# A nurse is assessing a patient who has been receiving haloperidol for schizophrenia. Which assessment finding would be most indicative of neuroleptic malignant syndrome (NMS)?

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## 문제

A nurse is assessing a patient who has been receiving haloperidol for schizophrenia. Which assessment finding would be most indicative of neuroleptic malignant syndrome (NMS)?

A 28-year-old patient with schizophrenia has been receiving haloperidol 10 mg twice daily for the past week. The nurse notices the patient appears confused and has developed a high fever.

## 보기

1. Bradycardia and hypotension
2. Muscle flaccidity and decreased reflexes
3. Bradypnea and clear lung sounds
4. Hyperthermia and muscle rigidity **✔ 정답**

**정답: 4**

## 해설

Hyperthermia and muscle rigidity are the most indicative signs of NMS, a life-threatening reaction to antipsychotics. Other options represent less critical findings like autonomic instability or side effects.

## 심화 해설

Understanding Neuroleptic Malignant Syndrome (NMS)

Neuroleptic malignant syndrome is a rare but life-threatening idiosyncratic reaction to antipsychotic medications, most notably first-generation (typical) agents like haloperidol. The pathophysiology is not fully understood but is primarily linked to central dopamine receptor blockade in the hypothalamus, basal ganglia, and spinal cord. This blockade disrupts thermoregulation and motor control, leading to the classic clinical tetrad.

Analyzing the Clinical Presentation

The scenario describes a young adult on a therapeutic dose of haloperidol who acutely develops confusion and a high fever. This presentation should immediately trigger a focused assessment for NMS. The hallmark features, as corroborated by the systematic review, are fever and rigidity, coupled with autonomic instability [2]. The patient's confusion represents the altered mental status component, and the high fever is a direct result of dysregulated thermoregulation. The most indicative finding you would assess for next is extreme muscular rigidity, often described as "lead-pipe" rigidity, which is a direct consequence of dopamine antagonism in the nigrostriatal pathway.

Why the Correct Answer is Hyperthermia and Muscle Rigidity

Option 4 correctly identifies the two most diagnostically significant features of typical NMS. The systematic review explicitly states that typical NMS is "characterized by fever, rigidity, and autonomic instability" [2]. These are not merely common symptoms; they are the core defining characteristics. Hyperthermia, often exceeding 38°C (100.4°F), is a result of impaired hypothalamic thermoregulation and increased heat production from sustained muscle contraction. The muscle rigidity is profound, generalized, and unresponsive to usual interventions, differentiating it from simple extrapyramidal symptoms.

Differentiating from Other Options

The other options represent findings that are inconsistent with the typical hyperadrenergic and hypermetabolic state of NMS.

- Option 1: Bradycardia and hypotension. Autonomic instability in NMS typically manifests as tachycardia and labile hypertension, reflecting a hyperadrenergic state, not bradycardia and hypotension. This makes this option incorrect.

- Option 2: Muscle flaccidity and decreased reflexes. This is the direct opposite of the "lead-pipe" rigidity that is a hallmark of NMS. Flaccidity is not a feature of this syndrome.

- Option 3: Bradypnea and clear lung sounds. The severe muscle rigidity in NMS often involves the chest wall, leading to decreased chest compliance and rapid, shallow breathing (tachypnea), not bradypnea. Respiratory failure is a serious complication, but it does not present as slow breathing with clear lung sounds.

Clinical Reasoning and Diagnostic Challenges

It is crucial to recognize that NMS can present atypically, particularly in the emergency setting, where the classic features of fever and rigidity may be absent, complicating timely diagnosis [2]. However, in a classic case like this one, triggered by a high-potency typical antipsychotic, the combination of altered mental status, hyperthermia, and muscle rigidity is pathognomonic. The case report on a mixed serotonin syndrome/NMS presentation further highlights that these syndromes can overlap, but the profound muscle rigidity is the key clinical discriminator pointing more strongly toward NMS . Early recognition and immediate discontinuation of the offending agent are the most critical nursing interventions to prevent progression to rhabdomyolysis, acute renal failure, and death.

References (research sources)

- [2]Lorazepam in Managing Atypical Neuroleptic Malignant Syndrome: A Systematic Review of Case Reports.Meta-analysis/systematic reviewChen A, Bae M. (2025) · DOI: 10.5811/westjem.41514

## 임상 시나리오

NMS Recognition & Emergency ResponseKey assessment findings and immediate actions for suspected Neuroleptic Malignant Syndrome
Suspect NMS in any patient on antipsychotics who develops hyperthermia (>38°C), severe muscle rigidity ("lead-pipe"), and altered mental status. This is a medical emergency.

Immediately stop the offending agent (e.g., haloperidol). The classic triad is fever, rigidity, and autonomic instability (labile BP, tachycardia). Monitor for tachypnea and diaphoresis.

CautionDo not confuse NMS with heat stroke or infection. Creatine kinase (CK) levels are often markedly elevated (>1,000 IU/L) due to muscle breakdown, which can lead to rhabdomyolysis and acute kidney injury.

## 핵심 개념

- **Neuroleptic Malignant Syndrome (NMS)** — A life-threatening idiosyncratic reaction to antipsychotic medications, characterized by fever, severe muscle rigidity, autonomic instability, and altered mental status.
- **Haloperidol** — A first-generation (typical) antipsychotic agent that works primarily by blocking dopamine D2 receptors, carrying a high risk for extrapyramidal symptoms and NMS.
- **Lead-pipe rigidity** — A type of severe, diffuse muscle rigidity that is a hallmark sign of NMS, resulting from dopamine receptor blockade in the basal ganglia.
- **Autonomic instability** — Dysfunction of the autonomic nervous system seen in NMS, manifesting as labile blood pressure, tachycardia, diaphoresis, and cardiac dysrhythmias.
- **Dopamine receptor blockade** — The primary mechanism of action for typical antipsychotics, which in the hypothalamus and basal ganglia leads to the hyperthermia and motor symptoms of NMS.

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