FLUID AND ELECTROLYTE MANAGEMENT IN CHILDREN BY DR G I McGIL UGWU CONSULTANT PAEDIATRIC NEPHROLOGIST DELSUTH
OUTLINE OF PRESENTATION • PRE-TEST FOR FLUID THERAPY • LEARNING OBJECTIVE • INTRODUCTION • NORMAL BODY FLUID AND ELECTROLYTES • MAINTENANCE THERAPY • REPLACEMENT/DEFICIT THERAPY • CONCLUSION • TAKE HOME POINTS • REFERENCES
PRE-TEST FOR FLUID THERAPY • In the fetus and newborn, • Extracellular fluid (ECF) is smaller than Intracellular (ICF) • Postnatal diuresis causes decrease in the ICF • Both NA+ and water are predorminantly lost during postnatal diuresis • Premature babies have higher total body water/weight than term neonates.
Concerning ECF and ICF, • By one year of age, the amount of ECF and ICF are largely equal • In adulthood, ECF constitutes 10-20% while ICF constitutes 20-25% • Females have higher ICF than males • The increase in ICF is largely due to cell growth in an individual.
Concerning ECF and plasma, • plasma is part of ICF • plasma volume is greater than ECFvolume • plasma water is about 10% of the body weight • blood volume is about 8% of the body weight 4. Intestitial fluid A Is part of ECF BIs part of ICF CConstitutes about 13% of the total body weight D Can be increased by acsitis and pleural effusion
Based on the caloric expenditure model, each calorie expended requires provision of water in the ratio of: • 2ml/1cal/day at rest • 1ml/1cal/day at rest • 1ml/2cal/day at rest • 2ml/2cal/ady at rest
Also according to the caloric requirement, the ranges of Na+ nd K+ required is • 3mEq of Na+/100ml of water and 2mEqK+/100ml of water • 4mEq of Na+/100ml of water and 4mEq of K+/100ml of water • 1mEq of Na+/100ml of water and 1mEq of K+/100ml of water • 2.5mEq of Na+/100ml of water and 2.5mEq/100ml of water
Concerning plasma and intestitial fluid, • plasma is the same as intravascular fliud • hydrostatic pressue drives fliud int the plasma from the intestitial fluid • Oncotic pressure drives fluid from the plasma to the intestitial fluid • Oncotic pressure retains fluid in the intestitial fluid
In the composition of the ECFand ICF • Na and Cl are the predominant cation and inion in the ECF • K. Proteins and phosphates are the predominant cation and inion in the ECF • The amount of K in the ICF is about 10x that in the ECF • ICF fluid is governed by the balance of hydrostatic and oncotic pressures
Concerning Maintenance fluid • This is the amount of fluid and electrolytes rquired required for dly excretion of waste products • There ia a wide variation in the daily intake of electrolytes and water in childen • 60% of total excreted water is lost in the urine, 35% through the lungs and skin and 5% in the stool • 40% is lost in the urine 35% thfough the lungs and skin and 25% in the stool
A child of 4yrs who weighs about 16kg will require about • 1.2litres of fluid/day • 1.5litres of fluid/day • 1.3litres of fluid/day • 2litres of fluid./day • The gaols of maintenance fluid are • prevent dehydration • prevent electrolyte imbalance • prevent ketoacidosis • prevents protein degradation
Maintenance fluid should contain glucose so as to • minimize carbohydrate metabolism • 5g of glucose/100ml of fluid gives about 10Cal of energy • 5g of glucose /100ml gives about 17Cal/l • 5g of glucose/100ml represents about 20% of the daily calorie requrement
Concerning maintenance fluid again • Children can be maintained on maintenance fluid for upto two weeks • 10% dextrose is enough for the maintenance in the 1 day old newborn • The recommended fluid for a 6 and a ½ yr old child is 4.4% in 1/5 saline • The recommended for the 6 and a ½ old child is ½ saline in 5% dextrose
Maintenance fluid requirement in a newborn is • 60ml/kg/day on day one • followed by 10ml/day increament • followed by 20ml/day increament • followed by 30ml/day increament
Maintenance fluid requirement in a newborn is • 60ml/kg/day on day one • followed by 10ml/day increament • followed by 20ml/day increament • followed by 30ml/day increament • Deficit fluid • is the fluid lost over a time • can be expressed as a % of the body weight • In GI losses, K and HCO3 are lost predominantly through diarrhoea • the most lost solute diarrhoea is Na
In assessing dehydration in a child less than 2yrs • mild dehydration = 3% body weight Moderate dehydartion= 5% body weight Severe dehydration = 8% body weight • mild dehydration=5% body weight Moderate dehydration= 7% body weight Severe dehydration= 10% body weight • deficit is replaced is replaced over 1-6hours • deficit is replaced over 12hours
Dehydration • can be isonatremic, hyponatremic and hypernatremic • The amount of Na given is 0.5Meq/L/Hr or 12mEq/L /day • in correcting dehydration, hypernatremic dehydration it is advisable to use Na free solutions • hypernatremic dehydration is corrected over 24hours
In correcting shock • 0.9% saline in 5% dextrose is the fluid of choice • fluid is given over 30mins-1hr • the amount of fluid is 40ml/kg • the amount given is subtracted from the calculed fluid loss and given over the remaing hours of correction
Concerning On-going loss • fluid is replaced ml for ml • about 10ml/kg/loose stool is adequate replacement fliud • the choice choice of fluid should be appropriately the maintenance fluid for the chid’s age/weight • normal can with or without K can be used • On-going loss is assessed • every 4hrs • every 8hrs • every 1hr • every 12hrs
The following considerations should be borne in mind • hyponatremia may develop anytime during the course of therapy • the electrlytes should be checked every 24hours • in elctrolyte values are abnormal they should be checked every 8hours • a reduced urine output always indicates renal failure
Oral rehydration therapy • is prefered for uncomplicated moderate dehydration • for mild dehydration, 50ml/kg over 4hours is adequate • 90ml/kg for moderate dehydration over 4hours is adequate • both mild and moderate dehydration are foolowed with 100ml/kg/day
Feeding must be continued while ORT is on • ORT can be used to correct severe dehydration • The current WHO packs contain less solutes than the previous packs • ORS is contraindicated in a child with vomiting
INTRODUCTION • Water is the most plentiful constituent of the human body • Total body water varies from age to age, being highest in the youngest, with the preterm baby having the highest. • TBW is divided into ICF and ECF. • In the fetus and the newborn, ECF is larger than the ICF • The normal postnatal diuresis causes a decrease in the ICF
Coupled with the increse in ICF due to cell growth, by one yr of life, the ratio of ICF to ECF almost equals that in adulthood where ECF constitutes 20-25% of the body weight and ICF 30-40%, close to twice the ECF volume. • With puberty, the increased muscle mass in males makes them to have higher ICF than females • There is however no significant diff in the postpubertal ECF of males and females. • The ECF is further divided into plasma water and the intestitial water. The plasma water is 5% of the body weight and with a hematrocit of 40%, blood volume is usually 8% of the body weight. This is however higher in the newborn and infact it is 10% in preterms
The volume of plasma water is altered by pathological conditions such as dehydration, anaemia, plycythaemia, haert failure, abnormal plasma osmolality and hypoalbuminaemia. • The intestitial fluid, normaly 13% of body weight, can increase drmatically with edema, such as heart failure, protein losing enteropathy, liver failure, nephrotic syndrome and sepsis. • An increase in interstitial fluid also occurs in ascitis and pleural effusion.
There is always a delicate equilibrum betwee the intravascular fluid (plasma) and the interstitial fluid, which is governed by the hydrstatic and oncotic pressure. • While the hydrostatic pressure drives fluid from the intravascular space to the interstitial fluid, oncotic pressure prevents fluid from moving from the intravascular compactment to the interstitium • The composition of the solutes in the ICF and ECF are diff. • Na and Cl are dorminant cation and anion in the ECF respectively and are much lower in the ICF.
K is the most abundant cation in the ICF and its ICF content is about 30% that in the ECF. Proteins, organic anions and pphosphate are the most plentifull anions in the ICF • Based on the caloric expenditure model, each calorie expended requires provision of water in theratio of 1ml/cal metabolized/day at rest. • Also according to the caloric expenditure model, Na and K ranges/100ml of maintenance fliud is 3mEq/100ml and 2mEq/100ml respectively.
NORMAL ELECTROLYTES IN CHILDREN The concentration of the major cations and anions in the intracellular space and the plasma, expressed in mEq/L. • Electrolyte composition
MAINTENANCE THERAPY • Can be given orally or intravenously for patients who cannot tolerate orally • This is the amount of fluid electrolytes required for the dialy metabolism and also corrects the fluid necessary for obligate excretion of wiaste products esp solutes (see above) • Usually there is a wide variation in the daily intake of water and electrolyes.
Only exceptions are children who receive fixed amount of fluids such as in SIADH secretion, also children who receive f;luids via N/G tube, or as intravenous total parentheral nutrition • Maintenance fluids are most commonly necessary in preoperative and postoperative surgical patients • There are however nonsurgical conditions that require maintenance fluid calculation • Most important thing is to recognize when to commence maintenance therapy
The goals of maintenance fluids are • Prevent dehydration • Prevent electrolyte disorders • Prevent ketoacidosis • Prevent protein degradation
Maintenance are generally composed of a solution of water, glucose, Na+, K+. Other electrolytes are such as Ca2=, PO4- etc • Addition of glucose of a minimum of 5gm/100ml (5%dextrose, to the fluids provides about 17kcal/100 which is about 20% of the daily requirement but is enough tominimize tissue catabolism to the point that protein stores are ‘spared’ from providing substrate for gluconeogenesis. • Ketosis from fat metabolism is also prevented.(remem our goals)
However patients will lose weight on this regimen. That is why patients are started on total parentheral nutrition just after a few days on maintenace fluids. • Also maintenance fluids lack essential requirements such as proteins, fat, vitamins and minerals. • The maintenance values are calculated as a guide based on the body weght of the child.
Body weight method for calculating maintenance is as follows: Body Weigth Fluid per day 0-10kg 100ml/kg 11-20kg 1, 000ml + 50ml/kg each kg >10kg >20kg 1, 500ml + 20ml/kg for each kg >20kg
As a guide of fluid loss from the body • Urine accounts for 60% • Insensible loss from skin and lungs accounts for 35% • Stool accounts for 5% • These are however very variable as it also depends on certain extrenous factors , such as humidity,temperature hyperventilation drugs etc
Solution available maintenace therapy (the commecially available fluids): Solution Composition • Normal saline(0.9%NaCl) 153mEq Na+/L • One-half saline(0.45%NaCl) 77mEqNa+/L • One-third saline (0.33%NaCl) 57mEqNa+/L • One-quarter saline(0.2%NaCl) 38.5mEq Na+/L • One-fifth saline(0.18%NaCl) 30.8mEqNa+/L
5gm of glucose/100ml (5% dextrose) to any of the solution provides a calorie of about 20.5Kcal/100ml. • One-fifth saline normally comes with 4.3% dextrose (17.6Kcal/100ml) • Ringers lactate 130mEqNa+/L • (Also contains 4mEqK+/L, 109mEq/L Cl-, 28mEqHCO3-/L and 3mg/dl of calcium • Hartman’s solution
Choice of fluid • (1) First-Line choice for children above 20-25kg is 0.45% saline (1/2 saline) with 5%dextrose • Consider adding KCl, up to 40mmol/L once plasma concentration is known • (2) Second-Line choice • 0.9% saline(normal saline) in 5% dextrose
Children more than one month but 20-25kg • ( 1)1/4saline in 5% dextrose. They do best with this because of thgeir high water needs /Kg • Second-Line choice • 1/5th saline in 4.3% dextrose • (3) Third-Line ½ saline ff normal saline , each in 5% dextrose saline
Summary as follows: Weight ml/kg/24hrs ml/kg/hour 10kg or less 100 4 Additionally for each kg >10 upto 20kg 50 2 Additional ly for each kg >20kg thereafter 20 1 Maximum maintenance 2000ml per 24hrs for girls 2500ml per 24hrs for boys
Neonates ,1month and <, (choice of fluid is usually 10% dextrose. K+ is usually added on day 2 especially if feeding has commenced so as to make available K+ for the newly forming cells as it is the dorminant cation intracellularly (dose 2mEq/kg/day). Also add Na+ from day 2 at 3mEq/L
Choice of fluid/day Day Amount 1 60ml/kg 2 90ml/kg 3 120ml/kg 4 and > 150ml/kg That is 30ml/kg increament /day till day4
The reason for the daily increament sep in sick term babies is that the GFRonly improves as from day 3, and in preterms, respiratory outcome are likely to be worse if Na+ is added before naturesis which starts as from birth, and weight loss has started. Do not automatically add electrolytes on day 2; check the serum electrolytes first.
NOTE: Above regimen for the neonates may be altered: • (i) Gestation- very premature babies have very high insensible loss and may require higher amount of fluid • Incubator humidity is very important in these babies • (ii) Clinical state-eg edema (reduce fluids or increase more slowly), dehydratiom (may require more fluids) • Perinatal asphyxia- may need to reduce ml/kg/day
Weight- dly weighing are required in NICU babies. Beware of increasing the fluid or consider reduction in a baby in NICU if there is weight gain in the first one week of life. • Serum sodium- the best guide to hydration in the first few days of life, especially in preterm, hypernatremia; hypernatremia indicates dehydration
RESTRIC FLUID TO 2/3RD MAINTENANCE FOR ALL CHILDREN IF BRONCHIOLITIS/PEUMONIA/MENINGITIS/ENCEPHALITIS
REPLACEMENT THERAPY • Broadly divided in two major parts: Correcting or replacing deficit, and replacing On- going loss • Deficit Therapy • GI tract is a potential losss of considerale amount of water and electrolytes and so lead to intravascular contraction and electrolyte imbalance. • GI losses are often associated with loss of K+ leading to hypokalemia. The stool also contains a heavy amount of HCO3-, so diarrhoea leads to metabolic acidosis
In the absence of vomiting, diarrhoea or NG drainage, GI losses are usually minimal, but when ever losses occur, its usually considered eccessive and increase in the water requirement is equal to the volume lost • Because GI water and electrlyte losses can be precisely measured, it is possible to use an appropriate replacement fluid. • Deficits are usually replaced within1-6hrs, depending on the rate of loss. • Diarrhoea is a common cause of fluid loss in children and lead to dehydration • The first step in caring for a child with dehydration is to acceess the degree of dehydration clinically.
Clinical Evaluation of Dehydration Mild Dehydration (3-5%): normal or increased pulse, decrease urine output, thirsty, normal physical examination.(5% for infants or<20kg and 3% for older children or >20kg Noderate Dehydration (7-10%): tachycardia, little or no urine output, irritable/lethargic, sunken eyes and fontanel, decreased tears, dry muccuos membranes, mild tenting of the skin, delayed capillary refill, cool and pale. Severe Dehydration (10-15%): rapid and weak pulse, decreased blood pressure, no urine output, very sunken eyes and fontanel, no tears, parched muccuos membranes, tenting of the skin, very delayed capillary refill, cold and mottled.
These are however estimates and infact all physical characteristics used to describe differing degrees of dehydration are really measures of the integrity or relative degree of expansion of the extracellulr fluid space. • Water deficit can be determined by subtracting the patient’s current weight from his/her weight just before dehydration.