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PEDIATRIC PERIOPERATIVE FLUID THERAPY

PEDIATRIC PERIOPERATIVE FLUID THERAPY. Evangeline Ko-Villa, MD, DPBA Clinical Associate Professor UP-PGH Department of Anesthesiology. Objectives. Review relevant physiological considerations in the pediatric population Review how to evaluate intravascular volume

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PEDIATRIC PERIOPERATIVE FLUID THERAPY

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  1. PEDIATRICPERIOPERATIVE FLUID THERAPY Evangeline Ko-Villa, MD, DPBA Clinical Associate Professor UP-PGH Department of Anesthesiology

  2. Objectives • Review relevant physiological considerations in the pediatric population • Review how to evaluate intravascular volume • Discuss the different types of IV fluids • Discuss regimens for perioperative fluid and blood replacement therapy

  3. Body Fluid Compartments TOTAL BODY WATER (60%) EXTRACELLULAR FLUID (1/3 TBW) INTRACELLULAR FLUID (2/3 TBW) INTERSTITIAL FLUID (3/4 ECF) PLASMA (1/4 ECF) TRANSCELLULAR FLUID Accurate for children 6 months of age and older

  4. Body Fluid Compartments B o d y C o m p o s i t i o n (%)

  5. Body Fluid Compartments • ICF – 2/3 TBW • The proportion of ECF is much greater to that of the ICF in the preterm infants. • Upon birth, there is gradual shift from the ECF to the ICF

  6. Blood Volumes • Preterm 100 ml/kg • Term 90 ml/kg • Infant 80 ml/kg • School Age 75 ml/kg • Adult 70 ml/kg Source: A Practice of Anesthesia for Infants and Children by Cote 4th ed

  7. Features of a fetal kidney: low RBF, low GFR Reasons behind these features: 1. low systemic arterial pressure 2. high renal vascular resistance 3. low permeability of glomerular capillaries 4. small size and number of glomeruli Renal System

  8. Renal System • 1st 3 -4 days of life: circulatory changes ↑ RBF and ↑GFR • 1 month of age: kidneys are 60% mature. This is sufficient to handle almost any contingency. • 2 yrs: complete maturation of renal function

  9. Renal System Immature tubular cells cannot completely reabsorb Na+ under the stimulus of aldosterone ⇓ Neonate continue to excrete Na+ in the urine despite the presence of a severe Na+ defect Implication: “obligate sodium loser”

  10. Renal System: Concentrating Capacity • Limited in the neonate • Max urine osmolality is only ½ of adult levels (700-800 meq/L vs 1300 – 1400 meq/L) • Contributory factors: low circulating ADH levels ↓ renal responsiveness to ADH ↓ tonicity in the medulary insterstitium Implication: Increases free water losses during excretion of a solute loss

  11. Renal System: Diluting Capacity • A water-loaded infant can excrete dilute urine with osmolality as low as 50 mOsm/kg. • The diluting capacity becomes mature by 3 to 5 weeks of postnatal life.

  12. Cardiovascular System relatively low contractile mass/gram of cardiac tissue ⇓ limited ability to ↑ myocardial contractility ↓ in ventricular compliance ⇓ extremely limited ability to ↑ stroke volume Implication: need to ↑HR to ↑cardiac output

  13. Cardiovascular System • cardiac Ca2+ stores are ↓ due to immaturity of sacroplasmic reticulum ⇒ dependent of exogenous Ca2+ Implication: Neonatal heart is vulnerable to myocardial dysfunction in the presence of citrate-induced hypocalcemia

  14. Hematologic System • Neonates have higher baseline Hb values (14 – 20 g/dl) • They have a higher percentage of fetal Hb • At birth, vitamin K dependent factors are at 20 – 60% of adult levels

  15. Neonatal Fluid Management • At birth: ECF is greater than ICF • A few days after birth: ECF contraction and wt loss due to ANP induced diuresis 2° to ↑ pulmonary blood flow & stretch of left atrial receptors • This is followed by ↑ water and Na requirements to match those of the growing infant Implication: Fluids should be restricted until the postnatal weight loss has occurred.

  16. Neonatal Fluid Management • If a baby requires IV fluids from birth, they shld be given 10% dextrose in the following volumes Day 1 60 ml/kg/day Day 4 150 Day 2 90 Day 5 150 Day 3 120 • Na+ 3 mmol/kg/day & K+ 2 mmol/kg/day shld be added after the postnatal diuresis or if Na+ drops • A premature neonate may require an additional 30 ml/kg/day and additional Na+

  17. Neonatal Fluid Management • Fluid requirements are titrated to the: patient’s changing weight urine output serum sodium

  18. Evaluation of Intravascular Volume • Physical Examination • Laboratory Exam • Hemodynamic Measurements

  19. Clinical and laboratory assessment of the severity of dehydration in children

  20. Clinical and laboratory assessment of the severity of dehydration in children

  21. Choice of fluids • Crystalloids • Colloids • Blood products • Whole blood • pRBC • FFP • Platelets

  22. Crystalloids • sterile aqueous solutions which may contain glucose, various electrolytes, organic salts and nonionic compounds • rapidly equilibrates with ECF

  23. Composition of Crystalloids

  24. Crystalloid Solutions • 2 ways of classification a. based on use b. based on tonicity

  25. Crystalloid Solutions: Based on Use • Maintenance-type solutions • water loss • hypotonic solutions • Replacement-type solutions • water and electrolyte losses • isotonic electrolyte solutions • Fluids for special purposes

  26. Crystalloid Solutions: Based on Tonicity • Balanced salt solutions • electrolyte composition similar to ECF • Hypotonic with respect to Na

  27. Crystalloid Solutions: Based on Tonicity • Normal Saline • isotonic (6.0) and isoosmotic (308) • contains no buffers or electrolytes • large volume: dilutional hyperchloremic acidosis

  28. Crystalloid Solutions: Based on Tonicity • Hypertonic Salt Solutions • Na concn range from 250 – 1200 meq/L • Rapid volume expansion after infusion of small amounts (e.g. 250 mL) • t½: similar to isotonic saline • may cause hemolysis at point of injection

  29. Glucose containing solutions • Glucose—given intravenously—is rapidly metabolized, leaving free water behind • distributes across all compartments rapidly

  30. Crystalloids • Advantages • Inexpensive • Very low incidence of adverse reactions • Disadvantages • Short lived hemodynamic improvement (intravascular t½: 20 – 30 mins.) • Peripheral/pulmonary edema

  31. Final Word on Crystalloids • What is the best crystalloid? Isotonic crystalloids are preferred over hypotonic crystalloids

  32. Do we have to routinely give glucose containing solutions? • Routine dextrose administration is no longer advised for otherwise healthy children receiving anesthesia. • There is a growing consensus to selectively administer intraoperative dextrose only in pts at greatest risk for hypoglycemia and in such situations to consider the use of fluids with lower dextrose concentrations (1% or 2.5%)

  33. Colloids • contains high MW substances - proteins, large glucose polymers • maintain plasma oncotic pressure • intravascular t½: 3 – 6 hrs.

  34. Colloids: Classification • Natural Protein Colloid • Albumin or Plasma Protein fraction • Synthetic Protein Colloids • Hetastarch • Dextrans • Gelatins

  35. Albumin • Colloid “gold standard” • Derived from human pool plasma → heated to 60 C for 10 hrs → ultrafiltration • MW: 69 kDa • Available as: 5% and 25% • Albumin 5% osmotically equivalent to an equal volume of plasma

  36. Albumin • Use with caution in patients with increased intravascular permeability (e.g. critically ill, sepsis, trauma, burn)

  37. Albumin: Side Effect • Rare • Might still have weak anticoagulation effects through platelet aggregation inhibition or heparin-like effects on antithrombin III • These effects are thought to be clinically insignificant if volume replacement with albumin is kept below 25% of the patient’s blood volume.

  38. Final word on Albumin Data supporting the continued use of albumin for general fluid resuscitation in children are lacking and in children with traumatic brain injury, it may actually be harmful. Its utility may exist in specific subgroups such as neonates and patients undergoing cardiac surgery.

  39. Hetastarch • modified natural polysaccharides Amylopectin Hetastarch

  40. Hetastarch Described in terms of: • Concentration • Average mean MW • Molar substitution • C2:C6 ratio

  41. Hetastarch: Concentration • Definition – grams in 100 ml • Available as: 3%, 6% and 10%

  42. Hetastarch: average mean MW • Low - <70 kDa • Medium - 130 – 270 kDa • High - >450 kDa higher MW ⇒ longer volume effect ⇒ greater side effect

  43. Hetastarch: Molar Substitution Definition: CH3CH2OH : glucose units • Low (0.4 – 0.5) • High (0.62 – 0.7) higher MS ⇒ longer volume effect ⇒ greater side effect

  44. Hetastarch: C2:C6 ratio • Hydroxyethyl group attached at C2 hinder breakdown • Higher ratio of C2:C6⇒ in slower enzymatic degradation and prolonged action without increasing side effects.

  45. HES Solutions Properties and Availability

  46. HES: Unwanted Side Effects • Hypocoagulable effect - seems to interfere with the function of vWF, factor VIII and platelets • Renal toxicity - induce renal tubular cell swelling & create hyperviscous urine • Pruritus - accumulation on HES molecules under the skin

  47. Voluven • Pediatric dose: mean dose of 16 + 9 ml/kg • Contraindication: known hypersensitivity to HES CHF or pulmonary edema renal failure with oliguria not related to hypovolemia pts receiving dialysis treatment severe hyperNa+ or hyperCl+ intracranial bleeding

  48. Final word on Hetastarch • There are still limited clinical trials in children. • It appears that the new generation HES are much safer in comparison to the older generation HES.

  49. Gelatins • polypeptides produced by degradation of bovine collagen • ave MW: 30,000 – 35,000 kDa • requires repeated infusions • no dose limitation

  50. Gelofusine: Pharmaceuticals Characteristics

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