Dehydration on the CCFP exam

Approach

• Ask what he has drunk, eaten and passed as urine over the last few days.
• Count the losses: vomiting, diarrhea, fever, sweating, fast breathing, and more urine than usual.
• Look for a fast pulse, low blood pressure, dizziness on standing, a dry mouth and less urine.
• Older adults feel less thirst and may not ask for water. Confusion or a fall can be the first sign.
• Think of it in any illness that stops drinking: pneumonia, a urinary infection, a sore mouth, delirium.

Approach

• Weigh the patient. A weight from just before the illness gives the best measure of what was lost.
• In young children, combine signs: how the child looks, sunken eyes, a dry mouth, no tears, capillary refill and heart rate.
• Read the mouth with care. Ulcers, drooling or mouth breathing make it useless as a sign.
• Fever, a normal glucose, ketones in urine, or concentrated urine do not tell mild from severe loss.
• In teens and adults, use pulse, blood pressure lying and standing, and dizziness on standing. Capillary refill and skin turgor tell little at this age.
• In older adults, a dry mouth and slack skin are common without fluid loss. Weight, pulse, pressure, urine output and new confusion help more.
• In pregnancy, pulse rises and blood pressure falls as a normal change. Compare with the patient's own baseline.

Approach

• Add three parts: the deficit, the ongoing losses, and normal daily needs.
• Size the deficit from weight lost or from the grade of dehydration. A bigger grade needs a bigger volume.
• Replace the deficit promptly, and keep adding fluid for each stool or vomit.
• A child who can take sips starts with oral rehydration solution, in small amounts given often.
• Consider one oral dose of ondansetron for vomiting from gastroenteritis, age 6 months or more, with mild to moderate loss or failed oral fluids. Start oral fluids 15 to 30 minutes later.
• Ondansetron is not routine when diarrhea is the main problem. If pain stops the drinking, treat the pain, then try again.
• Move to a nasogastric tube (through the nose to the stomach) or IV fluid for severe loss, or when oral fluids truly fail.

Approach

• Draw sodium, potassium, chloride, bicarbonate, urea, creatinine and glucose as the IV goes in. Repeat them as you treat.
• Urea high next to creatinine fits low volume. A slightly low sodium does not mean she is well filled.
• Vomiting loses stomach acid: low chloride, low potassium and high bicarbonate. That is a metabolic alkalosis.
• Pregnancy lowers bicarbonate a little through faster breathing. A high bicarbonate is the opposite, so it comes from the vomiting.
• Start IV fluid, and recheck the electrolytes and urine output as you treat.
• Track pulse, blood pressure, urine output and repeat results. Change the fluid as they settle.

Approach

• Review every drug and every recent dose change: diuretics, laxatives, and SGLT2 inhibitors (diabetes pills that pass sugar into the urine).
• Stop the drug that adds to the loss. Restarting a laxative while stools are still watery adds to what you replace.
• Look outside the gut: high blood sugar, pneumonia, a urinary infection, heat, burns, a mouth too sore to drink, pregnancy.
• Ketones with glucose in the urine point to diabetes. Ketones alone fit a child who has not eaten.
• A child's sore throat with viral features needs no routine strep test.
• Treat the cause now. Pain relief is what lets a child with a sore mouth drink.

Approach

• Pregnancy lowers the bar to admit her and to give IV fluid.
• Look for the cause: infection, or a problem with the pregnancy itself.
• Check electrolytes. Replace the potassium and the rest of the deficit before she goes home.
• Fetal heart and fundal height do not measure her fluid loss. At this stage, neither is usually found.
• Before discharge, recheck urine output, standing pulse and blood pressure, and potassium.