A client has received lidocaine as an axillary block for his surgical procedure. The nurse checks his pulse rate 5 minutes after administration and determines that his pulse is slightly irregular and slow. What should be the nurse's assessment regarding this information?

1. this is an expected response to local anesthesia
2. the nurse may have mistakenly administered adenosine
3. a decrease in pain results in a slower pulse
4. lidocaine toxicity may have occurred