Dehydration (pediatrics): Clinical sciences

Chapters:

Watch video only

Introduction0:00–0:31

Dehydration is a condition characterized by an excessive loss of body water. In children, dehydration most often results from acute gastrointestinal illnesses that cause vomiting, diarrhea, and decreased fluid intake.
Less commonly, it can result from conditions associated with non-gastrointestinal fluid losses, such as polyuria, third spacing, or burns.
Treatment of dehydration depends on its severity, which can be estimated from clinical findings. Now, if a pediatric patient presents with a chief concern suggesting dehydration, first perform an ABCDE assessment to determine if they’re unstable or stable.

Unstable Patient0:31–2:43

If unstable, stabilize their airway, breathing, and circulation. Next, obtain IV or intraosseous access, and administer a bolus of an isotonic crystalloid, such as normal saline.
Finally, place your patient on continuous vital sign monitoring, and if needed, provide supplemental oxygen. Then, obtain a focused history and physical examination, and order a BMP and urine studies including urine osmolarity, specific gravity, and sodium.
History usually reveals vomiting or diarrhea, which is often accompanied by decreased fluid intake. They also could have increased insensible losses from fever, excessive sweating, or sometimes extensive burns.
Less commonly, your patient may have an underlying condition causing polyuria, such as diabetes mellitus or diabetes insipidus.
Patients with severe dehydration are generally unstable and present with signs of shock. Pulses are typically weak, and perfusion is poor.
These patients usually have skin tenting and very dry mucous membranes, with severely reduced or absent urine output. In children, late findings include drowsiness or lethargy, and vital signs will reveal tachycardia and hypotension in more severe cases.
As for labs, the BMP may reveal hypo- or hypernatremia. You might also see hypokalemia, especially in patients with profuse diarrhea; or hyperkalemia, in the setting of acute kidney injury.
A decreased bicarbonate level indicates metabolic acidosis, which is often caused by diarrhea; whereas an increased bicarbonate level indicates metabolic alkalosis, which often results from excessive vomiting.
The blood urea nitrogen level and serum creatinine are also typically elevated. Finally, urine studies will reveal increased urine osmolarity, increased urine specific gravity, and decreased urine sodium.

Severe dehydration2:43–5:24

These clinical findings indicate severe dehydration, which means your patient has a volume loss of 10 percent or more. Patients with severe dehydration are critically ill and require immediate resuscitation to restore intravascular volume and improve perfusion.
If you haven’t already done so, administer a 20 milliliter per kilogram bolus of normal saline, and repeat boluses until your patient no longer demonstrates signs of shock.
Then, replace the remaining fluid deficit. Now, to calculate your patient's total deficit, multiply the estimated percentage of dehydration by their weight in kilograms.
Each kilogram represents one liter of fluid. For example, a 10-kilogram child with a 10 percent deficit has lost one kilogram, which equals one liter of fluid.
Next, subtract the volume of fluid boluses that you’ve already given from the total deficit, to determine the remaining fluid deficit.
Replace this remaining deficit over 24 hours. While you do so, you’ll also need to provide isotonic maintenance fluids for insensible losses and replace ongoing losses from diarrhea or vomiting with a suitable replacement solution.
Maintenance fluids should contain appropriate concentrations of glucose and potassium. Before adding potassium to maintenance fluids, make sure your patient is voiding and that their serum potassium is not elevated.
Here’s your first clinical pearl! Children with diarrhea and hypotonic fluid intake can lose excessive amounts of sodium and water, which triggers ADH secretion, and consequently leads to hyponatremia.
If sodium levels fall rapidly, these patients can develop signs and symptoms of hyponatremic encephalopathy, such as vomiting and seizures.
Treat hyponatremic encephalopathy with hypertonic saline but remember to correct sodium levels slowly to decrease the risk of osmotic demyelination syndrome; and avoid hypotonic solutions as they can worsen hyponatremia.
In contrast, hypernatremic dehydration often results from an inability to take in fluid like with poor breastfeeding. In these patients, water loss exceeds sodium loss, and intravascular volume is relatively preserved, so signs of dehydration usually appear later.
Children with hypernatremic dehydration often appear very irritable, with a high-pitched cry and a “doughy” skin texture.
Once you identify it, remember to correct hypernatremia slowly, to prevent iatrogenic cerebral edema! Okay, now that we’ve discussed unstable patients, let’s return to the ABCDE assessment and look at stable ones.

Stable Patient5:24–6:00

First, obtain a focused history and physical examination. Again, history usually reveals vomiting or diarrhea with decreased fluid intake, fever, and excessive sweating.
In some cases, your patient might also have excessive losses from polyuria or burns. Any history of fluid loss should make you suspect dehydration.
Now, to confirm dehydration and assess its severity, you’ll need to look at your patient’s exam findings. Let’s talk about what you’d expect to see in patients with mild dehydration.

Mild Dehydration6:00–7:25

Here, the exam typically reveals an alert patient with normal heart rate, blood pressure, and pulses. These patients also have normal perfusion, but skin turgor might be normal or slightly reduced.
Mucous membranes are usually tacky, tear production is normal, and most patients have mildly reduced urine output. These clinical findings are highly suggestive of mild dehydration, which corresponds to a volume loss between 3 and 5 percent.
Here’s another clinical pearl! If a recent pre-illness weight is available, you can use your patient’s weight loss to determine the degree of dehydration.
However, since pre-illness weight is not always known, clinical findings are more commonly used to estimate the degree of dehydration.
Alright, now let’s move on to treatment. Patients with mild dehydration have a fluid deficit of 50 to 60 milliliters per kilogram, which should be replaced over 4 to 6 hours.
Most of these children can be treated with oral rehydration, using a solution containing an appropriate sodium to glucose ratio.
Avoid using sweetened drinks like tea, fruit juice, or soda for rehydration, since their high sugar concentration can cause osmotic diarrhea, and their low sodium content can cause or aggravate hyponatremia.

Moderate Dehydration7:25–9:03

Alright, let’s switch gears and talk about findings you’d expect to see in patients with moderate dehydration. Here, the exam typically reveals an alert patient with tachycardia and normal blood pressure.
You may detect weaker pulses, but perfusion is usually normal. Additionally, you’ll often notice reduced skin turgor and dry mucous membranes, with reduced tear production and urine output.
These clinical findings are highly suggestive of moderate dehydration, which means your patient has a volume loss between 6 and 9 percent.
Because patients with moderate dehydration can develop electrolyte abnormalities, you should also obtain a BMP. Results may reveal hypo- or hypernatremia, as well as hypo- or hyperkalemia; and bicarbonate levels could be decreased or elevated.
Finally, the blood urea nitrogen level is often elevated, and in some cases, the serum creatinine is slightly elevated as well As for management, you may decide to administer a 20 milliliter per kilogram bolus of normal saline, especially if your patient can’t take fluids by mouth.
Once you’ve done this, calculate the remaining fluid deficit, and replace it over 24 hours, with a physiologically appropriate oral rehydration solution or isotonic intravenous fluids.
At the same time, provide isotonic maintenance fluids for insensible losses and replace ongoing losses from diarrhea or vomiting with an appropriate replacement solution.
And, before adding potassium to maintenance fluids, make sure your patient is voiding and that their serum potassium is not elevated.
Alright, as a quick recap… Dehydration results from excessive water loss and can be categorized as mild, moderate, or severe depending on clinical findings.

Review9:03–9:51

Patients with severe dehydration are generally unstable and require volume resuscitation to restore intravascular volume, followed by replacement of the remaining fluid deficit and maintenance fluids.
On the other hand, patients with mild or moderate dehydration are generally stable. Those with mild dehydration are typically treated with oral rehydration therapy, while those with moderate dehydration may require a bolus of intravenous normal saline, followed by replacement of the remaining fluid deficit using oral rehydration or intravenous fluids.
In addition, all patients with dehydration should receive maintenance fluids to replace