Epidural waveform analysis (EWA) provides a simple confirmatory adjunct for loss-of-resistance (LOR): when the needle/catheter tip is correctly positioned inside the epidural space, pressure measurement results in a pulsatile waveform. Epidural waveform analysis can be carried out through the tip of the needle or the catheter. In this randomized trial, the objective is to compare epidural waveform analysis through the needle (EWA-N) and through the catheter (EWA-C) for thoracic epidural blocks.
The epidural space is most commonly identified with loss-of-resistance (LOR). Though sensitive Epidural waveform analysis (EWA) provides a simple confirmatory adjunct for LOR. When the needle (or catheter) is correctly positioned inside the epidural space, pressure measurement at its tip results in a pulsatile waveform synchronized with arterial pulsations Currently, there exist two different methods for EWA. Since local anesthetic (LA) is administered through the catheter, pressure transduction through its tip ensures that it is properly positioned inside the epidural space prior to LA injection. Alternately, EWA can be performed through the needle prior to blind advancement of the epidural catheter. Thus, in this randomized trial, the aim is to compare epidural waveform analysis through the needle (EWA-N) and through the catheter (EWA-C) for thoracic epidural blocks. The hypothesis is that, compared to EWA-C, EWA-N will result in a shorter performance time.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
SINGLE
Enrollment
120
In the EWA-N group, 5 mL of normal saline are injected through the epidural needle after the occurrence of loss-of-resistance (LOR). The needle is connected to the pressure transducer. A satisfactory endpoint is defined as the presence of waveforms synchronized with arterial pulsations. In the absence of pulsatile waveforms, the operator injects an additional 2.5 mL-bolus of normal saline through the epidural needle and reconnects the latter to the pressure transducer. If no waveforms are detected after the second injection, the operator removes the needle and reattempts the epidural block at a different intervertebral level. A maximum of 3 levels is permitted: if waveforms are still absent at the third level, the operator simply accepts LOR as the technical endpoint.
In the EWA-C group, the epidural catheter is advanced 5 cm beyond the needle tip after the occurrence of LOR. Subsequently, the operator injects 5 mL of normal saline through the catheter and the latter is connected to the pressure transducer via the sterile, rigid extension tubing. A satisfactory endpoint is defined as the presence of waveforms. In the absence of pulsatile waveforms, the operator injects an additional 2.5 mL-bolus of saline through the catheter and reconnects the latter to the pressure transducer. If no waveforms are detected after the second injection are still absent at the third level, the operator simply accepts this position for catheter placement (intent-to-treat analysis).
Hospital Clínico Universidad de Chile
Santiago, RM, Chile
Ramathibodi Hospital
Bangkok, Thailand
Performance time of block
temporal interval in minutes between skin infiltration and local anesthetic administration through the epidural catheter (after obtaining a satisfactory waveform either through the needle or through the catheter depending on randomized group assignment).
Time frame: From skin infiltration until local anesthetic administration through the needle or catheter, up to 60 minutes
Incidence of successful epidural block
bilateral block to ice in at least 2 dermatomes
Time frame: 15 minutes after the administration of local anesthetic through the epidural catheter
Procedural pain during epidural block assessed by the numeric rating scale
pain in the back of the patient, related to the performance of the epidural block, using a numeric rating scale from 0 to 10 points (0=no pain and 10= worst imaginable pain)
Time frame: From the performance of the epidural block until induction of general anesthesia, up to 2 hours
Postoperative pain related to surgical incision assessed by the numeric rating scale
pain at rest and upon deep breathing/coughing, measured using a numeric rating scale from 0 to 10 points ((0=no pain and 10= worst imaginable pain)
Time frame: twice a day from the arrival at PACU or until catheter removal, up to 5 days
Local anesthetic consumption
amount of local anesthetic consumed
Time frame: once a day from the arrival at PACU or until catheter removal, up to 5 days
Breakthrough opioid consumption (if required)
amount of opioids consumed
Time frame: once a day from the arrival at PACU or until catheter removal, up to 5 days
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Incidence of adverse events
side effects related to the performance of the epidural block (eg, dural/vascular puncture, paresthesia) or breakthrough opioids (nausea, vomiting, pruritus, somnolence, respiratory depression)
Time frame: Once a day from catheter insertion until removal, up to 5 days