Handheld ultrasound device provides comparable epidural depth estimates to console machine
A handheld ultrasound device (AU), which uses an integrated algorithm for measurements, provides epidural depth estimates comparable to those obtained with a console ultrasound machine (GU), according to a new study.
“The AU device may be a reasonable alternative to more sophisticated ultrasound devices in determining the epidural space and depth in a nonobese obstetric population receiving labour epidurals,” said researchers.
In the 47 participating pregnant women (mean age, 32±6 years), the mean body mass index was 29±5 kg/m2. More than half (58 percent) were undergoing labour with epidural placement for the first time. All participants were anticipating vaginal delivery and wanted to receive epidural analgesia. [Int J Obstet Anesth 2019;39:68-73]
The mean discrepancy in epidural depth measurements between the AU and GU devices was –0.29 cm (95 percent CI, –1.08 to 0.49). Similar magnitudes of difference were observed at the three lumbar interspaces assessed: L2/3 (mean difference [MD], –0.398 cm, –0.498 to –0.298; p<0.0001), L3/4 (MD, –0.300 cm, –0.430 to –0.169; p<0.0001) and L4/5 (MD, –0.226 cm, –0.414 to –0.038; p=0.02).
The differences in midpoint measurements between the AU and GU devices, in the horizontal and vertical planes, were 0.022 and 0.016 cm. The L3/4 interspace assessment conducted using the AU device matched that of the GU device 94 percent of the time.
Comparing findings against the Tuohy needle depth (ND) measurements, researchers found that the epidural space depth measurement of the GU had a difference of –0.33 cm off (–0.49 t o –0.16; p<0.0001). In comparison, the difference between AU and ND was –0.62 cm (–0.79 to –0.44; p<0.0001), as determined in a previous publication. [Anesth Analg 2018;126:1995-1998]
“The key finding of this study is that the AU and GU provided comparable and accurate epidural depth estimates,” said researchers. “The mean difference between the epidural depths measured by AU and GU … reflects minimal differences between devices.”
Moreover, “both ultrasound devices accurately estimated depth to epidural space compared to the ND obtained during epidural insertion. The 95 percent CIs suggests that both ultrasound devices will allow anaesthesia providers to anticipate loss of resistance within 0.8 cm,” though both devices consistently yielded estimates that were shallower than the ND.
In the present study, participants underwent ultrasound with both AU and GU devices. The AU device was first placed at the gluteal cleft before it was moved vertically along the spine, identifying L4/5, L3/4 and L2/3 along the way. The device screen showed rendered models of each interspace, along with an estimated depth. Ultrasound with the GU device was then performed by the same operator.
“Additional studies are needed to compare the AU and GU to the landmarks/palpation technique, and to assess if the AU is as effective and useful compared to more sophisticated ultrasound devices for neuraxial assessment in an obese population,” said researchers.