Fluids and Electrolytes Composition of Fluid Compartments ICF = K, Mg, Phos, proteins Na determines intracellular/extracellular osmotic pressure ECF = plasma & interstitial fluid very similar. Plasma has a higher protein concentration. Na is confined to the ECF(1/3 plasma, 2/3 interstitial space) - IVF w/Na expands the interstitial space more than it does the intravascular space.
Fluids and Electrolytes Maintenance Fluid: Composition What is D5 NS + 20KCl? –D5 = 5% glucose = 5g dextrose/100mL of solution or 50g/L (prevents mobilization of protein as fuel source) –1L NS = 154mEq Na, 154mEq Cl –20KCl = 20mEq KCl per L What is LR? –1L LR = Na 130 mEq, K 4 mEq, Ca 3 mEq, Cl 109 mEq and lactate 28 mEq. –The electrolyte content is isotonic (273 mOsmol/L) in relation to the ECF (approx. 280 mOsmol/L). –The pH of the solution is 6.6.
Fluids and Electrolytes Maintenance IVF: Adults MIVF rate calculation: 4 / 2 / 1 rule (per hour) –For the first 10kg → 4mL/kg/hr –For the next 10-20kg → 2mL/kg/hr –For each kg after 20kg → 1mL/kg/hr Typical MIVF: D5 1/2NS +20KCl Electrolyte requirements: –Sodium = 2-3 mEq/kg/day –Potassium = mEq/kg/day
Fluids and Electrolytes IVFs After Surgery Fluid Loss during surgery L/hour, + blood loss Calculate initial MIVF rate with rule, then adjust for blood loss Use LR/NS for first 24 hours, then switch to D5 2 NS +20KCl Daily BMPs while NPO to manage electrolytes
Fluids and Electrolytes Resuscitation Remember your ABC’s C = includes IV access –Important: what is adequate IV access? Evaluate hemodynamic status: look at BP, HR, skin perfusion, temperature, mental status Start with isotonic crystalloid fluids Initial bolus: 20mL/kg in children, 2L in adults Assess response to bolus: –If responsive, continue evaluation –If unresponsive, THERE IS A PROBLEM THAT YOU NEED TO IDENTIFY NOW: bleeding, cardiac tamponade, spinal cord injury, tension PTX, MI, myocardial contusion, air embolism
Fluids and Electrolytes Assessment of Volume Status Daily weights Swelling/edema Edema pattern on CXR UOP –UOP > 0.5mL/kg/h adults –UOP for children > 1mL/kg/h
Fluids and Electrolytes Case #1: Presentation H&P: 6wk-old, first-born M p/w 5d h/o projectile nonbilious, postprandial emesis - otherwise, pt w/good appetite PE: firm, mobile “olive” in epigastrum, and visible gastric peristaltic waves U/S: pyloric muscle elongated & thickened (4mm thick) Questions: What is the diagnosis? What is the associated metabolic/electrolyte abnormality? What is the management?
Fluids and Electrolytes Electrolyte Abnormalities GI (vomiting/diarrhea) – K and Cl Stomach – H and Cl Bile/Pancreas – bicarb Hypochloremic, hypokalemic metabolic alkalosis
Fluids and Electrolytes Hyperkalemia Renal failure (missed dialysis), hemolysis Peaked T waves on EKG Management – confirm lab value (r/o lab hemolysis) –Calcium gluconate for heart (stabilizes membranes) –NaBicarb, 10U insulin, 1 amp dextrose –Kayexalate / Dialysis Hyokalemia can cause an ileus
Fluids and Electrolytes Hyponatremia SIADH, Rule out hyperglycemia (pseudohyponatremia) Water restriction, diuresis, replacment Slow Na correction (1mEq/hr) –Avoid central pontine myelinosis Hypernatremia – tx with free water
Fluids and Electrolytes Hypercalcemia Seen in hyperthyroidism, parathyroid tumors, bone metastates, renal failure –Bones, stones, moans, psychiatric overtones Tx: NS + lasix –Avoid LR (has Ca) –Avoid thiazide diuretics (retains Ca) –Calcitonin, dialysis
Fluids and Electrolytes Case #1: Resolution Dx: Hypertrophic pyloric stenosis (HPS) Metabolic abnormality: hypochloremic, hypokalemic metabolic alkalosis with paradoxical aciduria –Loss of H+ and Cl- with vomiting –Initial excretion of Na-bicarbonate in response to Cl loss –Aldosterone acts to promote K excretion for Na retention –Finally, H exchanged for Na, resulting in paradoxic aciduria Treatment: –+/- NS bolus, when UOP is demonstrated, K is added to IVF –D5 ½ NS x maintenance –Must resolve electrolyte abnormalities prior to surgery –Pyloromyotomy: laparoscopic vs. open –Advance PO intake as tolerated
Fluids and Electrolytes Take Home Points rule for calculation of MIVF rate ABC(DE) is important in many situations Bolus IVF are not the same as MIVF Action is required if a patient is unresponsive to initial resuscitation