Background: It is our experience that a deposition of an anesthetic solution in the ventral area of the paravertebral space near the parietal pleura and the sympathetic trunk produces extended unilateral block. Because sympathetic block effects in this extended paravertebral block are not reported yet, we undertook this singly blinded, controlled study on the sympathetic change in volunteers.
Methods: A total of 22 ml 1% lidocaine was injected at the T11 level into the ventral area of the right-sided paravertebral space in 16 volunteers. The distribution of analgesia, heart rate, blood pressure and body temperature (measured by 12 skin sensors) was monitored. On a later occasion the volunteers underwent a control injection of saline.
Results: Unilateral analgesia (with no contralateral element) was induced in every subject injected with lidocaine, contrasted with no block induction with saline. Loss of pin-prick sensation was observed within 10 min after injection and involved a mean of 12 (range 8-13) dermatomes. A sympathetic block was indicated by cutaneous temperature increase within at least 6 dermatomes. Increase of arterial blood pressure was obtained in all volunteers with no change in pulse rate. No side effects or complications occurred. Epidural spread of the local anesthetic was unlikely because of the absence of contralateral cutaneous analgesia and temperature increase.
Conclusion: One-sided extended analgesia (sensory loss) follows the paravertebral injection of lidocaine. A large ipsilateral sympathetic block is observed without change in pulse rate and with no hypotension. These are all characteristics of an optimal regional block.