Also known as fluid overload, hypervolemia is a condition characterized by excessive fluid volume. It is an upsurge of too much blood plasma, causing an elevated volume of blood. [1, 2]
It is an expansion of the extracellular fluid volume, including the intravascular or interstitial space. This may present as an overproduction of isotonic fluid, composed of water and sodium, occurring extracellularly. Overindulgence of which in the intravascular compartment often go hand in hand with an elevated total body sodium and consequently, an increase in the percentage body water. [ 3, 4, 5]
Hypervolemia: Pathologic Process
Normally, the body can create processes with which it can compensate and relinquish fluid and electrolyte equilibrium. This is usually done with the help of hormones such as aldosterone, atrial natriuretic peptide (ANP) and antidiuretic hormone (ADH). These hormones cause the nephrons in the kidneys to release the essential water and sodium needed by the body. 
Hypervolemia may occur in instances where there is an elevation of intravascular volume levels. This may be due to shifts in fluids from the interstitium to plasma, reduced excretion of sodium and water, excessive intravenous fluids, and excessive retention of water and sodium from chronic renal stimuli attempting to conserve both. 
An elevation of the extracellular fluid volume produces circulatory overload and subsequently, an abnormally amplified cardiac contractility, increased mean artery pressure (MAP), and an elevated capillary hydrostatic pressure. The latter, as a consequence, causes shifts of fluids to the interstitial space, and hence, producing edema. 
If severe hypervolemia is at hand, or patient has a previous history if cardiac dysfunction, compensatory mechanisms may fail. Urinary excretion of sodium and water may fall short. Antidiuretic hormone and aldosterone may not be diminished from mean arterial pressure elevation. Hence, pulmonary edema and heart failure may prevail. 
Causes of Hypervolemia
This condition of fluid volume excess may be product of compromised mechanisms for regulating water and sodium, as seen in congestive heart failure, hepatic failure and renal failure. Blood backs up and returns to the veins as the heart function fails, causing fluid increase among the veins. Liver malfunction can take part in excessively high levels of blood plasma. When kidneys, on the other hand, fail, adequate excretion of fluids is no longer feasible. 
Other reasons for inaccurate sodium and water retention include low protein sources, use of corticosteroids, glomerulonephritis, nephritic syndrome, nephropathy, hyperaldosteronism, and liver cirrhosis. All of which have rooted from defective means of controlling water and electrolyte balance. [2, 8]
Excessive fluid volume may also stem from too much intake of sodium and fluids. Examples of which include ingestion of diet high in sodium, overhydration of intravenous fluids, and even as a reaction from rapid blood transfusion. [4, 8, 9]
Lastly, hypervolemia may be brought about by fluid shift into the intravascular space. This may occur in response to fluid remobilization during burn therapy, as a result of giving of albumin, and from mannitol or any hypertonic fluid administration. 
Hypervolemia: Signs and Symptoms
Manifestations of excess plasma fluid volume, or hypervolemia, include the following:
- Shortness of breath and increased respiratory rate, both due to decrease in red blood cells. Dilution of blood produces a compensatory increase in respiration to improve oxygenation.
- Increased pulses with bounding character stemmed from circulatory overload and concomitant elevation of cardiac contractility.
- Labored breathing and difficulty of breathing caused by an increase in fluid volume among pleural spaces
- Crackles upon auscultation brought about by increased hydrostatic pressure in pulmonary blood vessels.
- Moist skin as compensation for increase fluid excretion thru sweating
- Hypertension, along with increases in both the central venous pressure (CAP) and pulmonary artery pressure (PAP), due to increased mean arterial pressure and circulatory overload
- Jugular vein distention from elevated blood volume and preload
- Weight gain, the best sign of extracellular fluid volume excess, from excessive total body fluid due to circulatory overload
- Edema, as shift of fluids from plasma to interstitium from elevations in both mean arterial pressure and capillary hydrostatic pressure
- A third heart sound, or an S3 gallop, on auscultation due to rapid filling and ventricular overloading at diastole
- Ascites and fluid in the abdomen from buildups of excessive fluid in the different regions of the body
- Paroxysmal nocturnal dyspnea and orthopnea, both from fluid collection in the lungs
- Abnormalities in renal function leading to azotemia, oliguria, change in electrolyte levels, and specific gravity alterations.[1, 3, 4, 7]
Methods in Diagnosing Hypervolemia
Hypervolemia is primarily diagnosed thru its signs and symptoms. However, diagnostic examinations that can be of help include a dilutional decrease in hematocrit levels, serum sodium of normal value, low blood urea nitrogen (BUN), decreased serum potassium level, low serum osmolality, low urine sodium excretion of less than 10meq per day, decreased oxygen level, and signs of pulmonary congestion on chest radiographs. 
Treatment and Management of Hypervolemia
The following are therapeutic interventions in the management of hypervolemia:
- Restriction of sodium and water intake. Monitor input of fluids, including that of oral, enteral and parenteral. Avoid foods with high sodium content.
- Diuretics may be given. Loop diuretics, such as furosemide, are recommended for heart failure and severe hypervolemia.
- To assess the severity of electrolyte loss and monitor the patient’s response to diuresis, his weight and his urine output must be regularly determined and monitored.
- Medications, like nitroglycerin and morphine, can be administered for dilatation of blood vessels and subsequent reduction of pulmonary congestion.
- Hydralazine and Captopril, afterload reduction medications, can also be given for relief of pulmonary edema
- Renal replacement therapies, such as hemodialysis and peritoneal dialysis, may be performed among patients with renal failure or those with severe hypervolemia.
- Continuous arteriovenous and venovenous hemoinfiltrations both aims for sufficient removal of excess fluids from those patients not necessitating dialysis.
- Other palliative measures comprise of antiembolism stockings to mobilize edema, oxygen inhalation, bed rest, and, of course, treatment of underlying cause of hypervolemia.[5, 6, 7]
- Fluids and Electrolytes Made Incredibly Easy. 2005. Lipincott Williams and Wilkins.
- Baird, M, et al. Manual of Critical Care Nursing: Nursing Interventions and Collaborative Management. 2010 November. Elsevier Health Services.
- Pathophysiology: A 2 in 1 Reference for Nurses. Lipincott Williams and Wilkins
- Hagerstwon, M. Portable Fluids and Electrolytes. Lippincott Williams and Wilkins.
- Complications of Transfusion: Transfusion Medicine. Merck Manual Professional