From the Guidelines
To measure a negative fluid balance of 2 liters, you need to track all fluid inputs and outputs over a specific time period, typically 24 hours, and calculate the difference between the total output and total input, as recommended by various guidelines, including those for fluid management in sepsis 1. When measuring fluid balance, it is essential to record all fluid intake, including oral fluids, IV fluids, medications, and liquid foods. Then, measure all fluid outputs, including urine, vomit, diarrhea, wound drainage, nasogastric drainage, and estimated insensible losses (typically 500-800 ml/day through respiration and perspiration) 1. A negative fluid balance of 2 liters means the total output exceeds the total input by 2 liters. For example, if a patient has 1500 ml of input and 3500 ml of output in 24 hours, they have a negative fluid balance of 2000 ml (2 liters). Some key points to consider when measuring fluid balance include:
- Accurate measurement requires proper collection devices like urinary catheters, calibrated containers, and diligent documentation 1.
- Significant negative fluid balance may indicate dehydration, requiring clinical assessment for signs like decreased skin turgor, dry mucous membranes, hypotension, or tachycardia, as seen in patients with sepsis or those undergoing fluid restriction 1.
- The WHO guideline recommends continuing infusion at 5–10 ml/kg/h in certain scenarios, but also advises to reduce the rate of fluid infusion if clinical signs of fluid overload are present 1.
- Clinical reassessment to detect fluid overload and/or pulmonary oedema is crucial, as recommended by four of the guidelines 1.
- The NICE guidelines recommend seeking senior help at 2 L of fluid resuscitation, highlighting the importance of monitoring fluid balance closely 1.
From the Research
Measuring Negative Fluid Balance
To measure someone having a negative fluid balance of 2 litres, several factors need to be considered:
- Fluid intake and output: This includes all sources of fluid intake, such as oral fluids, intravenous fluids, and fluids from other sources like tube feedings or blood transfusions, as well as all sources of fluid output, including urine, stool, sweat, and drainage from wounds or fistulas 2.
- Weight changes: Since 1 litre of fluid is equivalent to 1 kilogram of body weight, a negative fluid balance of 2 litres would correspond to a weight loss of 2 kilograms 2.
- Clinical assessment: Clinicians should also assess the patient's overall clinical condition, including signs of dehydration, such as dry mouth, decreased urine output, and decreased blood pressure 2.
Monitoring Fluid Balance
Monitoring fluid balance is crucial in critically ill patients, as both fluid overload and fluid depletion can have serious consequences:
- Fluid overload can lead to complications such as pulmonary edema, cardiac failure, and abdominal compartment syndrome 3, 4.
- Fluid depletion, on the other hand, can lead to dehydration, hypotension, and decreased perfusion of vital organs 3, 4.
- The choice of intravenous fluid can also impact patient outcomes, with balanced crystalloids potentially being associated with fewer complications than 0.9% saline 3, 4, 5.