Examine individual changes

'{{Cleanup-jargon|date=June 2009}} {{Infobox Disease | Name = Hypovolemia | Image = | Caption = | DiseasesDB = | ICD10 = {{ICD10|E|86||e|70}}, {{ICD10|R|57|1|r|50}}, {{ICD10|T|81|1|t|80}} | ICD9 = {{ICD9|276.52}} | ICDO = | OMIM = | MedlinePlus = | eMedicineSubj = | eMedicineTopic = | MeshID = D020896 | }} In [[physiology]] and [[medicine]], '''hypovolemia''' (also '''hypovolaemia''') is a state of decreased [[blood volume]]; more specifically, decrease in volume of [[blood plasma]].<ref>[http://www.medterms.com/script/main/art.asp?articlekey=3871 MedicineNet > Definition of Hypovolemia] Retrieved on July 2, 2009</ref><ref>[http://medical-dictionary.thefreedictionary.com/hypovolemia TheFreeDictionary.com --> hypovolemia] Citing Saunders Comprehensive Veterinary Dictionary, 3 ed. Retrieved on July 2, 2009</ref> It is thus the intravascular component of [[volume contraction]] (or loss of blood volume due to things such as hemorrhaging or dehydration), but, as it also is the most essential one, ''hypovolemia'' and ''volume contraction'' are sometimes used synonymously. It differs from [[dehydration]], which is defined as excessive loss of [[body water]].<ref>[http://www.medterms.com/script/main/art.asp?articlekey=2933 MedicineNet > Definition of Dehydration] Retrieved on July 2, 2009</ref> Furthermore, hypovolemia defines water deficiency only in volume rather than specifically water. ==Causes== Common causes of hypovolemia are [[dehydration]], [[bleeding]], vomiting<ref name="Carlson">Carlson, N. R. (2005). Foundations of Physiological Psychology: Custom edition for SUNY Buffalo. Boston, MA: Pearson Custom Publishing.</ref>, severe [[Burn (injury)|burns]]<ref>http://www.totalburncare.com/orientation_burn_shock.htm</ref><ref>http://www.patient.co.uk/doctor/Resuscitation-in-Hypovolaemic-Shock.htm</ref> and drugs such as [[diuretic]]s or [[vasodilator]]s typically used to treat [[hypertension|hypertensive]] individuals. Rarely, it may occur as a result of a [[blood donation]]<ref>{{cite journal |author=Danic B, Gouézec H, Bigant E, Thomas T |title=[Incidents of blood donation] |language=French |journal=Transfus Clin Biol |volume=12 |issue=2 |pages=153–9 |year=2005 |month=June |pmid=15894504 |doi=10.1016/j.tracli.2005.04.003 |url=}}</ref>, sweating<ref name="Carlson" />, and alcohol consumption<ref name="Carlson" />. It is also common during surgery due to the use of anaesthetics, nil-by-mouth, and in-operation bleeding. ==Bodily response== To respond to hypovolemia is a task for the body [[fluid balance]] systems as well as [[osmotic balance]] systems. Following an acute response this function is accomplished by two sets of receptors; one in the kidneys and the other in the heart. ====Acute response==== {{See|Baroreflex}} The first response to hypovolemia is an inversed [[baroreflex]], where a lack of activation of [[baroreceptor]]s results in elevation of [[total peripheral resistance]] and [[cardiac output]] via increased [[contractility]] of the heart, [[heart rate]], and arterial [[vasoconstriction]],<ref>{{cite journal |author=Banic A, Sigurdsson GH, Wheatley AM |title=Influence of age on the cardiovascular response during graded haemorrhage in anaesthetized rats |journal=Res Exp Med (Berl) |volume=193 |issue=5 |pages=315–21 |year=1993 |pmid=8278677 |doi=10.1007/BF02576239 |url=}}</ref> which tends to increase blood pressure. There is also ''autoreperfusion'', in which decreased blood pressure results in decreased filtration of fluid out of capillaries, in effect causing a volume shift from [[interstitial fluid]] to blood plasma. ====Kidney==== {{Main|Renin-angiotensin system}} The kidneys have a specialized set of cells called [[granular cell]]s that enable the recognition of changes in [[blood flow]] to the kidneys.<ref name="Carlson"/> Naturally, these cells detect the presence of hypovolemia and react accordingly to the loss of blood volume. These cells secrete a [[hormone]] called [[renin]] when there is a decrease in the flow of blood to the kidneys.<ref name="Carlson"/> Renin flows into the blood and there, initiates the conversion of a protein called [[angiotensinogen]] to [[angiotensin]].<ref name="Carlson"/> In order to exert its effects on the body, angiotensin I must be converted by [[enzyme]]s into its active form, angiotensin II. Physiologically, angiotensin II stimulates the release of hormones by the posterior [[pituitary gland]] (ADH, also known as [[vasopressin]]) and the [[adrenal cortex]] ([[aldosterone]]). Aldosterone causes the kidneys to reabsorb [[sodium]], leading to the reabsorption of water. ADH (vasopressin) also causes the kidneys to reabsorb water. Angiotensin II increases [[blood pressure]] by contracting arterial muscles. ====Heart==== :''Further reading:[[Atrial natriuretic peptide]]'' The next set of receptors responsible for detecting volumetric insufficiency are located in the heart atria. Commonly referred to as stretch receptors, these atrial [[baroreceptor]]s detect the amount of blood that is being pumped back into the heart from the veins.<ref name="Carlson"/> The body constantly returns blood to the heart through veins. Therefore, when the volume of blood being transported back to the heart is decreased, these receptors detect the change in the amount of blood thereby reducing the release of [[atrial natriuretic peptide]]. ====Thirst==== {{Main|Extracellular thirst}} Both the activation of the [[renin angiotensin system]] and the decrease in [[atrial natriuretic peptide]], along with their other functions, contribute to elicit [[thirst]], by affecting the [[subfornical organ]].<ref>{{cite journal | author=M.J. McKinley and A.K. Johnson | title=The Physiological Regulation of Thirst and Fluid Intake | journal=News in Physiological Sciences | volume=19 | issue=1 | year=2004 | pages=1–6 | url=http://physiologyonline.physiology.org/cgi/content/full/19/1/1 | accessdate=2006-06-02 | pmid=14739394 | doi=10.1152/nips.01470.2003 }}</ref> ===Other responses=== Furthermore, as intravascular fluid decreases, blood pressure is reduced and some compensation occurs as fluid from other cellular compartments moves into the vasculature. Fluid is passively transferred from all of the fluid compartments in the body, including [[intracellular]], [[interstitial]] and other extravascular compartments.<ref name="Carlson" /> ==Diagnosis== {{Unreferenced section|date=February 2009}} Clinical symptoms may not be present until 10–20% of total whole-blood volume is lost. Hypovolemia can be recognized by [[elevated pulse]], diminished blood pressure<ref>http://www.stagesofshock.com/stage3/index.html</ref>, and the absence of [[perfusion]] as assessed by skin signs (skin turning pale) and/or [[capillary refill]] on [[forehead]], [[lip]]s and [[nail beds]]. The patient may feel dizzy, faint, nauseated, or very thirsty. These signs are also characteristic of most types of [[Shock (circulatory)|shock]]. Note that in children, compensation can result in an artificially high blood pressure despite hypovolemia. Children will typically compensate (maintain blood pressure despite loss of blood volume) for a longer period than adults, but will 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. Also look for obvious signs of external bleeding while remembering that people can bleed to death internally without any external blood loss. Also consider possible mechanisms of injury that may have caused internal bleeding such as ruptured or bruised internal organs. If trained to do so and the situation permits, conduct a [[Advanced_Trauma_Life_Support#Secondary_Survey|secondary survey]] and check the chest and abdomen for pain, deformity, guarding, discolouration or swelling. Bleeding into the abdominal cavity can cause the classical bruising patterns of [[Grey Turner's sign]] or [[Cullen's sign]]. ===Stages of Hypovolemic Shock=== Most sources state that there are 4 stages of hypovolemic shock<ref name="ambulancetechnicianstudy.co.uk">http://www.ambulancetechnicianstudy.co.uk/shock.html</ref><ref name="dynamicnursingeducation.com">http://dynamicnursingeducation.com/class.php?class_id=47&pid=18</ref>, however a number of other systems exist with as many as 5 stages<ref>http://www.stagesofshock.com/stage1/index.html</ref>. The 4 stages are sometimes known as the "Tennis" staging of hypovolemic shock, as the 4 stages of % volume of blood loss mimic the scores in a game of tennis: 15, 15-30, 30-40, 40<ref name="ambulancetechnicianstudy.co.uk"/><ref name="dynamicnursingeducation.com"/>. ====Stage 1==== * Up to 15% blood volume loss (750mls)<ref name="ambulancetechnicianstudy.co.uk"/> * Compensated by constriction of vascular bed * Blood pressure maintained * Normal respiratory rate * Pallor of the skin * Slight anxiety ====Stage 2==== * 15–30% blood volume loss (750–1500&nbsp;ml)<ref name="ambulancetechnicianstudy.co.uk"/> * Cardiac output cannot be maintained by arterial constriction * Tachycardia >100bpm * Increased respiratory rate * Blood pressure maintained * Increased diastolic pressure * Narrow pulse pressure * Sweating from sympathetic stimulation * Mildly anxious/Restless ====Stage 3==== * 30–40% blood volume loss (1500–2000&nbsp;ml)<ref name="ambulancetechnicianstudy.co.uk"/> * Systolic BP falls to 100mmHg or less * Classic signs of hypovolemic shock * Marked tachycardia >120 bpm * Marked tachypnea >30 bpm * Decreased systolic pressure * Alteration in mental status (Anxiety, Agitation) * Sweating with cool, pale skin ====Stage 4==== * Loss greater than 40% (>2000mls)<ref name="ambulancetechnicianstudy.co.uk"/> * Extreme tachycardia with weak pulse * Pronounced tachypnea * Significantly decreased systolic blood pressure of 70 mmHg or less * Decreased level of consciousness * Skin is sweaty, cool, and extremely pale (moribund) ==Treatment== {{Unreferenced section|date=February 2009}} Minor hypovolemia from a known cause that has been completely controlled (such as a blood donation from a healthy patient who is not anemic) may be countered with initial rest for up to half an hour. Oral fluids that include moderate sugars and [[electrolytes]] are needed to replenish depleted sodium ions. Furthermore the advice for the donor is to eat good solid meals with proteins for the next few days. Typically, this would involve a fluid volume of less than one [[liter]], although this is highly dependent on body weight. Larger people can tolerate slightly more blood loss than smaller people{{Unclear section|date=April 2010}}. More serious hypovolemia should be assessed by a physician. ===First aid=== External bleeding should be controlled by direct pressure. If direct pressure fails, other techniques such as elevation and pressure points should be considered. The [[tourniquet]] should be used in the case of hemorrhage that can not be controlled by any other means. The use of a tourniquet can kill all the tissue below its application upon a limb, making amputation necessary. If a first-aid provider recognizes internal bleeding the life-saving measure to take is to immediately call for emergency assistance. ===Field care=== Emergency oxygen should be immediately employed to increase the efficiency of the patient's remaining blood supply{{Citation needed|date=April 2010}}. This intervention can be life-saving{{Citation needed|date=April 2010}}. The use of [[intravenous drip|intravenous fluids]] (IVs) may help compensate for lost fluid volume, but IV fluids cannot carry oxygen in the way that blood can, however [[blood substitutes]] are being developed which can. Infusion of colloid or crystalloid IV fluids will also dilute clotting factors within the blood, increasing the risk of bleeding. It is current best practice to allow permissive hypotension in patients suffering from hypovolaemic shock<ref>http://www.trauma.org/archive/resus/permissivehypotension.html Permissive Hypotension</ref> both to ensure clotting factors are not overly diluted but also to stop blood pressure being artificially raised to a point where it "blows off" clots that have formed. ===Hospital treatment=== If the hypovolemia was caused by medication, the administration of antidotes may be appropriate but should be carefully monitored to avoid shock or the emergence of other pre-existing conditions{{Citation needed|date=April 2010}}. [[Blood transfusion]]s coupled with surgical repair are the definitive treatment for hypovolemia caused by [[Physical trauma|trauma]]{{Citation needed|date=April 2010}}. See also the discussion of [[Shock (circulatory)|shock]] and the importance of treating reversible shock while it can still be countered. For a patient presenting with hypovolemic shock in hospital the following investigations would be carried out: *Blood tests: U+Es/Chem7, FBC, Glucose, Cross-match *Central Venous Line/Blood Pressure *Arterial Line/Arterial Blood Gases *Urine output measurments (via urinary catheter) *Blood pressure *SpO2 Oxygen saturations The following interventions would be carried out: *IV access *Oxygen as required *Surgical repair at sites of haemorrhage *Inotrope therapy ([[Dopamine]], [[Noradrenaline]]) *Fresh frozen plasma/whole blood ==History== {{Unreferenced section|date=February 2009}} Hypovolemia has historically been termed ''desanguination'' (from Latin ''sanguis'', blood), meaning a massive loss of blood. The term was widely used by the [[Hippocrates]] in traditional medicine practiced in the Greco-Roman civilization and in Europe during the Middle Ages. The word was possibly used to describe the lack of personality (by death or by weakness) that often occurred once a person suffered [[hemorrhage]] or massive blood loss. Today the term [[exsanguination]] is more widely used and is commonly used in medical settings<ref>Exsanguination in trauma: A review of diagnostics and treatment options Injury, Volume 40, Issue 1, Pages 11-20 L. Geeraedts Jr., H. Kaasjager, A. van Vugt, J. Frölke</ref>. ==See also== * [[Volume status]] * [[Hypervolemia]] * [[Exsanguination]] ==References== {{Reflist}} ==External links== * {{CrispThesaurus|00004050}} * {{DiseasesDB|29217}} * http://www.daxor.com - Daxor designed and developed the BVA-100 Blood Volume Analyzer. It is the first instrument approved by the FDA to provide rapid direct measurement of a patient's true blood volume. {{Water-electrolyte imbalance and acid-base imbalance}} [[Category:Blood]] [[Category:Medical emergencies]] [[de:Hypovolämie]] [[es:Hipovolemia]] [[fr:Hypovolémie]] [[lt:Hipovolemija]] [[pl:Hipowolemia]] [[pt:Hipovolemia]] [[ru:Гиповолемия]] [[fi:Hypovolemia]] [[sv:Hypovolemi]]'