Background. Because a number of patients have reported an increase in heart rate with the intraosseous, or IO, injection, it is important to evaluate changes in the cardiovascular system with this injection technique. The purpose of this study was to determine the cardiovascular effects of an IO injection of 2 percent lidocaine with 1:100,000 epinephrine and 3 percent mepivacaine. Methods. With the use of a repeated-measures design, the authors randomly assigned 42 subjects to receive IO injections of 1.8 milliliters of 2 percent lidocaine with 1:100,000 epinephrine or 1.8 mL of 3 percent mepivacaine in a double-blinded manner at two appointments. At each appointment, the authors monitored electrocardiographic findings, cardiac rate, systolic and diastolic blood pressure, and mean arterial pressure before, during and after administration of anesthetic solutions. Results. With the 2 percent lidocaine with 1:100,000 epinephrine solution, 28 (67 percent) of 42 subjects experienced an increase in heart rate that might be attributed to the effect of the epinephrine. In 22 (79 percent) of these subjects, the heart rate returned to within 5 beats of baseline values within four minutes after solution deposition. The authors found no significant increase in heart rate in subjects receiving the 3 percent mepivacaine. No significant differences (P > .05) were found in mean diastolic, mean systolic or mean arterial blood pressure values between the subjects receiving 2 percent lidocaine with 1:100,000 epinephrine and those receiving 3 percent mepivacaine. Conclusions. The majority of subjects receiving the IO injection of the 2 percent lidocaine-epinephrine solution experienced a transient increase in heart rate. No significant increase in heart rate was seen with the IO injection of 3 percent mepivacaine. Clinical Implications. While patients would likely notice the heart rate increase with the lidocaine-epinephrine solution, it would not be clinically significant in most healthy patients. In patients whose medical condition, drug therapies or epinephrine sensitivity suggests caution, 3 percent mepivacaine is a good alternative for IO injections.
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