Answer :
Final answer:
The key indicator of toxicity from lidocaine in this context is a heart rate of 42 beats per minute. This suggests the patient is experiencing bradycardia, a significantly slowed heart rate, consistent with cardiac effects of lidocaine toxicity.
Explanation:
A systemic reaction and toxicity to lidocaine in adult patients can be indicated by several symptoms. In this particular context, the crucial symptom from the provided options is a Heart rate of 42 beats/min. There are several indicators of a systemic reaction to this medication, but changes in heart rate are especially significant. Lidocaine toxicity can cause cardiovascular effects such as bradycardia (slowed heart rate), which is a heart rate of less than 60 beats per minute. Hence, a heart rate of 42 beats per minute indicates potential toxicity and requires immediate medical attention.
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