Other method for assessment of dehydration and providing fluid therapy
(academic method):
In this method the clinical evaluation of dehydration is as follow:
1. mild dehydration ( 3-5%): mean 5% loss of the body weight by water.
2. moderate dehydration ( 7%): mean 7% loss of the body weight by water.
3. sever dehydration (10%): mean 10% loss of the body weight by water.
Mild and moderate dehydration can be treated effectively by ORS, 50 ml/kg of
ORS should be given within 4 hours to patient with mild dehydration, and 100
ml/kg of ORS should be given within 4 hours to patient with moderate
dehydration, supplementary ORS is given to replace ongoing loss 10 ml/kg for
each stool.
For sever dehydration:
1. restore intravascular volume:
Normal saline (or ringer lactate): 20 ml/kg over 20 minutes ( repeat until
intravascular volume restored).
2. calculate 24 hours water need:
This is by addition of deficit water to maintenance water.
To calculate deficit water: is by multiplying the percent of dehydration by the body
weight ( in grams).
Maintenance water:
Water is a crucial component of maintenance fluid therapy because of the
obligatory daily water losses. These losses are both measurable (urine, stool) and
not measurable (insensible losses from the skin and lungs). Failure to replace these
losses leads to a child who is thirsty, uncomfortable, and, ultimately, dehydrated .
-- Sources of Water Loss
Urine: 60%
Insensible losses:
∼35% (skin and lungs)
Stool: 5%
To calculate maintenance water:
the first 10 kg of body weight need 100 ml/kg.
the second 10 kg body weight need 50 ml/kg.
the third 10 kg body weight need 25 ml/kg.
e.g. patient his body weight 25 kg need 1000+500+125= 1625 ml.
the maximum total fluid per day is 2400 ml, the maximum fluid rate is 100 cc per
hour.
Urine output is normally the largest cause of water loss. Diseases such as renal
failure and SIADH can lead to a decrease in urine volume. The patient with
oliguria or anuria has a decreased need for water and electrolytes; continuation of
maintenance fluids produces fluid overload. In contrast, postobstructive diuresis,
the polyuric phase of acute tubular necrosis, diabetes mellitus, and diabetes
insipidus increase urine production. To prevent dehydration, the patient must
receive more than standard maintenance fluids when urine output is excessive The
approach to decreased or increased urine output is similar .
Place patient on insensible fluids (25–40% of maintenance)
Replace urine output mL/mL with ½ normal saline
3. select an appropriate fluid:
Administer half of the calculated fluid during the first 8 hours (after subtract the
bolus from it), and administer the remaining fluid over the next 16 hours.
4. replace the ongoing loss as they occur.
Children weighing less than 20-25 kg do best in maintenance fluid with solution
contain 1/4 N.S., the glucose in maintenance fluid is 5% dextrose provide 17 k.
calories per 100 ml. this is enough to prevent starvation ketoacidosis.
Types of dehydration :
1- isonatremic deh.; serum Na is normal ( 135-145 Meq/L ) , it is account for 75%
of deh.
2- hyponatremic deh. ; s. Na < 135 Meq/L, account for 10% of dehy. It occur
when fluid loss with higher Na concentration as occur with renal salt wasting, or
diarrhea with high Na content (e.g. cholera ).
Hyponatremia produce more substantial intravascular volume depletion due to the
shift of water from the extracelluler to the intracellular space . as brain cell swell
thereis an increase in intracranial pressure and this responsible for most
neurological symptoms .
Clinical features :
Anorexia , emesis ,malaise , headache , confusion , lethargy , seizure and coma .
hyponatremia also cause muscle cramps andweakness .
Treatment :
It is important to avoid rapid correction of hyponatremia , avoid correction of s. Na
more than 12 Meq. / day ( because if rapid correction it cause central pontine
myelonysis ). So the initial goal is correction of intravascular volume by isotonic
solution ( N.S. or ringer lactate ) . most patients with hyponatremic dehydration do
well with same strategy that is outlined with isotonic dehydration .
D5,1/5 N.S. with 20 Meq/L KCl is usually effective , 1/2 the fluid will be
administered over the 1st 8 hours ( K should not be given until the patient voids ) ,
and Na is monitored to ensure appropriate correction and Na concentration of the
fluid is adjusted appropriately , if develop seizer give infusion of 3% saline 12
cc/Kg
Hypernatremic dehydration :
It is the most dangerous form , hypernatremia can cause serious neurological
damage including hemorrhage and thromboses this is to movement of water from
intracellular space to intracellular space causing brain cell shrinkage and tearing
blood vessels . also this movement of water protect the intravasculer volume thus
children with hypernatremia appear less ill than children with a similar degree of
dehydration from other types . urine output may be preserved longer and may be
less tachy cardia . so unfortunately this lead to brought children to medical
attention in delayed and more profound dehydration .
Other symptoms of hypernatremia ; irritability , lethargy , fever and hypertonicity .
Treatment :
To avoid risk of cerebral oedema , s. Na concentration should not be decreased
more than 12 Meq/L/day , so we can apply this schedule;
1- restore intra vascular volume ; by I. v. fluid N.S. 20 cc/k.g. over 20 minutes and
reassess.
2-determine the time of correction based on the initial Na concentration;
S.Na : 145-157 Meq/L : 24 hours
158-170 Meq/L : 48 h.
171-183 Meq/L : 72 h.
Typical fluids ; D5,1/4 N.S. (with 20 Meq/l Kcl ) or D5,1/2 N.S.
3- follow up s. Na concentration.
4-adjust fluid based on clinical status ;
If s. Na decrease too rapidly; increase Na concentration of i.v. fluid decrease the
rate of i.v. fluid.
If s. Na decrease too slowly ; decrease Na concentration of the i.v. fluid or increase
the rate of fluid.
5- replace the ongoing loss as they occure.