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PHAR 191 exam 1
Fluids, Electrolytes, Acid-Base, PN
| Question | Answer |
|---|---|
| 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. |
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steponmegrace
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