Does ultrasound guidance improve the efficiency and timeliness to successful neuraxial blockade in obese parturients?
Abstract Number: S-5
Abstract Type: Original Research
Ultrasound imaging is becoming a popular modality to facilitate neuraxial anesthetic techniques (1). In morbidly obese pregnant patients, palpation of anatomic landmarks can be challenging, leading to prolonged procedure times and multiple attempts. Ultrasound may provide a significant role in identifying lumbar level, midline, and depth to epidural space for obese patients (2). This study evaluated whether use of ultrasound decreased the time and number of attempts for successful neuraxial blockade in obese obstetrical patients.
This is a prospective, randomized study of pregnant patients with a BMI > 35 (N=50) undergoing epidural placement for labor pain or cesarean section. In the study group, ultrasound imaging of the spine was used to determine midline, interspace level, and an optimal needle insertion point. In the control group, optimal needle insertion point was determined using palpation of anatomic landmarks. Time to perform the ultrasound and procedure, and the number of attempts were recorded and analyzed.
The mean time to perform neuraxial blockade was 13.2 minutes without ultrasound and 12.1 minutes with ultrasound (p value 0.1329). The mean number of attempts was 1.7 without ultrasound and 1.0 with ultrasound (p value 0.1504). There was a statistically significant decrease in the number of attempts when accounting for increasing BMI (p value 0.048).
Thus far in this ongoing study, the use of ultrasound for neuraxial blockade does not cause a statistically significant decrease in the time to perform the procedure. However, ultrasound does cause a statistically significant decrease in the number of attempts as BMI increases.
Previous studies have indicated that BMI alone may not accurately predict the ease of neuraxial procedures. Adipose distribution affects ease of spinous process palpation, which may be a more consistent predictor of difficult epidural placement (3).
This is an ongoing study (currently N=19 in ultrasound group, N=16 in control group) and completion of data collection (before the upcoming SOAP meeting) may show more statistically significant differences when comparing the ultrasound and non-ultrasound groups.
1: Carvalho JC. Ultrasound-facilitated epidurals and spinals in obstetrics. Anesthesiol Clin. 2008 Mar;26(1):145-58, vii-viii.
2: Balki M, Lee Y, Halpern S, Carvalho JCA. Ultrasound imaging of the lumbar spine in the transverse plane: The correlation between estimated and actual depth to the epidural space in obese parturients. Anesth Analg. June 2009;108(6):1876-81.
3: Ellinas EH, Eastwood DC, Patel SN, Maitra-D'Cruze AM, Ebert TJ. The effect of obesity on neuraxial technique difficulty in pregnant patients: a prospective, observational study. Anesth Analg. 2009 Oct;109(4):1225-31.