From the Guidelines
Underfilled edema occurs when there is decreased effective arterial blood volume, leading to activation of the renin-angiotensin-aldosterone system and subsequent sodium and water retention, whereas overfilled edema results from primary sodium retention without a decrease in effective arterial blood volume. The distinction between underfilled and overfilled edema is crucial for determining the appropriate therapeutic strategy to restore normal fluid balance in the body. Underfilled edema is commonly seen in conditions like heart failure, liver cirrhosis, and nephrotic syndrome, where the body perceives a need to retain fluid despite overall fluid excess 1. On the other hand, overfilled edema typically occurs in kidney disorders such as acute or chronic kidney disease, where the kidneys fail to properly excrete sodium and water 1. Some guidelines recommend fluid resuscitation with crystalloid in patients with hypovolemia, while others suggest that fluid overload should be avoided, especially in patients with likely fluid intolerance 1. The management of fluid balance is critical to prevent complications, and a state of near-zero fluid and electrolyte balance has been shown to reduce the risk of developing complications in patients undergoing major abdominal surgery 1. Key considerations in the management of underfilled and overfilled edema include careful assessment of fluid status, use of diuretics and sodium restriction, and avoidance of excessive fluid administration or restriction. In patients with underfilled edema, addressing the underlying condition and carefully managing fluid balance is essential, whereas in patients with overfilled edema, diuretics and sodium restriction are often effective in restoring normal fluid balance 1. Overall, understanding the mechanisms and treatment approaches for underfilled and overfilled edema is essential for clinicians to provide optimal care and improve patient outcomes. Some studies suggest that the use of diuretics and the restriction of dietary sodium can help maintain volume balance and prevent the recurrence of fluid retention 1. Additionally, the use of mechanical methods of fluid removal, such as ultrafiltration or hemofiltration, may be necessary in patients with diuretic-resistant heart failure 1. In summary, underfilled and overfilled edema are two distinct types of fluid retention that require different treatment approaches, and careful management of fluid balance is critical to prevent complications and improve patient outcomes. The most recent and highest quality study on this topic is 1, which provides recommendations for perioperative nutrition and fluid management. This study highlights the importance of maintaining a state of near-zero fluid and electrolyte balance to reduce the risk of developing complications in patients undergoing major abdominal surgery. Therefore, clinicians should prioritize careful assessment of fluid status and use of evidence-based guidelines to manage underfilled and overfilled edema.
From the Research
Definition of Underfilled and Overfilled Edema
- Underfilled edema refers to a condition where there is a decrease in effective blood volume, often due to arterial underfilling as a result of decreased cardiac output, arterial vasodilation, or both 2.
- Overfilled edema, on the other hand, is characterized by an excess of fluid in the body, leading to swelling and congestion in various organs and tissues 3.
Pathophysiology of Edema
- Edema can result from an imbalance in the regulatory mechanisms that control sodium and water retention in the body 2.
- In conditions such as cardiac failure, cirrhosis, and pregnancy, the kidney retains more sodium and water, leading to increased blood volume and edema 2.
- However, in some cases, such as acute cardiogenic pulmonary edema, there can be a reduction in blood volume due to the loss of hypo-oncotic fluid into the extravascular spaces 4.
Clinical Implications
- The management of edema requires careful consideration of the underlying pathophysiology and the use of appropriate therapies, such as diuretics and fluid management strategies 5, 6.
- The goal of treatment is to normalize total body sodium and volume, while minimizing the risk of adverse outcomes, such as renal dysfunction and electrolyte imbalances 3, 5.