# A nurse is caring for a patient receiving morphine sulfate via patient-controlled analgesia (PCA) pump for postoperative pain management. Which nursing intervention is the highest priority to ensure patient safety?

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> subject: Pharmacology

## 문제

A nurse is caring for a patient receiving morphine sulfate via patient-controlled analgesia (PCA) pump for postoperative pain management. Which nursing intervention is the highest priority to ensure patient safety?

## 보기

1. Monitor the patient's pain level using a 0-10 numeric rating scale every 2 hours
2. Assess the patient's bowel sounds and last bowel movement to prevent constipation
3. Educate the patient about proper use of the PCA button and lockout intervals
4. Monitor respiratory rate, depth, and oxygen saturation continuously **✔ 정답**

**정답: 4**

## 해설

Continuous monitoring of respiratory rate, depth, and oxygen saturation is the highest priority to detect opioid-induced respiratory depression, a life-threatening adverse effect. Other interventions (pain assessment, bowel care, patient education) are important but secondary to respiratory safety.

## 심화 해설

Understanding the Priority: Why Respiratory Monitoring Comes First

When caring for a patient using a morphine PCA pump, all the listed interventions are important components of comprehensive nursing care. However, the question asks for the highest priority intervention to ensure patient safety. This requires applying the nursing principle of prioritization based on the risk of immediate, life-threatening harm. Morphine, a potent opioid analgesic, exerts its primary adverse effect through central nervous system depression, which directly compromises the drive to breathe.

Pathophysiology of Opioid-Induced Respiratory Depression (OIRD)

Morphine acts as an agonist at mu-opioid receptors located in the brainstem respiratory centers, particularly the pre-Bötzinger complex. Activation of these receptors diminishes the chemosensitivity of these centers to rising levels of carbon dioxide (CO₂). Normally, an increase in arterial CO₂ is the most powerful stimulus to increase respiratory rate and depth. Under the influence of morphine, this response is blunted. The patient’s respiratory rate slows, and tidal volume decreases, leading to a progressive accumulation of CO₂ and a critical drop in oxygen saturation. This sequence can progress to apnea and respiratory arrest if not detected and reversed promptly. This physiological mechanism establishes respiratory depression as the most dangerous acute complication of opioid therapy, directly informing why monitoring for it is the highest safety priority [1, 3].

Clinical Application and Monitoring Parameters

The correct intervention is to monitor respiratory rate, depth, and oxygen saturation continuously. A falling respiratory rate is the earliest and most sensitive clinical indicator of OIRD. A rate below 10-12 breaths per minute in an adult warrants immediate intervention, including withholding the next dose, stimulating the patient, and potentially administering an opioid antagonist. Continuous pulse oximetry is a valuable adjunct, but it is crucial to understand its limitation: oxygen saturation is a late sign of hypoventilation, especially in patients receiving supplemental oxygen. A nurse must assess the quality of respirations, including depth and regularity, not just the oximetry reading. The clinical trials referenced, while exploring different routes and contexts for morphine administration, uniformly incorporate rigorous respiratory monitoring as a fundamental safety protocol, reinforcing its non-negotiable status in postoperative care [1, 3, 4].

Analysis of Other Options

The other options represent important, but lower-priority, nursing actions. Pain assessment (Option 1) is essential for evaluating analgesic efficacy and guiding dose adjustments, but untreated pain, while distressing, is not immediately life-threatening in the same way that respiratory failure is. Preventing and managing opioid-induced constipation (Option 2) is a key comfort and safety issue, as severe ileus can lead to significant complications, but it develops over days, not minutes. Patient education on PCA use (Option 3) is a critical safety step that should be performed before and during PCA therapy to prevent dosing errors, but once therapy is underway, the immediate physiological monitoring for a known adverse effect takes precedence. The hierarchy of physiological needs places airway and breathing at the apex, making continuous respiratory assessment the unequivocal priority.

## 임상 시나리오

PCA Opioid Safety: Respiratory MonitoringPreventing Opioid-Induced Respiratory Depression (OIRD)
The highest priority for a patient on a morphine PCA pump is continuous monitoring of respiratory rate, depth, and oxygen saturation. Morphine blunts the brainstem's response to rising CO2, risking apnea.

Assess sedation level using a valid scale. A patient who is difficult to arouse is at extreme risk. Do not rely solely on pulse oximetry; capnography (EtCO2) provides the earliest warning of hypoventilation.

CautionIf respiratory rate falls below 8 breaths/min or sedation deepens, stop the PCA, stimulate the patient, administer naloxone as prescribed, and call the Rapid Response Team. Never assume a low SpO2 alarm is a machine error.

## 핵심 개념

- **Opioid-Induced Respiratory Depression (OIRD)** — A life-threatening adverse effect where opioids diminish the brainstem's sensitivity to CO2, leading to decreased respiratory rate, depth, and potential apnea.
- **Patient-Controlled Analgesia (PCA)** — A drug delivery system that allows patients to self-administer small, preset doses of analgesic medication, commonly an opioid, to manage pain.
- **Pre-Bötzinger Complex** — A cluster of neurons in the brainstem considered the primary generator of the respiratory rhythm, highly sensitive to suppression by mu-opioid receptor agonists.
- **Mu-opioid Receptors** — Specific receptors in the central nervous system to which morphine binds, producing analgesia as well as adverse effects like respiratory depression and sedation.

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