Pediatric Fluids Lesson 12 PDF

- Infant =1-12 months - Have larger TBW and ECF - Child = 1-12 years - Pharmacologic principles - Less fat and muscle compared to adults - Fat and muscle increase with age - Have greater body water content than adults - The younger the child is, the greater...

- Infant =1-12 months - Have larger TBW and ECF - Child = 1-12 years - Pharmacologic principles - Less fat and muscle compared to adults - Fat and muscle increase with age - Have greater body water content than adults - The younger the child is, the greater the % of total body water - The older the kid, the less insensible water loss - The so what... water soluble drugs will have a greater Vd in children - Due to dilutional effect, a lower plasma concentrations occur rapidly after administration of water-soluble drugs - A larger drug loading dose may be required to achieve the desired concentration - Higher plasma concentrations of lipid soluble drugs due to decreased fat and muscle volume - Estimating blood volume - Preterm 90-100 mL/kg - Newborn 80-90 mL/kg - 3 mo-2years 80 mL/kg - 2+ years 80 mL/kg - Kidney - First year RBF and GFR are half of adult values - Diminished ability to concentrate urine -- increases free water loss - Preterm infant has increased excretion of Na and elevated serum creatine - Liver - Immature liver function - Hepatic enzyme metabolism and HBF reduced - Higher free drug concentration of highly protein bound drugs - Increased drug eliminations half-lives i.e. reduced drug elimination - Advantages of limited NPO - Less cranky kids - Some evidence of decreased HTN and need for glucose containing solutions - pH gastric volume -- no difference noted with clear liquids - gastric emptying for clear liquids is 10-20 mins and for solids is 77-277 mins (wider range) - Routine preop fluids not routinely done when children are expected to eat and drink after the procedure - Fluids are indicated if concurrent illness, poor nutritional states, hyperalimentation, endocrine/metabolic abnormalities, longer surgical procedures - Pyloromyotomy is a medical emergency, not a surgical one so there is time to optimize pt with fluids - Review Poiseuille's law - Fluid choice = isotonic fluids for surgical loss, deficits, and third spacing - Glucose containing solutions - Hypoglycemia isn't often seen in healthy patients -- surgical stress induces hyperglycemia - Give as a secondary IV on a rate-controlled pump - Glucose above 45 to prevent neurologic injury - Glucose containing solutions may be indicated for at risk populations during maintenance e.g. debilitated infants, small for age, cardiac surgery, premature infants because they've had less time to store glycogen in the liver - Neonate - Particularly susceptible to dehydration and fluid overload - Limited ability to handle Na - Glycemic issues - Fluid replacement - 4/2/1 rule - If \>20kg, add 40 to their weight for hourly maintenance - complete replacement is frequently unnecessary - remember factors that increase fluid requirements e.g. fever, prematurity, decreased renal concentrating ability - Replace fluids the same way we do in adults -- first half in first hour, ¼ in second hour, ¼ in third hour - Blood loss - Replace 1:1 with blood or colloid - Replace 1:3 with crystalloid - Third spacing = capillary leak and surgical trauma causing extravasation of isotonic, protein-containing fluid into nonfunctional compartments - Virtual loss = anesthetic-induced relaxation of sympathetic tone produces vasodilation and relative hypovolemia - Neonate - Insensible water losses are several times greater because there are transepidermal water loss - Exposed neonates (GI exposed) have more evaporative losses - Greater loss via respiration - Premies have low plasma osmotic pressure and protein so even mild fluid overload can result in edema and CHF - Tools for fluids = warm fluids, bubble filter, blood set-up - Temperature and ventilatory effects - Acute hypercarbia is compensated for by loss of bicarb and Cl ions and water from the cells to the interstitum shrinks ICF and increased ECF - Hypocarbia and hypothermia shift fluid water, bicarb, and Cl into cells - Assessing IV volume - Is HR persistently high or does it vary with stimulation - Is pulse pressure narrow? - Narrowed pulse pressure indicates reduced stroke volume (dehydration is the biggest culprit in kiddos!) - Narrow = pulse pressure less than 25% of SBP - Is the BP low? Does it vary with PPV? - Fluid challenge = bolus 10-20 mL/kg - Delivery of cold, dry anesthetic gases via ETT bypasses normal anatomical humidification and increases the fluid loss from the respiratory tract - Opioids increase the release of ADH - ADH stimulates release of aldosterone to conserve water from the renal reabsorption of sodium and excretion of potassium