Air embolism caused by blower mister during off-pump coronary artery bypass surgery: is it preventable?

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We read with interest the article by Shim et al. [1] The authors need to be congratulated for highlighting a potentially lethal complication of the carbon dioxide (CO2) blower mister in off-pump coronary artery bypass surgery (OPCAB) [1], despite the gas being>25 times more soluble in blood and tissue than in air. One of the challenges during OPCAB is to keep the arteriotomy site bloodless to allow accurate suturing [1,2]. Several techniques such as intermittent irrigation with saline solution, use of a CO2 blower mister, intraluminal coronary shunts and use of sling to occlude the coronary artery have been described [1,2]. There is no consensus as to which of these should be the preferred method. We also use the CO2 blower mister routinely in our OPCAB practice,butalways in conjunctionwithanappropriately sized intraluminal coronary shunt. It is noteworthy that in cases of CO2 embolism that have been reported, no shunts were used during the procedures [1,2]. We believe that the shunts will protect against CO2 embolism by acting as a physical barrier within the arteriotomy. Besides, by effectively maintaining a bloodless field, shunts permit theuseof a lower gasflow(about 3 l min 1 vs 7 l min 1 as reported by the authors),whichwould further protect against the risk of gas embolism. Placement of snares around coronary arteries does help in providing a bloodless field [1]. However, as the authors have commented, in the presence of calcified coronary arteries, the snares do not work and hence the authors had to increase the rate of CO2 to 7 l min , which, in our opinion, is truly hazardous [1]. The snares cannot be used if the patients have had previous percutaneous coronary intervention (PCI) [2]. Besides, there is potential for external trauma, regional ischaemia and snare-related injuries causing new stenoses [3,4]. Intraluminal coronary shunts can continuously protect the endothelium fromthe ‘sand-blasting’ effect of a blowermister [3,4]. It maintains distal coronary perfusion, resulting in improved haemodynamic performance [4,5]. Several recent studies have documented that shunts do provide significant nutritive flow even in small arteries [3], resulting in less troponin leak [5]. It also improves the technical precision by ‘presenting’ the artery for anastomosis and protects the back wall of the artery from inadvertent needle suture [3]. The earlier concerns of endothelial trauma by intraluminal coronary shunts are ameliorated by newer models that are very pliable with atraumatic tips, have better flow dynamics and are available in sizes down to 1 mm [3,4]. In acknowledging the case report by Shim et al., we take the opportunity to re-appraise the usefulness of intracoronary shunts in OPCAB surgery.