Review for 10.1186/1471-230X-13-48 (2013)

Reviewer's report
Title:The effect of general anesthesia on gastric myoelectric activity in
experimental pigs
Version: 1Date:17 December 2012
Reviewer: Jakob Wallden
Reviewer's report:
Overall comments.
The study evaluates the effect of different anaestetic methods on gastric electric
activity measures with an electrogastrograph. The aim of the study is clearly
defined and the methods used are relevant. The study is a methodological study
to find a good laboratory model to study electrogastrograhy in anesthestesied
pigs. The results indicates that the anaesthetics used in the study have very little
effects on the electrogastrographic variables. The study is a useful contribution in
the field, but the paper must undergo a major revision mainly regarding the
statistical methods used, how data are presented and with a more relevant
discussion.
Major Compulsory revisions.
1. Statistics:
I have major concerns regarding the statistics in the manuscript.. The authors
states that they have a great number of observations and define a one-minute
interval as an observation. The one minute interval is used for the running
spectral analysis and when using the one-minute interval, in the way they have
used the statistics, they consider each interval as an independent observation.
In each pig, all one-minute observations during an observation period (before /
after anesthesia) are dependent of each other and the authors should first
calculate mean values of DF and DP for each observation period. The 120
minute period with anesthesia might be divided into at least two parts.
The Mann Whitney -test is not the appropriate test as the observations before
and after anesthesia are dependent. (The Mann-Whitney is a test for
independent observations). The significance tests in the manuscript cannot even
be considered to be evaluated.
The authors should instead state the difference betweens the observations in
each pig. (Its the difference that is the interesting. )The statistics used should
analyze the difference before and after anesthesia as dependent observations.
I recommend that the authors should consult a statistician to perform a major
revision of the presentation of ALL data. Statistics used may be Wilcoxons sign
rank test or ANOVA-analysis.
2. The numbering of references in the text does not correspond to the reference
list.
3. In the methods section, the description of the EGG-variables are confusing.
The percent activity stated in the methods are not presented in the results
section. Please clearify how all variables presented are obtained from the MMS
software.
4. Result and discussion sections must be revised according to the statistical
revision. When using a confidence interval, the authors must state what kind of
CI it is (mean? median? 95%? 99%) and present the intervall in an appropiate
way.
5. In the discussion, omit section with great number of analyzed intervals. You
only have five pigs in each group!
6. Do not repeat the results in the discussion section! Discuss the results instead.
7. Focus the discussion more on how to set up a model to study EGG in
anesthesied pigs and the difference and similarities between human and pigs in
the gastric motility. There might be other studies on gastric motility (manometry?,
scintigraphy?) that shows similarities.
8. In the discussion please comment the potential of ketamin and azaperone to
have impact on the study results. Is the baseline a real baseline? A
dopamine-antagonist as azaperone might have a potential effect to stabilize the
control of gastric motility (DA-antagonists have antiemetic effect) and thereby
maintain the normal electrogastrograhic pattern and influence all results. Please
discuss the issue.
9. Please make a general conclusion regarding the effects of anesthesia on EGG
in humans after presenting available studies. Also relate these conclusions to
your results in the porcine model.
10. What do the authors mean with "used safely" in the final conclusion? Safe for
the pigs? Safe for EGG-results? There is no discusssion regarding this
conclusion. In this context also discuss the potential of the anesthetics to have
impact on results. They might, without affecting the DF and DP, affect how other
drugs affect gastric motility.
11. There is no discussion why thiopenthal seems to be the most appropiate
anesthetic.
12. When creating tables, state the statistical test used with significance levels.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests.