The optimal programmed intermittent epidural bolus (PIEB) regimen for labour
analgesia remains unknown. Some studies indicate that better drug spread in the
epidural space results from greater injection pressure; however, there have been
few reports regarding the maximum pressure generated during an epidural bolus
injection using different catheters and infusion rates.

The purpose of this study was to assess the effect of different epidural catheter
gauge and infusion rate combinations on the bolus injection pressure generated by
various infusion pumps capable of delivering a programmed intermittent bolus.

Materials and Methods: We evaluated the flow and pressure characteristics of 11
commonly used epidural catheters combined with three different infusion
pumps able to deliver epidural infusions according to the PIEB regimen. Pressure
changes were measured over time at infusion rates of 100, 250 and 400 ml·h-1
and with a bolus volume of 10 ml.

Results: We performed 660 measurements. The mean maximal pressure generated during bolus injection was 86-863 mmHg and varied according to the catheter, infusion rate and pump combination used.Higher pressure was associated with higher infusion rates and higher catheter gauges, as well as use of wire reinforcement, in some cases triggering the occlusion pump alarm.

Conclusions: Significant differences were observed in the in vitro maximum pressure
value among the various catheter and flow rate combinations used in PIEB regimens.
The optimal flow rate, catheter and pump infusion pattern combination may allow for delivery of the high pressure bolus without triggering the occlusion alarm.


06 / Does epidural catheter size and infusion rate affect injection pressure in different programmed intermittent epidural bolus regimens? An in vitro study