Reliability of pressure waveform analysis to determine correct epidural needle placement in labouring women

Abstract

SummaryPressure waveform analysis provides a reliable confirmatory adjunct to the loss-of-resistance technique to identify the epidural space during thoracic epidural anaesthesia, but its role remains controversial in lumbar epidural analgesia during labour. We performed an observational study in 100 labouring women of the sensitivity and specificity of waveform analysis to determine the correct location of the epidural needle. After obtaining loss-of-resistance, the anaesthetist injected 5 ml saline through the epidural needle (accounting for the volume already used in the loss-ofresistance). Sterile extension tubing, connected to a pressure transducer, was attached to the needle. An investigator determined the presence or absence of a pulsatile waveform, synchronised with the heart rate, on a monitor screen that was not in the view of the anaesthetist or the parturient. A bolus of 4 ml lidocaine 2% with adrenaline 5 lg.ml À1 was administered, and the epidural block was assessed after 15 min. Three women displayed no sensory block at 15 min. The results showed: epidural block present, epidural waveform present 93; epidural block absent, epidural waveform absent 2; epidural block present, epidural waveform absent 4; epidural block absent, epidural waveform present 1. Compared with the use of a local anaesthetic bolus to ascertain the epidural space, the sensitivity, specificity, positive and negative predictive values of waveform analysis were 95.9%, 66.7%, 98.9% and 33.3%, respectively. Epidural waveform analysis provides a simple adjunct to loss-of-resistance for confirming needle placement during performance of obstetric epidurals, however, further studies are required before its routine implementation in clinical practice.

Analysis of epidural waveform for cervical epidural steroid injections confirmed with fluoroscopy

“…However, all the results were obtained from the patients before surgery or from women in labor via the thoracic and lumbar epidural injections. [ 7 – 9 , 11 ]…”

Pressure waveforms to assess epidural placement: is there a role on delivery suite?

“…These can be obtained by connecting a transducer to either the epidural needle or the catheter. This method is attractive in its simplicity and lack of specialised equipment, and is the method used by Al‐Aamri et al in their paper in this issue . Waveform analysis has been studied and been shown to be beneficial in surgical patients requiring thoracic epidurals.…”

“…Al‐Aamri et al's paper is only the second study to evaluate epidural pressure waveforms in labouring women. Sebbag et al conducted a pilot study of 10 parturients in labour, but were unable to detect any pressure waveforms through the needle or via the epidural catheter, in spite of the epidurals providing adequate analgesia .…”

“…Therefore, any technique that aims to reduce the incidence of primary failure of labour analgesia is welcome. This issue of Anaesthesia contains an article by Al‐Aamri et al that examines the use of epidural pressure waveforms to achieve this . But how does this technique fit into the gamut at our disposal to prevent primary analgesic failure?…”

Epidural pressure waveforms

“…Al‐Aamri et al. used pressure waveforms to help determine correct epidural needle placement . I was reminded of the teaching I received in the early 1980s, as a newly appointed registrar at Dudley Road hospital (now City Hospital).…”