[Difficulty of epidural puncture for obstetric analgesia: risk factors]

Predicting technical difficulties in performing an epidural block can affect the anesthesiologist's choice of technique or decisions about who should carry it out. Our aim was to determine patient characteristics associated with difficulty in performing an epidural block for obstetric analgesia.

We designed a prospective observational study in 540 pregnant women who requested epidural analgesia for obstetric labor. Patient characteristics (age, weight, height), anatomical features (body constitution, visible and/or palpable spinal apophyses, structural anomalies), technical features (number of attempts, repositioning of the needle), anesthesiologist's experience (resident or staff), block success, time taken to accomplish the procedure, and obstetrical variables (parity, gestational age, cervical dilatation).

The factor that best correlates with puncture difficulty in the obstetric patient is the presence of visible or palpable spinal apophyses and palpation prior to carrying out the block. Factors like weight, body constitution, or anesthesiologist's experience seem to influence the rate of success or failure of the epidural block for obstetric analgesia, although to a lesser degree.

The most important factor for predicting success of an epidural block for obstetric analgesia in our practice is the presence of palpable spinal apophyses.