Fluid and Electrolyte Physiology

Fluid and Electrolyte Physiology - Fluid and Electrolyte...

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Unformatted text preview: Fluid and Electrolyte Physiology Physiology Dr. Raymon Grogan 11/6/06 Total Body Fluid by Compartment Total Total Body Water Electrolyte Composition of Body Fluid Compartments Fluid Composition of Parenteral Fluids (mEq/L) (mEq/L) Fluid Na+ K+ Ca2+ Cl- HCO3- pH ECF 142 4 5 103 27 7.4 LR 130 4 2.7 109 28 6.5 .9% NaCl 154 154 4.5 .45% NaCl 77 77 4.5 .2% NaCl 30 30 4.5 3% NaCl 513 513 4.5 5% NaCl 855 855 4.5 5% Albumin 145 7.4 Composition of GI Fluids (mEq/L) Composition Source Saliva Gastric Daily Loss Na+ 1000 K+ Cl- HCO3- 30-80 20 70 30 1000-2000 60-80 15 100 0 Panc 1000 140 5-10 60-90 40-100 Bile 1000 140 5-10 100 40 SB 2000-5000 140 20 100 25-50 LB 200-1500 75 30 30 0 Sweat 200-1000 20-70 5-10 40-60 0 Hyponatremia Hyponatremia Defined as serum [Na+] less than 136 Defined mEq/L mEq/L Water shifts into cells causing cerebral Water edema edema 125 mEq/L – nausea and malaise 120 mEq/L – headache, lethargy, 120 obtundation obtundation 115 mEq/L – seizure and coma Hyponatremia Hyponatremia 1. Assess plasma osmolality 2. Assess volume status of patient 3. Assess Urine Sodium Concentration Needed for definitive diagnosis, not needed for Needed treatment purposes treatment 4. Calculate Na+ Deficit Hypervolemic, Euvolemic, Hypovolemic 0.6 x weight (kg) x (130 – plasma [Na+]) 5. Correct at no more than 0.5mEq/L per hour 5. or 12 mEq/L per 24 hours or Isosmotic and Hyperosmotic Hyponatremia Hyponatremia Iso and Hyperosmotic hyponatremia are due to Iso excessive solutes in plasma. Isosmotic • Pseudohyponatremia – No treatment necessary Hyperlipidemia Hyperproteinemia • Isotonic Infusions Glycine Mannitol Hyperosmotic – Treat underlying cause • Hyperglycemia Each 100 mg/dl of glucose reduces [Na+] by 1.6 mEq/l • Hypertonic Infusions Glycerol Mannitol Glycine Hyposmotic Hyponatremia Hyposmotic 1. Assess volume status Hypervolemic – cirrhosis, heart failure, Hypervolemic nephrotic syndrome nephrotic Euvolemic – polydipsia, SIADH Hypovolemic – most common cause • Excessive renal (diuretic) or GI (emesis, diarrhea) Excessive losses losses Treatment of Hyponatremia Treatment Iso or Hyperosmotic Correct underlying disorder Hyposmotic Iso or hypervolemic – fluid restriction Hypovolemic • Asymptomatic – fluid resuscitate with isotonic Asymptomatic saline saline • Symptomatic or plasma [Na+] less than 110 mEq/L Calculate Na+ deficit Correct at a rate no greater than 0.5 mEq/L/hour or 12 Correct mEq/L/day mEq/L/day Correction of Sodium Deficit Correction Example: A 60 kg woman with a plasma sodium Example: concentration of 120mEq/L: concentration Sodium deficit = TBW x (130 – [Na+]p) Sodium deficit = 0.5 x 60 x (130-120) = 300mEq 3% NaCl contains 513 mEq sodium/L Volume of 3% NaCl needed = 300/513 = 585 mL At 0.5 mEq/L/hr a correction of 10 mEq should be done At over 20 hours over So, 585 mL/20 hours = 29 mL/hour of 3% NaCl Hypernatremia Hypernatremia Defined as serum [Na+] greater than 146 Defined mEq/L mEq/L Lethargy, weakness, and irritability that Lethargy, progress to seizure, coma, and death progress Usually occurs in adults with altered Usually mental status or no access to water mental Hypernatremia Hypernatremia 1. Assess volume status 2. Measure urine [Na+] 3. Calculate water deficit 4. 4. 0.6 x weight (kg) x ([Na+]/140 -1) Correct with free water no faster than 0.5 mEq/L/hour or 12 mEq/L/day 0.5 Hypernatremia Hypernatremia Hypovolemic – loss of hypotonic fluids Diuresis, vomiting, diarrhea Isovolemic – loss of free water Diabetes insipidus, hypodipsia Hypervolemic – gain of hypertonic fluids Hypertonic saline administration Treatment of Hypernatremia Treatment Hypovolemic Hypovolemic Replace the free water deficit Hypervolemic Diuretics (lasix) to excrete sodium in urine Diuretics combined with hypotonic saline for partial volume replacement volume Treatment of Hypernatremia Treatment Isovolemic Diabetes Insipidus Loss of hypotonic urine secondary to lack of ADH Loss production (central) or lack of response to ADH by kidney (nephrogenic) kidney Hallmark is hypotonic urine (200-500 mOsm/L) with Hallmark hypertonic plasma hypertonic Treat by correcting free water deficit In central DI must also administer 5 – 10 units of In DDAVP Q6H to prevent ongoing free water loss DDAVP Hyperkalemia Hyperkalemia Defined as a serum [K+] greater than 4.6 mEq/L Changes in cellular transmembrane potentials can lead Changes to lethal cardiac arrhythmias to Most often associated with renal impairment coupled Most with exogenous K+ administration or drugs that increase K+ K+ Transcellular shifts – acidosis, succinylcholine, insulin Transcellular deficiency, massive tissue destruction deficiency, Massive blood transfusions Pseudohyperkalemia - Thrombocytosis, hemolysis, Pseudohyperkalemia leukocytosis leukocytosis Urine K+ excretion rate can be used to determine exact Urine cause of hyperkalemia cause Hyperkalemia Hyperkalemia Drugs causing hyperkalemia – K+ sparing Drugs diruetics, ACEI, NSAIDs, Heparin, Cyclosporin, Tacrolimus, Bactrim Cyclosporin, EKG Changes 5.5 – 6.5 mEq/L – peaked T-waves 6.5 – 7.5 mEq/L – loss of P-waves > 8.0 mEq/L – widened QRS Treatment of Hyperkalemia Treatment 1. 1. If EKG changes administer 10 mL of 10% Calcium Gluconate 10% 2. 1 amp D50 with 10 units IV insulin 2. (onset 10-20 minutes, duration 2-3 hours) (onset 3. Albuterol 10 -20 mg (onset 4-5 hours, 3. duration 2-3 hours) duration 4. Kayexalate 15-30 g (oral onset 4-5 4. hours, enema onset 1 hour) hours, Dialysis Hypokalemia Hypokalemia Defined as serum [K+] less than 3.6 Defined mEq/L mEq/L Occurs in up to 20% of hospitalized Occurs patients patients 2.5 mEq/L – muscular weakness, myalgia <2.5 mEq/L – cramps, parasthesias, ileus, <2.5 tetany, rhabdomyolisis, PVCs, A-V block, V-tach, V-fib V-tach, Hypokalemia Hypokalemia Inadequate intake Increased excretion – diarrhea, diuretics, Increased alkalosis, glucocorticoids, RTA alkalosis, Transcellular shifts – beta-agonists, Transcellular theophylline, insulin, hyperthyroidism, barium barium Replace no faster than 20 mEq/H Replace peripherally and 100 mEq/H centrally peripherally ...
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This note was uploaded on 12/21/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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