|
|
||||||||
Eur J Cardiothorac Surg 2001;19:834-839
© 2001 Elsevier Science NL
Department of Thoracic and Cardiovascular Surgery, Saga Medical School, 5-1-1 Nabeshima, Saga City, Saga 849-8501, Japan
Received 10 October 2000; received in revised form 14 February 2001; accepted 26 March 2001.
Corresponding author. Tel.: +81-952-34-2345; fax: +81-952-34-2061
e-mail: okazaki{at}post.saga-med.ac.jp
| Abstract |
|---|
|
|
|---|
Key Words: Off-pump coronary artery bypass grafting Coronary endothelial injury Less invasive cardiac surgery
| 1. Introduction |
|---|
|
|
|---|
In the present study, the coronary endothelial injuries related to coronary snaring and gas insufflation were observed using scanning electron microscopy (SEM) in dogs. Protective effects of coronary snaring with elastic sutures, humidified gas insufflation, and heparin and dipyridamole-added humidification were also evaluated morphologically.
| 2. Methods |
|---|
|
|
|---|
2.2. Animal surgeries
Thirty-six adult mongrel dogs, weighing 2030 kg, were anesthetized with an intravenous injection of pentobarbital sodium (15 mg/kg body weight) then endotracheally intubated. General anesthesia was maintained by inhalation of isoflurane under mechanical ventilation. The animal was placed in the right lateral position. The chest was entered through the fifth intercostal space and the pericardium was incised and retracted to expose the left coronary arteries. After systemic heparinization (150 U/kg), the first diagonal branch was snared with non-elastic monofilament (3-0 Prolene, Ethicon Inc., Somerville, NJ, USA) or elastic sutures (Elastic, Matsuda Medical Inc., Tokyo, Japan) proximally and distally. A 5 mm longitudinal coronary incision was made between snares. The coronary arteriotomy was exposed to non-humidified carbon dioxide gas (5 l/min), humidified carbon dioxide gas (5 l/min) with lactated Ringer solution, or humidified carbon dioxide gas (5 l/min) with heparin (1000 U/100 ml) and dipyridamole (10 mg/100 ml) added lactate Ringer solution for 10 or 20 min in each group using Visuflo Surgical Site Visualization System (Baxter Research Medical Inc., Midvale, UT, USA). After 10 or 20 min gas insufflation completed, the coronary arteriotomy was repaired with 8-0 monofilament sutures. Both of proximal and distal coronary snarings were released, then, the coronary artery was reperfused for 1 h.
The animal after the simulation of off-pump CABG with coronary snaring and gas insufflation was euthanized with a lethal dose of intravenous pentobarbital and potassium after additional heparinization (additional 150 U/kg) to prevent post-mortem thrombus formation. The heart was excised with the ascending aorta and was perfused with lactated Ringer solution for rinsing. Perfusion fixation of the heart was then performed to preserve the ultrastructures of the coronary endothelium using 2.5% glutaraldehyde in 0.1 M cacodylate buffer with 3% sucrose at a perfusion pressure of 120 cmH2O. The tissue specimens including damaged coronaries with snaring or gas insufflation were stored in the same fixative until it was studied.
2.3. Observation of the coronary endothelium by scanning electron microscopy
After rinsing with 0.1 M cacodylate buffer, the tissue specimens were dehydrated through an ethanol series and freeze-dried. The tissue specimens including the coronary endothelial surfaces were coated with gold (IB-3 ion coater, Eiko Ltd., Mito, Japan), and then observed by SEM (JSM-5200LV, JEOL Ltd, Tokyo, Japan).
To achieve semi-quantitative analysis of the coronary endothelial damage, the adverse effect on the endothelium, which was mainly located at the opposite side to the arteriotomy, was graded as follows: grade 1, appeared normal; grade 2, few blood cells deposited; grade 3, many blood cells deposited; grade 4, few endothelial cells delaminated with blood cells deposited; grade 5, many endothelial cells delaminated with blood cells deposited.
To detect the differences between simple and heparin-dipyridamole-added humidified gas insufflation, the percent endothelial surface area covered by deposited blood cells was calculated using a computer image analysis system (MacSCOPE, Mitani Co. Ltd., Fukui, Japan) on the SEM specimens.
2.4. Statistical analysis
Results are expressed as the mean±standard deviation (SD). Statistical analyses were performed by the MannWhitney test to compare the data between the groups. Differences were considered significant at the level of P<0.05. Multiple comparisons were done using single MannWhitney tests with Bonferroni-correction as post-hoc comparisons if applicable.
| 3. Results |
|---|
|
|
|---|
|
|
|
|
|
|
|
|
|
| 4. Discussion |
|---|
|
|
|---|
The quality of the coronary anastomosis of off-pump CABG is, however, still a great concern. Poirier and her colleagues demonstrated that the anastomoses during off-pump CABG had lesser degree of intraluminal stenosis when performed with the use of a myocardial wall stabilizer [13]. During anastomosis in off-pump CABG, how to keep bloodless surgical field without endothelial injury remains an issue. Although surgeons usually use coronary snaring for coronary occlusion and/or gas insufflation to clear the anastomotic site [14,15], these procedures may cause coronary endothelial injury [16], which may promote blood clotting and smooth muscle cell migration and proliferation at the anastomosis [17].
In the present study, the adverse effects on the coronary endothelium caused by coronary snaring using non-elastic sutures and non-humidified gas blowing were morphologically demonstrated by SEM observation with blood reperfusion after anastomosis completed. In spite of only 60 min blood-reperfusion at the anastomotic site without reverse of systemic heparinization, blood cells were remarkably deposited on the area where the coronary endothelial cells were delaminated. In the clinical settings with much longer blood perfusion and recovered coagulation system after surgery, more blood cells can be expected to be deposited on the injured area with endothelial cells denuded, which will result in thrombus formation at the anastomosis [18]. Furthermore, smooth muscle cell proliferation will be activated [17]. Endothelial injury during off-pump CABG potentially results in the post-operative graft occlusion.
The protective efficacy of elastic coronary snaring and humidified gas blowing on the coronary endothelium was also shown in the present study. However, cognizable blood cells were still deposited on the morphologically intact endothelium. Activation of cell adherences (P-selectin, ICAM-I, GP-IIbIIIa etc.) in the vicinity of anastomosis may occur in off-pump CABG with coronary endothelium functionally damaged. In case of heparin and dipyridamole-added humidification, blood cells deposited on the endothelium reduced when compared with simple humidification. Although coronary anastomosis within 10 min in off-pump CABG may be free from coronary endothelial injury related to simple humidified gas insufflation, heparin and dipyridamole-added humidification potentially have some advantages in case of technically difficult anastomosis that will take more time. Further investigation to reduce endothelial damage and to realize optimal bloodless surgical fields in off-pump CABG should be continued to achieve as reliable anastomoses in off-pump CABG as in conventional CABG.
In conclusion, coronary snaring resulted in coronary endothelial injury, which was ameliorated by using elastic sutures instead of non-elastic sutures. Non-humidified gas insufflation made blood cells deposited and endothelial cells delaminated with time. Humidified gas insufflation attenuated these adverse effects. Heparin and dipyridamole-added humidification had potential advantage in terms of reducing deposited blood cells on the endothelium over simple humidification.
| Acknowledgments |
|---|
| Footnotes |
|---|
| Appendix A. Conference discussion |
|---|
|
|
|---|
Dr Okazaki: In the clinical setting we usually use the flow rate of 5 1/min, so in this experimental study we tested the same flow rate, but in our preliminary study, we tested more than 10 1/min. It caused much severe damage with edema on the artery. So I think it is important to us to use as low as possible a flow rate, I mean, to protect the endothelium from gas.
Mr R. Ascione (Bristol, UK): I can't really understand the rationale of doing this study when it is well known over the last 2 years that the way of doing off-pump surgery is by using an intracoronary shunt and a blower humidifier to enhance visualization. Currently the need of using a proximal snare is only for a few seconds, I mean 510 seconds, to open the coronary, to insert the shunt and then you release it. So you are going to have a shunt perfusing the heart during the anastomosis. The shunt is keeping the coronary site open so you can stitch it very nicely.
Also I have a small concern regarding your methodology. You didn't check the effect of your perfusate on the endothelium. You give it at 120 mmHg continuously, whereas the normal flow mostly is during the diastolic phase of the cardiac cycle with a lower pressure, and you did not take into account the effect of the surgical technique itself, like opening the coronary and stitching, on your endothelium.
Dr Okazaki: For the first question and comment you said what?
Mr Ascione: I was just saying that now we are in the era of intracoronary shunts and a blower humidifier to enhance visualization during the anastomosis. So there is no need of snaring for 20 min a coronary, which has been shown already with previous studies to make some problem on the endothelium.
Dr Okazaki: In our preliminary study, we also tested the coronary shunting system, but if we used an oversized shunt, we can see sort of damage of the coronary endothelium. So it is important for us to use a little bit smaller shunt.
Mr Ascione: That is a very good point, the sizing of the shunt is very important and indeed one should choose a shunt just a little bit smaller than the actual size of the coronary to prevent injury. One can actually accept a bit of bleeding as the blower-humidifier will enhance visualization anyway.
Dr Okazaki: And the second question?
Mr Ascione: Was regarding your methodology, as I think you didn't take into account the effect of your perfusate and of surgery itself on the endothelium. I mean the coronary incision and the stitching going through might effect the endothelium. Also you infused the perfusate at a pressure of 120 mmHg continuously, whereas we know that most of the blood perfusion to the heart happens during the diastolic phase of the cardiac cycle with lower blood pressure.
Dr Okazaki: At first I would like to explain the coronary endothelial damage associated with the surgical maneuver. By only suturing we can see severe damage around the anastomotic site, even in case of on-pump CABG.
And the second question, the reperfusion pressure of the blood you mentioned, the pressure in this experiment, we applied usually 100150 mmHg for systolic pressure and almost 80 mmHg of diastolic pressure, because we used dog, and in case of dog, the blood pressure is usually a little bit higher than human, I think, even under general anesthesia. so the mean reperfusion pressure was almost 100 or 120 mmHg.
And I showed the perfusion pressure of 120 cmH2O was for preparation of the coronary, to view the coronary endothelium by scanning electron microscope. I mean, if coronary collapsed, we cannot see the coronary endothelium. so in tissue specimens, coronary should be wide open, similar to a living setting. So we applied 120 cmH2O pressure for perfusion fixation.
Dr S. Ener (Bursa, Turkey): I just want to make a comment because I have been doing OPCAB surgery since 97, and I have got experience with 400 cases. Actually this study doesn't compare with the actual practice, because we don't use continuous blowing, and for every stitch we use only a few seconds. Then the moisture or the misted blowing may be less necessary than we thought with such studies.
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
M. Masoumi, M. R Saidi, F. Rostami, H. Sepahi, and D. Roushani Off-Pump Coronary Artery Bypass Grafting in Left Ventricular Dysfunction Asian Cardiovasc Thorac Ann, February 1, 2008; 16(1): 16 - 20. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. P. Collison, A. Agarwal, and N. Trehan Controversies in the use of intraluminal shunts during off-pump coronary artery bypass grafting surgery. Ann. Thorac. Surg., October 1, 2006; 82(4): 1559 - 1566. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Wippermann, J. M. Albes, K. Liebing, M. Breuer, M. Kaluza, J. Strauch, and T. Wahlers Simple on-site assembled blower-mister device provides sufficient humidification and visualization in off-pump surgery. Ann. Thorac. Surg., September 1, 2006; 82(3): 1134 - 1136. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. Paparella, A. Galeone, M. T. Venneri, M. Coviello, G. Scrascia, N. Marraudino, M. Quaranta, L. de Luca Tupputi Schinosa, and S. J. Brister Activation of the coagulation system during coronary artery bypass grafting: Comparison between on-pump and off-pump techniques J. Thorac. Cardiovasc. Surg., February 1, 2006; 131(2): 290 - 297. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Persson and J. van der Linden Can Wound Desiccation Be Averted During Cardiac Surgery? An Experimental Study Anesth. Analg., February 1, 2005; 100(2): 315 - 320. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. G. Demaria, S. Fortier, and L. P. Perrault Coronary endothelial damage during off-pump CABG related to coronary-clamping and gas insufflation Eur. J. Cardiothorac. Surg., December 1, 2001; 20(6): 1270 - 1271. [Full Text] [PDF] |
||||
![]() |
Y. Okazaki, K. Takarabe, and T. Itoh Reply to Demaria et al. Eur. J. Cardiothorac. Surg., December 1, 2001; 20(6): 1272 - 1272. [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |