Dehydration

This article is about excessive loss of body water. For other uses, see Dehydration (disambiguation).

Dehydration

Nurses encourage a patient to drink an oral rehydration solution to treat the combination of dehydration and hypovolemia secondary to cholera. Cholera leads to GI loss of both excess free water (dehydration) and sodium (hence ECF volume depletion—hypovolemia).
Specialty| Critical care medicine

Dehydration is a deficit of total body water,[1] with an accompanying disruption of metabolic processes. Most people can tolerate a 3-4% decrease in total body water without adverse effects. A 5-8% decrease can cause fatigue and dizziness. Loss of over ten percent of total body water can cause physical and mental deterioration, accompanied by severe thirst. Death occurs at a loss of between fifteen and twenty-five percent of the body water.[2] Mild dehydration is characterized by thirst and general discomfort.

It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mild dehydration can also be caused by immersion diuresis, which may increase risk of decompression sickness in divers. Dehydration can cause hypernatremia (high levels of sodium ions in the blood) and is distinct from hypovolemia (loss of blood volume, particularly blood plasma).

People may rehydrate by drinking fluids such as oral rehydration solution. Fluids may also be given into a vein or by subcutaneous injection (sc). In the elderly sc appears to be safer than intravenous but is less effective.[3]

## Contents

* 1 Signs and symptoms
* 2 Cause
* 3 Diagnosis
* 3.1 Definition
* 4 Prevention
* 5 Treatment
* 6 See also
* 7 References
* 8 Further reading
* 9 External links

## Signs and symptoms[edit | edit source]

The hallmarks of dehydration include thirst and neurological changes such as headaches, general discomfort, loss of appetite, decreased urine volume (unless polyuria is the cause of dehydration), confusion, unexplained tiredness, purple fingernails, and seizures. The symptoms of dehydration become increasingly severe with greater total body water loss. A body water loss of 1-2%, considered mild dehydration, is shown to impair cognitive performance.[4] While in people over age 50, the body's thirst sensation diminishes with age, a study found that there was no difference in fluid intake between young and old people.[5] Many older people suffer symptoms of dehydration. Dehydration contributes to morbidity in the elderly population, especially during conditions that promote insensible free water losses, such as hot weather. A Cochrane review on this subject defined water-loss dehydration as "people with serum osmolality of 295 mOsm/kg or more" and found that the main symptom in the elderly (people aged over 65) was fatigue.[clarification needed][6]

## Cause[edit | edit source]

Risk factors for dehydration include but are not limited to: exerting oneself in hot and humid weather, habitation at high altitudes, endurance athletics, elderly adults, infants, children and people living with chronic illnesses.[7]

Dehydration can also come as a side effect from many different types of drugs and medications.[8]

In the elderly, blunted response to thirst or inadequate ability to access free water in the face of excess free water losses (especially hyperglycemia related) seem to be the main causes of dehydration.[9] Excess free water or hypotonic water can leave the body in two ways – sensible loss such as osmotic diuresis, sweating, vomiting and diarrhea, and insensible water loss, occurring mainly through the skin and respiratory tract. In humans, dehydration can be caused by a wide range of diseases and states that impair water homeostasis in the body. These occur primarily through either impaired thirst/water access or sodium excess.[10]

## Diagnosis[edit | edit source]

Ultrasound of the blood vessels of the neck that supports the diagnosis of severe dehydration[11]

### Definition[edit | edit source]

Dehydration occurs when water intake does not replace free water lost due to normal physiologic processes, including breathing, urination, perspiration, or other causes, including diarrhea, and vomiting. Dehydration can be life-threatening when severe and lead to seizures or respiratory arrest, and also carries the risk of osmotic cerebral edema if rehydration is overly rapid.[12]

The term "dehydration" has sometimes been used incorrectly as a proxy for the separate, related condition of hypovolemia, which specifically refers to a decrease in volume of blood plasma.[1] The two are regulated through independent mechanisms in humans;[1] the distinction is important in guiding treatment.[13]

## Prevention[edit | edit source]

For routine activities, thirst is normally an adequate guide to maintain proper hydration.[14] Minimum water intake will vary individually depending on weight, environment, diet, and genetics.[15] With exercise, exposure to hot environments, or a decreased thirst response, additional water may be required. In athletes in competition, drinking to thirst optimizes performance and safety, despite weight loss, and as of 2010, there was no scientific study showing that it is beneficial to stay ahead of thirst and maintain weight during exercise.[16]

In warm or humid weather, or during heavy exertion, water loss can increase markedly, because humans have a large and widely variable capacity for sweating. Whole-body sweat losses in men can exceed 2 L/h during competitive sport, with rates of 3–4 L/h observed during short-duration, high-intensity exercise in the heat.[17] When such large amounts of water are being lost through perspiration, electrolytes, especially sodium, are also being lost.

In most athletes exercising and sweating for 4–5 hours with a sweat sodium concentration of less than 50 mmol/L, the total sodium lost is less than 10% of total body stores (total stores are approximately 2,500 mmol, or 58 g for a 70-kg person).[18] These losses appear to be well tolerated by most people. The inclusion of sodium in fluid replacement drinks has some theoretical benefits[18] and poses little or no risk, so long as these fluids are hypotonic (since the mainstay of dehydration prevention is the replacement of free water losses).

## Treatment[edit | edit source]

Urine color chart

Main article: Management of dehydration

The treatment for minor dehydration that is often considered the most effective is drinking water and stopping fluid loss. Plain water restores only the volume of the blood plasma, inhibiting the thirst mechanism before solute levels can be replenished.[19] Solid foods can contribute to fluid loss from vomiting and diarrhea.[20] Urine concentration and frequency will return to normal as dehydration resolves.[21]

In some cases, correction of a dehydrated state is accomplished by the replenishment of necessary water and electrolytes (through oral rehydration therapy, or fluid replacement by intravenous therapy). As oral rehydration is less painful, non invasive, inexpensive, and easier to provide, it is the treatment of choice for mild dehydration.[citation needed] Solutions used for intravenous rehydration must be isotonic or hypertonic.[citation needed] Pure water injected into the veins will cause the breakdown (lysis) of red blood cells (erythrocytes).[citation needed]

When fresh water is unavailable (e.g. at sea or in a desert), seawater or drinks with significant alcohol concentration will worsen dehydration. Urine contains a lower solute concentration than seawater; this requires the kidneys to create more urine to remove the excess salt, causing more water to be lost than was consumed from seawater.[22] If a person is dehydrated and taken to a medical facility, IVs can also be used.[23][24][25][26]

For severe cases of dehydration where fainting, unconsciousness, or other severely inhibiting symptom is present (the patient is incapable of standing or thinking clearly), emergency attention is required. Fluids containing a proper balance of replacement electrolytes are given orally or intravenously with continuing assessment of electrolyte status; complete resolution is normal in all but the most extreme cases.[27]

## See also[edit | edit source]

* Hydrational fluids
* Terminal dehydration
* Dryness (medical)
* Oral Rehydration Therapy

## References[edit | edit source]

1. ↑ 1.0 1.1 1.2 Mange K, Matsuura D, Cizman B, Soto H, Ziyadeh FN, Goldfarb S, Neilson EG (November 1997). "Language guiding therapy: the case of dehydration versus volume depletion". Annals of Internal Medicine. 127 (9): 848–53. doi:10.7326/0003-4819-127-9-199711010-00020. PMID 9382413. S2CID 29854540.
2. ↑ Ashcroft F, Life Without Water in Life at the Extremes. Berkeley and Los Angeles, 2000, 134-138.
3. ↑ Danielsen, MB; Andersen, S; Worthington, E; Jorgensen, MG (December 2020). "Harms and Benefits of Subcutaneous Hydration in Older Patients: Systematic Review and Meta-Analysis". Journal of the American Geriatrics Society. 68 (12): 2937–2946. doi:10.1111/jgs.16707. PMID 33411351.
4. ↑ Riebl SK, Davy BM (November 2013). "The Hydration Equation: Update on Water Balance and Cognitive Performance". ACSM's Health & Fitness Journal. 17 (6): 21–28. doi:10.1249/FIT.0b013e3182a9570f. PMC 4207053. PMID 25346594.
5. ↑ Hall, Harriet (August 17, 2020). "Are You Dehydrated?". Skeptical Inquirer. 4 (No. 4 l=https://skepticalinquirer.org/exclusive/are-you-dehydrated/). `{{cite journal}}`: `|issue=` has extra text (help)
6. ↑ Hooper L, Abdelhamid A, Attreed NJ, Campbell WW, Channell AM, Chassagne P, et al. (April 2015). "Clinical symptoms, signs and tests for identification of impending and current water-loss dehydration in older people". The Cochrane Database of Systematic Reviews. 4 (4): CD009647. doi:10.1002/14651858.CD009647.pub2. hdl:2066/110560. PMC 7097739. PMID 25924806.
7. ↑ "Dehydration Risk factors - Mayo Clinic". www.mayoclinic.org. Archived from the original on October 24, 2016. Retrieved December 14, 2015.
8. ↑ "Archive copy". Archived from the original on January 18, 2021. Retrieved February 16, 2021.`{{cite web}}`: CS1 maint: archived copy as title (link)
9. ↑ Borra SI, Beredo R, Kleinfeld M (March 1995). "Hypernatremia in the aging: causes, manifestations, and outcome". Journal of the National Medical Association. 87 (3): 220–4. PMC 2607819. PMID 7731073.
10. ↑ Lindner G, Funk GC (April 2013). "Hypernatremia in critically ill patients". Journal of Critical Care. 28 (2): 216.e11–20. doi:10.1016/j.jcrc.2012.05.001. PMID 22762930.
11. ↑ "UOTW#59 - Ultrasound of the Week". Ultrasound of the Week. September 23, 2015. Archived from the original on October 31, 2018. Retrieved May 27, 2017.
12. ↑ Dehydration at eMedicine
13. ↑ Bhave G, Neilson EG (August 2011). "Volume depletion versus dehydration: how understanding the difference can guide therapy". American Journal of Kidney Diseases. 58 (2): 302–9. doi:10.1053/j.ajkd.2011.02.395. PMC 4096820. PMID 21705120.
14. ↑ "Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate : Health and Medicine Division". www.nationalacademies.org. Archived from the original on December 21, 2018. Retrieved February 7, 2018.
15. ↑ Godman H (September 2016). "How much water should you drink?". Harvard Health. Archived from the original on February 8, 2018. Retrieved February 7, 2018.
16. ↑ Noakes TD (2010). "Is drinking to thirst optimum?". Annals of Nutrition & Metabolism. 57 Suppl 2 (s2): 9–17. doi:10.1159/000322697. PMID 21346332.
17. ↑ Taylor NA, Machado-Moreira CA (February 2013). "Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion rates and electrolyte composition in resting and exercising humans". Extreme Physiology & Medicine. 2 (1): 4. doi:10.1186/2046-7648-2-4. PMC 3710196. PMID 23849497.
18. ↑ 18.0 18.1 Coyle EF (January 2004). "Fluid and fuel intake during exercise". Journal of Sports Sciences. 22 (1): 39–55. CiteSeerX 10.1.1.321.6991. doi:10.1080/0264041031000140545. PMID 14971432. S2CID 14693195.
19. ↑ Murray R, Stofan J (2001). "Ch. 8: Formulating carbohydrate-electrolyte drinks for optimal efficacy". In Maughan RJ, Murray R (eds.). Sports Drinks: Basic Science and Practical Aspects. CRC Press. pp. 197–224. ISBN 978-0-8493-7008-3. Archived from the original on July 31, 2020. Retrieved February 16, 2021.
20. ↑ "Healthwise Handbook," Healthwise, Inc. 1999
21. ↑ Wedro B. "Dehydration". MedicineNet. Archived from the original on October 31, 2018. Retrieved June 10, 2014.
22. ↑ "Can Humans drink seawater?". National Ocean Service. National Ocean Service NOAA Department of Commerce. Archived from the original on November 20, 2018. Retrieved February 16, 2021.
23. ↑ "SimpleSurvival Find Water". Archived from the original on July 29, 2020. Retrieved February 16, 2021.
24. ↑ "Tracker Trail - Mother Earth News - Issue #72". Archived from the original on May 11, 2013. Retrieved February 16, 2021.
25. ↑ "EQUIPPED TO SURVIVE - A Survival Primer". Archived from the original on December 30, 2019. Retrieved February 16, 2021.
26. ↑ "Five Basic Survival Skills in the Wilderness". Archived from the original on October 24, 2013. Retrieved October 26, 2013.
27. ↑ Ellershaw JE, Sutcliffe JM, Saunders CM (April 1995). "Dehydration and the dying patient". Journal of Pain and Symptom Management. 10 (3): 192–7. doi:10.1016/0885-3924(94)00123-3. PMID 7629413.

## Further reading[edit | edit source]

* Byock I (1995). "Patient refusal of nutrition and hydration: walking the ever-finer line". The American Journal of Hospice & Palliative Care. 12 (2): 8–13. doi:10.1177/104990919501200205. PMID 7605733. S2CID 46385519.
* Steiner MJ, DeWalt DA, Byerley JS (June 2004). "Is this child dehydrated?". JAMA. 291 (22): 2746–54. doi:10.1001/jama.291.22.2746. PMID 15187057.

## External links[edit | edit source]

| Look up dehydration in Wiktionary, the free dictionary.

|

* Definition of dehydration by the U.S. National Institutes of Health's MedlinePlus medical encyclopedia Archived July 5, 2016, at the Wayback Machine

Classification|

* ICD-10: E86
* ICD-10-CM: E86.0
* ICD-9-CM: 276.51
* DiseasesDB: 3520

|

External resources|

* MedlinePlus: 000982
* eMedicine: article/801012

* v
* t
* e

Acid–base disorders

Acidosis|

| Metabolic|

* High anion gap
* Ketoacidosis
* Diabetic ketoacidosis
* Alcoholic ketoacidosis
* Lactic
* Normal anion gap
* Hyperchloremic
* Renal tubular

|

Respiratory|

* Respiratory

Alkalosis|

* Metabolic
* Contraction alkalosis
* Respiratory

Other|

* Mixed disorder of acid-base balance
* Acid–base homeostasis

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