BNF for Children 2011-2012

BNFC 2011–2012 9.2.2 Parenteral preparations for fluid & electrolyte imbalance 461Fluid requirements for children over 1month:BodyweightUnder10 kg24-hour fluid requirement100 mL/kg10–20 kg 100 mL/kg for the first 10 kg+ 50 mL/kg for each 1 kg body-weight over10 kgOver 20 kg100 mL/kg for the first 10 kg+ 50 mL/kg for each 1 kg body-weightbetween 10–20 kg+ 20 mL/kg for each 1 kg body-weight over20 kg(max. 2 litres in females, 2.5 litres in males)Important The baseline fluid requirements shown in thetable above should be adjusted to take account of factorsthat reduce water loss (e.g. increased antidiuretic hormone,renal failure, hypothermia, and high ambient humidity) orincrease water loss (e.g. pyrexia or burns).Caution During parenteral hydration, fluids and electrolytesshould be monitored closely and any disturbancecorrected by slow infusion of an appropriatesolution. The volume of fluid infused should take intoaccount the possibility of reduced fluid loss owing toincreased antidiuretic hormone and factors such asrenal failure, hypothermia, and high humidity.Dilutional hyponatraemia is a rare but potentially fatalrisk of parenteral hydration. It may be caused by inappropriateuse of hypotonic fluids such as sodium chloride0.18% and glucose 4% intravenous infusion, especiallyin the postoperative period when antidiuretichormone secretion is increased. Dilutional hyponatraemiais characterized by a rapid fall in plasma-sodiumconcentration leading to cerebral oedema and seizures;any child with severe hyponatraemia or rapidly changingplasma-sodium concentration should be referredurgently to a paediatric high dependency facility.Safe practiceSodium chloride 0.18% and glucose 4% intravenousinfusion fluid should not generally be used for fluidreplacement in children because of the risk of hyponatraemia;availability of this infusion should berestricted to critical care and specialist wards, suchas renal, liver, and cardiac units. Local guidelines onintravenous fluids should be consulted.Replacement therapy: initial intravenous replacementfluid is generally required if the child is over 10%dehydrated, or if 5–10% dehydrated and oral or enteralrehydration is not tolerated or possible. Oral rehydrationis adequate, if tolerated, in the majority of those lessthan 10% dehydrated. Subsequent fluid and electrolyterequirements are determined by clinical assessment offluid balance.Neonates Neonates lose water through the skin andnose, particularly if preterm or if the skin is damaged.The basic fluid requirement for a term baby in averageambient humidity is 40–60 mL/kg/day plus urinarylosses. Preterm babies have very high transepidermallosses particularly in the first few days of life; they mayneed more fluid replacement than full term babies andup to 180 mL/kg/day may be required. Local guidelinesfor fluid management in the neonatal period should beconsulted.Intravenous sodiumIntravenous sodium chloride in isotonic (0.9%) solutionprovides the most important extracellular ions innear physiological concentrations and is indicated insodium depletion. It may be given for initial treatment ofacute fluid loss and to replace ongoing gastro-intestinallosses from the upper gastro-intestinal tract. Intravenoussodium chloride is commonly given as a componentof maintenance and replacement therapy, usuallyin combination with other electrolytes and glucose,see notes above. Sodium chloride solutions should beused cautiously in renal insufficiency, cardiac failure,cardio-respiratory diseases, hepatic cirrhosis and inchildren receiving glucocorticoids. Hyponatraemiawith serious consequences may occur if maintenanceand replacement fluids do not meet sodium requirements(see Caution, dilutional hyponatraemia, above).Chronic hyponatraemia should ideally be corrected byfluid restriction. However, if sodium chloride is required,the deficit should be corrected slowly to avoid the risk ofosmotic demyelination syndrome; the rise in plasmasodiumconcentration should be no more than10 mmol/litre in 24 hours.Sodium chloride and glucose solutions are indicatedwhen there is combined water and sodium depletion.A1:1 mixture of isotonic sodium chloride and 5% glucoseallows some of the water (free of sodium) to enter bodycells which suffer most from dehydration while thesodium salt with a volume of water determined by thenormal plasma Na + remains extracellular. Maintenancefluid should accurately reflect daily requirements andclose monitoring is required to avoid fluid and electrolyteimbalance. Illness or injury increase the secretion ofanti-diuretic hormone and therefore the ability toexcrete excess water may be impaired. Injudicious useof hypotonic solutions such as sodium chloride 0.18%and glucose 4% may also cause dilutional hyponatraemiaespecially in children (see Caution on dilutionalhyponatraemia, above); if necessary, guidance should besought from a clinician experienced in the managementof fluid and electrolytes.Combined sodium, potassium, chloride, and waterdepletion may occur, for example, with severe diarrhoeaor persistent vomiting; replacement is carried out withsodium chloride intravenous infusion 0.9% and glucoseintravenous infusion 5% with potassium as appropriate.Compound sodium lactate (Hartmann’s solution) canbe used instead of isotonic sodium chloride solutionduring or after surgery, or in the initial management ofthe injured or wounded.Neonates The sodium requirement for most healthyneonates is 3 mmol/kg daily. Preterm neonates, particularlybelow 30 weeks gestation, may require up to6 mmol/kg daily. Hyponatraemia may be caused byexcessive renal loss of sodium; it may also be dilutionaland restriction of fluid intake may be appropriate. Sodiumsupplementation is likely to be required if the serumsodium concentration is significantly reduced.Hypernatraemia may also occur, most often due todehydration (e.g. breast milk insufficiency). Severe9 Nutrition and blood