HYPERVOLEMIA: CAUSES AND CONSEQUENCES - MEDICINE - 2024

The hypervolemia refers to increased plasma volume (blood volume) due to electrolyte imbalance. This condition can occur in different pathologies, such as patients with kidney, liver or heart failure.

It can also be seen in patients who have an increased secretion of antidiuretic hormone (ADH). Therefore, the patient suffers from oliguria, that is, he urinates little and this causes the fluid to accumulate in the body.

Schematic representation of dilute blood circulation and edema as a consequence of hypervolemia. Source: Image: Edonasela / Wikipedia.com/Ryaninuk

It can also be induced by inadequate fluid therapy. In most cases, hypervolemia endangers the life of the patient. Among the consequences of an uncontrolled increase in plasma volume is an increase in cardiac output.

In addition, it can trigger the following clinical pictures: acute lung edema, seizures, venous engorgement, ascites or brain edema, among others.

However, in the case of pericardial tamponade, the induction of hypervolemia by the administration of fluids can be favorable. This action helps improve ventricular filling pressure, thereby achieving adequate cardiac output.

Another important fact is that in hypervolemia the hematocrit will always be decreased, regardless of its origin. This is due to the fact that the number of red blood cells present are diluted by the increase in plasma volume.

However, there are other parameters that may vary depending on the origin of the hypervolemia, such as sodium concentration and mean corpuscular volume.

Causes

- Pregnancy

Pregnancy is a condition in which a series of changes occur in the woman. These changes are physiological. In this sense, it can be ensured that the hypervolemia observed during pregnancy is normal, as the blood volume increases as the body prepares for significant blood loss during childbirth.

So is the decrease in blood pressure, the increase in cardiac output and venous return as pregnancy progresses. The latter reach their maximum between weeks 16 to 20, remaining elevated until delivery.

However, hypervolemia represents a danger in pregnant women with underlying heart disease. For example, pregnant patients with left ventricular obstruction with a systolic function below 40%, pregnant women with pulmonary hypertension, or Marfan syndrome with aortic root dilation above 4 cm.

These patients should avoid pregnancy until their problem is resolved, in case of becoming pregnant under these conditions, it is suggested to interrupt it, since the physiological hypervolemia that occurs during pregnancy represents a very high risk of death for the patient.

- Inadequate parenteral hydration

The replacement of fluids requires to be handled by professionals, since ignorance in this regard can lead to serious problems for the patient.

Administering parenteral hydration in patients who have organic dysfunction such as cirrhosis or heart failure is counterproductive. In this case, hydration favors the appearance of edema, ascites, among other complications.

On the other hand, the administration of glucose by parenteral route in patients with malnutrition can generate the appearance of arrhythmias and pulmonary edema.

Likewise, the administration of fluids in patients with inflammatory and infectious processes, diabetes, among other pathologies, is of care. In these cases, the endothelial barrier may be injured and therefore the fluid may pass from the intravascular to the interstitial space, favoring the swelling of the patient.

Finally, the administration of some drugs can influence the behavior of fluids. Fluid retention is common in patients treated with corticosteroids and non-steroidal anti-inflammatory drugs.

For all these reasons, it is that patients who receive parenteral hydration should be monitored in terms of three aspects, which are: clinical signs, laboratory tests and hemodynamic parameters:

Clinical signs

Among the clinical signs that should be monitored are: blood pressure, amount of diuresis, temperature, heart and respiratory rate, and the patient's alertness.

Lab tests

Among the laboratory tests that can be altered are: electrolytes (sodium, potassium and chlorine), glucose, urea, creatinine, arterial gases and plasma osmolarity.

Hemodynamic parameters

While, among the hemodynamic parameters, it can be said that the most important is the measurement of central venous pressure (CVP).

However, it is also very useful to measure pulmonary capillary pressure, cardiac output, hemoglobin saturation of mixed venous blood (SO2vm), oxygen supply and consumption.

- Hyperhydration

Another common mistake is overhydration or overhydration. There are three types of hyperhydration, isotonic, hypotonic, and hypertonic.

Isotonic hyperhydration

It occurs in the exaggerated administration of isotonic physiological saline or in decompensated pathological processes (liver cirrhosis, nephrotic syndrome, congestive heart failure). In this case, sodium is normal, mean corpuscular volume (MCV) is normal, and hematocrit is low.

Hypotonic hyperhydration

This type of hyperhydration occurs due to excessive consumption of water or excessive fluid therapy with solutions without salt. It is characterized by low sodium, increased MCV, and low hematocrit.

Hypertonic hyperhydration

This type of hyperhydration occurs in people who have swallowed a large amount of salt water or who have had excessive fluid therapy with hypertonic solutions. Sodium is high, while MCV and hematocrit are low.

- Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

In this syndrome, the antidiuretic hormone (ADH) or vasopressin may be elevated or decreased. In the event that there is an increase in ADH secretion by the hypothalamus, a decrease in plasma osmolarity, hyponatremia, and hypotension occur.

Under this scenario, the patient presents oliguria. Urine, in addition to having little volume, is very concentrated. While at the plasma level the situation is different, as the blood is diluted by an increase in fluid. Sodium can decrease to values ​​below 120 mEq / L.

The most common signs and symptoms are: nausea, vomiting, weight gain, palpitations, confusion, irritability, loss of consciousness, seizures, and even coma.

SIADH is caused by overstimulation of the hypothalamus caused by stress, by the presence of tumors in the area or by drugs, such as: antidepressants, nicotine, chlorpropamide or morphine, among others.

Consequences

An increase in plasma volume can cause a series of signs and symptoms in the patient. These are increased cardiac output, dyspnoea, weight gain, ascites, peripheral edema, pulmonary edema, paroxysmal nocturnal dyspnea, third heart sound, jugular venous hypertension, basal crackles, seizures, or coma.

References

1. Hypervolemia. Wikipedia, The Free Encyclopedia. 8 Mar 2013, 04:04 UTC. 1 Aug 2019, 15:29 wikipedia.org
2. "Inappropriate antidiuretic hormone secretion." Wikipedia, The Free Encyclopedia. 1 Sep 2017, 17:07 UTC. 1 Aug 2019, 17:33 org
3. Sánchez-Suen K, Padilla-Cuadra J. Pericardial tamponade. Medical record. Costarric. 2001; 43 (1): 07-10. Available from: scielo.sa
4. García R. Hypervolemia of pregnancy and related circulatory problems. Spanish clinical journal. 1948; 30 (6): 373-377.
5. Paul F. Intravenous fluid therapy in adult inpatients. BMJ 2015; 350: g 7620. Available in: bmj.com
6. Muñoz M, Jaime L, Pérez A, García A, Gómez A. Intravenous fluid therapy in emergencies and emergencies. Department of Pharmacology. Teatinos Campus, University Clinical Hospital of Malaga. Available at: medynet.com