Background: Lower systemic toxicity reported with ropivacaine and levobupivacaine may produce less reliable recognition of inadvertent intravenous injection during regional anesthesia. This study was undertaken to determine whether ropivacaine and levobupivacaine are suitable for use as intravenous test doses by evaluating central nervous system (CNS) symptoms after intravenous bolus injection.
Methods: Institutional approval and informed consent were granted for the study. One hundred twenty patients scheduled to undergo elective surgery were randomly assigned to receive 5 ml intravenous saline, 100 mg lidocaine, 25 mg ropivacaine, or 25 mg levobupivacaine before anesthesia. Patients reported CNS symptoms after injection and were monitored for hemodynamic change.
Results: Intravenous ropivacaine or levobupivacaine produced CNS symptoms in only 52% and 57% of patients, respectively, compared with 87% of patients after lidocaine (P < 0.02). Despite preparatory instruction, many patients receiving ropivacaine or levobupivacaine did not spontaneously volunteer symptoms because they were subtle and admitted symptoms only after in-depth questioning by the investigator.
Conclusions: Plain ropivacaine and levobupivacaine (25 mg) solutions are unsuitable for use as intravenous test doses during regional anesthesia because CNS symptoms are insufficient. When using ropivacaine or levobupivacaine for regional anesthesia, for test dose purposes, the authors recommend the addition of epinephrine to the local anesthetic solution or the use of a separate agent with more predictable CNS characteristics.