# Situation: A 64-year-old woman is brought to a stroke-ready hospital with sudden right-sided weakness and slurred speech that began 90 minutes ago. She weighs 104 kg. Noncontrast computed tomography (CT) shows no hemorrhage, and the team plans intravenous (IV) alteplase for acute ischemic stroke. Alteplase 0.9 mg/kg is ordered, with 10% of the total dose given as a bolus over 1 minute. How many milligrams should the bolus contain? Round off to one decimal place.

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## 문제

Situation: A 64-year-old woman is brought to a stroke-ready hospital with sudden right-sided weakness and slurred speech that began 90 minutes ago. She weighs 104 kg. Noncontrast computed tomography (CT) shows no hemorrhage, and the team plans intravenous (IV) alteplase for acute ischemic stroke.

Alteplase 0.9 mg/kg is ordered, with 10% of the total dose given as a bolus over 1 minute. How many milligrams should the bolus contain? Round off to one decimal place.

## 보기

1. 81.0 mg
2. 9.0 mg **✔ 정답**
3. 9.4 mg
4. 90.0 mg

**정답: 2**

## 해설

0.9 mg/kg × 104 kg = 93.6 mg, but the maximum total dose of alteplase for stroke is 90 mg. The bolus is 10% of 90 mg = 9.0 mg, and the remaining 81.0 mg is infused over 60 minutes.

## 심화 해설

The calculation for alteplase dosing in acute ischemic stroke follows a weight-based formula with a critical safety cap. For this patient, the initial calculation is 0.9 mg/kg × 104 kg = 93.6 mg. However, the maximum total dose is 90 mg, so the total dose is capped at 90 mg. The bolus is 10% of the capped total dose: 90 mg × 0.10 = 9.0 mg. The remaining 81.0 mg is given as a continuous infusion over 60 minutes.

The maximum total dose of alteplase for acute ischemic stroke is 90 mg, regardless of patient weight above 100 kg. This cap was established in the landmark NINDS trial and remains the standard for IV thrombolysis [1]. In clinical practice, patients weighing more than 100 kg receive the same 90 mg total dose as a 100 kg patient, which effectively means a reduced per-kilogram dose for heavier individuals [1].

The bolus calculation must always be based on the capped total dose, not the uncapped weight-based calculation. If a nurse incorrectly used 93.6 mg as the total dose, the bolus would be 9.4 mg — a dosing error. Watch out! Always apply the 90 mg maximum before calculating the 10% bolus.

Weight estimation errors are a known source of alteplase dosing mistakes. In the NINDS study, dosing was based on estimated weight, and errors occurred in both directions [2]. A retrospective review comparing estimated versus actual weight found clinically meaningful differences that could affect dosing accuracy [3]. For patients near or above the 100 kg threshold, accurate weight measurement is especially important because the dose cap changes the calculation logic [3].

| Dosing component | Standard formula | This patient (104 kg) |
| --- | --- | --- |
| Total dose (uncapped) | 0.9 mg/kg × actual weight | 93.6 mg |
| Total dose (capped) | Maximum 90 mg if weight > 100 kg | 90 mg |
| Bolus (10%) | 10% of capped total dose | 9.0 mg over 1 minute |
| Infusion (90%) | Remaining dose over 60 minutes | 81.0 mg |

The bolus is administered intravenously over 1 minute, followed immediately by the remaining 90% as a continuous infusion over 60 minutes. This two-step administration is a multistep process that increases the risk of dosing errors, particularly when weight is estimated rather than measured [2]. The bolus must be drawn up and labeled separately from the infusion to prevent accidental administration of the entire dose at once.

Key point! For any patient weighing 100 kg or more, the total alteplase dose is fixed at 90 mg. The bolus is always 9.0 mg, and the infusion is 81.0 mg. This simplifies the math for heavier patients but requires the nurse to recognize when the cap applies.References (research sources)

- [1]Impact of Tissue Plasminogen Activator Dosing on Patients Weighing More Than 100 kg on 3-Month Outcomes in Acute Ischemic Stroke.Research articleGaravaglia J, Sherman J, Yetzer H, Regier M, Smith M (2017) · DOI: 10.1016/j.jstrokecerebrovasdis.2016.12.015

- [2]Dosing errors did not have a major impact on outcome in the NINDS t-PA stroke study.Research articleMessé SR, Kasner SE, Cucchiara BL, Demchuk A, Tanne D, Ouyang B (2011) · DOI: 10.1016/j.jstrokecerebrovasdis.2010.01.002

- [3]Estimated versus actual weight when dosing rt-PA in acute ischemic stroke: is there a difference?Research articleGraves A, VerHage A, Richlik B, Makic MB (2013) · DOI: 10.1097/JNN.0b013e318298641b

## 임상 시나리오

Alteplase Dosing in Acute Ischemic StrokeSafety cap and bolus calculation
Calculate weight-based dose as 0.9 mg/kg, but apply the maximum total dose of 90 mg for any patient over 100 kg.

The bolus is 10% of the capped total dose, given over 1 minute. The remaining 90% infuses over 60 minutes.

CautionAlways cap the total dose at 90 mg before calculating the bolus. Using the uncapped weight-based dose leads to a dosing error.

## 핵심 개념

- **Alteplase** — Recombinant tissue plasminogen activator used for acute ischemic stroke thrombolysis.
- **Maximum total dose** — Safety cap of 90 mg for alteplase in stroke, regardless of weight over 100 kg.
- **Bolus dose** — Initial rapid IV injection, 10% of total alteplase dose given over 1 minute.
- **NINDS trial** — Landmark study establishing the 90 mg maximum alteplase dose for stroke.
- **Weight-based dosing** — 0.9 mg/kg calculation for alteplase, capped at 90 mg total.

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