Intravenous fluids.

Posted on: Thursday, September 20th, 2018 @ 11:02 PM - By: Mohemet - Seen 6181 Times

Intravenous (IV) Fluids & Solutions:

This article discusses the different types and indications of IV fluids and solutions. In general IV fluids are divided in to two types: Crystalloids and Colloids. The diagram below illustrates more:

  • Shock therapy: 20 ml/kg/0.5-1 hr either NS 0.9% or RL. It is indicated in case of severe dehydration to improve renal circulation and can be repeated to maximum 3 times.

e.g. A 10 kg infant presented with severe dehydration, the shock therapy will be 200ml NS or RL over 1 hour.

RL is more suitable to be used in shock therapy but in certain conditions such as DKA NS should be used.
  • Deficit therapy: It’s indicated in case of dehydration to replace water and electrolyte losses. The type of fluid is either GS 1/5 (wt < 10kg) or GS 1/2 (wt > 10kg). It’s calculated according to degree of dehydration and age of the patient. See table below

e.g. 9 month-old infant who weighs 8kg presented with severe dehydration, calculate shock and deficit therapy.

Shock therapy is 2o ml/kg/1hr, so it equals 8*20 = 160ml/1hr RL or NS.

Deficit therapy is according above table, he is < 1 year and has severe dehydration (15%), so deficit therapy is 150ml/kg, it equals 150*8 = 1200ml GS 1/5.

For duration of infusing Deficit therapy see below.
  • How to assess degree of dehydration? according to the below table:

  • Maintenance therapy: It’s given to replace ongoing losses. The type of fluid is either GS 1/5 (wt < 10kg) or GS 1/2 (wt > 10kg). It’s calculated according to Holliday-Segar method as below:
  • 1st 10 kg — 100ml/kg
  • 2nd 10kg— 50ml/kg
  • 3rd and above 10kgs—20ml/kg

e.g. –For 7 kg infant maintenance therapy is 100ml/kg >>100ml*7 = 700ml GS 1/5 (because wt is less than 10kg).

— For 14 kg infant maintenance therapy is 100ml/kg for 1st 10kgs (100*10 = 1000ml) and 50ml/kg for second 10kgs (50*4 = 200ml), so it equals 1400ml GS 1/2 (because wt is more than 10kg).

— For 28 kg child maintenance therapy is 100ml/kg for 1st 10kgs (100*10 = 1000ml) and 50ml/kg for second 10kgs (50*10 = 500ml)and 20ml/kg for 3rd 10kgs (20*8 = 160ml), so it equals 1000+500+160 =16600ml GS 1/2 (because wt is more than 10kg).

–For 40 kg child maintenance therapy is 1900ml GS 1/2.

NOTE: maximum amount of maintenance therapy is 2400ml/24hr (100ml/hr) even if the patient weighs 100 kg for instance.
  • Duration of Deficit and Maintenance therapy:  Total amount of fluid should be given within 24 hrs. Total amount of fluid = Shock + Deficit + Maintenance / 24 hr period. one shoot of Shock therapy is given over 1 hr, the remaining amount is given over 23 hr period. See below example to understand more.

**Case scenario: A 15 month-old male infant whose weight is 12 kg, presented with diarrhea and vomiting, he is difficult to arouse, unable to drink, has sunken eye, decreased urine output, and dry tongue. Calculate total fluid that’s required for re-hydrating this infant.

–First of all, this infant has severe dehydration (difficult to arouse, unable to drink), so he needs Shock therapy 20ml/kg/1hr, he is 12kg, the amount is 12*20 = 240ml/1hr NS or RL. We reassess the infant to know is he still dehydrated (by general condition, blood pressure, urine output..), if not, we give another shoot 20ml/kg/1hr of shock therapy, if not responded yet another shoot will be infused (maximum 3 shoots). Assume that this infant responded with 2 shoots, so:

****Total amount of fluid to be given Shock therapy + Deficit + Maintenance / 24 hr period,

*Shock therapy = 12*20 = 240ml/hr, needed 2 shoots so it’ll be 480ml/2hrs NS or RL.

*Deficit therapy according to above table, age>1yr and severe dehydration >> 9% (90ml/kg) >> 90*12= 1080ml GS 1/2 (because wt > 10kg).

*Maintenance therapy according to Holiday-Segar method is 1100ml GS 1/2 (because wt > 10kg).

(Deficit + Maintenance) – shock therapy will be given over remaining hours, in this case (1080+1100)-480ml = 1700ml GS 1/2 over 22 hours (because we gave 2 shoots of shock therapy and it took 2 hrs).

This amount 1700ml will be divided by two 1700ml/2=850ml, the first half is infused over 1st 8 hrs, the second half is infused over remaining hrs.

So in this case 480ml NS over 2 hours, then 850ml GS1/2 over 8 hrs, then 850ml GS1/2 over 14 hrs.

**NOTE: the above calculation is for both isonatremic and hyponatremic dehydration, while for hypernatremic dehydration the shock therapy is the same, but Deficit and Maintenance therapy instead of being infused over 24 hr period, it should be infused slowly over 48 hr period to avoid rapid lowering of serum sodium level and development of cerebral edema. ( serum sodium should be lowered at a rate not more than 12meq/L/day). The type of fluid also differs in hypernatremic dehydration, it’s always GS1/2 regardless wt of the patient.
  • For the next days only maintenance therapy is calculated.
  • the amount of maintenance therapy will be decreased to 2/3rd or 1/2 in case of edema, nephrotic syndrome, heart failure. For e.g. in infant 16kg with HF>> Maintenance is 650ml instead of 1300ml.

***How to calculate the rate of infusion:

drop factor is different according to IV set, it may be 15, 20 or 60 (microdrip) and it’s written on IV set. If it 2o it means that 2o drops = 1ml, if it 15 it means 15 drops= 1ml because size of drops are bigger. Drop factor of usual IV set is 20.

In above case we said infuse 850ml/8hr so rate of infusion (No. of drops per minute)=

and rest of fluid 850 ml will be infused over 14 hours, so rate of infusion (No. of drops per minute)=

Or it can be infused using infusion pump which easily controls rate of infusion by automatic setting, or using flow regulator which controls rate of infusion in ml/hr, for e.g. in our case 850ml/8hrs = 106ml/hr, so switch the regulator to 106ml/hr. Below photo is flow regulator.

**Daily electrolyte requirement in children:

  • Na = 3 meq/Kg/day
  • K = 2 meq/Kg/day
  • Cl = 2-3 meq/Kg/day

e.g. for 10kg infant daily sodium requirement is 30meq/L/day, daily K requirement is 20meq/L/day and daily Cl requirement is 20-30meq/L/day.

For 10 kg infant Maintenance therapy is 1oooml GS1/5 + 20meq K inside 1000ml (10meq/500ml), each ml of KCL vial is 2meq, so add 5ml to each pint of fluid. Type of GS should be 1/5th, why? because NS 0.9% contains 154 Na + 154 Cl meq/L, GS1/2 (0.45%) means 154/2 >> so it contains 77 meq/L Na, while GS1/5 (0.18%) means 154/5>> so it contains 30.8meql, and daily Na requirement for 10kg is 3*10 = 30meq so GS1/5 provides the exact amount of daily sodium need.

KCL should be added to Maintenance therapy after urine output is positive, and maximum amount to be given is 40meq/L (20ml/L = 10ml/pint).

To know how to calculate IV fluid for Neonates, Click here

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