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PHAR 191 exam 1

Fluids, Electrolytes, Acid-Base, PN

IBW for men 50 + 2.3(ht in inches>60)
IBW for women 45.5 + 2.3(ht in inches >60)
Cockcroft-Gault equation for estimating Creatinine clearance in men ((140-age)x IBW)/(72 x SCr)
Cockcroft-Gault equation for estimating Creatinine clearance in women ((140-age)x IBW)/(72 x SCr) x0.85
What weight to use in Cockcroft-Gault equation Always use IBW unless actual<IBW, then use actual.
Calculating TBW in men 0.6 x actual body weight
Calculating TBW in women 0.5 x actual body weight
What weight to use when calculating TBW Always use actual body weight, unless actual is >120% of ideal. Then use ideal
Maintenance fluid requirement 1500ml + 20mL(each kg>20kg)
What electrolytes, etc are found mostly in the ICF? Potassium, phosphorus, proteins, magnesium
What electrolytes, etc are found mostly in the ECF? Sodium, chloride, bicarbonate, calcium
Calculate how much fluid are in ICF compartment? 2/3 of TBW
Calculate how much fluid is in ECF compartment? 1/3 of TBW
Calculate how much fluid is in interstitial compartment? 1/4 of TBW
Calculate how much fluid is in intravascular compartment? 0.08TBW
What fluids are hypotonic? 1/2NS, D5W
What do hypotonic fluids do in the body? Favors shift of water from ECF to ICF
What fluids are isotonic? NS, LR
What kind of patient should not receive Lactated Ringers? Patients with liver disease, since their livers cannot metabolize the lactate. Lactate with build up at cause lactic acidosis.
What fluids are hypertonic? 3% NaCl, D5W1/2NS
What do hypertonic fluids do in the body? Favors shift of water from ICF to ECF
Difference between crystalloids and colloids? Colloids are not a true solution, so cannot pass through the semipermeable membrane. Will increase osmotic pressure initially.
Describe TBW depeletion Loss of hypotonic fluid (more water is lost than sodium), resulting in an increase in serum osmolality. *hypovolemic hypernatremia* aka dehydration (only a little NaCl lost in the urine, most is reabsorbed)
Describe ECF depletion Loss of isotonic fluid (loss same amount of water as to sodium), will see no change in serum osmolality
Clinical symptoms of dehydration Dry mucous membranes, decreased skin turgor, weight loss
Best type of fluid to give when intravascular volume depletion? *aka resuscitation* Isotonic (NS or LR)
Maintenance fluids Used to prevent dehydration in hospitalized patients, give hypotonic fluids (1/2NS)
mEq/L of sodium in NS 154 mEq/L
mEq/L of sodium in 1/2NS 77 mEq/L
mEq/L of sodium in 3% NaCl 512 mEq/L
mEq/L of sodium in Lactated Ringer's 130 mEq/L
mEq/L of potassium in LR 4 mEq/L
mEq/L of calcium in LR 3 mEq/L
Hypertonic hyponatremia "Pseudohyponatremia" that occurs when other osmotically active molecules in large quantities 'dilute' the Na+. Usually due to hyperglycemia, but lipids and protein can also cause this.
Treatment of hypertonic hyponatremia Appropriate treatment of the hyperglycemia
Hypotonic hyponatremia with increased ECF (hypervolemic hyponatremia) Patient has excess sodium and TBW, but TBW excess >Na excess. Usually due to cardiac, renal, or hepatic failures that lead to edema. The kidney doesn't filter the edema fluid, only intravascular.
Treatment of hypervolemic hyponatremia Na restriction, fluid restriction, loop diuretics (often)--loss of intravascular fluid will cause edema to move to replace it
Hypotonic hyponatremia with normal ECF (euvolemic hyponatremia) Presence of excess free water thanks to SIADH.
Causes of SIADH water intoxication, lung CA, pulmonary infection, CNS disorders. Drugs: cycllophosphamide, vincristine, Haldol, SSRIs, TCAs, carbamazepine, NSAIDs, narcotics, thiazides
Tx of euvolemic hyponatremia Remove or treat underlying cause. Fluid restriction. Consider loop diuretic with NaCl replacement (slow)
Max rate of sodium infusion 12 mEq/L/day, 0.5mEq/hr in 1st 12 hours
Possible consequence of infusing sodium too fast Central pontine myelinolysis
Acute treatment of SIADH conivaptan, tolvaptan (ADH antagonists)
Chronic treatment of SIADH demeclocycline, lithium
Hypotonic hyponatremia with decreased ECF (hypovolemic hyponatremia) Decreased Na and water, but sodium loss>water loss
Casues of hypovolemic hyponatremia Thiazide (especially HCTZ >25mg/day), wound drainage, GI losses, burns
Treatment or hypovolemic hyponatremia Correct cause (decrease dose of diuretic), NS to replace fluids and sodium
Hypovolemic hypernatremia TBW depeletion, aka dehydration--loss of hypotonic fluid so sodium increase, osmolality increase
How to calculate water deficit TBW x [SNa/140 -1]
Daily Na requirements 1-1.5 mEq/kg/day
Hypervolemic hypernatremia High sodium, net positive fluid balance. Due to excessive provision of NaCl-containing fluids
Euvolemic hypernatremia Diabetes Insipidus-polyuria due to decreased ADH (kidney not concentrating urine).
Drug causes of Diabetes Insipidus Nephrogenic, ethanol, phenytoin
Non-drug causes of diabetes insipidus central, CVA
treatments for diabetes insipidus Remove cause if possible. Stimulate ADH release with DDAVP, chlorpropamide, or vasopressin
Calculate sodium deficit TBW x (desired Na - actual Na)
Calculate change in sodium (mEq of saline given - SNa) / (TBW + 1L)
Causes of hypokalemia Many drug causes, GI losses, low intake
S/S of hypokalemia muscle cramps, ECG changes, arrythmias
Relation between magnesium and potassium Hypomagnesemia can cause hypokalemia. If hypokalemic and not correct with supplementation, check magnesium
How to give potassium? NEVER BY IV PUSH--THIS IS A LETHAL INJECTION! give infusion by central or peripheral line
Max rate of potassium infusion 10 mEq/hr (may do 20 mEq/hr only if in ICU, and has to be central line)
Dosing of potassium If 3.0-3.4, give 40mEq If 2.5-2.9, give 80mEq If <2.5, give 120mEq
Dosing potassium when CrCl <50mL/min Reduce dose by 1/2
Potassium salt to use in concurrent alkalosis Potassium chloride
Causes of hyperkalemia Increased intake, decreased elimination, pseudohyperkalemia (hemolysis, due to lab draw error)
Treatments of hyperkalemia that buy time Calcium gluconate (to stabilize myocardium) sodium bicarbonate Insulin and glucose (redistribute K+ into ICF) Albuterol nebulized (drive K+ into ICF)
Treatments of hyperkalemia that remove K+ Kayexalate (sodium polystyrene sulfonate) Loop diuretics
Correct calcium equation 0.8 (4- S alb) + S Ca
When would you want to check free ionized calcium? When SCa is <7.0
Dosing for hypophosphatemia If 2.3-2.7, give 0.16 mmol/kg If 1.5-2.2, give 0.32 mmol/kg If <1.5, give 0.64 mmol/kg
Dosing of phos when renal <50mL/min Reduce dose by 1/2
Max rate of phos 7.5mmol/hr
Main consequence of hypophosphatemia Impaired diaphragmatic contractility and acute respiratory failure
Choosing which phosphate salt to use Chose sodium phosphate over KPhos unless patient's K+ is low
Time of infusion for phos Infuse over 4-12 hours
Max rate of magnesium infusion Max 1g/hr due to renal threshold for reabsorption (would pee it all out beyond that)
Potential causes of hypocalcemia Citrate anticoagulants (chelate with calcium), alcohol (renal wasting), pancreatitis or fat malabsorption (decrease absorption of calcium)
Treatment of hypermagnesium Calcium gluconate, loop diuretics and normal saline IV fluid to enhance elimination
Cause of metabolic alkalosis Loss of acid (gastric or renal), eg diuretic use, NG suction, vomiting
Firstline treatment of metabolic alkalosis Remove Cause!! Then, replace Cl with NS if Cl sensitive. May use acetazolamide (carbonic anhydrase inhibitor, allows bicarb to be excreted in kidneys)
Metabolic alkalosis pearls Look for sources of acetate and citrate (these will increase bicarb levels). Compensation is a decrease in ventilation with an increase in CO2
Metabolic acidosis Find anion gap to see if elevated or normal
Anion gap equation Na - (Cl + HCO3) (>12 is anion gap)
Gap acidosis pneumonic MUD PILES methanol, uremia, diabetc ketoacidosis, propylene glycol, ischemia, isoniazid, lacted acidosis or lack of food, ethylene glycol, salicylates
Non-gap acidosis pneumonic USED CAR Uteral diversion, saline infusion, exogenous acid, diarrhea, carbonic anhydrase inhibitors, adrenal insufficiency, renal tubular acidosis
Treatment of metabolic acidosis First-line: remove cause! NaHCO3 tablets, soln, citrate tablets. Polycitra. Tromethamine if need to avoid excess Na.
Indications for PN bowel obstruction, short bowel syndrome, peritonitis (if leads to an ileus), GI fistulas (if enteral access not possible), pancreatitis (if enteral access not possible), severe intractable V/D, preop malnutrition (if enteral access not possible and 7 days
Dosing weight for PN Find IBW. Calculate BMI. Categorize BMI (if 25 or over, use adjusted). Calculate adjusted.
How to find BMI kg/(m square)
Calculate AdjBW for PN IBW + (0.25[actual - IBW])
Caloric requirement for maintenance 20-25 kcal/kg/day
Caloric requirement for repletion or critical illness 25-30 kcal/kg/day
Caloric requirement for trauma or burn 30-35 kcal/kg/day
Protein (AA) requirements for maintenance 0.8-1 g/kg/day
Protein (AA) requirements for repletion 1.3-1.5 g/kg/day
Protein (AA) requirements for critical illness or trauama 1.5-2 g/kg/day
Protein (AA) requirements for burn 1.5-2.5 g/kg/day
Finding lipid amount for PN Should be 20-30% of total kcal (use 30% if patient hyperglycemic already)
Number of kcal/g of amino acids 4 kcal/g
Number of kcal/g of dextrose 3.4 kcal/g
Number of kcal/g of lipids 10 kcal/g
Max rate of dextrose infusion 4mg/kg/min
Desired rate of dextrose infusion 2-4mg/kg/min
3 ways to find dextrose amount to put in PN 1. Use max inf rate of 4mg/kg/min 2. Use 50-60% of total calories 3. Amount of kcal left over after protein + lipids added
What to do when calculate dextrose amount to put in PN Convert to mg/kg/min to check dextrose rate (want between 2-4 mg/kg/min)
Find total mL of PN and rate of infusion (FOR FINAL , NOT INITIAL) Typically use 70% dextrose stock, 20% lipid stock, 15% AA stock. Convert g to mL. Add 100mL for electrolytes. Divide total mL by 24 hour.
Initiating a PN No more than 15-200g dextrose (max 2mg/kg/min) Give less AA on day 1. Minimum final concentration of lipids should be 2% (20g/1000ml)
Daily and initial monitoring for PN BMP, Mag, Phos, weight
Weekly and initial monitoring for PN Albumin, prealbumin, LFTs, Tbili, Trig, INR
As needed monitoring for PN trace elements
Refeeding syndrome Will see: hypophosphatemia, hypokalemia, hypomagnesemia. May result from aggressive initial PN or severe malnutrition. May supplement extra phos in first PN.
When to withold IV lipid emulsion When patient has triglycerides >400 mg/dL (need to increase dextrose goal to make up for lost lipid kcal)
Cholestasis PN-associated liver dysfunction. Elevated Alk Phos and Bili. Mild AST/ALT elevations
Steatosis PN-associated liver dysfunction. Moderate AST/ALT elevations. Mild elevation or normal Alk Phos and Bili.
Cycled PN May resolve or improve liver dysfunction. Minimum infusion time usually 8 hours
Blood glucose nadir with PN Hypoglycemia would occur 15-60 minutes after cessation of PN unfusion. Screen with initial cycle and whenever changes made to cycled regimen.
Created by: steponmegrace