Fluid and Electrolytes Zach Gregg

Total Body Water 60% body weight (50% in women) ECW- 20% body weight ICW- 40% body weight 33% TBW 67% TBW Interstitial – 15% body weight Intravascular – 5% body weight 25% TBW 8% TBW

ECW Intravascular Interstitial Water supplies the blood Equilibrated rapidly with Maintenance essential to survival intravascular compartment Increases in size after an operation, burn, trauma, or severe illness (3 rd Spacing) Plasma is separated from interstitium by an endothelial cell layer and basement membrane

Electrolytes ECW ICW Na+ 142 Na+ 10 K+ 4 K+ 140 Cl- 110 Cl- 3 HCO HCO Inorg. Phos- 12 Org. Phos- 137

Na+/K+ ATPase Actively pumps 3 Na+ out of cell and 2K+ inside cell Energy from ATP Regulated by –Insulin –Aldosterone

Daily Requirements Water – cc/kg Sodium – 1mEq/kg Potassium – 0.5-1mEq/kg Chloride – 1.5 mEq/kg

Fluid Loss Urine Output –Highest daily water loss –0.5cc/kg/hr Sufficient UO to excrete the daily solute load 70kg pt = 35cc/hr

Fluid Loss Insensible –Skin ml/day –Breathing – 400 ml/day –Feces – ml/day Potential –Saliva – 1000 ml/day –Bile – ml/day –Gastric – 1000 ml/day –Pacreatic – 1000 ml/day –Small intestine – 3000 ml/day

Maintenance Fluid 100/50/20 per 24 hrs for 70kg –First 10 kg x 100cc/kg = 1000 cc –Second 10 kg x 50cc/kg = 500 cc –Remaining 50 kg x 20cc/kg = 1000 cc 2500 cc/day

Maintenance Fluid 4/2/1 per hr for 70kg –First 10 kg x 4cc/kg = 40 cc –Second 10 kg x 2cc/kg = 20 cc –Remaining 50 kg x 1cc/kg = 50 cc 110 cc/hr

Fluid Components per Liter Resuscitative Fluids –NS (0.9%) 154mEq Na +, 154mEq Cl - –LR 130mEq Na +, 110mEq Cl -, 4mEq K +, 28mEq HCO 3 -, 3mEq Ca Maintenance Fluids –½ NS (0.45%) 77mEq Na +, 77mEq Cl - Colloid

Fluid Pearls Resuscitation – isotonic fluid (LR or NS), no dextrose, if ongoing losses consider using colloid Post-op – LR or NS until pt euvolemic, then switch to maintenance Bolus – Isotonic, no dextrose Mobilization – movement of fluid from 3 rd space into intravascular space

Hypovolemia Acute volume loss –Tachycardia –Hypotension –Decreased UO Gradual volume loss –Loss of skin turgor, dry mucus membranes –Thirst –Changes in mental status Low CVP Hemoconcentration (Increased HCT) BUN:Cr > 20:1 Metabolic acidosis due to hypoperfusion

Hypervolemia Large UO Pitting edema JVD Crackles on lung exam Hypoxia CXR – cephalization of vessels, pulm edema

Hyponatremia Serum Na+ < 130mEq/L Sx- Nausea, emesis, weakness, MS changes, seizure Hypovolemic –Causes – Na+ and water are lost and replaced with hypotonic solutions Renal – salt wasting nephropathy GI – diarrhea, vomiting, fistulas Excessive sweating 3 rd spacing – ascites, peritonitis, pancreatitis, burns Hypoaldosteronism –Tx – replete with NS, no faster than 0.5 mEq/L/hr to avoid central pontine myelinolysis

Hyponatremia Euvolemic –Causes – SIADH, psychogenic polydipsia –Tx – free water restrict Hypervolemic –Causes - Renal failure, nephrosis, CHF, cirrhosis

Hypernatremia Serum Na+ > 145 Sx – altered level of consciousness, seizure, coma, signs of dehydration Causes – DI, hyperosmolar diuresis, EtOH suppresses Vasopressin release Tx – Calculate free water deficit = 0.6 x wt(kg) x (measured Na )/140 –Replace first ½ in 24hrs, then 2 nd ½ in 24 hrs. No faster then 10mEq/day to avoid cerebral edema –Use D5W, ½ NS or ¼ NS

Hypokalemia K+ < 3.5 Sx – fatigue, weakness, ileus, N/V, arrhythmia, rhabdomylosis, flaccid paralysis, resp compromise –EKG - long QT, depressed ST, low T waves, U waves Causes – vomiting, NGT drainage, diarrhea, high output enteric/pancreatic fistula, hyperaldo, loop diuretics Tx – replete 10 mEq KCl for every 0.1 below 4.0, if persistent hypoK+, may also need Mg 2+ replacement

Hypokalemia EKG - long QT, depressed ST, low T waves, U waves

Hyperkalemia K+ > 5.0 Sx – weakness, N/V, abdominal cramping, diarrhea, arrhythmias –EKG – peaked T waves, prolonged PR, widened QRS, V-fib, arrest Causes – lab error, iatrogenic, renal failure, acidosis, hemolysis, crush injury, reperfusion after 4hrs ischemia Tx – cardiac monitoring –1 amp calcium gluconate (stabilizes myocardium) –1 amp glucose, 10units IV insulin (shifts K+ intracellular) –Kayexalate, dialysis

Hyperkalemia EKG – peaked T waves, prolonged PR, widened QRS, V- fib, arrest

Hypocalcemia Ca2+ < 8.5 Sx – parasthesias, muscle spasms, tetany, seizures, Chvostek, Trousseau’s –EKG – prolonged QT, can progress to complete heart block or V-fib Causes – pancreatitis, tumor lysis syndrome, blood transfusion, renal failure, thyroid or parathyroid surgery, diet deficient in Vit D or Ca, inability to absorb fat soluble viatmins Tx – For chronic hypoCa give supplemental Ca and Vit D. For symptomatic give IV Ca

Hypercalcemia Ca2+ > 10.5 Sx – stones, moans, groans, psychologic overtones Causes – CHIMPANZEES Tx – Identify cause and treat, severe/symptomatic hyperCa tx with IVF, bisphosphonates if due to release of Ca from bone