A postoperative laparoscopic appendectomy patient is receiving morphine PCA for pain. Which finding alerts you to the potential of a narcotic overdose?

A respiratory rate of 8 breaths per minute is a significant indicator of potential narcotic overdose due to the depressive effects opioids like morphine can have on the central nervous system, particularly on respiratory drive. When a patient receives a continuous or demand-based supply of morphine through patient-controlled analgesia (PCA), there is a risk of overmedication leading to respiratory depression. A respiratory rate falling below 12 breaths per minute is often considered a critical threshold, and 8 breaths per minute indicates a serious level of depression that could lead to hypoxia and other complications. Monitoring the respiratory rate is therefore crucial in patients receiving opioid therapy to ensure they remain within a safe range.

Other factors, such as changes in heart rate and blood pressure, while important to monitor, do not indicate an overdose as directly or with as immediate clinical consequence as a severely decreased respiratory rate. An increased heart rate may sometimes occur due to pain or anxiety rather than narcotic overdose, and decreased blood pressure could result from various causes unrelated to opioid overdose. Thus, the respiratory rate provides specific and immediate insight into the patient's respiratory function and is critical for assessing the risk of overdose when administering opioids.