Certified Nurses Operating Room (CNOR) Practice Exam

What heart rate indicates a sign of malignant hyperthermia?

1. 100 bpm

2. 120 bpm

3. 140 bpm

4. 160 bpm

The correct answer is: 120 bpm

A heart rate of 120 bpm is indicative of a potential sign of malignant hyperthermia (MH), especially when viewed in the context of other clinical signs. Malignant hyperthermia is a rare but severe reaction to certain anesthetics and muscle relaxants that can lead to rapid increases in metabolism, muscle rigidity, and hyperthermia. One of the initial vital sign alterations often observed in patients experiencing MH is tachycardia, where the heart rate exceeds the normal range, typically above 100 bpm. A heart rate of 120 bpm suggests a heightened physiological response, which can be a marker for the body's stress response during a malignant hyperthermia crisis. Vital signs should be continuously monitored during surgical procedures, and observations of a heart rate at or above 120 bpm, coupled with other symptoms like elevated body temperature and muscle rigidity, can prompt immediate intervention. Recognizing these important signs early leads to prompt management, which is essential in mitigating the severe consequences of MH. Higher heart rates, such as 140 bpm and 160 bpm, are certainly concerning and may indicate worsening conditions, but a heart rate of 120 bpm is often an earlier indicator for vigilance and assessment in the context of malignant hyperthermia.