Which finding during assessment would be most concerning for a patient receiving phenytoin?

• A. Blood pressure 74/50
• B. Heart rate 110/min
• C. Oxygen saturation 98%
• D. Respiratory rate 16 breaths/min

Answer: (A)

The most important idea here is recognizing a life-threatening cardiovascular reaction to phenytoin, especially if given IV. Phenytoin can cause hypotension due to vasodilation and decreased cardiac output, and this risk is higher with rapid IV administration. A blood pressure of 74/50 is a severe drop and represents a dangerous level of hypotension that needs immediate attention: stop the phenytoin infusion, assess ABCs, monitor vitals, and treat per protocol (e.g., notify the provider and initiate fluids as ordered).

The other findings are less alarming in this moment. A heart rate of 110/min could be from pain, anxiety, or mild distress and isn’t as immediately threatening as profound hypotension. Oxygen saturation is normal and respiratory rate is within normal limits, indicating adequate ventilation and oxygenation at that time.