Fluid Balance Calculation for the Shift
The correct fluid balance is
+100 mL. This is determined by systematically totaling all measured intake and output for the 06:00 to 14:00 shift according to the ward’s defined parameters.
Step 1: Calculate Total Intake
Intake includes oral fluids, IV infusions, and the diluent volume of IV medications.
-
IV infusion: The rate changes during the shift. From 06:00 to 10:00 (4 hours) at
40 mL/hour, the volume is
160 mL. From 10:00 to 14:00 (4 hours) at
60 mL/hour, the volume is
240 mL. Total IV infusion =
400 mL.
-
IV antibiotic diluent: The medication was diluted in
100 mL and administered at 08:00. This entire volume counts as intake =
100 mL.
-
Oral fluids: The recorded volumes are
120 mL,
200 mL, and
180 mL. Total oral intake =
500 mL.
Total intake = 400 + 100 + 500 =
1,000 mL.
Step 2: Calculate Total Output
Output includes urine and emesis.
-
Urine: The recorded voided volumes are
300 mL,
250 mL, and
200 mL. Total urine output =
750 mL.
-
Emesis: A single episode of
150 mL occurred at 09:00.
Total output = 750 + 150 =
900 mL.
Step 3: Determine Fluid Balance
Fluid balance = Total intake − Total output =
1,000 mL −
900 mL =
+100 mL.
A positive value indicates that intake exceeded output during this shift. For this patient with liver cirrhosis and increasing abdominal girth,
a positive fluid balance of +100 mL over eight hours may reflect ongoing fluid retention, a common complication of cirrhosis related to portal hypertension and hypoalbuminemia. While the volume itself is modest, the trend is clinically meaningful and should be monitored alongside daily weights and abdominal girth measurements.
Key point! When calculating fluid balance, the diluent used to reconstitute or dilute IV medications must be included as intake. This is a frequent omission in clinical practice and a common source of error in documentation and examination questions.
Watch out! The IV infusion rate changes at 10:00. You must calculate the two time intervals separately (4 hours at each rate) rather than averaging the rates or using the final rate for the entire shift.
Clinical Significance of Accurate Fluid Balance Charting
Fluid balance monitoring is a core nursing responsibility, particularly for patients with liver cirrhosis, heart failure, or renal impairment. A systematic review by Leinum et al. identified that
fluid balance charting is often incomplete and prone to calculation errors, which can compromise patient safety and clinical decision-making . Common problems include missing oral intake, omission of IV medication diluents, and arithmetic mistakes—exactly the components tested in this scenario.
The review also highlighted that educational interventions and standardized protocols can improve the completeness and accuracy of fluid balance documentation . This underscores why ward policies, such as clearly defining what counts as intake and output, are essential. In this scenario, the policy explicitly includes IV medication diluent volume as intake, which is a best-practice approach to reducing underreporting of fluid administration.
For patients with conditions that alter fluid distribution, such as cirrhosis with ascites, accurate fluid balance data inform decisions about diuretic therapy, fluid restriction, and the need for paracentesis. Grimaldi et al. noted that
fluid balance assessment is a core nursing competency, yet variability in how nurses account for insensible losses and other components can affect clinical reasoning . While insensible water loss is not included in this particular calculation, the broader principle is that standardized, complete charting reduces variability and supports safer care.
| Component | Volume (mL) | Category |
|---|
| IV infusion 06:00–10:00 (40 mL/hr × 4 hr) | 160 | Intake |
| IV infusion 10:00–14:00 (60 mL/hr × 4 hr) | 240 | Intake |
| IV antibiotic diluent | 100 | Intake |
| Oral fluids (120 + 200 + 180) | 500 | Intake |
| Urine (300 + 250 + 200) | 750 | Output |
| Emesis | 150 | Output |
| Total intake | 1,000 | |
| Total output | 900 | |
| Fluid balance | +100 | |
Why the Other Options Are Incorrect
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+20 mL: This would result from omitting the IV antibiotic diluent (100 mL) from intake, or from miscalculating one of the other components.
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+180 mL: This could arise from incorrectly calculating the IV infusion as 40 mL/hr for the entire 8 hours (320 mL) plus the antibiotic (100 mL) and oral fluids (500 mL), totaling 920 mL intake against 900 mL output, yielding +20 mL—not +180 mL. Alternatively, it may reflect an arithmetic error in summing oral fluids or urine.
-
+250 mL: This value could result from using the higher IV rate (60 mL/hr) for the full 8 hours (480 mL) plus the antibiotic (100 mL) and oral fluids (500 mL), totaling 1,080 mL intake against 900 mL output, yielding +180 mL—not +250 mL. The +250 mL option likely stems from a different combination of errors, such as adding the emesis to intake or miscalculating the urine total.
The systematic review by Leinum et al. emphasized that
calculation errors are a significant contributor to inaccurate fluid balance records, and these errors can directly affect clinical decisions such as diuretic dosing or fluid restriction . In a patient with cirrhosis and ascites, an erroneously high positive balance might lead to unnecessary diuretic escalation, while an erroneously low or negative balance could mask true fluid overload.