Parturient's posture during epidural puncture affects the distance from skin to epidural space.

STUDY

OBJECTIVE

To assess the factors affecting the distance from skin to epidural space.

DESIGN

Prospective observational study of consecutive cases over a 2-year period.

SETTING

Inpatient obstetric unit in a French university hospital.

PATIENTS: 2,123 consecutive term parturients who received epidural anesthesia for cesarean section or epidural analgesia for labor and vaginal delivery.

INTERVENTIONS: At the time of epidural puncture, the interspace used and the patient's posture (sitting or left lateral decubitus) were recorded, and the distance from the skin to the epidural space (DS-ES) was measured to the nearest 0.5 cm using a marked epidural needle.

MEASUREMENTS AND MAIN

RESULTS

The relationship between patient factors [height, weight, body mass index (BMI; weight/height2), presence of scoliosis] and technical factors (interspace, patient's posture at puncture) versus DS-ES was investigated using multiple regression analysis. DS-ES correlated positively with the parturient's weight and BMI. In addition, DS-ES was significantly greater when epidural puncture was performed in the lateral position as compared with the sitting position.

CONCLUSION

Both the patient's weight and position during epidural needle placement are important factors influencing DS-ES. A change from the sitting to the lateral position may increase DS-ES, causing catheter dislodgment and consequent inadequate analgesia. Clinical studies relating DS-ES to inadequate analgesia must take these factors into account.