Hypovolemia, otherwise known as fluid volume deficit, is an emergency condition where the water and electrolytes are lost in equal proportion (ratio of serum electrolyte and water is the same). This differentiates hypovolemia to dehydration which refers to the loss of water alone with sodium levels increased. Fluid volume deficit may occur alone or in combination with other imbalances.
Causes of Hypovolemia
When bodily fluids are lost rapidly, fluid volume deficit will likely occur. The risk is increased if an individual has poor fluid intake. Causes of hypovolemia include abnormal fluid losses as a result of vomiting, diarrhea, gastrointestinal suction and sweating.
Furthermore, an individual is predisposed for hypovolemia with:
- Diabetes Insipidus
- Adrenal insufficiency
- Osmotic diuresis
- Third-space fluid shifts or the movement of fluid from the vascular system to other body spaces for example the edema formation in burns or ascites in liver dysfunction
Depending on the degree of fluid loss, hypovolemia can develop rapidly and can be mild, moderate or severe. The following are clinical manifestations of fluid volume deficit:
- Acute weight loss
- Decreased skin turgor
- Concentrated urine
- Postural hypotension
- Weak, rapid heart rate
- Flattened neck veins
- Increased temperature
- Decreased central venous pressure
- Cool, clammy skin (due to peripheral vasoconstriction)
- Muscle weakness
- Monitor fluid intake and output. Measurement of the client’s intake and output is first measured by the nurse and evaluated for at least at 8-hour intervals is the first step to assessing the presence of hypovolemia. For severe cases, hourly measurements are required by the doctor. When hypovolemia is developing, fluid losses exceeds fluid intake. The loss of body fluids may be noticed in many forms such as polyuria or the excessive urination, diarrhea and vomiting. As the condition progresses and fluid volume deficit has fully developed, the kidneys tries to conserve fluids which can lead to oliguria or urinary output less than 30 ml/hr in adults. The nurse also monitors the body weight measurements as acute weight loss is a significant manifestation of hypovolemia. Acute weight loss of 0.5 kg suggests fluid loss of 500 ml.
- Closely monitor client’s vital signs. Weak, rapid pulse and postural hypotension should alert the nurse. Postural hypotension is noted when systolic pressure drops greater than 15 mmHg when the client moves from a lying position to sitting. Body temperature also decreases in hypovolemia.
- Monitor skin turgor on a regular basis. Turgor refers to the elastic property of the skin. Pinching the skin of a normal healthy person will immediately return to its normal position when released. Individuals with hypovolemia have poor skin turgor. Meaning to say, their skin slowly comes back to normal state after being released. In severe cases, skin may be elevated for many seconds. Turgor is best assessed over the sternum, inner aspects of thigh or forehead. When caring for an elderly client, this test is not valid as old people normal has poor skin turgor as elasticity decreases with age.
- Monitor urinary concentration. Concentration of urine is measure by the urine specific gravity. Normal values for urine specific gravity is 1.005 to 1.030.
- Monitoring mental function. Clients with severe depletion of fluid volume have poor mental function as a result of decreased cerebral perfusion. Decreased peripheral perfusion may result in cold extremities. Low central venous pressure is indicative of hypovolemia in clients with normal cardiopulmonary function.
- Prevent further fluid depletion. The nurse must implement measures to minimize or prevent further fluid losses. For instance, a client with diarrhea should be given antidiarrheal medications to control the cause of fluid loss. The client should also be given small volumes of oral fluids frequently.
- Fluid replacement. As mentioned above, oral fluids should be administered to the client to help correct fluid loss. One consideration in giving oral fluids is the likes and dislikes of the client. Another thing to put into consideration is the type of fluid lost. In cases the client cannot take in fluids orally, enteral or parenteral route can be used. Intravenous route is required if acute or severe fluid loss is noted. For hypotensive clients with hypovolemia, isotonic electrolyte solutions such as Lactated Ringer’s or 0.9% Sodium Chloride are frequently used to expand plasma volume. When the client becomes normotensive, hypotonic electrolyte solutions are given such as 0.45% sodium Chloride to provide both electrolytes and free water for renal excretion of metabolic wastes.
Hypovolemia can rapidly develop, hence it is important to implement fluid replacement and correct cause of fluid depletion as soon as possible. Further fluid loss may result to renal damage due to prolonged hypovolemia.