# Situation: A 62-year-old man is brought to the emergency room (ER) because of a severe headache, blurred vision, and new confusion since this morning. He stopped taking his amlodipine and losartan 2 weeks ago. His blood pressure is 220/130 mmHg on repeated readings, and a head computed tomography (CT) scan shows no bleeding. The provider diagnoses hypertensive emergency, starts an intravenous nicardipine infusion, and orders that the mean arterial pressure (MAP) be lowered by no more than 25% in the first hour. What is the lowest MAP the nurse should accept at the end of the first hour? Round off to the nearest whole number.

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=629793  
> language: ko  
> 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 62-year-old man is brought to the emergency room (ER) because of a severe headache, blurred vision, and new confusion since this morning. He stopped taking his amlodipine and losartan 2 weeks ago. His blood pressure is 220/130 mmHg on repeated readings, and a head computed tomography (CT) scan shows no bleeding.

The provider diagnoses hypertensive emergency, starts an intravenous nicardipine infusion, and orders that the mean arterial pressure (MAP) be lowered by no more than 25% in the first hour. What is the lowest MAP the nurse should accept at the end of the first hour? Round off to the nearest whole number.

## 보기

1. 165 mmHg
2. 131 mmHg
3. 143 mmHg
4. 120 mmHg **✔ 정답**

**정답: 4**

## 해설

Mean arterial pressure is (systolic + 2 × diastolic) ÷ 3 = (220 + 260) ÷ 3 = 160 mmHg. A reduction of no more than 25% means the MAP should not fall below 160 × 0.75 = 120 mmHg at the end of the first hour. Lowering it faster risks cerebral and coronary ischemia.

## 심화 해설

Calculating the MAP and the 25% limit
In a hypertensive emergency, severe hypertension is causing acute organ damage; here, headache, blurred vision, and new confusion point to the brain. Treatment uses a titratable intravenous drug such as nicardipine, but the pressure is lowered in a controlled way. The order is to reduce the mean arterial pressure (MAP) by no more than 25% in the first hour. The MAP is calculated as (systolic + 2 × diastolic) ÷ 3 = (220 + 260) ÷ 3 = 160 mmHg. A reduction of no more than 25% means the MAP should not fall below 160 × 0.75 = 120 mmHg at the end of the first hour.

Why diastolic pressure is counted twice
About two thirds of each cardiac cycle is spent in diastole, so the average pressure driving blood into the organs is closer to the diastolic value than to the systolic value. Weighting the diastolic pressure twice gives a practical estimate of the true mean. The MAP is the pressure that perfuses the brain, heart, and kidneys, which is why targets in hypertensive emergency are often expressed as a percentage of the MAP rather than of the systolic pressure.

| Option | How it was obtained | Error |
| --- | --- | --- |
| 165 mmHg | 220 × 0.75 | Applies 25% to the systolic, not the MAP |
| 131 mmHg | (220 + 130) ÷ 2 = 175; 175 × 0.75 | Uses a simple average instead of the MAP formula |
| 143 mmHg | (2 × 220 + 130) ÷ 3 = 190; 190 × 0.75 | Doubles the systolic instead of the diastolic |
| 120 mmHg | (220 + 2 × 130) ÷ 3 = 160; 160 × 0.75 | Correct |

Why the pressure is lowered gradually
Chronic hypertension shifts the range over which the brain can keep its own blood flow steady, a process called cerebral autoregulation. In this client, the brain has adapted to very high pressures. If the MAP falls too far too fast, cerebral blood flow drops below what the adapted vessels can maintain, causing cerebral, coronary, or renal ischemia, including stroke. The nurse titrates the infusion against frequent blood pressure readings, watches the neurological status closely, and reports a fall below the target or any new deficit.

Watch out! Exam calculation items build distractors from real mistakes. Check that you used the MAP formula, not a simple average, that the diastolic value is doubled, and that the percentage is applied to the MAP. Round only at the final step.

Exam takeaway
Key point! MAP = (SBP + 2 × DBP) ÷ 3. In hypertensive emergency, the MAP is usually lowered by no more than 25% in the first hour to protect organ perfusion. For 220/130 mmHg, the MAP is 160 mmHg and the lowest acceptable MAP after the first hour is 120 mmHg.

## 임상 시나리오

MAP Target in Hypertensive EmergencyControlled lowering with IV nicardipine
MAP = (systolic + 2 × diastolic) ÷ 3. For 220/130 mmHg: (220 + 260) ÷ 3 = 160 mmHg.

Lowering by no more than 25% in the first hour: 160 × 0.75 = 120 mmHg, the lowest MAP to accept.

Titrate the infusion against frequent readings and watch the neurological status, because the brain has adapted to high pressure through altered autoregulation.

CautionLowering the pressure too fast can cause cerebral and coronary ischemia; report a MAP below the target or any new neurological deficit.

## 핵심 개념

- **Hypertensive emergency** — Severe hypertension with acute organ damage, such as encephalopathy, requiring controlled IV lowering of blood pressure.
- **Mean arterial pressure** — The average arterial pressure over one cardiac cycle, estimated as systolic plus twice diastolic, divided by three.
- **Nicardipine** — A dihydropyridine calcium channel blocker given by IV infusion and titrated to lower blood pressure.
- **Cerebral autoregulation** — The ability of brain vessels to keep blood flow steady across a range of pressures, which shifts in chronic hypertension.

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