Rapid Responses to:
|
|
Rapid Responses: Rapid Responses published:
-
![[Read Rapid Response]](/icons/misc/sectionDOWN.gif)
BMJ should publish a correction about the front cover
- Michael Rosen (19 August 2002)
-
Why 'intention to treat'?
- James Austin (21 August 2002)
-
More details of anaesthetic technique
- Julian P Stone (21 August 2002)
-
Re: Potentially a septic technique for epidurals
- Andrew W Ross (24 August 2002)
-
Re: Why 'intention to treat'?
- Neil F Moran (25 August 2002)
-
Re: Why 'intention to treat'?
- John A Laurenson (27 August 2002)
-
Epidurals and backache: not again?
- Felicity Reynolds (27 August 2002)
-
Re: Re: Potentially a septic technique for epidurals
- Martin N. Scanlon (27 August 2002)
-
Re: Re: Why 'intention to treat'?
- Martin N. Scanlon (27 August 2002)
-
Re: Re: Re: Potentially a septic technique for epidurals
- John A Crowhurst (3 September 2002)
-
Long term back pain after labour analgesia
- Ulisse Corbanese, Paolo Dal Cero, Clemente Possamai (18 September 2002)
-
Re: Re: Why 'intention to treat'?
- Bernhard H Heidemann (27 October 2002)
|
|
|||
|
Michael Rosen, Professor
Send response to journal:
|
The picture on the front cover shows a male doctor undertaking an epidural block with gloves on but NO gown. This highly dangerous behaviour risks contamination of equipment, especially the catheter. The BMJ should publish a prominent correction. |
|||
|
|
|||
|
James Austin, SpR Anaesthetics PICU St Mary's, London, W2 1NY
Send response to journal:
|
It has become trendy, nearly mandatory to use intention-to-treat analyses in randomised controlled trials. Was this really the most appropriate analysis here? We want to know "do epidurals themselves cause (or increase the risk of) backache?", not "does the policy of offering / recommending epidurals cause backache?" The authors rightly point out that a high crossover rate weakens this intention-to-treat analysis. Surely a received-treatment analysis would give more useful information? |
|||
|
|
|||
|
Julian P Stone, Anaesthetic SpR St George's Hospital, London SW17
Send response to journal:
|
The study by Howell and collegues does not provide information on certain variables within the epidural group. For example, was the epidural drug regimen standardised or left up to the individual anaesthetist? Although motor block after an edidural is not thought to be a significant causative factor in backache [1] further details would be welcome. Were all the patients lying or sitting for the epidural to be sited and might this be significant? Details about the ease of epidural siting may also be of benefit as several attepts to position a "difficult" epidural may possibly result in postpartum backache. 1. Longterm backache after childbirth:prospective search for causative factors. BMJ 1996 Jun 1;312(7043):1384-8 |
|||
|
|
|||
|
Andrew W Ross, Head of Anaesthesia Mercy Hospital for Women East Melbourne Australia
Send response to journal:
|
Where was the gown asks Professor Rosen? I agree but where also was the mask - for the patient and the operator's protection? |
|||
|
|
|||
|
Neil F Moran, Consultant Obstetrician Mahatma Gandhi Memorial Hospital, Durban, South Africa
Send response to journal:
|
James Austin makes a good point. This study does not tell us whether epidural results in more back pain. It tells us whether a woman who plans to have an epidural ends up with more back pain than one who doesn't. What women will want to know is whether the epidural itself results in more back pain. If available, this information will have a major influence on whether a woman plans to have an epidural or not. Would it be possible for the authors of the paper to present us with an alternative analysis according to treatment actually received, rather than the intention-to- treat analysis? |
|||
|
|
|||
|
John A Laurenson, Consultant Anaesthetist Wansbeck General Hospital, Ashington, Northumberland, NE63 9JJ
Send response to journal:
|
I must agree with the comments of Dr Austin of 21 August 2002 regarding the paper "Randomised study of long term outcome after epidural versus non-epidural analgesia during labour" BMJ 2002;325:357-9. With a crossover of 33% in the epidural group and of 28% in the non- epidural group, an intention-to-treat analysis is significantly weakened. This becomes clearest when the crossover approaches 50%, at which time the treatment and control groups become identical with regard to the treatment received. Scientifically, an intention-to-treat analysis is generally the prefered method, but in this study it would have been useful if the authors had also published the results of a received-treatment analysis. Then it would be possible to compare the backpain outcome for patients who actually received an epidural with those who did not. |
|||
|
|
|||
|
Felicity Reynolds, Emeritus professor of obstetric anaesthesia St Thomas' Hospital, London SE1 7EH
Send response to journal:
|
Anaesthetists have reason to be grateful to the BMJ for being willing to publish yet another trial, albeit a small one, demonstrating that epidural analgesia is not associated with long term backache. On each occasion this outcome appears to come as a surprise, so the finding is worth repeating. The editor published with alacrity the retrospective studies that gave the erroneous result that epidurals did cause backache,[1,2] but took more persuading to publish prospective studies with negative results [3] (and flatly refused to publish one showing epidurals were good for babies - good news is no news). Readers may find it useful to know that further clinical details of this study can be found in an earlier publication by Howell and her colleagues [4] in which 184 women were randomised to epidural and 185 to non-epidural analgesia, primary outcome backache 3 and 12 months after delivery. The authors state that crossover between treatment groups is inevitable in such trials. Not so. Researchers in the University of Texas Southwestern Medical Center, Dallas, have published a series trials in which to date a total of 3727 women were randomised to receive either epidural or systemic analgesia. They made progressively more successful efforts to improve analgesia in the non-epidural arm by the use of generous patient controlled analgesia regimens. In the latest study [5] the crossover amounted to 3.1%. The cover picture relating to this article is misleading, not only because, as other correspondents indicate, the epiduralist should be wearing mask (most important) and gown, but also in the caption "Do epidurals cause long term backache? No more than other forms of pain relief in labour." It is not the pain relief that causes backache, it is having a baby! Felicity Reynolds, Emeritus Professor of Obstetric Anaesthesia, St Thomas Hospital, London. References 1. MacArthur C, Lewis M, Knox EG, Crawford JS. Epidural anaesthesia and long term backache after childbirth. BMJ 1990; 301: 9-12. 2. Russell R, Groves P, Taub N, ODowd J, Reynolds F. Assessing long term backache after childbirth. BMJ 1993; 306: 1299-1303. 3. Russell R, Dundas R, Reynolds F. Long term backache after childbirth: prospective search for causative factors. BMJ 1996; 312: 1384-8. 4. Howell CJ, Kidd C, Roberts W, Upton P, Jones PW, Johanson RB. A randomised controlled trial of epidural compared with non-epidural analgesia in labour. Br J Obstet Gynaecol 2001,108:27-33. 5. Sharma SK, Alexander JM, Messick G et al. A randomized trial of epidural analgesia versus intravenous meperidine analgesia during labor in nulliparous women. Anesthesiology 2002;96:546-51. |
|||
|
|
|||
|
Martin N. Scanlon, Staff anesthesiologist Rockyview Hospital, Calgary, Canada. T2J 0K1
Send response to journal:
|
Re: need for gloves AND GOWN when placing epidural: it is my usual practice to wear sterile gloves, mask but not gown when placing epidurals, and I believe most of my colleagues follow suit. As far as I am aware, our institution does not have an abnormally high rate of epidural abscess. Do you have any actual EVIDENCE to back your statements regarding proper sterile technique, or is it just your opinion? |
|||
|
|
|||
|
Martin N. Scanlon, Staff anesthesiologist Rockyview Hospital, Calgary, Canada. T2J 0K1
Send response to journal:
|
Intention to treat is an appropriate analysis because it is closest to what happens in the real world. Say for example those women randomised to recieve epidurals all chose to discontinue them because they got back ache during insertion. If not included in the epidural group the results would be terribly skewed. |
|||
|
|
|||
|
John A Crowhurst, Reader in Obstetric Anaesthesia, Imperial College Queen Charlotte's Hospital, London W12 0HS
Send response to journal:
|
There is no proof that wearing a gown is necessary to minimize neuraxial infection when siting an epidural or other neuraxial block. However, common sense and experience demonstrates that an epidural cather can easily flip beyond the sterile field and touch the anesthesiologist's arms. Furthermore, extending bare and hairy arms over one's sterile equipment and field is not an acceptable aseptic technique - especially when many neuraxial blocks are sited outside the OR. (See the picture in the BMJ 24 MAR 1999; 318. This is similar to the ones published, and has been used by this author and others to illustrate most features of a 'Septic Technique'.) Does one see improperly clad neurosurgeons inserting drains or other equipment into the vertebral column, skull or other areas in intimate contact with the CNS? I suggest not, because they are only too aware of the catastrophic effects of infection. When one looks at infections associated with neuraxial blocks, poor aseptic technique is usually a significant factor. Other associated factors are: Procedure done outside the OR; Organism almost always from patient's skin or the operator; Difficulty with the procedure; Epidural catheters left in situ a long time (> 48 hours) END |
|||
|
|
|||
|
Ulisse Corbanese, anaesthetist Department of Anaesthesia and Intensive Care, Ospedale S. Maria dei Battuti, I-31015 Conegliano, Paolo Dal Cero, Clemente Possamai
Send response to journal:
|
We read the interesting paper by Howell and colleagues about long-term back pain after labour analgesia.1 However, we were concerned about some methodological aspects. The Authors used an intention-to-treat analysis to determine whether epidural analgesia is associated with backache, or not. Intention-to-treat analysis preserves the effects of randomisation, analysing noncompliant patients in the groups they were randomised into, and provides an estimate of the practical impact of the treatment under "real world" conditions, particularly with treatments difficult to tolerate. Although it is generally the best choice for the primary analysis, sometimes intention-to-treat could answer a different question that the one you are interested in. In fact, we believe that this is the case as the real question is: does epidural labour analgesia cause long-term back pain? Actually, using intention-to-treat the backache rate in the non-epidural group is diluted by the 28% of cases who received epidural and, vice versa, in the epidural group the backache rate is diluted by a 33% of women who had not. This way we obtain the incidence of back pain in the two arms of the study but we cannot really answer the underlying question. We think that reporting also a per-protocol analysis (i.e. comparing the outcomes of women who really had epidural with those of women that had not) would have added relevant information, making this study comparable with most previous research, as well. In our opinion, also the statistical power might be a concern, as the overall number of women who had epidural was 144, slightly less than the original 150 calculated by the Authors. Moreover, to maintain the same level of statistical power, the sample size should have been increased proportionally to non-compliers rate. Using the formula in the appendix 2, we estimate that with non-compliers rates of 28% (non-epidural) and 33% (epidural) respectively, the two study arms should have contained 289 and 334 cases. Therefore, if our calculation is correct, a type II error cannot be definitely excluded comparing the incidences of long-term back pain. Appendix 2 Adjustment of sample size according to proportion of non-compliers. Nc = N * (1/(1-R)2)
were: References 1. Howell CJ, Dean T, Lucking L, Dziedzic K, Jones PW, Johanson RB. Randomised study of long term outcome after epidural versus non-epidural analgesia during labour. BMJ 2002; 325(7360): 357. 2. Lachin JM. Statistical consideration in the intention-to-treat principle. (Accessed September 10, 2002 at http://www.bsc.gwu.edu/~jml/download/ittansl2.doc) |
|||
|
|
|||
|
Bernhard H Heidemann, Clinical Lecturer in Anaesthesia Royal Infirmary of Edinburgh, Edinburgh, EH16 9SU
Send response to journal:
|
It has been suggested by several of the correspondents that the authors of this trial ought to have published an analysis on the basis of treatment received alongside the intention to treat one. If one keeps anaylysing the same data in different ways, one will eventually arrive at a significant finding. If two different ways of anaylsing data are planned from the outset than this has to be taken into account when calculating the sample size. The description of sample size calculation for this study or rather its predecessor study is contained in [1]. As another respondent has already argued the actual sample size is insufficient to exclude a type II error. More importantly, however, is the difference between the groups this study could have picked up. The authors chose a twofold increase in the incidence of back pain in the epidural group. Many obstetric anaesthetists and even more parturients would think a much lesser increase in the incidence clinically important. [1] Howell CJ, Kidd C, Roberts W, Upton P, Lucking L, Jones PW, et al. A randomised controlled trial of epidural compared with non-epidural analgesia in labour. Br J Obstet Gynaecol 2001; 108: 27-33. |
|||