An Anatomical, Sonographic, and Computed Tomography Study of the Transversus Abdominis Plane Block in Cat Cadavers

Round 1

Reviewer 1 Report

Dear authors:

This is a very well designed and written manuscript. It is interesting for the reader and with great practical applicability.

Just a couple of comments:

Figure 1. Legend. Since it is a black and white figure, yellow rectangles cannot be described.

Statistical method. Could you indicate the units in which you reflect the results? Mean +/- Standard deviation or Media and range.

Results: Line 348. The number of stained nerves per approach are expressed in Mean +/- Standard deviation, but being a small number of cats/nerves, did the results have a normal distribution? Would the median (range) be a better option to display these results?

Once again, congratulations for a great study.

Author Response

Figure 1. Legend. Since it is a black and white figure, yellow rectangles cannot be described.

Changed. Thank you.

Statistical method. Could you indicate the units in which you reflect the results? Mean +/- Standard deviation or Media and range.

Done. Thank you.

Results: Line 348. The number of stained nerves per approach are expressed in Mean +/- Standard deviation, but being a small number of cats/nerves, did the results have a normal distribution? Would the median (range) be a better option to display these results?

Thank you. We performed statistical analysis for data not normally distributed for this. Contrast distribution (mm) is normally distributed; therefore, we presented the data as mean +/- SD. Nerve staining is not normally distributed, and we presented the data as median (range). We modified the manuscript accordingly and we add a sentence in the statistical analysis.

Reviewer 2 Report

The use of new analgesia techniques is a field of pain study, especially in small species, in which surgeries such as ovariohysterectomy or castration are routine procedures. The use of locoregional techniques offers benefits to the patient and the doctor, since by reducing the administered dose, the adverse effects of their systemic use are reduced, and multimodal analgesia for pain management techniques is used. The present is well written and illustrated and provides an extensive anatomical and pharmacological basis to use this technique, together with top-tier technologies such as CT scan. I have left some minor observations.

Line 39: Before introducing US-guided TAP, I would recommend briefly add about the importance/advantages of locoregional anesthesia in small animals. For example, as stated in the simple summary (lines 13-14).

Line 47: After this sentence, the authors could indicate in which routinary surgeries TAP could be applied and what could/are the advantages over other techniques to enrich the importance of evaluation this locoregional technique.

Line 65-66: Could the authors include the range of volume that has been used to date in TAP blocks?

Line 90: Please, include which breeds were included in the present study. In line 246 it is mentioned that males and females were included. I suggest adding this in the methodology section as well.

Line 371: In the discussion section, the importance of the anatomical differences between cats and dogs could be briefly mentioned.  

Line 373: Previously, in lines 95-96, “computed tomography” was already abbreviated as “CT”. I recommend using this abbreviation throughout the manuscript.

Line 400: Are the characteristics of other drugs a factor that needs to be considered when using TAP block? Or is it a research area where additional studies must be performed? This information could be also discussed.

Line 411-412: If there are other possible factors that the authors suppose could alter the efficacy of TAP block, they could be added here.

Author Response

Line 39: Before introducing US-guided TAP, I would recommend briefly add about the importance/advantages of locoregional anesthesia in small animals. For example, as stated in the simple summary (lines 13-14).

A sentence has been added.

Line 47: After this sentence, the authors could indicate in which routinary surgeries TAP could be applied and what could/are the advantages over other techniques to enrich the importance of evaluation this locoregional technique.

A sentence has been added.

Line 65-66: Could the authors include the range of volume that has been used to date in TAP blocks?

Done.

Line 90: Please, include which breeds were included in the present study. In line 246 it is mentioned that males and females were included. I suggest adding this in the methodology section as well.

Done.

Line 371: In the discussion section, the importance of the anatomical differences between cats and dogs could be briefly mentioned.

Thank you for your suggestion. The sonoanatomy between the two species should not be much different. However, this was not a comparative study so we have limited the discussion to our findings as this would not be relevant to the goals of the study.

Line 373: Previously, in lines 95-96, “computed tomography” was already abbreviated as “CT”. I recommend using this abbreviation throughout the manuscript.

Changed throughout.

Line 400: Are the characteristics of other drugs a factor that needs to be considered when using TAP block? Or is it a research area where additional studies must be performed? This information could be also discussed.

Thank you for your suggestion. We have discussed several factors that could influence the efficacy and safety of a TAP block in the context of a cadaver study with some potential implications in-vivo. For example, these factors could include needle position, type of needle used, 2- versus 3-point injections, anatomical variability, spread distribution (including potential intraperitoneal staining), injectate volume, drug concentration, etc. We have also stated that we are now conducting a prospective, randomized, masked clinical trial investigating the analgesic efficacy of bupivacaine following a TAP block in cats as one of the potential avenues for investigation. The discussion on how the pharmacology of a drug could affect the onset and duration of action of a TAP block is more relevant to the upcoming clinical trial as the manuscript is already long in length.

Line 411-412: If there are other possible factors that the authors suppose could alter the efficacy of TAP block, they could be added here.

Thank you. Please see answer above.