3. Haemodilution

Haemodilution

This PatientPlus article is written for healthcare professionals so the language may be more technical than the condition leaflets. You may find the abbreviations list helpful.

This is increased plasma volume, leading to low haematocrit and hyponatraemia.

Water intoxication can arise from:

  • Administration of too much intravenous fluid
  • Ingestion of too much water, especially if electrolyte levels are depleted

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Haemodilution occurs physiologically in pregnancy. This may result in lower haemoglobin concentrations than in the non-pregnant state. However, many women function well and do not require iron supplementation. It is common in chronic heart failure, where it may contribute to poor outcome.[1] At-risk groups for water intoxication include:

  • Infants under one year old
  • Athletes, eg marathon runners/extreme athletes and hikers who drink excessively during prolonged exertion[2][3]
  • Also associated with the use of MDMA (ecstasy) with prolonged dancing and high water intake at raves/events[4]
  • The mentally ill in association with polydipsia

Symptoms

  • Confusion
  • Nausea/vomiting
  • Seizures
  • Coma

It may be fatal.

Signs

Brain oedema.

Treat the underlying cause. Correct electrolyte balance in severe cases of water intoxication.

Pharmacological

Diuretics.

  • Acute normovolaemic haemodilution (ANH) may be used in operations where there is a large anticipated blood loss. It involves removing some of a patient's own blood and replacing it with fluids, to maintain normal volume. This process ensures that the blood that is lost during the operation is diluted, ie fewer red blood cells are in it. This reduces the load on the heart and allows the blood to flow more easily through the capillaries.The patient's own blood is returned after the operation.
  • Haemodilution improves the flow properties of the blood so that, theoretically, oxygen and nutrient supply to the brain is improved, eg after a cerebrovascular event, and damaged brain cells may survive. This treatment had been shown to reduce brain infarct size in animals with experimental stroke and it was first tried in the 1970s. However, a recent Cochrane review of the (considerable amount of) research showed that there were no benefits from this treatment.[5]
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Further reading & references

  1. Androne AS, Katz SD, Lund L, et al; Hemodilution is common in patients with advanced heart failure. Circulation. 2003 Jan 21;107(2):226-9.
  2. Noakes T; Hyponatremia in distance runners: fluid and sodium balance during exercise. Curr Sports Med Rep. 2002 Aug;1(4):197-207.
  3. Noakes TD, Sharwood K, Collins M, et al; The dipsomania of great distance: water intoxication in an Ironman triathlete. Br J Sports Med. 2004 Aug;38(4):E16.
  4. Cherney DZ, Davids MR, Halperin ML; Acute hyponatraemia and 'ecstasy': insights from a quantitative and integrative analysis. QJM. 2002 Jul;95(7):475-83.
  5. Asplund K. Cochrane Review. Haemodilution for acute ischaemic stroke; October 2002
Original Author: Dr Hayley Willacy Current Version:
Last Checked: 22/01/2010 Document ID: 2218  Version: 21 © EMIS

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

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