# Situation: A 46-year-old man is admitted to the medical ward after 3 days of profuse watery diarrhea and poor oral intake. He has no history of heart or kidney disease. He weighs 64.8 kg; he weighed 67.0 kg at a clinic visit 1 week ago. His blood pressure is 104/66 mmHg lying and 82/54 mmHg sitting, his pulse is 116/min, his oral mucosa is dry, and he has no edema. The physician orders 1,000 mL of 0.9% sodium chloride to infuse over 8 hours by gravity through a set with a drop factor of 20 drops/mL. After 3 hours, 700 mL remain in the bag. His lungs are clear, and hospital policy allows the nurse to recalculate a gravity rate for the remaining volume and time if the new rate is within 25% of the ordered rate. At what rate should the nurse now regulate the infusion? Round off to the nearest whole number.

> source: MyMerci (mymerci.kr)  
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> subject: Nursing Practice III — Care of Clients with Problems in Surgery, Oxygenation, Fluid and Electrolytes, Infectious, Inflammatory and Immunologic Response, Cellular Aberrations

## 문제

Situation: A 46-year-old man is admitted to the medical ward after 3 days of profuse watery diarrhea and poor oral intake. He has no history of heart or kidney disease. He weighs 64.8 kg; he weighed 67.0 kg at a clinic visit 1 week ago. His blood pressure is 104/66 mmHg lying and 82/54 mmHg sitting, his pulse is 116/min, his oral mucosa is dry, and he has no edema.

The physician orders 1,000 mL of 0.9% sodium chloride to infuse over 8 hours by gravity through a set with a drop factor of 20 drops/mL. After 3 hours, 700 mL remain in the bag. His lungs are clear, and hospital policy allows the nurse to recalculate a gravity rate for the remaining volume and time if the new rate is within 25% of the ordered rate. At what rate should the nurse now regulate the infusion? Round off to the nearest whole number.

## 보기

1. 42 drops/min
2. 47 drops/min **✔ 정답**
3. 58 drops/min
4. 140 drops/min

**정답: 2**

## 해설

The ordered rate is 1,000 mL ÷ 8 h = 125 mL/h. The remaining 700 mL must run over the remaining 5 hours: 700 ÷ 5 = 140 mL/h, which is 12% above the ordered rate and within the 25% policy. In drops: 140 mL/h × 20 drops/mL ÷ 60 min = 46.7, rounded to 47 drops/min.

## 심화 해설

Clinical context

This scenario combines two nursing responsibilities that are tested together in licensure exams: recognizing the clinical picture of volume depletion and safely recalculating a gravity IV infusion rate when the actual delivered volume differs from the ordered plan. The patient’s 3-day history of profuse watery diarrhea, poor oral intake, dry oral mucosa, postural blood pressure drop from 104/66 mmHg lying to 82/54 mmHg sitting, and tachycardia of 116/min all point to hypovolemia. The weight change from 67.0 kg to 64.8 kg represents a loss of approximately 2.2 kg, which in an adult is roughly equivalent to 2.2 L of body water loss and supports the assessment of significant fluid deficit.

Step 1: Recalculate the ordered flow rate

The original order is 1,000 mL over 8 hours. The ordered hourly rate is 125 mL/h. After 3 hours, the expected volume infused at the ordered rate would have been 375 mL, leaving 625 mL in the bag. However, 700 mL remains, which means only 300 mL has actually infused over 3 hours. The infusion has been running slower than ordered, at an actual rate of 100 mL/h instead of 125 mL/h.

Step 2: Determine the new rate for the remaining volume and time

The remaining 700 mL must now be delivered over the remaining 5 hours. The recalculated hourly rate is 700 ÷ 5 = 140 mL/h. This is 15 mL/h above the originally ordered 125 mL/h, which is a 12% increase. Because hospital policy permits adjustment up to 25% above the ordered rate, this new rate is within the allowed range and can be implemented without contacting the physician.

Step 3: Convert mL/h to drops/min

The administration set has a drop factor of 20 drops/mL. The formula for gravity flow rate is:

(mL/h × drop factor) ÷ 60 min = drops/min

Substituting the values: (140 × 20) ÷ 60 = 2,800 ÷ 60 = 46.7 drops/min. Rounded to the nearest whole number, the nurse should regulate the infusion at 47 drops/min.

Why the other options are incorrect

| Option | Rate | Reason it is incorrect |
| --- | --- | --- |
| 1 | 42 drops/min | This corresponds to 126 mL/h, which is close to the original ordered rate but fails to correct the volume deficit that accumulated during the first 3 hours. It would leave the patient behind schedule. |
| 3 | 58 drops/min | This corresponds to 174 mL/h, which exceeds the ordered rate by 39% and violates the 25% policy limit. It would deliver fluid too rapidly for a patient whose lungs are currently clear but who remains at risk for overload. |
| 4 | 140 drops/min | This is a common error that occurs when the mL/h value (140) is mistaken for drops/min without applying the drop factor conversion. It would deliver 420 mL/h, which is dangerously fast. |

Clinical reasoning and safety considerations

The nurse must always compare the recalculated rate against the original order and the institutional policy before adjusting the clamp. A rate increase of 12% is clinically reasonable here because the patient has clear lungs, no history of heart or kidney disease, and ongoing evidence of volume depletion. However, if the recalculated rate had exceeded the 25% threshold, the nurse would need to notify the prescriber rather than independently adjusting the infusion.

The assessment of fluid status in this patient is consistent with the consensus that dehydration is a clinical diagnosis based on history, physical findings, and supporting data such as acute weight loss and orthostatic vital sign changes [2]. No single laboratory value or vital sign alone defines dehydration; rather, the combination of findings guides the decision to continue volume replacement. In this case, the absence of pulmonary crackles and the absence of peripheral edema support the safety of a modest rate increase to catch up on the prescribed volume.

Watch out! A drop factor of 20 drops/mL is a macrodrip set. The conversion step from mL/h to drops/min is essential and is a frequent source of calculation errors. Always verify whether the question asks for mL/h or drops/min before selecting the answer.

Key point! When an infusion falls behind schedule, the nurse does not automatically double the rate. The correct approach is to recalculate the remaining volume over the remaining time, compare the new rate to the ordered rate, and apply the institutional policy for allowable variance. Here, the 12% increase falls within the 25% limit, so 47 drops/min is the appropriate adjustment.

Integration with the evidence base

Accurate delivery of prescribed IV fluid depends on both the calculation and the mechanical properties of the infusion system. One study evaluating different infusion control methods found that the actual infused volume can deviate significantly from the intended volume depending on the device and whether corrections are applied over time [1]. This reinforces the importance of regular monitoring of the IV site, the drip chamber, and the remaining bag volume, rather than assuming that a set clamp position will continue to deliver the intended rate. For this patient, the nurse’s observation that 700 mL remained at the 3-hour mark was the trigger for recalculation, and the subsequent adjustment to 47 drops/min represents a deliberate, policy-compliant correction rather than an arbitrary change.References (research sources)

- [1]Infusion volume control and calculation using metronome and drop counter based intravenous infusion therapy helper.Research articlePark K, Lee J, Kim SY, Kim J, Kim I, Choi SP (2013) · DOI: 10.1111/ijn.12063

- [2]A multidisciplinary consensus on dehydration: definitions, diagnostic methods and clinical implications.GuidelineLacey J, Corbett J, Forni L, Hooper L, Hughes F, Minto G (2019) · DOI: 10.1080/07853890.2019.1628352

## 임상 시나리오

Gravity IV Rate RecalculationSafe catch-up within policy limits
The ordered rate is 125 mL/h. After 3 hours, 700 mL remains, so the new rate is 140 mL/h over 5 hours, a 12% increase that is within the 25% policy.

Convert to drops/min: 140 mL/h × 20 drops/mL ÷ 60 min = 46.7, rounded to 47 drops/min.

CautionDo not confuse mL/h with drops/min; always divide by 60 when using a drop factor of 20 drops/mL. Reassess volume status and lung sounds before increasing the rate.

## 핵심 개념

- **Drop factor** — Number of drops per mL delivered by IV tubing, here 20 drops/mL.
- **Orthostatic hypotension** — Drop in BP from lying to sitting/standing indicating volume depletion.
- **Hypovolemia** — Reduced circulating blood volume, suggested by tachycardia, dry mucosa, and weight loss.
- **Gravity infusion** — IV flow driven by gravity, requiring manual rate calculation in drops/min.
- **Recalculated rate** — New infusion rate adjusted for remaining volume and time within policy limits.

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