Hypovolemia

Hypovolemia
Synonyms Oligemia, hypovolaemia, oligaemia, hypovolæmia
Specialty Emergency medicine
Symptoms headache, fatigue, nausea, profuse sweating, dizziness

Hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma.[1][2] It is thus the intravascular component of volume contraction (or loss of blood volume due to things such as bleeding or dehydration), but, as it also is the most essential one, hypovolemia and volume contraction are sometimes used synonymously.

Hypovolemia is characterized by sodium depletion, and thus is distinct from (although often overlapping with) dehydration, excessive loss of body water.[3]

Causes

Common causes of hypovolemia are:[4]

Diagnosis

Symptoms may not be present until 10–20% of total whole-blood volume is lost.

Hypovolemia can be recognized by tachycardia, diminished blood pressure,[8] and the absence of perfusion as assessed by skin signs (skin turning pale) and/or capillary refill on forehead, lips and nail beds. The patient may feel dizzy, faint, nauseated, or very thirsty. These signs are also characteristic of most types of shock.

Note that in children compensation can result in an artificially high blood pressure despite hypovolemia. Children typically compensate (maintain blood pressure despite loss of blood volume) for a longer period than adults, but deteriorate rapidly and severely once they do begin to decompensate. This is another reason (aside from initial lower blood volume) that even the possibility of internal bleeding in children should almost always be treated aggressively.

Obvious signs of external bleeding should be noted while remembering that people can bleed to death internally without any external blood loss. ("Blood on the floor, plus 4 more" = intrathoracic, intraperitoneal, retroperitoneal, pelvis/thigh)

There should be considered possible mechanisms of injury that may have caused internal bleeding, such as ruptured or bruised internal organs. If trained to do so and if the situation permits, there should be conducted a secondary survey and checked the chest and abdomen for pain, deformity, guarding, discoloration or swelling. Bleeding into the abdominal cavity can cause the classical bruising patterns of Grey Turner's sign or Cullen's sign.

Stages

Usually referred to as a "class" of shock. Most sources state that there are 4 stages of hypovolemic shock;[9] however, a number of other systems exist with as many as 6 stages.[10]

The 4 stages are sometimes known as the "Tennis" staging of hypovolemic shock, as the stages of blood loss (under 15% of volume, 15–30% of volume, 30–40% of volume and above 40% of volume) mimic the scores in a game of tennis: 15, 15–30, 30–40 and 40.[11] It is basically the same as used in classifying bleeding by blood loss.

The signs and symptoms of the major stages of hypovolemic shock include:[12]

Stage 1 Stage 2 Stage 3 Stage 4
Blood lossUp to 15% (750 mL)15–30% (750–1500 mL)30–40% (1500–2000 mL)Over 40% (over 2000 mL)
Blood pressureNormal (Maintained
by vasoconstriction)		Increased diastolic BPSystolic BP < 100Systolic BP < 70
Heart rateNormalSlight tachycardia (> 100 bpm)Tachycardia (> 120 bpm)Extreme tachycardia (> 140 bpm) with weak pulse
Respiratory rateNormalIncreased (> 20)Tachypneic (> 30)Extreme tachypnea
Mental statusNormalSlight anxiety, restlessAltered, confusedDecreased LOC, lethargy, coma
SkinPallorPale, cool, clammyIncreased diaphoresisExtreme diaphoresis; mottling possible
Capillary refillNormalDelayedDelayedAbsent
Urine outputNormal20–30 mL/h20 mL/hNegligible

Investigation

In a hospital, physicians respond to a case of hypovolemic shock by conducting these investigations:

Treatment

Field care

The most important step in treatment of hypovolemic shock is to identify and control the source of bleeding.[13]

Medical personnel should immediately supply emergency oxygen to increase efficiency of the patient's remaining blood supply. This intervention can be life-saving.[14]

The use of intravenous fluids (IVs) may help compensate for lost fluid volume, but IV fluids cannot carry oxygen the way blood does—however, researchers are developing blood substitutes that can. Infusing colloid or crystalloid IV fluids also dilutes clotting factors in the blood, increasing the risk of bleeding. Current best practice allow permissive hypotension in patients suffering from hypovolemic shock,[15] both avoid overly diluting clotting factors and avoid artificially raising blood pressure to a point where it "blows off" clots that have formed.

Hospital treatment

Fluid replacement is beneficial in hypovolemia of stage 2, and is necessary in stage 3 and 4.[12] See also the discussion of shock and the importance of treating reversible shock while it can still be countered.

The following interventions are carried out:

  • IV access
  • Oxygen as required
  • Fresh frozen plasma or blood transfusion
  • Surgical repair at sites of bleeding

Vasopressors (like (dopamine and noradrenaline) should generally be avoided, as they may result in further tissue ischemia and don't correct the primary problem. Fluids are the preferred choice of therapy.[16]

History

In cases where loss of blood volume is clearly attributable to bleeding (as opposed to, e.g., dehydration), most medical practitioners prefer the term exsanguination for its greater specificity and descriptiveness, with the effect that the latter term is now more common in the relevant context.[17]

See also

References

  1. ↑ "Hypovolemia definition - MedicineNet - Health and Medical Information Produced by Doctors". Medterms.com. 2012-03-19. Retrieved 2015-11-01.
  2. ↑ "Hypovolemia | definition of hypovolemia by Medical dictionary". Medical-dictionary.thefreedictionary.com. Retrieved 2015-11-01.
  3. ↑ "Dehydration definition - MedicineNet - Health and Medical Information Produced by Doctors". Medterms.com. 2013-10-30. Retrieved 2015-11-01.
  4. ↑ Sircar, S. Principles of Medical Physiology. Thieme Medical Pub. ISBN 9781588905727
  5. ↑ Danic B, Gouézec H, Bigant E, Thomas T (June 2005). "[Incidents of blood donation]". Transfus Clin Biol (in French). 12 (2): 153–9. doi:10.1016/j.tracli.2005.04.003. PMID 15894504.
  6. ↑ "Burn Shock / House Staff Manual". Total Burn Care. Retrieved 2015-11-01.
  7. ↑ "Resuscitation in Hypovolaemic Shock. Information page | Patient". Patient.info. Retrieved 2015-11-01.
  8. ↑ "Stage 3: Compensated Shock". Archived from the original on 2010-06-11.
  9. ↑ Hudson, Kristi. "Hypovolemic Shock - 1 Nursing CE". Archived from the original on 2009-06-06.
  10. ↑ "Stage 1: Anticipation stage (a new paradigm)". Archived from the original on 2010-01-16.
  11. ↑ Greaves, Ian; Porter, Keith; Hodgetts, Timothy; et al., eds. (2006). Emergency Care: A Textbook for Paramedics. Elsevier Health Sciences. p. 229. ISBN 9780702025860.
  12. 1 2 Elizabeth D Agabegi; Agabegi, Steven S. (2008). Step-Up to Medicine (Step-Up Series). Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 978-0-7817-7153-5.
  13. ↑ Bulger, E. M., Snyder, D., Schoelles, K., Gotschall, C., Dawson, D., Lang, E., ... & White, L. (2014). An evidence-based prehospital guideline for external hemorrhage control: American College of Surgeons Committee on Trauma. Prehospital Emergency Care, 18(2), 163-173.
  14. ↑ Takasu A, Prueckner S, Tisherman SA, Stezoski SW, Stezoski J, Safar P. (2000), Effects of increased oxygen breathing in a volume controlled hemorrhagic shock outcome model in rats., PMID 10959021
  15. ↑ "Permissive Hypotension". Trauma.Org. 1997-08-31. Retrieved 2015-11-01.
  16. ↑ "Failure of dobutamine to improve liver oxygenation during resuscitation with a crystalloid solution after experimental haemorrhagic shock". Pubmed-NCBI. 1996-08-31. Retrieved 2017-11-21.
  17. ↑ L. Geeraedts Jr.; H. Kaasjager; A. van Vugt; J. Frölke (2009). "Exsanguination in trauma: A review of diagnostics and treatment options". Injury. 40 (1): 11–20. doi:10.1016/j.injury.2008.10.007. PMID 19135193.
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