Technical report: optimal quantity of saline for epidural pressure waveform analysis

Area of Science:

• Anesthesiology
• Pain Management
• Medical Devices

Background:

• Epidural waveform analysis (EPWA) confirms optimal epidural catheter placement by assessing thecal pressure waveform transmission.
• The ideal injectate volume for optimizing EPWA remains underexplored.

Purpose of the Study:

• To determine the optimal injectate volume for epidural waveform analysis (EPWA).
• To compare the responsiveness of different epidural catheter types for EPWA.

Main Methods:

• A randomized controlled trial involving 60 patients compared three epidural catheter types: stimulating single-hole (S1), stimulating three-hole (S3), and non-stimulating three-hole (NS3).
• Epidural pressure waveform transmission was assessed using serial 2.5 mL saline injections up to 10 mL.
• Patient follow-up by acute pain services confirmed adequate postoperative epidural analgesia.

Main Results:

• Three-hole catheters (S3 and NS3) demonstrated significantly higher responsiveness compared to single-hole catheters (S1) at low injectate volumes (P = 0.003 for S3, P = 0.012 for NS3).
• No significant difference in waveform transmission was observed between S3 and NS3 catheters (P = 0.25).
• Optimal responsiveness was achieved with 5 mL of saline for S1 catheters and 2.5 mL for S3 catheters, with no further improvement beyond these volumes.

Conclusions:

• Stimulating three-hole (S3) epidural catheters are more effective than single-hole (S1) catheters for waveform transmission during EPWA at low injectate volumes.
• An initial injectate volume of 5 mL is recommended for EPWA, irrespective of catheter type, to ensure optimal results.