Parenteral fluid therapy is the essential component of critical child care, required not only to correct dehydration but also to provide maintenance fluid!
Electrolyte requirements in children who cannot be given oral fluids due to critical sickness, surgery, persistent vomiting or any other reason.
PRINCIPLES OF Parenteral fluid therapy
Some general principles for parenteral fluid therapy are as follows, while therapy in specific circumstances is discussed later.
Indications: Parenteral fluid therapy is mainly indicated in children with —
a) Severe dehydration, hypotension or shock, when immediate volume replacement is life-saving;
b) Persistent vomiting, with poor tolerance to oral feeds.
c) Critical medical/surgical illnesses e.g. coma, status epilepticus, severe respiratory distress etc. when oral feeding is either not possible, or contraindicated, or carries high risk of aspiration.
d) Systemic disorders e.g. renal failure or CCF that require fine-tuning of fluid intake.
Routes: Parenteral fluid therapy requires secure IV access with a peripheral venous line. In emergency, intra osseous infusion may be used temporarily for rapid fluid correction till IV access is secured.
Parenteral fluid therapy requirements of each child vary according to their age, body weight, presence/severity of dehydration and primary disease, though approximate requirements may be calculated as sum-total of following —
a) Maintenance requirements, essential for basal metabolism as well as to replenish normal Parenteral fluid therapy losses via urine, stools and insensible means (lungs and skin). Though dependent on metabolic rate (1 ml water for each caloric expenditure), maintenance fluid & electrolyte requirements may be practically calculated by actual body weight.
Calculated requirements need to be increased by 20-30% in conditions with higher insensible losses e.g. fever, hyperventilation, warmer care etc.; and decreased by 20-30% in conditions with oliguria e.g SIADH in comatose children or lower insensible losses e.g. hypothermia. Maintenance requirements need to be severely curtailed in renal failure.
b) Deficit requirements depend on the severity of dehydration as well as its type (iso-/hypo-/hypernatremic). Gives fluid and electrolyte requirements in dehydration of variable severity. (Electrolyte requirements have been calculated assuming 60:40 Parenteral fluid therapy losses from ECF and ICF, as common in isotonic dehydration).
* In Isonatremic dehydration, assuming 60:40 loss from ECF & hDF respectively.
c) Concomitant Parenteral fluid therapy and electrolyte losses in stools, gastric aspirate etc. need periodic assessment and replacement with suitable fluids. Electrolyte requirements for this replacement depend on composition of body fluid/s, which are being lost.
Choice of Parenteral fluid therapy depends on the estimated electrolyte requirements, need for nutrition (dextrose vs non-dextrose fluids) and primary disease. Various IV fluids with different electrolyte/dextrose concentrations are available commercially or can be prepared in hospital pharmacy under strict aseptic precautions.
• Considering normal requirements, N/5 saline in 5% Dextrose, with 10 ml/L of potassium chloride is preferred IV Parenteral fluid therapy for maintenance purpose, which provides – 30 meq Sodium, 20 meq potassium and 40 gm of glucose per liter.
• Choice of Parenteral fluid therapy for deficit correction varies according to the route of fluid-loss e.g. stools, gastric aspirate etc. and laboratory electrolyte values. In general, Ringer lactate (Nat 131 meqiL) or N/2 dextrose saline (Na: 77 meq) is preferred for this purpose in usual cases of diarrhea-induced dehydration.
*Ringer lactate, despite higher sodium content, is preferred due to the priority of replacing ECF losses and restore plasma volume (which has normal Na content of 130 meq/L). Ringer lactate has additional advantage of containing lactate that is converted into bicarbonate and prevents metabolic acidosis.
Na, K and Cl values in meo,/L, glucose in gm/L
* also contains lactate 29 meq, which is ih vivo metabolized into bicarbonate to prevent acidosis
Monitoring: All cases on IV Parenteral fluid therapy should be monitored for changing needs of fluids/electrolytes, possibility of switch-over to oral rehydration therapy and complications e.g. over hydration, electrolyte disturbances, infection, thrombophlebitis or local extravasation.