Ultrasound Scanning Technique for Epidural Needle Insertion by a Single Operator
Abstract Number: 197
Abstract Type: Original Research
Background: There has been considerable interest in the use of ultrasound to guide epidural needle insertions. Most research has focused on pre-puncture ultrasound, followed by needle insertion using traditional loss-of-resistance. One ongoing challenge is the ability to perform ultrasound guidance during needle insertion with a single operator. We describe the ultrasound scanning technique to perform single-operator guidance and evaluate the performance.
Method: Twenty-one subjects undergoing elective cesarean section were consented to undergo a pre-puncture ultrasound scan for orientation and measurements. Following this scan, the paramedian epidural needle was placed using in-plane paramedian ultrasound guidance in the operating room using a mechanical needle guide on the ultrasound transducer. The depth to the epidural space on the image, needle insertion depth, and location of puncture site were measured.
Results: Good ultrasound images were obtained on 20 of the 21 subjects; one subject had unusual appearance of anatomy in the images and ultrasound guidance was abandoned. In 18 subjects, using real-time ultrasound guidance, the needle successfully entered the epidural space, as defined by good loss-of-resistance. In one subject, despite ultrasound guidance, entry into the epidural space was not achieved. Ultrasound guidance was also abandoned for one subject due to discomfort from the needle insertion. Both these cases were in the first 10 subjects. The needle insertion site was found to be on average 34mm below the middle of the pre-puncture transducer centre position. The actual needle insertion depth, when compared to the pre-puncture measurement, yielded a 95% confidence interval of -14.7mm to 15.4mm according to the Bland-Altman analysis.
Conclusions: With a proper understanding of the geometry of the relationship between the ultrasound transducer and needle guide as well as accuracy of the guidance, the proposed ultrasound technique is feasible with a single operator. It also aids in selecting the puncture site and needle insertion angle. We have also shown that it is useful to acquire pre-puncture information about transducer position and expected needle insertion depth to reduce the scanning time in the operating room, however the large error margin on these measurements makes it essential to fine tune the transducer positioning in the operating room and use traditional loss-of-resistance to confirm the needle entry into the epidural