LETTERS TO EDITOR

Abstract

To the editor,

Various techniques have been described for identification of the epidural space.¹ We describe an interesting finding of sacral bulge during identifying epidural space in pediatric patients.

A 5 year old, ASA II, 15kgs, child was posted for elective posterolateral thoracotomy for empyema thoracis. Child was induced with intravenous fentanyl and propofol, and tracheal intubation was achieved using atracurium as muscle relaxant. To provide postoperative analgesia, an epidural infusion of low dose bupivacaine was planned. We decided to pass 24 G epidural catheter through caudal approach. Under aseptic conditions, with patient in lateral position, sacral epidural space was identified using 20 G Tuohy’s needle. We failed to thread the catheter even after two attempts We decided to pass a lumbar catheter instead. Same needle was introduced in L4-5 space using loss of resistance to air technique.  When the air was pushed in, we could see an obvious and evident bulge with air leak in the sacral hiatus region (Figure-1) probably due to air escaping through the hiatal opening in the subcutaneous tissue. Catheter was secured and a compression dressing was applied. The surgery was uneventful and post operatively epidural infusion of low dose bupivacaine with opioids was given for three days and then the catheter was removed. The child was followed up and discharged on 15th post operative day.

Several techniques as well as  different types of devices (viz, Page’s giving way method, Dogliotti’s loss of resistance technique, Gutierrez’s hanging drop method, Baraka’s running infusion, Cork’s ultrasonic method, Odom’s indicator, McIntosh Balloon, Brunner’s spring loaded plunger, Sagarnaga’s bursting bubbles) have been described over the years for identifying the epidural space.¹ Most of these methods are based on the principle of demonstration of sub atmospheric pressure or sudden loss of resistance. In children, small anatomical structures and catheter insertion under general anesthesia poses difficulty to identify epidural space.² We believe this ‘Caudal Bulge sign’ observed by us, though accidently, is more evident in thin patients.

Various complications associated with the use of air for the loss of resistance technique are pneumocephalus, spinal cord and nerve root compression, retroperitoneal air, subcutaneous emphysema, venous air embolism and inadequate analgesia and paresthesia.³Air is no longer used for LOR in infants and children due to these risks. The technique described by us utilizes two puncture sites and may have potential to decrease the amount of air retained in the space, hence probably reducing the air related complications. Perhaps our observation of ‘sacral bulge sign’ may increase the reliability of loss of resistance technique in pediatric patients, though it requires double puncture.  However, we on no account recommend using air in LOR technique or making two punctures to identify the space, but believe that the observation may make an interesting subject for further studies.