K of > 4.5 mEq/L; (rapid rise/ increased effect) ^ cell excitability; heart is most sensitive, tall peaked T-waves, bradycardia, dysrhythmias Muscle cramps and twitches, paresthesia; ^ GI motility, diarrhea. K levels ^ in acidosis. MURDER |
| Treatment of Hyperkalemia | Stop taking potassium; Give potassium excreting diuretics like lasix (furosemide); A hypertonic IV solution that contains glucose and insulin; Cardiac monitoring, treat arrhythmias Patient education about diet & meds |
| Sodium | Major cation of the ECF; 135-145 mEq/L; Often attached to Cl or HCO3 to maintain acid-base balance; Na absorbed from GI tract & eliminated through feces, urine and sweat. |
| Sodium control measures in the body | Levels are controlled by thirst mechanism, ADH, glomerular filtration, renin-angiotensin-aldosterone system, ANP, osmotic pressure and sodium-potassium pump |
| Hyponatremia | < 135 mEq/L; As Na levels decrease.. difference in the Na level between ECF & ICF also decreases; Less Na is available for depolarization; H20 is pulled from the ECF to ICF causing cells to swell. Heart & resp effected. sleepnes n/v confusion, weakness. |
| Hyponatremia Interventions | Diet Therapy increase Na/ Fluid restriction or free water restrict; Diuretics to decrease fluid volume in case of fluid overload; IV saline solutions to replace Na & fluid in burns or trauma, ADH antagonists |
| Hypernatremia | >145 mEq/L; ECF Na levels rise; Gradient increases allowing Na to move rapidly across cell membrane (cell dehydration); Increases excitation or irritability of cells; ^ osmolarity of ECF causing water to move from cells to ECF. (pullmonary edema) FRIED |
| Hypernatremia Interventions | Dietary Na restriction; Adequate water intake; IV fluid replacement w/ hypotonic solutions to restore fluid balance; Diuretics that promote Na loss: lasix, bumex, edecrin (If hypovolemic, may need to replace with isotonic solution) |
| Chloride | 95-110 mEq/L; Most abundant anion in ECF; Helps to maintain acid-base balance; Combines with cations to provide electroneutrality and osmotic pressure; Essential for gastric acid |
| Calcium | 9-10mg/dL; Most abundant cation, stored in bones & teeth;Regulated by the parathyroid gland. |
| Phosphorus | 3-4.5 mg/dL, Most abundant anion in the ICF; differs with men or women;Mostly stored in bones & teeth; Has an inverse relationship to Ca, when one is increased the other is decreased A component of ATP needed for active transport |
| Hypocalcemia | < 9.0 mg/dL; Low serum Ca increases the permeability of excitable membranes to Na;Severity of symptoms depends on degree of Ca imbalance; Bone loss; Ca is reduced when parathyroid function is decreased. CATS |
| Hypercalcemia | > 10.5 mg/dL; Occurs when the Ca regulating system is not working;Causes excitable tissues to be less sensitive, muscle weakness; faster clotting times for blood; increased heart rate early on, can progress to cardiac arrest. increased urinary output, |
| Hypocalcemia Interventions | Hypocalcemia – replace calcium/vitamin D |
| Hypercalcemia Interventions | Hypercalcemia- wash it out with IV fluids and diuretics. Dialysis if severe; Cardiac monitoring |
| Hypophosphatemia | < 3.0 mg/dL,Only have clinical manifestations when decrease in levels is severe or prolonged; Related to decreased energy metabolism & altered levels of other electrolytes; Can be caused by decreased absorption, increased excretion or intracellular shift |
| Hyperphosphatemia | > 4.5 mg/dL; High levels of phosphorus cause hypocalcemia; Treat the calcium problem with something that is low in phosphorous (non-dairy sources) |
| Magnesium | 1.3-2.1 mEq/L; 2nd most abundant cation in the ICF; Essential to cardiac function; Assists with DNA, RNA and protein synthesis; Activates B-complex vitamins; Necessary for sodium-potassium pump, blood coagulation &bone formation |
| Hypomagnesemia | < 1.3 mg/dL; Caused by decreased intake or loss; Changes in excitability of membranes; Ca & K imbalance; Allows greater release of acetylcholine at the nerve synapses (Tetany, paresthesias & hyperactive DTR) Replace with IV Mg..malnutrition (alcoholism |
| Starling’s forces – | states that the fluid movement due to filtration across the wall of a capillary is dependent on the balance between the hydrostatic pressure gradient & the oncotic pressure gradient across the capillary. |
| Hypermagnesemia | > 2.1 mg/dL; Decreased excitability of membranes; Bradycardia, peripheral vasodilation and hypotension; treat with Dietary management & Diuretics (stay away from antacids, nuts, meat) |
| Hydrostatic Pressure | Hydrostatic pressure is the pressure exerted by a fluid at equilibrium due to the force of gravity |
| Those at risk for life-threatening, severe electrolyte imbalances | are the elderly, those with chronic renal or endocrine disorders, those taking medications that alter fluid and electrolyte status |
| MURDER associated with Hyperkalemia | M- muscle cramps; U- urine oligurria; R- Respiratory distress; D- decreased cardiac (HR) E- EKG changes- R-reflexes, hyperactive. |
| FRIED (Hypernatremia) | F- fever; R-restlessness; I- increase urinary retention; E-Edema D-decrease urinary output |
| Hypocalcemia CATS | C convulsions A- arrhythmia T-tetany S-spasms |
| Chvotek's and Trousseau's signs | Chvotek's cheek spasm (when you check/ tap facial nerve)....and Trousseau's signs arm carpel spasm (when you fill the cuff 1-4 min) |
| Chemical reactions that sustain life depend on a balance between acids and bases, normal pH 7.35-7.45 | Acids give up H+ (pH <7); Bases accept H+ (pH above 7); Deviation from normal compromises electrolyte balance, enzyme activity, muscle contraction & cellular function; pH < 6.8 or > 7.8 is usually fatal. |
| Acidosis | An excess of hydrogen ions; Arterial pH of < 7.35; Can have metabolic or respiratory cause |
| Chemical buffers regulate acid- base balance | – immediately combine with excess acid or base to neutralize harmful effects until other regulators take over |
| Respiratory system regulate acid- base balance | – uses hypo or hyperventilation to regulate acid excretion or retention within minutes of a pH change |
| Kidneys regulate acid- base balance | – excrete or retain more acids or bases as needed to restore normal balance over a period of hours or days. Most powerful regulating force...move HCO3, move acid or form acids or HCO3 to correct acid base imbalances |
| Metabolic acidosis is a result of: (4) | Overproduction of H ions; Underelimination of H ions; Underproduction of HCO3 ions; Overelimination of bicarbonate ions. Ketones, lactic acid, aspirin, kidney disorder, GI disorders. |
| Overproduction of Hydrogen (acidosis) | Breakdown of fatty acids (starvation, or DKA) breakdown of fat stores for food large number of H ions released; Hypermetabolism- lactic acidosis anerobic metabolism; Excessive ingestion of acids (alcohol, aspirin) |
| Underelimination of Hydrogen (acidosis) | Kidney failure causes acidosis when the tubules cannot excrete H ions.Too many H ions are retained. |
| Underproduction of Bicarbonate(acidosis) | HCO3 is made in the kidneys and pancreas; Renal failure, hepatic or pancreatic dysfunction can affect bicarbonate production and retention. |
| Overelimination of Bicarbonate (acidosis) | A common cause of the overelimination of bicarbonate is diarrhea. (IBS) (Illieostomy) |
| Metabolic Acidosis Lab Data | (ABGs) Low pH, Low bicarbonate level < 21 mEq/L, Normal PaCO2; (Electrolytes) Elevated potassium; Normal chloride with elevated anion gap; Elevated chloride with normal anion gap |
| Respiratory Acidosis | Impaired respiratory function causes an inadequate exchange of O2 & CO2; increase in CO2 causes a corresponding increase in H ions; CO2 retention causes acidosis |
| Carbonic Anhydrase Equation: | CO2 + H2O <> H2CO3 <> H + HCO3 H2CO3= carbonic acid |
| Causes of CO2 Retention | Respiratory Depression (opiates) ;Inadequate chest expansion (trauma, obesity, aceties,); Airway obstruction (asthma, choking) ; Reduced alveolar-capillary diffusion (pneumonia, aspirating vomit) |
| Respiratory Acidosis Lab Data | (ABGs) Low pH, Elevated PaCO2, Low PaO2; (Electrolytes) Elevated potassium, Variable serum bicarbonate levels |
| Alkalosis | An excess of bases; A decrease in hydrogen ions; Arterial pH above 7.45; Can be caused by metabolic or respiratory problems. in relative the number acids decrease the bases don't decrease. in actual |
| Metabolic Alkalosis (2) | Base excess and/ or acid deficit |
| Base excess – | oral or parenteral ingestion of bases. Excessive use of antacids. Citrate excesses during rapid blood transfusion, lactate excesses during hyperalimentation or IV sodium bicarbonate. (antacids, too many blood products at once d/t preservative) |
| Acid deficit – | Cushing’s syndrome, vomiting (throwing up HCl), thiazide diuretics, prolonged NG suctioning (same effect as vomiting) Also loss of K and Ca |
| Manifestations of Metabolic Alkalosis | CNS agitation, lightheaded, confusion, hyperreflexia (hypocalcemia, hypokalemia); Neuromuscular – Muscle cramps, tetany, weakness; Cardiac – rapid, thready, hypovolemia, hypotension, increased risk of dig toxicity ;Resp. – Tachypnea, deep respirations |
| Metabolic Alkalosis Lab Data | (ABGs) High pH > 7.45, Elevated bicarbonate > 28 mEq/L, Rising PaCO2 (trying to correct with acid CO2), Normal PaO2; (Electrolytes) Decreased potassium (trying to maintain elctrolyte neutrality) , Decreased calcium |
| Respiratory Alkalosis | Caused by hyperventilation; Anxiety or improper settings on ventilator; Direct stimulation of respiratory centers in the brain b/c of fever, to compensate for metabolic acidosis, CNS lesions and drugs |
| Respiratory Alkalosis Lab Data | (ABGs) High pH, Low bicarbonate level (attempt to compensate for high pH), Low PaCO2; (Electrolytes) Low potassium, Low calcium, |
| Interventions for Alkalosis | Prevent further losses of hydrogen, potassium, calcium and chloride ions; Restore fluid balance; Monitor change; Fluid and electrolyte replacement; Monitor lab values |
| Interpreting Arterial Blood Gases (Use a systematic approach) | What is the pH: normal, acid or alkaline? What is the PaCO2: normal, acid or alkaline? What is the HCO3: normal, acid or alkaline? Which of the two matches the pH? Is there movement in the opposite direction of the remaining value? |
| relative excess or relative deficiency | shift between compartments in response to fluid deficit or overload |
| actual excess or relative deficiency | too much produced or not enough ingested |
| Buffers in the body | bicarbonate HCO3 (ICF & ECF); phosphate (ICF)(bones); and proteins (hemoglobin)(ICF); albumin (ECF) |
| CO2- pH relationship | related to the CO2 concentration....more CO2 the more acidic |
| Stage 1 acidosis | Hydrogen ions begin to accumulate; chemical buffers bind with them, no symptoms yet |
| Stage 2 acidosis | ecess H ions that can't be bound by buffers low pH. Increased respiratory rate lowers the PaCO2, allowing more H to bind with HCO3. ABG shows decreased HCO3 and decreasing CO2. |
| Stage 3 acidosis | |
| metaboloc acidosis and hyperkalemia occur together because.... | |
| stage 4 acidosis | |
| stage 5 acidosis | |
| stage 6 acidosis | excess H ions alter the normal balence of K, Na, and Ca leading to reduced excitability of nerve cells. CNS depression, lethargy, confusion, coma |
| anion gap | the difference between cation and anion is the anion gap |
| acid base imbalance is compensated if... | pH is within normal range |
| less you have of HCO3.... | the more acidic you are |
| high acid= high potassium | potassium is moving out of the cell into ECF |
| high pH= low calcium | calcium is binding to other things |
| compensating for acid base imbalance | look to the side that pH is on...for example if pH is 7.37 it would be more an issue of too acidic, and continue with tic tac toe to determine nature of problem. |
| pH and paO2 values should match | High paO2= basic low paO2= acidic (more commonly seen) |
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