Situation: A hospital will introduce smart infusion pumps with a drug library on its adult medical-surgical wards next month. A nurse manager joins the team that reviews the infusion process before the pumps go live. The team scores each possible failure for severity (S), occurrence (O), and detection (Det), each from 1 to 10; a higher detection score means the failure is harder to detect. The team's rule is to redesign first the failure with the highest risk priority number, RPN = S × O × Det. Wrong concentration chosen from the library: S 8, O 3, Det 5 Rate entered with a misplaced decimal point: S 9, O 2, Det 6 Infusion attached to the wrong access line: S 10, O 2, Det 4 Occlusion alarm silenced and not rechecked: S 6, O 5, Det 3 Which failure should the team redesign FIRST?

RPN = S × O × Det: wrong concentration 8 × 3 × 5 = 120; decimal error 9 × 2 × 6 = 108; wrong line 10 × 2 × 4 = 80; silenced alarm 6 × 5 × 3 = 90. The highest RPN is the wrong-concentration failure (120), so it is redesigned first under the team's rule. The highest severity or the highest occurrence alone does not decide the priority.

RPN calculation and priority setting

The team’s stated decision rule is explicit: redesign the failure with the highest Risk Priority Number (RPN), where RPN = Severity (S) × Occurrence (O) × Detection (Det). A higher detection score means the failure is harder to detect, so detection contributes to risk in the same multiplicative direction as severity and occurrence. The calculation for each failure is shown below.

Failure mode	S	O	Det	RPN (S × O × Det)
Wrong concentration chosen from the library	8	3	5	120
Rate entered with a misplaced decimal point	9	2	6	108
Infusion attached to the wrong access line	10	2	4	80
Occlusion alarm silenced and not rechecked	6	5	3	90

The highest RPN is 120 for the wrong-concentration failure, so that failure is redesigned first. The highest severity alone does not determine priority: the wrong access line has severity 10, but its lower occurrence and easier detection produce an RPN of only 80. Likewise, the highest occurrence alone does not decide priority: the silenced alarm has occurrence 5, but its RPN is 90. The multiplicative RPN integrates all three dimensions, which is the team’s stated rule.

Key point! When a question gives an explicit prioritization formula such as RPN = S × O × Det, apply the formula exactly. Do not substitute clinical intuition about which error “feels” most dangerous; the highest single subscore does not override the calculated RPN.

Why wrong-concentration errors matter with smart pumps

Smart infusion pumps with a drug library are designed to intercept dosing errors, but the library itself introduces a selection step. A clinician must choose the correct drug name and concentration from a list. If the wrong concentration is selected from the library, the pump may deliver a clinically plausible but incorrect dose, and the error can be difficult to detect at the bedside because the pump displays the selected value as if it were the intended order. This aligns with the observation that smart pumps fail to prevent specific error types and may introduce new errors related to library use ^[1].

The wrong-concentration failure in this scenario has a detection score of 5, meaning it is moderately hard to detect. A wrong concentration may not produce an immediate alarm; the infusion can run silently while the patient receives the incorrect strength. By contrast, the wrong access line has a lower detection score of 4, suggesting the team believes it is somewhat easier to identify, perhaps through line tracing or visual inspection.

Clinical context: concentration versus rate errors

Rate errors, especially decimal point misplacement, are a well-documented source of IV medication harm ^[2]. In this scenario, the decimal error has the second-highest severity (9) and the highest detection score (6), meaning it is the hardest to detect among the four failures. However, its occurrence is only 2, which lowers the RPN to 108. A failure that is severe and hard to detect but rare may still rank below a failure that is less severe but occurs more often and is only moderately detectable.

The wrong-concentration failure has occurrence 3, higher than the decimal error’s occurrence of 2. This higher frequency, combined with moderate severity and moderate detectability, pushes its RPN above the decimal error. The calculation reflects a systems view: risk is a product of how bad the outcome is, how often the failure happens, and how likely it is to escape notice.

Implications for the nurse manager’s redesign team

Because the wrong-concentration failure ranks first, the team would begin by examining how the drug library is structured and how nurses select concentrations. Potential redesign targets include standardizing the library to limit concentration choices, requiring barcode scanning before selection, adding a hard stop for concentration mismatches, or redesigning the display so concentration appears more prominently. These strategies are consistent with cataloging smart pump error types and matching them to prevention strategies ^[1].

The near-miss data from smart pump logs can also support this work. When a user selects a wrong concentration and then cancels the selection, the pump log records that “good save” ^[3]. Watch out! A high rate of canceled wrong-concentration selections would suggest the failure is occurring more often than the team’s occurrence score of 3 reflects, which would further justify prioritizing this failure. Interoperability between the pump and the electronic health record may reduce some selection errors, but the library selection step remains a human-dependent point of failure ^[4].

The correct answer is the wrong-concentration failure because its RPN of 120 is the highest, not because it is the most severe or the most frequent failure in isolation.