Hypovolemia / Hemorrhagic Shock

Written by: SphynxCatVP
Link to original: http://sphynxcatvp.nocturna.org/articles/sc-donors-hypovolemia.html

What is Hypovolemia?

Hypovolemia basically means low blood volume. "Hypo" means low, "vol" is for volume, and "emia" refers to blood. The reduction of blood volume in hypovolemia means there is a reduction of oxygen carrying capcity. Thus, symptoms of hypovolemia may include cold hands and feet, light headedness, infrequent urination, increased heart rate, and weakness.

Low blood volume due to hemorrhage is most commonly be caused by accidental trauma or internal ailments such as gastro-intestinal bleeding. Dehydration can also contribute to hypovolemia, though it's usually not a cause under normal circumstances.

Losing about 1/5 or more of the normal amount of blood in your body causes hypovolemic/hemorrhagic shock to various degrees. Loss of red blood cells decreases oxygen carrying capacity - the body compensates by increasing cardiac output (your heart rate and blood pressure) to maintain oxygen levels, and also steps up oxygen extraction. For mild to moderate blood loss, fluid solutions (saline or Lactated Ringer's Solution [a/k/a "LRS"] ) may be used to restore fluid volume.

In more severe stages of hypovolemia, however, blood transfusions are required because the blood loss (and resultant lack of oxygen carrying capacity) is too much for the body to compensate for, even with IV fluids. The patient may exhibit high anxiety, especially if they're prone to anxiety in the first place, as well as shivering from feeling constantly cold.

Stages of Hypovolemia

Stage I Hemorrhage

Involves up to 15% (apx. 750ml) of blood volume. There is typically no change in vital signs and fluid resuscitation is not usually necessary.

  • Compensated by constriction of vascular bed
  • Blood pressure maintained
  • Normal respiratory rate
  • Pallor of the skin
  • Slight anxiety

Stage II Hemorrhage

Involves 15-30% (apx. 750–1500 ml) of total blood volume. A patient is often tachycardic (rapid heart beat) with a narrowing of the differencebetween the systolic and diastolic blood pressures. The body attempts to compensate with peripheral vasoconstriction (narrowing of blood vessels). Skin may start to look pale and be cool to the touch. The patient may exhibit slight changes in behavior. Intravenous fluid resuscitation with crystalloids (Saline solution or Lactated Ringer's solution) is all that is typically required. Blood transfusion is not typically required.

  • Cardiac output cannot be maintained by arterial constriction
  • Tachycardia >100bpm (rapid heart rate)
  • Increased respiratory rate
  • Blood pressure maintained
  • Narrow pulse pressure
  • Sweating from sympathetic stimulation
  • Mildly anxious/Restless

Stage III Hemorrhage

Involves loss of 30-40% (apx. 1500–2000 ml) of circulating blood volume. The patient's blood pressure drops, the heart rate increases, peripheral perfusion (shock), such as capillary refill worsens, and the mental status worsens. Fluid resuscitation with crystalloid (Saline solution or Lactated Ringer's solution) and blood transfusion are usually necessary.

  • Systolic blood pressure falls to 100mmHg or less
  • Classic signs of hypovolemic shock
  • Marked tachycardia >120 bpm (heart rate - beats per minute)
  • Marked tachypnea >30 bpm (rapid breathing - breaths per minute)
  • Decreased systolic pressure
  • Alteration in mental status (Anxiety, Agitation)
  • Sweating with cool, pale skin

Stage IV Hemorrhage

Involves loss of over 40% (>2000mls) of circulating blood volume. The limit of the body's compensation is reached and aggressive resuscitation is required to prevent death.

  • 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 Options

Stage II or worse should always always ALWAYS be evaluated and treated by medical professionals.

Stage I may be treated at home, but monitor carefully if the cause is unknown (internal bleeding does not always leave visible signs or bruising) so that if it gets worse , proper treatment can be obtained as soon as possible.

Other Information

Blood pressure (BP) is the pressure exerted by circulating blood on the walls of blood vessels, and is one of the principal vital signs. During each heartbeat, BP varies between a maximum (systolic) and a minimum (diastolic) pressure. The mean BP decreases as the circulating blood moves away from the heart through arteries, has its greatest decrease in the small arteries and arterioles, and continues to decrease as the blood moves through the capillaries and back to the heart through veins.