Remarkable Update of the Original Rx Pediatric Dehydration App

As a full-scope family medicine physician, severely ill infants and children can be some of the most stressful situations in our practice. Although norovirus and rotavirus infections are common, they can make children extremely ill — as can other more severe forms of gastroenteritis such as Shigella, salmonella or E. coli.  All of these infections, including sepsis, or trauma can make a previously healthy child critically ill in a matter of hours.

Knowing how to replace fluids in children is both art and science. Calculations for bolus therapy, which are first provided to resuscitate the child, are covered in Pediatric Advanced Life Support (PALS). For children, this is typically 20ml/kg of isotonic saline.

For decades, providers have been taught the calculations of maintenance fluids from the paper published by Holliday and Segar in 1957.  The Holliday-Segar method is still used to this day with providers utilizing the “4-2-1” rule. The fluid replacement can be calculated for 24hrs or on an hourly basis. The calculations are as follows:

  • 100 ml/kg for the 1st 10 kg of wt
  • 50 ml/kg for the 2nd 10 kg of wt
  • 20 ml/kg for the remaining wt

Which results in the following “4-2-1” rule:

  • 100 ml/kg/24-hours = 4 ml/kg/hr for the 1st 10 kg
  • 50 ml/kg/24-hours = 2 ml/kg/hr for the 2nd 10 kg
  • 20 ml/kg/24-hours = 1 ml/kg/hr for the remainder

The “higher level” calculations above this are those for maintenance and replacement of electrolytes: sodium, chloride and potassium. These are based on the clinical assessment of the child’s volume status.   

For providers working in NICU and PICU settings, fluid calculations are second nature. For the rest of us, we have to think about it a bit! Typically, I turn to the various pediatric emergency apps that allow for weight/age/Broslow based treatments for a variety of situations including hypovolemia. My pediatric emergency app of choice has been Pedi STAT.

Here at, we have reviewed Pedi STAT previously. We also included it in several “Top 10” app lists for Pediatrics and Family Medicine. Over the years, alternatives to Pedi STAT have come along including PalmPedi, BluCard, Pedi Crisis, Paediatric Emergencies, Pediatric Anesthesia, and Rx Pediatric Dehydration. This last app has just been redesigned and released in an expanded textbook form called Fluid and Lytes. It focuses on the initial fluid resuscitation of children in a variety of situations including burns, renal, and liver disease. The app is authored by a group of pediatric intensivists in India. This app is meant to be used at the point of care for rapid calculations for volume replacement in a true pediatric emergency. However, its new version also can be used a medical reference and teaching tool. It can be easily read at home as well as on the wards, in the clinic, or ER.

Evidence-Based Medicine

The app uses accepted calculations for pediatric volume replacement that are evidence-based. The app includes numerous references with links as well as recommendations for further reading. The app developers are all peds critical care providers with years of treating ped dehydration cases in India. The new version of the app is now much more textbook-like in its layout as well.

What providers would benefit from this App?

Providers who care for critically ill children in and out of the hospital from the original audience of pediatric intensivists to first-responders, students, residents and faculty in emergency medicine, pediatrics, and family medicine.

  • Price
    • Free.
  • Likes
    • 17 chapters of easy-to-follow yet detailed text on peds lytes with case examples
    • Includes calculators for all common lytes calculations
    • High-quality graphics to complement the detailed text along with references with hyperlinks
  • Dislikes
    • Cannot pinch to zoom or otherwise enlarge graphics
    • Annoying “paper turning” sound effects
    • Not available for Android at this time


An outstanding update and significant expansion upon the earlier Rx Pediatric Dehydration app. This new eBook/calculator app covers a wide range of topics regarding pediatric electrolytes with a focus on initial fluid resuscitation. This is an app than every pediatrician and/or any provider who treats dehydrated children especially in austere environments.

  • Overall Score
    • 4.5 stars
  • User Interface
    • 4.0 stars

Textbook-like outline with easy-to-navigate chapters and numerous calculators.

  • Multimedia Usage
    • 4.5 stars

High-quality graphics and easy to use and accurate calculators.

  • Price
    • 5.0 stars

The app is free.


  • Real World Applicability
    • 4.5 stars

This complete redesign of the 2015 app effort is a home run. The app includes easier to use calculators, but now has morphed into a primer on peds lytes that anyone and everyone should read. A must have app for those who treat peds patients with significant dehydration.

  • Device Used For Review

iPhone 8 running iOS 12.3.1.

  • Available for Download for iPhone/iPad. Not yet available for Android.

Disclaimer: The views expressed are those of the author(s) and do not reflect the official policy of the Department of the Army, the Department of Defense or the U.S. Government.