Management of different types of dehydration

Illustrated Text Book of Pediatrics

In this article, we’re going to explain how to deal with different types of dehydration in terms of serum sodium level. We’re going to exemplify with one case but presents with distinct kinds of dehydration, then we apply fluid calculation for each type of dehydration. We can classify dehydration into mild, moderate and severe dehydration in severity point of view, but in regard with serum sodium level (normally is 135-145  mEq/L) there are again three types of dehydration:

Before reading this article I recommend to look over a previous article on IV fluid management to understand better. Follow this link to open in a new window: click here 

*Isonatremic dehydration (serum Na is 135-145 mEq/L)

*Hyponatremic dehydration (serum Na is <135 mEq/L)and

*Hypernatremic dehydration (serum Na is >145 mEq/L)

Case history and examination: 11 month-old infant who weighs 10kg brought to hospital because of vomiting and diarrhea for 3 days duration. He has fever, depressed fontanel, sunken eyes, delayed skin turgor and is difficult to arouse. Investigations: RFT: normal; GSE: shows pus cells ++;

from examination it revealed that this case has severe dehydration because has a major criterion of severe dehydration (difficult to arouse-lethargic-)

**1st scenario: If above case has serum Na:139:- so it’s isonatremic dehydration:

now how to calculate fluid therapy?

-Bolus is 20ml/kg/30min either NS or RL ==>> 200ml within 30 minutes (can be given up to 3 times), assume that we have given twice, 400ml/1hr has been given then.

-Deficit therapy: age <1 yr and it’s severe dehydration therefore type of fluid is GS1/5 and amount is 150ml/kg.

Thus it will be 1500ml of GS1/5.

-Maintenance therapy: per Holliday-Segar method is 100ml/kg and type of fluid is GS1/5 (age < 1yr).

Hence it will be 1000ml of GS1/5.

Deficit + Maintenance – Bolus ==>> 1500+1000-400 =2100ml GS1/5 over 23 hours (because two boluses have already been given within 1 hr).

In consequence, GS1/5 2100ml/23 hr ≈ 91 ml/hr, which can readily be infused with flow meter or infusion pump.

**2nd scenario: While if he has serum Na of 125:- so it’s hyponatremic dehydration:

treatment is just like above as for isonatremic dehydration. Bolus is either NS or RL 200ml/ 30min. Deficit with maintenance will be GS1/5 91 ml/hr (for calculation see above). Hence treatment is similar to isonatremic dehydration unless if there is severe (serum Na < 120) or symptomatic (patient develops seizure) hyponatremia. In these situations hypertonic NS 3% will be infused according to following equation:

dose of NS3% in ml/kg = 125 – actual serum sodium level ; 125 is the target level we want raising serum sodium to. Example: if serum Na is 115, dose will be = 125 – 115 = 10ml/kg, in our case it equals 100ml.

Remarks about NS 3% ⁽³⁾:

1- It should be given slowly at a rate of 1ml /minute.

2- The maximum dose / time is 10ml/kg. in patients with serum sodium < 115, treatment should be divided into multiple doses with 2 hours interval in between.

**3rd scenario: above case has serum Na:165:- so it’s hypernatremic dehydration:

In hypernatremic dehydration there are fundamental differences which are: in bolus therapy only NS should be given, unlike former two types RL must be avoided; type of the fluid for deficit and maintenance therapy almost always is GS1/2 regardless the age; and duration of infusion is not constant but changes according to the serum sodium level as follow: serum sodium should not be reduced >12 mEq/L/day then if serum Na level is:

*145-157 needs 24hr (1day)

*158-170 needs 48hr (2days)

*171-183 needs 72hr (3days)

*184-196 needs 96hr (4days)

A- Now assume that our case has a serum Na level of 155, we’re going to rehydrate the patient as below:

-Bolus is 20ml/kg/30min only NS (RL is contraindicated here) ==>> 2ooml within 3o minutes (can be given up to 3 times), assume that we have given twice, 400ml/1hr has been given then.

-Deficit therapy: type of fluid is GS1/2 and it’s severe dehydration therefore amount is 150ml/kg.

Thus it will be 1500ml of GS1/2.

-Maintenance therapy: per Holliday-Segar method is 100ml/kg and type of fluid is GS1/2 (it’s always GS1/2 in hypernatremic dehydration).

Duration of infusion is 1 day because serum Na level is 155 mEq/L, therefore:

Deficit + Maintenance – Bolus ==>> 1500+1000-400 =2100ml GS1/2 over 23 hours (because two boluses have already been given within 1 hr).

In consequence, GS1/2 2100ml/23 hr ≈ 91 ml/hr, which can readily be infused with flow meter or infusion pump.

Notice the differences: Bolus was only NS, and type of deficit + maintenance was GS1/2.

 

B- If the serum Na level is 168, we’re going to rehydrate the patient as below:

-Bolus is 20ml/kg/30min only NS (RL is contraindicated here) ==>> 2ooml within 3o minutes (can be given up to 3 times), assume that we have given twice, 400ml/1hr has been given then.

-Deficit therapy: type of fluid is GS1/2 and it’s severe dehydration therefore amount is 150ml/kg.

Thus it will be 1500ml of GS1/2.

-Maintenance therapy: per Holliday-Segar method is 100ml/kg and type of fluid is GS1/2 (it’s always GS1/2 in hypernatremic dehydration).

Duration of infusion is 2 days because serum Na level is 168 mEq/L, therefore:

Deficit = 1500ml +

Maintenance for day 1 = 1000ml +

Maintenance for day 2 = 1000ml = 3500ml / 48hrs ==>>> 1750 for day 1 + 1750 for day 2, now subtracting the bolus from day 1 ==>> 1750-400=1350ml/23hr GS1/2 for day 1, and for day 2 will be 1750ml/24hr GS1/2.

Notice the differences: Bolus was only NS; type of deficit + maintenance was GS1/2; and the amount for the same child was 2500ml GS1/5 when he had isonatremic and hyponatremic dehydration, but when he had hypernatremic dehydration (Na was 168) it was 1750ml GS1/2.

 

C- If the serum Na level is 180, we’re going to rehydrate the patient as below:

-Bolus is 20ml/kg/30min only NS (RL is contraindicated here) ==>> 2ooml within 3o minutes (can be given up to 3 times), assume that we have given thrice, 600ml/1.5hr has been given then.

-Deficit therapy: type of fluid is GS1/2 and it’s severe dehydration therefore amount is 150ml/kg.

Thus it will be 1500ml of GS1/2.

-Maintenance therapy: per Holliday-Segar method is 100ml/kg and type of fluid is GS1/2 (it’s always GS1/2 in hypernatremic dehydration).

Duration of infusion is 3 days because serum Na level is 180 mEq/L, therefore:

Deficit = 1500ml +

Maintenance for day 1 = 1000ml +

Maintenance for day 2 = 1000ml +

Maintenance for day 3 = 1000ml = 4500ml / 72hrs ==>>> 1500 for day 1 + 1500 for day 2 + 1500 for day 3, now subtracting the bolus from day 1 ==>> 1500-600=900ml/22.5hr GS1/2 for day 1, for day 2 will be 1500ml/24hr GS1/2 and for day 3 it equals 1500ml/24hr GS1/2.

Notice the differences: Bolus was only NS; type of deficit + maintenance was GS1/2; and the amount for the same child was 2500ml GS1/5 when he had isonatremic and hyponatremic dehydration, but when he had hypernatremic dehydration (Na was 168) it was 1750ml GS1/2, and when he had Na level of 180 it became 1500ml/24hr.

As mentioned above, serum Na should not be lowered too rapidly (>12mEq/L/day) to avoid development of cerebral edema. If it has already been reduced so quickly by mistake or any other reason, we have to give NS 3% to increase sodium level again then decreasing it slowly (because rapid lowering is very dangerous which might lead to cerebral edema and convulsion).

Dose of hypertonic NS 3% in this condition is 4ml/kg (1ml/min). Above case was 10kg, hence it will be 40ml over 40 minutes.

 

**There is a rapid way to calculate both deficit and maintenance fluid together in severe hypernatremic dehydration by giving 1.3-1.5 of maintenance. For instance in above case maintenance was 1000 * 1.5 = 1500ml, in 3rd scenario B as well as C, total fluid was calculated to be 1750 and 1500 ml respectively, which approximately near from the rapid method.

But! remember calculation with rapid method is not so accurate.

In all types of dehydration KCL should be added to maintenance therapy after urine output is positive and hyperkalemia has been excluded (as there is possibility of renal failure when the patient has severe dehydration), and maximum amount to be given is 40meq/L (20ml/L = 10ml/pint).

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