Three-Dimensional Ultrasound-Guided Real-Time Midline Epidural Needle Placement with Epiguide: A Prospective Feasibility Study.

Current 2-D ultrasound technology is unable to perform a midline neuraxial needle insertion under real-time ultrasound guidance using a standard needle and without an assistant. The aim of the work described here was to determine the feasibility of a new technology providing such capability, starting with a study evaluating the selected puncture site. A novel 3-D ultrasound imaging technique was designed using thick-slice rendering in conjunction with a custom needle guide (3DUS + Epiguide). A clinical feasibility study evaluated the ability of 3DUS + Epiguide to identify the epidural needle puncture site for a midline insertion in the lumbar spine. We hypothesized that (i) the puncture site identified by 3DUS + Epiguide was within a 5-mm radius from the site chosen by standard palpation, and (ii) the difference between the two puncture sites was not correlated to the patient characteristics age, weight, height, body mass index and gestational age. The mean (±standard deviation) distances between puncture sites determined by 3DUS + Epiguide and palpation were 3.1 (±1.7) mm and 2.8 (±1.3) mm, for the L2-3 and L3-4 interspaces of 20 patients, respectively. Distances were comparable to intra-observer variability, indicating the potential for a thick-slice rendering of 3-D ultrasound along the Epiguide trajectory to select the puncture site of a midline neuraxial needle insertion. The long-term potential benefits of this system include increased efficiency and use of anesthesia, and a reduction in the frequency and severity of the complications from incorrect needle insertions. Epidural success in the most difficult cases (e.g., the obese) will be the focus of future work.

A Prospective Observational Comparison Between Arm and Wrist Blood Pressure During Scheduled Cesarean Delivery.

BACKGROUND: Shivering is common during cesarean delivery (CD) under neuraxial anesthesia and may disrupt the measurement of noninvasive blood pressure (BP). BP measured at the wrist may be less affected by shivering. There have been no studies comparing trends in BP measured on the upper arm and wrist. We hypothesized that wrist systolic blood pressure (sBP) would accurately trend with upper arm sBP measurements (agree within a limit of ±10%) in parturients undergoing elective CD under spinal anesthesia or combined spinal-epidural anesthesia. METHODS: After initiation of spinal anesthesia, BP measurements were obtained simultaneously from the upper arm and wrist on opposite arms. The interval between measurements was 1 to 2 minutes, and data were collected for 20 minutes or until delivery. The primary outcome was agreement in dynamic changes in sBP measurements between the upper arm and the wrist. Bland-Altman plots indicating the levels of agreement between the methods were drawn for baseline measurements, over multiple measurements, and over multiple measurements on percentage change from baseline. RESULTS: Forty-nine patients were recruited and completed the study. The wrist sBP tended to overestimate the upper sBP for both baseline data (sBP bias = 13.4 mm Hg; 95% confidence interval = +10.4 to +16.4 mm Hg) and data obtained over multiple measurements (sBP bias = 12.8 mm Hg; 95% confidence interval = +9.3 to +16.3 mm Hg). For change in sBP from baseline over multiple measurements, the mean difference between the wrist and the arm sBP was -0.2 percentage points (99% limits of agreement -25 to +25 percentage points). CONCLUSIONS: The wrist measurement overestimated the reading relative to the upper arm measurement for multiple measurements over time. However, when the time series for each subject was examined for percentage change from baseline, the 2 methods mirrored each other in most cases. Nevertheless, our hypothesis was rejected as the limits of agreement were higher than ±10%. This finding suggests that wrist BP may not be an accurate method of detecting hypotension or hypertension during spinal or combined spinal-epidural anesthesia for CD.