1Department of Anaesthesia, Royal Liverpool Childrens Hospital, Eaton Road, Liverpool L12 2AP, UK. 2Department of Anaesthesia, Liverpool Womens Hospital, Crown Street, Liverpool L8 7SS, UK*Corresponding author
Accepted for publication: October 25, 2000
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Abstract |
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Br J Anaesth 2001; 86: 5657
Keywords: anaesthetic techniques, epidural; complications, catheter migration
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Introduction |
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Methods and results |
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The epidural catheter was inserted using an Epidural minipack kit (SIMS Portex Ltd, Hythe, UK), with the patient in the sitting position. After identifying the epidural space by loss of resistance to 0.9% saline, a 16G Portex epidural catheter was inserted, leaving 4 cm within the space. The remainder of the catheter was directed longitudinally up the patients back in the midline, over their left shoulder and the in-line filter was attached. Once inserted, one of following three dressing methods was randomly allocated using a sealed envelope technique in order to secure the catheter. In group T, a 10x25 cm Tegaderm dressing (3M Health Care, St Paul, MN, USA) was applied over a single redundant loop of catheter. In group F, the catheter was secured exactly as in group T, but in addition, the in-line epidural filter was fixed to the skin of the left shoulder by Mefix (Molnycke Health Care AB, Goteborg, Sweden). In group N, a Niko Epi-Fix dressing (Niko Surgical Ltd, Stonehouse, UK) was applied to the site of catheter insertion. The design of this fixative allows no redundant loop of catheter. Lengths of 10 cm width Mefix were applied to all of the borders of the respective Tegaderm and Niko Epi-Fix dressings. A length of 5 cm width Mefix was applied over the exposed catheter, from the upper border of the respective dressing superiorly along the patients back. The in-line filter was connected to a Graseby 9300 infusion pump (Graseby Medical Ltd, Watford, UK) via an extension set. Epidural analgesia was effected by continuous infusion (1015 ml h1) of 0.1% bupivacaine and 0.001% alfentanil. Patients did not ambulate during labour, but were allowed to adopt either sitting or lateral positions.
Following dressing application, the patient characteristics were recorded and the time was noted. The inter-vertebral space at which the epidural was sited, the use of a skin incision, the distance between the skin and the epidural space (cm), and the length of catheter visible at the skin surface (to the nearest 0.5 cm) were also recorded.
One hour after delivery, immediately before removing the epidural catheter, the time was noted, allowing the duration of the catheters presence to be calculated. Also recorded were the integrity of the dressing, whether any analgesia problems had been encountered and the length of catheter visible at the skin surface (to the nearest 0.5 cm).
The initial catheter reading minus the final measurement was defined as the catheter movement. Two aspects of catheter movement were considered. The first follows a convention adopted by previous workers,2 in which movement of the catheter can occur in a outward (+) or inward () direction, and was defined as directional movement (MOVD). The second addresses only the magnitude of catheter displacement, irrespective of direction, and was defined as absolute movement (MOVA).
Based on previous data,1 35 patients per group were required to detect an inter-group difference of 0.5 cm ( 0.05, ß 0.9). Data were analysed using analysis of variance and Dunnnetts post hoc test, Students t-test,
2 analysis and Pearsons correlation coefficients where appropriate (SPSS v.9.0).
Of the 135 patients recruited, 24 were not completely assessed because of progression to emergency Caesarean section. Of the remaining 111 patients, 35 were in group T, 39 in group F and 37 in group N. Six patients who experienced complete failure of analgesia with no demonstrable sensory block had final observations recorded and their epidural catheter resited. Five of these patients were in group N and one in group T (P<0.05; 2). There were no differences in patient characteristics, duration of catheter presence (P>0.05; analysis of variance) or final dressing integrity (P>0.05;
2) between groups. The use of a blade for skin incision, or choosing a different inter-vertebral space did not influence MOVD or MOVA (P>0.05; Students t-test). There was no significant correlation between duration of catheter presence and MOVD or MOVA.
No movement of the epidural catheter was observed in 28 patients, whilst inward movement was seen in 21 and outward in 62. Directional catheter movement (MOVD) for the three dressing groups is shown in Figure 1, with associated values for median and inter-quartile range. Patients in groups T and F had less directional movement than those in group N (P<0.01: analysis of variance). Only patients in group F displayed less MOVA than those in group N (P<0.05: analysis of variance).
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Comment |
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Outward movement of the epidural catheter was greatest when a Niko Epi-Fix dressing was used to secure the catheter, and was associated with significantly more failures in analgesia. However, when attempting to minimize movement of the catheter irrespective of direction, only the Tegaderm dressing with additional filter fixation confers a significant advantage over the Niko Epi-Fix.
We identified no correlation between epidural catheter movement and the duration of catheter presence, a finding in concordance with earlier work.6 Additionally, we showed that neither the use of a small skin incision at the site of catheter insertion, nor the selected inter-vertebral level affected movement of the epidural catheter. A previous study1 demonstrated that body mass index is related to amount of catheter movement. Our data confirmed this association in group F but was unable to show this in the remainder of the patients, perhaps because inadequate numbers of people were studied.
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References |
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