Interact CardioVasc Thorac Surg 2009;9:323-326. doi:10.1510/icvts.2009.206177
© 2009 European Association of Cardio-Thoracic Surgery
Best evidence topic - Valves |
Does the use of carbon dioxide field flooding during heart valve surgery prevent postoperative cerebrovascular complications?
Salvatore Giordanoa,* and
Fausto Biancarib
a Department of Surgery, Vaasa Central Hospital, Hietalahdenkatu 2-4, 65130, Vaasa, Finland
b Department of Surgery, Oulu University Hospital, Oulu, Finland
Received 1 March 2009;
received in revised form 29 April 2009;
accepted 30 April 2009
*Corresponding author. Tel.: +358 443346119; fax: +358 6323152.
E-mail address: salvatoregiordano{at}yahoo.it (S. Giordano).
 |
Abstract
|
|---|
A best evidence topic in cardiothoracic surgery was written according to a structured protocol. The question addressed was whether there is any benefit with the use of carbon dioxide (CO2) field flooding techniques in heart valve surgery, in order to reduce postoperative neurological complications. Altogether 202 articles were found using the reported search, and six of them were used to answer the clinical question. All but one trial, were prospective, randomised. Four studies reported a significantly lower intracardiac bubble count in the CO2 group. A significant reduction of p300 peak latencies in the CO2 group was observed in one study. Otherwise, neurocognitive test batteries did not reveal any advantages of CO2 field flooding in two studies. Three studies reported on postoperative cerebrovascular complications and the overall rate of stroke, transient ischemic attack (TIA) or prolonged reversible ischemic neurological deficit was 1.2% in the CO2 group and 2.5% in the control group (P=ns). Although the use of CO2 field flooding has been observed to be associated with a significantly lower count of intracardiac air bubbles, and improved survival in two small studies, so far there is no evidence of a sustained reduction of cerebrovascular complications with the use of this method.
Key Words: Evidence-based medicine; Heart valve surgery; Carbon dioxide field flooding; Air embolisation; Stroke
|
1. Introduction
|
|---|
A best evidence topic was constructed according to a structured protocol, which is described in detail in the ICVTS [1]. This article updates a previous best evidence topic published in 2004 [2].
|
2. Three-part question
|
|---|
In [patients undergoing heart valve surgery] can [carbon dioxide field flooding] reduce [postoperative neurological complications]?
|
3. Clinical scenario
|
|---|
You are a resident and you notice that surgeons use carbon dioxide (CO2) field flooding in order, they say, to reduce the risk of air embolism during heart valve surgery. Since CO2 is 25 times more soluble in blood and tissues than air [3], and CO2 emboli are better tolerated than air emboli [4], you resolve to check in the literature whether this method is neuroprotective.
|
4. Search strategy
|
|---|
Medline, Ovid and Cochrane databases were searched from date of inception to January 2009.
[CARBON DIOXID.mp AND VALVE SURGERY.mp]. In addition, the reference lists of all relevant articles were searched.
|
5. Search outcome
|
|---|
Two hundred and two abstracts were identified and ten were deemed to be relevant. Most of the papers were considered not relevant as none focused on its potential neuroprotective efficacy. Experimental studies were excluded from this analysis. Thus, we were able to review five prospective randomised trials and one prospective non-randomised study which we used to answer the question. Their results are summarised in Table 1.
|
6. Results
|
|---|
Flooding the surgical field with CO2 reduces the incidence of intracardiac air by 85%, possibly because of the density and solubility of CO2 [5]. The density of CO2 is 1.5 times that of air, so that CO2 empirically and preferentially fills the dependent parts of the surgical field [6].
Webb et al. [5] observed that, among patients undergoing heart valve surgery, those who had not CO2 field flooding had persistent air bubbles for at least 30 min after resumption of heart beat and usually for 45 min. Patients who underwent surgery with CO2 field flooding had no air bubbles remaining <1 min in 48 out of 56 patients. These patients were not randomised and the trans-oesophageal echocardiographer was not blinded to the study group assignment. In addition, the incidence of postoperative stroke or cerebrovascular complications were not reported.
In 2001, Martens et al. [7] reported the results of a prospective randomised study on CO2 insufflation into the thoracic cavity compared to conventional de-airing techniques. They did not find any statistically significant differences between the two groups in terms of mortality or neurocognitive function. However, mortality rate was lower in the CO2 field flooding group (3% vs. 16%, P-value not stated) and the number of high-risk patients was higher in the experimental group. Furthermore, postoperatively and 24 h after surgery, creatinine kinase MB was higher in the CO2 field flooding group (38.0±4.1 vs. 28.0±2.1, P=0.02).
In a prospective randomised trial, Kalpokas et al. [8] recorded the amount of intracardiac bubbles during open-heart valve surgery comparing mechanical de-airing and CO2 field flooding. At transesophageal echocardiography, the bubble count was higher in the mechanical de-airing group compared with CO2 flooding group and neurological complications were not detected in any of the study groups. The main problem with this study is its small size (only 18 patients randomised).
In 2004, Svenarud et al. [9] performed a prospective randomised trial including 20 patients undergoing first time single-valve replacement (mitral or aortic valve). Using transesophageal echocardiography, they observed a median number of microemboli of 161 in the CO2 group vs. 723 in the control group (P<0.001). No data on postoperative cerebrovascular complications have been reported by the authors and the study population was small.
In another randomised study, Skidmore et al. [10] recorded intracardiac bubbles and segmental wall motion in 43 patients who underwent heart valve surgery, 21 randomised to CO2 field flooding and 22 to air field flooding. Bubbles count was higher in the air group than CO2 group (mean: 3.06 vs. 1.78, P=0.10) and segmental wall motion at 1–60 min was better in the CO2 group (P=0.04), particularly in the inferior wall. The authors came to the conclusion that flooding surgical field with CO2 is associated to improved myocardial function and less air bubbles in the heart. They did not report any data regarding postoperative cerebrovascular complications, but they performed some neurocognitive testing in 28 patients, without detecting any significant difference.
More recently, Martens et al. [11] performed a prospective randomised trial on 80 patients undergoing open-heart valve surgery comparing CO2 surgical field flooding with conventional de-airing. They used six battery neurocognitive tests and recorded p300 wave auditory-evoked potentials in order to evaluate the brain function. The authors observed a significant reduction of p300 peak latencies in the CO2 group on the 5th postoperative day. Neurocognitive test batteries did not reveal any differences between groups. However, immediate postoperative mortality (2.6% vs. 4.9%, P=0.56), stroke, transient ischemic attack (TIA) or prolonged reversible ischemic neurological deficit (0% vs. 4.9%, P=0.18) were less frequently observed in the CO2 group, except confusional syndrome, which was higher in the CO2 group (12.8% vs. 4.9%, P=0.26). These differences did not reach statistical significance.
Three studies reported on postoperative cerebrovascular complications [7, 8, 11]. When the results of these studies were summed, the rate of stroke, TIA or prolonged reversible ischemic neurological deficit was 1.2% in the CO2 group and 2.5% in the control group (P=ns).
|
7. Clinical bottom line
|
|---|
In a previous best evidence topic on this issue [2], the authors concluded that the solubility of CO2 emboli justifies the efforts to replace intracavital air with CO2 in open-heart surgery to reduce gaseous emboli. However, the present review of currently available studies shows that there is no evidence on the neuroprotective efficacy with this method. Beside the costs of this technique, it has been reported that elevated blood levels of CO2 can be reached with field flooding techniques and it may result in acidosis [12, 13].
Although the use of CO2 field flooding has been observed to be associated with significantly lower count of intracardiac air bubbles, and improved survival in two small studies, so far there is no evidence of a sustained reduction of cerebrovascular complications with the use of this method.
|
References
|
|---|
- Dunning J, Prendergast B, Mackway-Jones K. Towards evidence-based medicine in cardiothoracic surgery: best BETS. Interact CardioVasc Thorac Surg 2003;2:405–409.[Abstract/Free Full Text]
- Barnard J, Speake D. In open-heart surgery is there a role for the use of carbon dioxide field flooding techniques to reduce the level of postoperative gaseous emboli? Interact CardioVasc Thorac Surg 2004;3:599–602.[Abstract/Free Full Text]
- Mits MA. CO2 biodynamics: a new concept of cellular control. J Theor Biol 1979;80:537–551.[CrossRef][Medline]
- Eguchi S, Sakurai Y, Yamaguchi A. The use of carbon dioxide gas to prevent air embolism during open-heart surgery. Acta Med Biol 1963;11:1–13.[Medline]
- Webb WR, Harrison LH Jr, Helmcke FR, Camino-Lopez A, Munfakh NA, Heck Ha Jr, Mulder PV. Carbon dioxide field flooding minimizes residual intracardiac air after open-heart operations. Ann Thorac Surg 1997;64:1489–1491.[Abstract/Free Full Text]
- Ng WS, Rosen M. Carbon dioxide in the prevention of air embolism during open-heart surgery. Thorax 1968;23:194–196.[Abstract/Free Full Text]
- Martens S, Dietrich M, Wals S, Steffen S, Wimer-Greinecker G, Moritz A. Conventional carbon dioxide application does not reduce cerebral or myocardial damage in open-heart surgery. Ann Thorac Surg 2001;72:1940–1944.[Abstract/Free Full Text]
- Kalpokas MV, Nixon IK, Kluger R, Beilby DS, Silbert BS. Carbon dioxide field flooding versus mechanical de-airing during open-heart surgery: a prospective randomized controlled trial. Perfusion 2003;18:291–294.[Abstract/Free Full Text]
- Svenarud P, Persson M, van der Linden J. Effect of CO2 insufflation on the number and behavior of air microemboli in open-heart surgery: a randomized clinical trial. Circulation 2004;109:1127–1132.[Abstract/Free Full Text]
- Skidmore KL, Jones C, DeWet C. Flooding the surgical field with carbon dioxide during open-heart surgery improves segmental wall motion. J Extra Corpor Technol 2006;38:123–127.[Medline]
- Martens S, Neumann K, Sodemann C, Deschka H, Wimmer-Greinecker G, Moritz A. Carbon dioxide field flooding reduces neurologic impairment after open-heart surgery. Ann Thorac Surg 2008;85:543–547.[Abstract/Free Full Text]
- O'Connor BR, Kussman BD, Park KW. Severe hypercarbia during cardiopulmonary bypass: a complication of CO2 flooding of the surgical field. Anesth Analg 1998;86:264–266.[CrossRef][Medline]
- Lippmann M. Complications of CO2 flooding the surgical field in open-heart surgery: an old technique revisited. Anesth Analg 1998;87:978–979.[Free Full Text]
|
|
Top
Abstract
1. Introduction