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Fluid & Electrolytes. Parenteral Fluid Therapy. Introduction. Clinicians who care for inpatients must be able to assess the need for parenteral fluid therapy and to specify the composition of the fluid and rate of administration.
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Fluid & Electrolytes Parenteral Fluid Therapy
Introduction • Clinicians who care for inpatients must be able to assess the need for parenteral fluid therapy and to specify the composition of the fluid and rate of administration. • The goal is to normalize the intracellular & extra cellular chemical environments that optimize cell and organ function. • Fluid composition (maintenance need , deficit , and ongoing losses).
Maintenance [Fluid] • Because it is difficult to remember basal metabolic rates for various ages & sizes during childhood [relate maintenance needs to body weight]
Maintenance [Fluid] (theories) • The Surface Area method (requires a table to determine surfece area ,the patient’s height & weight). • The Basal Calorie Method (requires a table). • The Holliday-Segar System (most frequently used because of the ease of the formula).
Maintenance [Fluid] ( holliday-segar theory) • For each 100 kcal expended , approximately 50 ml of fluid is required to for skin , for respiratory tract , and basal stool losses , and 55-65 ml of fluid is required for the kidneys to excrete an ultrafiltrate of plasma at 300 mosm/l , a S.G. of 1.010 without having to conc. The urine • the sum is rounded to 100 ml of fluid/100 kcal.
Are maintenance fluid and electrolytes all that children at bed rest in the hospital need? • Fever. • Catabolic State (additional solute). • Nutrition (includes additional osmoles). • Inflammation (fluid sequestration).
In the absence of disease,should intake & output be equal, or should u.o.p. always equal half of what is taken in?
Maintenance [Electrolytes] • Insensible loss contains virtually no electrolytes. • All electrolytes loss can be considered to be urinary. • Insensible water loss increase with activity , fever [ i.e. 12% increase for each 1ْ C rise in body temperature ].
Maintenance [Electrolytes] • Pulmonary insensible water loss increase with hyperventilation , as in asthma & D.K.A. , & decrease with exposure to highly humidified atmospheres or humidified ventilator systems. • Cutaneous losses may be especially high in low birth weight & VLBW infants with a large surface area & decreased skin thickness.
Should the sodium concentration of maintenance fluids provided to adolescent and adults differ from that generally provided to infants and children?
Maintenance [Electrolytes] • Both the amount of lytes. & the amount water for maintenance needs are based on metabolic rate , not on the body weight. • The lytes.-water ratio is fixed,so the composition of maintenance fluids should remain constant [G/S 0.2% + 20 meq/l KCl]
Maintenance [Electrolytes] • Adolescents & adults frequently are provided G/S 0.45% based on a need for sodium of 3 meq/kg , when the actual need is 3 meq/100 kcal.
Maintenance [Electrolytes] • The error of calculating sodium based on weight results in a linearly increasing amount with increasing weight , when fluid needs actually decrease with advancing weight . • This results in adults generally being provided more sodium than neede for maintenance support.
Deficit [Fluid] • If signs of hypovolemia are present (tachycardia & hypotension) , a rapid infusion of fluid (bolus) is indicated . • The amount generally administrated in a single bolus is 20 ml/kg (equivalent to 2% of body weight) for infants & children & 10 ml/kg for teenagers.
Deficit [Electrolytes] • Normal saline OR ringer lactate is used when a bolus of fluid is administrated (sodium concentration is compatable to serum , so intravascular volume is bolstered without fluid shift). • The total sodium loss is approximately 80 - 100 meq/l.
Deficit [Electrolytes] • Particularly when a bolus of N/S or ringer lactate has been provided , the remaining deficit is approximated by HALF normal saline ( G/S 0.45% ). • Once u.o.p. is assured , 20 meq/l KCl is added to replacement solutions. & if hypokalemia is concered,KCl supplement can increase.
Ongoing losses [Fluid] • Include (continued diarrhea or vomiting , aspirates from a NGT attached to suction , or the polyuria of an osmotic diuresis) • can be measured directly. • Other losses (abnormal internal collections with an ileus , peritonitis or edema) which are difficult to estimate.
Ongoing Losses [electrolytes] • Gastrointestinal losses can be replaced by half N/S. • Transudates reflect the composition of the intravascular space & have the higher sodium content of N/S or ringer lactate . • Radiant losses are sodium free.
Laboratory Evaluation • Na conc. : defines the type of dehydration , reflects the relative losses of water& lytes , not of total body sodium stores. • Serum K : hyperkalemia [reflects acidosis &diminished renal function] , hypokalemia [reflects significant stool losses ; with gastric losses ass. with alkalosis (pyloric stenosis) .
Laboratory Evaluation • Serum HCO3 : detecting metabolic acidosis or alkalosis. • BUN & serum creatinine : elevated in severe dehydration because of decreased glomerular filtration rate.
Parenteral Rehydration Without a Calculator of a Moderately Dehydrated Infant • An initial bolus of 20 ml/kg is provided to restore normal hemodynamics. • 20 ml/kg represents 2% of body weight . • If the initial deficit was estimated to be 10% , the reminder after the bolus is 8%.
Hypertonic Dehydration • Fluids is drawn into the intravascular space from the intracellular space . • The rapid administration of fluid , as recommended for isotonic states , can create fluid shifts that result in cerebral edema & intracranial bleedings.
Hypertonic Dehydration • The calculated deficit fluid and electrolyte needs are added to 2 days [48 hrs.] worth of maintenance fluid and electrolyte requirements ; the sum is divided by 48 and administrated at constant hourly rate for 48 hours.
Hypotonic Dehydration • The extra sodium loss can be calculated from the formula: [Na deficit =desired Na –actual Na ×0.6 × wt] • If seizures developed , intravenous administration of a 3% solution of NaCl at a rate of 1 ml/minute to a max. of 12 ml/kg. • Na correction must not exceed an increase of serum Na of 10 mEq/24 hrs.
Monitoring the Effectiveness of Parenteral Fluid & Electrolyte Therapy.
