Agreement Between Laterality of Tsui Test and Laterality of Color Flow Doppler Signals During Labor Epidural Analgesia
Condition: Labor Pain
MeSH terms: Labor Pain
Study type: Observational

Summary: 
      Epidural analgesia for relief of labor pain is a very common, safe and reliable technique
      that requires placement of a catheter in the epidural space. About 5% of labor epidural
      catheters may need to be re-sited due to failure of analgesia. This is often caused by
      malposition of the epidural catheter. Many factors may influence the position of the tip of
      the epidural catheter and the resulting spread of local anesthetic solution within the
      epidural space and consequently the quality of labor pain management. The electrical
      stimulation of the epidural catheter, commonly known as Tsui test, can reliably confirm its
      positioning within the epidural space if this stimulus produces a muscular twitch under a
      certain current amplitude threshold. This muscular response is unilateral in 90% of the
      cases, not having any relationship between unilaterality and unsatisfactory catheter
      performance. It is unknown if this unilateral response has any correlation with the actual
      position of the catheter tip in terms of right or left side of the epidural space.
      Furthermore, the Tsui test does not give any information on the spread of anesthetic solution
      into the epidural space. Recent investigation shows that color flow doppler ultrasound during
      fluid injection through the epidural catheter may be helpful in determining the laterality of
      the tip of the epidural catheter; furthermore it may be able to inform about the spread the
      anesthetic solution, which is a limitation of the Tsui test. The investigators will perform
      an observational study to investigate the response patterns of Tsui test and Color flow
      Doppler ultrasound in the obstetric population. Women who have delivered under epidural
      analgesia will be approached for the study before the epidural catheter is removed. The
      investigators aim to characterize the laterality and current thresholds of Tsui test response
      and the laterality of the lumbar epidural catheter tip by color doppler ultrasound. The
      investigators hope to describe the findings and to correlate them with other clinical
      outcomes.
    


Intervention name(s): Doppler ultrasonography; Tsui test
Intervention type(s): Device; Device
Intervention description(s): color flow Doppler ultrasonography; The stimulator is set at frequency of 1Hz with 0.2 msec pulse width and the current output ranging from 0 to 20 mA. The current output will be carefully increased from zero until motor activity is detected up to a maximum of 20 mA.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Women who have delivered vaginally under epidural analgesia will be approached for the
        study before the epidural catheter is removed.
      
Keywords: epidural catheter; epidural analgesia; labor epidural; ultrasound; Doppler; Tsui test