Title: Total Aortic Arch Replacement under Intermittent Pressure-augmented Retrograde Cerebral Perfusion

Transcription

1 Author's response to reviews Title: Total Aortic Arch Replacement under Intermittent Pressure-augmented Authors: Hiroshi Kubota Kunihiko Tonari Hidehito Endo Hiroshi Tsuchiya Hideaki Yoshino Kenichi Sudo Version: 2 Date: 4 October 2010 Author's response to reviews: see over

2 Reviewer's report Title: Total Aortic Arch Replacement under Intermittent Pressure-augmented Version: 1 Date: 28 August 2010 Reviewer: Mitsuhiro Kawata Reviewer's report: Dear the authors, Although this paper reports data in one patient only, the results warrant publication to raise awareness and prompt further research in this area. This IPA-RCP procedure was applied accidentally to the emergency case in order to prolong the safe limits of RCP. And also this technique was used in your hospital for the first time. Congratulations on successful results. It was very interesting that the rso2 wave changed following the pressure augmentation. Could you add the CV pressure wave into Figure 1, rso2 wave based on the same time scale? If you can do it, this report became more meaningful. Thank you for your suggestion. To our regret, we did not record the simultaneous CV pressure to rso2 wave. We fully agree with your comment. To know the interval between the peak of CVP and rso2 may give us the important information to know the mechanism of IPA-RCP more precisely. We will plan to record the CVP and rso2 simultaneously during IPA-RCP. I agree with your named "bottom raising effect" of IPA-RCP. I'm looking forward to your randomized comparative study in clinical cases of IPA-RCP and conventional RCP data. Thank you for the comments. We are now preparing to submit our data to be published. Sincerely, Mitsuhiro Kawata, Lecturer, Department of Cardiovascular Surgery,

3 Saitama Medical University Saitama Medical Center 1981 Kamoda, Kawagoe city, Saitama , Japan Level of interest: An article of outstanding merit and interest in its field Quality of written English: Acceptable Declaration of competing interests: I declare that I have no competing interests. Reviewer's report Title: Total Aortic Arch Replacement under Intermittent Pressure-augmented Version: 1 Date: 3 September 2010 Reviewer: Kazuo Kitahori Reviewer's report: Discretionary Revisions: I am very interested in this paper. In this paper, the authors demonstrated that IPA-RCP had some advantage of cerebral protection during circulatory arrest, compared to conventional RCP. Monitoring of rso2 is a good indicator for cerebral perfusion. Quick recovery of consciousness is also a good clinical outcome. It is very interesting and encouraging for aortic surgeons. Thank you for your comments. I have some questions. How do you select patients to use this technique? Or do you use it for all patients who undergo aortic arch operation? With good clinical results from the presented first case, for all patients who undergo thoracic aortic operation (including ascending aortic replacement) through median sternotomy, the IPA-RCP has been used.

4 Conventional RCP has some merit. For example, bloodless surgical field, easy manipulation of cardiopulmonary bypass machine. As you mentioned, IPA-RCP gave reverse flow for the arch vessels. It was not comfortable for surgeons. When do you convert the method from conventional RCP to IPA-RCP during the operation? Do you have any criteria of circulatory arrest time or rso2 level? For all cases from the second, the IPA-RCP method was applied two minutes after the initiation of the circulatory arrest (CA). Initially, the oxygenated blood is perfused through the superior vena cava at a pressure of mmhg. Two minutes later, the initial pressure augmented perfusion at 45 mmhg is attempted then lowered. The duration of the augmentation is 30 sec, and the perfusion pressure is then lowered to 20 mmhg. This 30 sec augmentation followed by a 2 min interval is repeated through the aortic reconstruction. Although there is no experimental background about the two min interval, considering the safety of the operation, keeping perfusionists practical concentration during a long CA period is thought to be important. We planned to make two min interval. Actually, as the reviewer mentions, backflow from the neck vessels occasionally disturb the operative field. We order to the perfusionist to cease the pressure augmentation to obtain comfortable operative field as occasion calls. You showed rso2 was maintained during IPA-RCP. I am very interested in zigzag movement of rso2. It must indicate augmentation of CVP pressure increased rso2, I think. How was the response of rso2 after CVP reached at 45 mmhg? Was it quick or was there some time lag? Thank you for your suggestion. To our regret, we did not record the simultaneous CV pressure and rso2 wave. We fully agree with your comment. To know the interval between the peak of CVP and rso2 may give us the important information to know the mechanism of IPA-RCP more precisely. We will plan to record the CVP and rso2 simultaneously during IPA-RCP. Did you place an epidural catheter for monitoring of CSF pressure? If you did, did you find any change of CSF pressure between IPA-RCP and conventional one?

5 Thank you for your comments. We did not place an epidural catheter for monitoring the CSF pressure. CSF pressure measurement is also important to know the mechanism of the IPA-RCP effectiveness. However, it is difficult to us to use it to clinical heparinized cases except the patients to be prevented from paraplegia. Level of interest: An article of outstanding merit and interest in its field Quality of written English: Acceptable Declaration of competing interests: I declare that I have no competing interests. Reviewer's report Title: Total Aortic Arch Replacement under Intermittent Pressure-augmented Version: 1 Date: 9 September 2010 Reviewer: Olivier JEGADEN Reviewer's report: The authors report a case of intermittent pressure augmentation of retrograde cerebral perfusion during circulatory arrest providing very good cerebral protection. The case is well reported. Results are interesting and open the way to a new concept. The interest of the report is emphasized with preliminary results of a randomized study given in comments. This study will be a good contribution in this field. Thank very much for your comments. Level of interest: An article of importance in its field Quality of written English: Acceptable Declaration of competing interests: I declare that I have no competing interests' below Reviewer's report

6 Title: Total Aortic Arch Replacement under Intermittent Pressure-augmented Version: 1 Date: 12 September 2010 Reviewer: Lionel Fernand F Camilleri Reviewer's report: General comments: The optimal method to protect the brain during aortic arch surgery is still unresolved. H Kubota and colleagues provide a novel management protocol for retrograde cerebral perfusion, derived from canine experimental works that add an interesting contribution to this field. Major compulsory revisions Paragraph conclusion 1. There is major difference between RCP in the experimental canine model and in humans in term of perfusion. In the canine model to overcome the problem of jugular vein valves, the RCP was administered through the maxillary vein, so the RCP could gain directly the cranial veins. In the majority of humans, the jugular vein had competent valves (de Brux JL. Ann Thorac Surg 1995) and it is hypothesized that the RCP gains the brain through a collateral network of veins (azygos, intercostal, medullary and vertebral veins). The usefulness of higher perfusion pressure could be either to distend the valves or more probably to increase the pressure in the collateral vein network to improve cerebral oxygenation. Some comments on this with references should be added to the discussion. Thank you for your important comments. In discussion, we lacked to describe about the jugular vein valves. According to your comments, we added the sentences as follows in conclusion. However, in the canine model, they administered the RCP through the maxillary vein to overcome the drawbacks of jugular vein valves to reach directly the cranial veins. In the majority of humans,

7 as de Brux et al. described, the jugular vein had competent valves and it is hypothesized that the RCP gains the brain through a collateral network of veins (azygos, intercostal, medullary and vertebral veins). The usefulness of higher perfusion pressure could be either to distend the valves or more probably to increase the pressure in the collateral vein network to improve cerebral oxygenation 5). Thus, the clinical effectiveness of the IPA-RCP through a cannulae inserted to the SVC is unknown field. 2. Some authors have recommended using higher pressure (range 30 to 50, mean 40 mm Hg for conventional RCP (Ganzel BL, J Thorac Cardiovasc Surg 1997). The authors indicated that they initially have planned to perform the operation using conventional RCP. They should explain why a15 mm Hg perfusion pressure has been chosen. Thank you for the comments. According to the comments, we added the sentences as follows. RCP by augmentation of CVP to 15 to 20 mmhg is routinely used for the additional brain protection during deep hypothermic circulatory arrest in our institute because much evidence has been accumulated to suggest an increased risk of perfusion-induced brain injury associated with RCP, especially when continuously high RCP pressures are used 4). 3. This case report underlines the imperious necessity of determination of rso2 to assess real time cerebral perfusion (only the anterior part of the brain is assessed by NIRS), detect and immediately solve cerebral malperfusion without any delay before irreversible damage develops. Some comments and reference on the usefulness of NIRS to adjust RCP conditions adequately should be added. Thank you for the comments. According to your comments, we added the sentences as follows. We examined the effect of the IPA-RCP by measuring rso 2 which is said to represent the brain blood perfusion. Although only the anterior part of the brain rso 2 is assessed by a TOS-96 brain oximeter, because most attenuation of near-infrared light in human cerebral tissues is due to

8 absorption by deoxyhemoglobin and oxyhemoglobin, the brain tissue is suitable for determination of rso2. Only determination of rso2 is an easily available method to assess the real-time adequacy of cerebral perfusion during time-restricted aortic arch surgery 6). 6) Ogino H, Ueda Y, Sugita T, Morioka K, Sakakibara Y, Matsubayashi K, Nomoto T. Monitoring of regional cerebral oxygenation by near-infrared spectroscopy during continuous retrograde cerebral perfusion for aortic surgery. Eur J Cardiothorac Surg. 14: 415-8, 1998 Some details concerning the baseline value of rso2: measures prior anaesthesia, at the beginning of the ECC, and at profound hypothermia, must be added. Thank you for the comments. According to the comments, we added the sentences as follows. Prior to the anesthesia, the rso 2 was 61% (Left) and 60% (Right).At the beginning of the cardiopulmonarybypass, the rso 2 was 55% (Left) and 56% (Right). At profound hypothermia, the rso 2 was 64% (Left) and 63% (Right), and it gradually decreased to 49% (Left) and 50% (Right). After commencing the IPA-RCP, the rso2 rose to around 60% at every augmentation, but it decreased when the augmentation ceased. 4. Results from a preliminary randomized comparative study are mentioned. It should be stated that these results are unpublished data otherwise it should be deleted. Thank you for your comment. These results of preliminary randomized comparative study are unpublished data. We are preparing these data to submit and to be published. Minor revision Paragraph case presentation Are pneumatic arm tourniquets during retrograde cerebral perfusion? Thank you for your suggestion. We did not use pneumatic arm tourniquets during RCP.

9 Considering the collateral mechanism of RCP effectiveness, as the reviewer mentioned, it may augment the effect of RCP or IPA-RCP. Pr L CAMILLERI Level of interest: An article of importance in its field Quality of written English: Acceptable Declaration of competing interests: I declare that i have no competing interests below