Hypovolemia is a condition, where the blood volume decreases, otherwise decrease in blood plasma volume occurs. Thus, it is the volume contraction’s intravascular component, or blood volume loss due to hemorrhage and dehydration. Hence, sometimes, volume contraction and hypovolemia are used synonymously. Hypovolemia is represented by depletion of sodium (salt), thereby differing from dehydration, and meaning excessive water loss from the body.
Historically, hypovolemia was termed desanguination meaning extensive loss of blood (derived from the Latin word sanguis, meaning blood). Hippocrates widely used this term. Actually, this word was used for describing the personality lack, either due to weakness or health, as a result of massive blood loss or hemorrhage.
Volume repletion occurs rapidly in patients suffering from severe hypokalemia, where the peripheral perfusion gets decreased due to delayed capillary refilling and cold extremities. It may also be rapid due to hypovolemic shock, which is severe hypovolemia along with hypotension. Delayed treatment may cause ischemic injury, irreversible multi-organ failure and shock. In such instances, three issues should be taken into consideration; the fluid replacement rate; fluid type infused, and buffer therapy for concurrent lactic acidosis.
Hypovolemic Shock Stages
Hypovolemic shock is a very emergency situation, where excess fluid and blood loss occurs that causes inability of heart to pump the essential blood needed to the body. This kind of shock may even make body organs cease working.
The 4 stages of hypovolemic shock are also referred to as Tennis staging, as the percentage of blood loss imitates the tennis scores as 15, 15-30, 30-40, 40. In general, it is similar to classification of bleeding, according to blood loss.
The stages include:-
- Blood volume loss Up to 15% (750 mL)
- Compensated by vascular bed constriction
- Blood pressure maintained
- Respiratory rate – Normal
- Pale skin
- Mental status: normal to slight anxiety
- Capillary refilling normal
- Urine output-normal
- Blood volume loss up to 15–30% (750 to 1500 mL)
- Heart rate >100bpm
- Cardiac output impossible to be maintained by arterial constriction
- Blood pressure is maintained
- Increased respiratory rate
- Narrow pulse pressure
- Increment in diastolic pressure
- Sweating (due to sympathetic stimulation)
- Delayed capillary refilling
- Mildly restless/anxious
- Urine output -20 to30 ml/hour
- Blood volume loss up to 30–40% (1500–2000 mL)
- Classic hypovolemic shock signs
- Systolic BP ≤100mmHg
- Respiratory rate >30 bpm (marked tachypnea)
- Heart rate >120 bpm (marked tachycardia)
- Cool, pale skin
- Confusion, agitation, anxiety
- Delayed capillary refill
- Urine output 20 ml/hour
- Blood Loss > 40% (greater than 2000 mL)
- Heart rate >140 bpm associated with weak pulse
- Pronounced tachypnea
- Significantly decreased systolic blood pressure of 70 mmHg or less
- Lethargy, decreased consciousness, coma
- Absent capillary refill
- Cool and pale skin (moribund)
- Urine output (negligible)
Hypovolemic shock occurs when the normal quantity of blood in the body is lost about 1/5th or more.
- Internal bleeding (gastrointestinal tract, and polycystic ovarian syndrome, where the ovarian cyst gets injured)
- Medications like vasodilators
- During surgery (it may be an effect of anesthesia, nil per oral, peri-operative bleeding)
- Blood donation (blood loss is minimal, and hence, electrolyte and sugar intake should be increased for the following few days)
- Alcohol consumption
The severity of the symptoms of shock depends on the extent of blood loss.
- Anxiety/ agitation
- Cool and clammy skin
- General weakness
- Decreased or nil urine output
- Rapid breathing
- Pale and moist skin
Clinical symptoms may not be present until 10–20% of total whole-blood volume is lost.
Diagnosis can be made on the basis of:-
- Absence of perfusion: it is assessed by skin changes like pale skin, capillary refilling on lip, nail beds and forehead, and the patient may experience dizzy, nausea, fainting or thirst. This is similar to the shock characteristics.
Reverse changes in blood pressure is seen, i.e., hypertension, in spite of hypotension. Children have the capability of maintaining their blood pressure for a prolonged period of time than the adults; however, when de-compensation occurs, the condition deteriorates rapidly. Apart from the low blood volume, the chances of internal bleeding are also more with children, and hence, it needs immediate medical attention, as profuse internal bleeding can even lead to death.
Thus, look out for mechanisms causing internal bleeding, as bruised or ruptured internal organs. Evaluate the abdomen and chest for pain, guarding, deformity, swelling and discoloration. Bleeding in the abdominal cavity may lead to classical bruising patterns seen in Cullen’s sign and Turner’s sign.
A detailed examination depicts signs of shock, such as:
- Low body temperature
- Low blood pressure
- Rapid and often weak pulse
- Blood tests (Chem7/U+Es, Cross-match, FBC, Glucose)
- Complete blood count (CBC)
- SpO2 Oxygen saturations
- Arterial Blood Gases
- Kidney function tests
- CT scan
- X -ray of doubtful areas in particular
- Urinary catheterization (it is a tube placed inside the bladder for measuring the urine output)
- Right heart catheterization(Swan-Ganz)
- Try keeping the person warm and comfortable for preventing hypothermia.
- Make the person in supine lying or flat position, and lift the feet about 12 inches; this increases the circulation.
- In case, the person has head, back, neck and leg injury, take care not to modify the position of the person unless it is an emergency situation that demands change of position.
- Avoid giving fluids through mouth.
- If the person possesses an allergic reaction, and if you know how to treat it, then do the first aid as needed.
- If the person needs to be transported, always keep him flat with head in the direction of gravity, whereas, foot in an elevated position.
- If spinal injury is suspected, stabilize the neck and head while carrying the person.
- The noted external bleeding must be stopped by applying direct pressure. If the method of applying direct pressure fails while treating hemorrhage, a tourniquet should be utilized. However, take care not to leave the tourniquet applied for > 10 minutes, as this makes the underneath tissues necrosed, due to decreased blood flow to the tissues, thereby reducing the nutrient supply and oxygen necessary to keep the tissues alive.
- The US Military have recommended that application of a tourniquet initially stops the bleeding, rather than direct pressure, whereas techniques like pressure points and elevation are of no use in such emergency situations.
- In case the first-aid provider notices any kind of internal bleeding, he should immediately contact for emergency medical assistance, as a life-saving measure.
- Emergency O2 must be administered for increasing the efficiency of the remaining blood supply of the patient. Many a times, this can prove to be a life-saving measure.
- Using IV fluids, when needed may provide assistance in compensating the lost fluid. However, IV fluids do not have the capability to transport oxygen similar to the blood; but certain blood substitutes can. Crystalloid or colloid IV fluid infusion dilutes the blood’s clotting factors, thereby causes an increment in the bleeding risk level.
- Allowing permissive hypotension during hypovolemic shock is recommended, as it ensures that the clotting factors of blood do not get over diluted, and doesn’t artificially raise the BP to a point where it may blow off all the clots formed.
In patient care:
The main objective here is to replace the lost fluid and blood.
- An IV line is maintained for allowing blood or its products to enter the body. This is useful in stage 2, 3 and 4 of hypovolemic shock.
- Blood transfusions along with surgical repair are the standardized treatment of hypovolemia occurring due to trauma.
Medications like epinephrine, norepinephrine, dopamine and dobutamine should be given, as these drugs increases BP and cardiac output (amount of blood that is pumped out of the heart).
- Norepinephrine (Vasopressors) should never be administered, as they do not treat the primary problem; instead, it reduces the tissue perfusion
- If the cause of hypovolemia is due to adverse reaction of any drug, then its antidotes are provided, but with caution, as this can trigger several pre-existing medical conditions.
- Heart monitoring, comprising of Swan-Ganz catheterization
- Urinary catheter for collecting and monitoring the urine production
The below-mentioned interventions may be carried out:
- Oxygen as being required
- IV access
- Inotrope therapy using Dopamine or Noradrenaline
- Surgical repair of hemorrhaged tissues
- Whole blood/fresh frozen plasma
- As we all know, hypovolemic shock is a medical emergency. Thus, symptoms and its outcomes can be varied depending on:
- Blood loss rate
- Amount of blood volume that is lost
- Illness or injury resulting in blood loss
- Associated chronic medical conditions, including diabetes, heart, kidney and lung diseases
- Generally, patients with mild hypovolemia have good prognosis compared to severe types.
- In spite of immediate emergency medical treatment, severe hypovolemia may result in death.
- Elderly have a poor prognosis compared to young adults.
- Kidney damage
- Heart attack
- Brain damage
- Gangrene of upper and lower limbs, thereby leading to amputation
- Preventing hypovolemia is very easy compared to treating it, after it has occurred.
- Quick and immediate treatment many reduce the risks involved in progressing to severe hypovolemic symptoms.
- Early first aid treatment can many a times, control the symptoms of shock.
Also see this : Hypervolemia – otherwise known as fluid overload, is a condition where there is excess fluid in the blood.