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Eur J Cardiothorac Surg 2004;26:571-579
© 2004 Elsevier Science NL

Differential brain and body temperature during cardiopulmonary bypass—a randomised clinical study

Hemanth Kaukuntla, Alison Walker, Deborah Harrington, Timothy Jones, Robert S. Bonser* On behalf of the Study Group1

Department of Cardiothoracic Surgery, Queen Elizabeth Hospital, University Hospital NHS Trust, Birmingham, B15 2TH, UK

Received 29 October 2003; received in revised form 17 April 2004; accepted 26 May 2004.

* Corresponding author. Tel.: +44-121-627-2543; fax: +44-121-627-2542
e-mail: robert.bonser{at}uhb.nhs.uk


   Abstract
Top
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Appendix A. Study group
 Appendix B. Conference...
 References
 
Objective: Maintenance of normothermia during cardiopulmonary bypass (CPB) may have advantages over hypothermia but there is a potential increased hazard of neurological injury. A novel aortic cannula (CobraTM catheter, Cardeon® Corp., Cupertino, CA, USA) which compartmentalises the aorta may allow simultaneous brain cooling during maintained corporeal normothermia. We investigated the thermal efficacy of this technique. Methods: We randomized 60 adult patients to normothermic CPB (n=30, temp=35 °C) or to differential temperature management (CobraTM cannula). Nasopharyngeal (NPT) and jugular bulb (JB) temperatures were used as surrogates for brain temperature while bladder temperature (BLT) represented the body (corporeal) temperature. Brain (radial) and corporeal (femoral) mean arterial pressure (MAP) together with jugular bulb and mixed venous saturations were monitored to assess perfusion adequacy. Transcranial Doppler was used to assess high intensity transient signals (HITS). All patients had neuropsychometric assessment pre-operatively and at 1 and 8 weeks post-operatively. Results: Demographic and CPB variables were comparable. A 3.2±0.46 °C differential between BLT and NPT was reached in all Cobra patients after 5.5±3.6 min (P<0.001). A 5 °C differential was reached in 29 patients after 12±7.5 min. The mean difference was 6.6±1 °C. MAP was maintained above 50 mmHg and venous saturations above 60% in both groups throughout. Blood requirements, extubation time and ITU stay were no different. Embolic counts and neuropsychometric outcomes were not different between groups. Conclusions: Differential temperature management using the CobraTM aortic catheter is possible. Further studies are necessary to establish whether the hypothesized advantages of combining corporeal normothermia with brain hypothermia can be realised.

Key Words: Cardiopulmonary bypass • Neuroprotection • Segmentation of aorta


   1. Introduction
Top
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 Appendix A. Study group
 Appendix B. Conference...
 References
 
Neurological injury, either obvious or subtle, continues to be a significant complication associated with cardiopulmonary bypass surgery (CPB). The incidence of cerebrovascular injury can be as high as 4.5–6.1% [1] in patients undergoing routine coronary artery bypass surgery (CABG). The incidence is higher in patients undergoing combined procedures of coronary artery bypass and valve surgery [2]. Patients unaffected by overt stroke may have cognitive deficits (30%) that can persist [3].

Various strategies have been used to decrease the incidence of cerebral injury when CPB is used in cardiac surgery. These include, hypothermia, interventions to decrease the embolic load and pharmacological neuroprotection [4]. Hypothermia has been utilised as a protective measure since the inception of CPB to reduce cerebral oxygen consumption. Further, it is accompanied by a fall in brain blood flow which may reduce embolic load [4].

However, over the past decade, there has been increasing interest in normothermic bypass surgery [5]. Various benefits have been reported, including increased cardiac output [6], improved myocardial function [7], reduction in respiratory demand, reduced bleeding and reduced time to extubation [8]. However, with these benefits came concerns of increased incidence of neurological deficits [9,10]. Thus, although hypothermia may be helpful in protecting the brain, increasing numbers of centres have used normothermia on the basis of systemic benefit. At present, standard CPB technology does not allow combination of brain cooling with corporeal normothermia. Such a technique could potentially further reduce the morbidity associated with cardiac surgery.

Recently a novel technique has been described in animal models using a new aortic cannula (CobraTM Catheter, Cardeon® Corp., USA), which enables cooling of the brain in isolation while maintaining normothermia to the body [11]. This is the targeted circulatory management® (TCM) technology. Besides utilising hypothermia as a neuroprotective strategy there is a potential to reduce the embolic load to the brain using this technique [12]. Although feasibility in humans has been recently reported [13,14], there has been no randomised, clinical trial to examine the efficacy of this technique in producing temperature gradients in humans. We studied the feasibility of using this technique to achieve a temperature gradient between the brain and the body in a prospective randomised clinical trial in humans comparing CobraTM Catheter TCM technology with standard normothermic CPB.


   2. Methods
Top
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 Appendix A. Study group
 Appendix B. Conference...
 References
 
2.1. Study design
In this single centre, open randomised study, 60 patients undergoing first time CABG, valve surgery or combined valve and CABG surgery were assigned to differential temperature management or control groups. The study was approved by the Local Research Ethics Committee and all patients gave informed consent. The main inclusion and exclusion criteria are described in Table 1. Randomisation was by computerised random numbers generation in groups of 6.


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  		Table 1. Inclusion and exclusion criteria

 
2.2. Anaesthesia, monitoring and trans-oesophageal echocardiographic assessment
A standardised anaesthetic technique was adopted using etomidate, pancuronium and fentanyl for induction and intravenous propofol and alfentanil for maintenance. All patients had a left radial arterial pressure line, triple lumen central venous cannulation, pulmonary artery flotation catheter and a retrograde jugular bulb oximeter line. Patients allocated to the Cobra® cannula group also had femoral arterial pressure monitoring. All patients had temperature monitored from the bladder (BLT), nasopharynx (NPT) and the jugular bulb (JB). A trans-oesophageal echocardiographic (TOE) examination was completed prior to the commencement of the operation to assess the grade of aortic arch atheroma and for the patients randomised to the study group, to size the Cobra® cannula [16]. Arch atheroma was classed in 4 grades: Grade (1): Normal; no identifiable intimal thickening, grade (2): Mild, increased intimal echo density with thickening, grade (3): Moderate; increased intimal echo density with atheroma >5 mm or grade (4): Severe; atheroma >5 mm in addition to one or more of the following: mobile or ulcerating lesions, extensive calcification, large protruding atheromatous debris or thrombus, porcelain aorta. Patients with grade 4 atheroma were withdrawn from the study.

Prior to sternotomy, baseline cardiac output studies were completed and transcranial Doppler probes were positioned (MultiDop X-4 DWL®, Sipplingen, Germany). Probes were positioned over both right and left middle cerebral arteries and data was continuously collected from sternotomy to chest closure to allow detection of high intensity transient signals (HITS). Data analysis was performed off-line. Specific interventions including cannula insertion and removal, application of the aortic cross clamp, initiation and end of CPB were marked to allow correlation of embolic load with interventions in both the study groups.

2.3. Arterial cannulation and device details
The Cardeon® CobraTM catheter is a CE mark product licensed to be used in patients undergoing cardiopulmonary bypass surgery. The device has two lumens within a single tube and there is an inflatable baffle (Fig. 1) . The cannula is inserted in the ascending aorta in the standard site, proximal to the innominate artery origin and is orientated to compartmentalise the aorta into a superior and inferior section (Fig. 2) . Inflation of the baffle with saline allows segmentation of the arch of aorta [11]. One channel (ARCH) then perfuses the upper compartment, which is in communication with the head and neck vessels (cranial circulation). The lower compartment which is perfused by the second channel (CORPOREAL) is in communication with the ascending aorta proximally and descending thoracic aorta distally (corporeal circulation). By varying the inflow temperature in the two channels it is possible to direct hypothermic blood flow superiorly while maintaining normothermia to the rest of the body. The baffle is non-occlusive and prevents malperfusion if flow in either channel is arrested [11]. A standard 26F aortic cannula was used in patients assigned to the control group.



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  		Fig. 1. Schematic diagram of the Cobra® cannula.

 


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  		Fig. 2. Schematic diagram of the cannula within the aorta demonstrating compartmentalisation and enabling delivery of hypothermic perfusion of the epiaortic vessels and normothermic perfusion of the distal corporeal circulation.

 
Patients allocated to the CobraTM cannula had arterial pressures monitored from the left radial and the femoral arteries. Left radial pressure reflected the pressure in the cranial circulation and the femoral cannula represented the pressure in the corporeal circulation when the baffle was inflated. Left radial artery pressure was chosen to ensure that the tip of the CobraTM cannula was not occluding the left subclavian artery besides reflecting the pressure in the cerebral circulation. Control patients had only left radial artery pressure monitored

2.4. Perfusion details and device placement
Only minor modifications were needed to enable the use of the CobraTM cannula (Figs. 3 and 4) . The bypass circuit was a standard circuit using a membrane oxygenator and a roller pump. After the blood is oxygenated, the arterial return divides into 2 separate channels with a fixed 2:1 diameter ratio. The larger channel is connected to the corporeal limb of the Cobra® cannula. The flow in the smaller channel which allows 1/3rd flow is directed via a second heater chiller to the arch limb of the Cobra® cannula. Each channel is connected to a separate arterial line filter before being connected to the cannula.



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  		Fig. 3. Schematic diagram of the perfusion apparatus during priming and prior to connection to the patient via the Cobra® aortic cannula (calibre of tubing is indicated in inches).

 


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  		Fig. 4. Schematic diagram of perfusion circuit post-cannulation. (Heavy arrows indicate direction of blood flow).

 
In both the study groups, a single bypass pump was used (Stockert ‘Shiley CAPS®’). The circuit was primed with 1500 ml of isotonic crystalloid solution. Following arterial cannulation, CPB was instituted using right atrial drainage. In the Cobra® group, venous blood drained into a hard shell reservoir and then into a combined heat exchanger and membrane oxygenator (Stockert ‘CAPS’ heater chiller®) (Heater-chiller 1). Oxygenated blood was then diverted in to two separate tubing circuits size adjusted to allow the 2:1 flow split, and connected to the inferior (Corporeal) (2/3) and superior (arch) (1/3) limbs of the cannula. The superior limb flow was further directed through a heat exchanger (Medtronic ECMO therm®) connected to a second heater chiller (Jostra HC 30®) to allow differential cooling (Figs. 3 and 4). In control patients the CPB circuit was unmodified.

Baseline oximetry and temperature measurements were obtained prior to commencement of CPB. In Cobra patients, the position of the cannula was verified by TOE prior to commencement of CPB. This verification was performed during venous cannulation. Absence of a pressure gradient >10 mmHg between left radial and femoral arterial pressures after baffle inflation together with identification of the position of the distal tip of the cannula beyond the origin of the left subclavian artery by TOE were accepted as indicative of satisfactory cannula placement.

On commencement of CPB, the baffle was inflated and the left radial pressure was checked to ensure non-occlusion of the left subclavian artery. Blood cooling to the superior limb (Arch) was commenced after the baffle inflation. Corporeal (bladder) temperature was maintained at normothermia (35–37 °C). In the Cobra group, the aortic cross clamp was applied after achieving a 3 °C temperature difference between the bladder (BLT) and the nasopharyngeal (NPT) temperatures. Saturations in the two circulations were monitored throughout. At set reference time points, nasopharyngeal, jugular bulb and bladder temperature were recorded. Superior limb (Arch) cooling was continued until an estimated 5 min prior to removal of the final aortic clamp. The second heat exchange mechanism was discontinued at this stage to allow passive rewarming of the superior circulation. The baffle remained inflated until just prior to decannulation provided left radial and femoral pressures were equal after discontinuation of CPB. In the control group, patients were maintained at normothermia (35–37 °C) throughout CPB. In all cases arterial inflow temperature was always maintained at ≤37.5 °C. Myocardial protection was afforded by intermittent antegrade cold blood cardioplegia. Coronary artery bypass surgery was performed using a standard technique with a single clamp period for distal anastomoses and partially occlusive side-biting clamps for proximal anastomoses.

2.5. End-points
The primary end-point was the ability of the CobraTM device to achieve and maintain a temperature gradient between the arch (nasopharyngeal and jugular bulb) and systemic circulations (bladder) >5 °C. Secondary end-points included the time to achieve a 3 and a 5 °C difference, maximum temperature difference and the time to achieve this difference. We also monitored the ability of the CobraTM Catheter to deliver adequate perfusion as indicated by (a) achieving intended bypass flows, (b) maintenance of jugular bulb oxygen saturation ([SjO2] of >50%[17,18] and (c) maintenance of mixed venous oxygen saturation [SvO2] of 65±10% [19]. Other outcome measures included in order to pilot further clinical studies were the number of high intensity transient signals recorded from sternotomy to the end of the procedure, neurological and neuropsychometric outcome, post-operative bleeding, time to extubation, blood product and inotropic requirement, infection rates and hospital length of stay.

All patients underwent neuropsychometric assessment pre-operatively, at 5–8 days post-operatively and 6–8 weeks post-surgery by a trained neuropsychometrist blinded to the group allocation. A standard battery of 10 tests was used, compliant with the international statement of consensus [15]. The test battery comprised, the Folstein Mini Mental Status Examination, Trail-making tests A and B, the letter cancellation test, a finger tapping test for both dominant and non-dominant hands, a non-verbal memory test, the symbol digit modalities test, the grooved pegboard test for both dominant and non-dominant hands and the Rey Auditory Verbal Learning Test. A neuropsychometric deficit was defined as a 20% reduction in performance in 2 or more tests. In addition, at 24–48 h post-operatively, all patients were assessed for overt neurological damage using the National Institute of Health Stroke Scale (NIHSS) by an observer blinded to group allocation.

2.6. Statistical analysis
The study was powered to detect a mean cranio-corporeal temperature differential of 8 °C between the CobraTM and control groups. Assuming a differential temperature standard deviation of 8 °C, this difference was detectable with a power of 90% at a 2.5% level of significance with 30 patients in each group. Categorical data were compared using {chi}2 testing. Continuous data was assessed for normality and compared using an independent t test or non-parametrically (Mann–Whitney U test) as appropriate. Data are presented as mean±SD or median (interquartile range). Statistical significance was assigned when the P value was ≤0.05.


   3. Results
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 Appendix A. Study group
 Appendix B. Conference...
 References
 
Sixty-six patients were enrolled and randomised. One patient was excluded prior to operation due to body surface area >2.6 m2. Five patients were withdrawn following randomisation, four due to detection of grade 4 aortic atheroma and one due to anaphylaxis at anaesthetic induction. Data from these patients was not analysed. Sixty patients were studied of which 30 were assigned to the CobraTM cannula group and the other 30 had a standard aortic cannula (26 F Sarns® aortic cannula). Demographic and CPB details were comparable (Table 2). There was one late death due to mediastinitis. No patients suffered overt neurological deficit on NIHSS testing.


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  		Table 2. Demographic, operative, perfusion and outcome details

 
In all Cobra patients, the cannula was positioned satisfactorily on TOE and pressure criteria and this check was undertaken during venous cannulation without incurring any delay. A 3.2±0.46 °C (P<0.001) differential between bladder and nasopharyngeal temperature was reached in all Cobra patients after 5.5±3.6 min. A 5 °C differential was reached in 29/30 patients after 12±7.5 min with a mean difference of 6.6±1 °C (range 3.1–8.3 °C). The mean bladder and nasopharyngeal temperature after 20 min of CPB in the control group were 36.3±0.29 and 36.9±0.37 (P<0.001) respectively, and in the Cobra group were 35±1.75 and 28.6±1.35 (P<0.001). The bladder, nasopharyngeal and jugular bulb temperature trends during specific time points in the Cobra® group are summarised in Fig. 5.



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  		Fig. 5. Mean jugular bulb (JB), nasopharyngeal (NP) and bladder (BLD) temperature in the Cobra group at specified time points. (CPB, cardiopulmonary bypass; 3 degree diff, time when 3 °C differential between nasopharyngeal and bladder temperature achieved).

 
Jugular bulb and mixed venous oxygen saturations (MVSO2) were maintained at >50% throughout CPB in both groups (Fig. 5). In addition, mean arterial pressures at radial and femoral sites were maintained >50 mmHg throughout CPB. After discontinuing CPB, one patient required baffle deflation in the Cobra group due to a radial-femoral pressure gradient of >10 mmHg. Pressures equalised in both the circulations immediately.

Total HITS counts were not different between the groups overall [Cobra median 16 (IQR 6.5–32.5) versus control median 17 (IQR 4.25–30)(P=0.93)] or in patients undergoing isolated CABG [Cobra median 10 (IQR 5.5–20.5) and control median 9 (IQR 3–23.5)(P=0.84)]. There was no difference in HITS detection at any specific intervention time.

At 1 week 74.1% for Cobra group (n=27) showed a neuropsychometric decline compared to 52% for standard group (n=25)(P=0.15). At 8 weeks following surgery, these figures were 10.3% for the Cobra group (n=29) and 11.5% for the control group (n=26)(P=1.0).

Blood temperature on returning to ITU was lower in the Cobra group (34.7 vs 35.8 °C) (P<0.001). Blood requirements, extubation time and ITU length of stay were comparable in the two groups while the hospital stay was shorter in the Cobra group (P=0.04) (Table 2).


   4. Discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
Appendix A. Study group
 Appendix B. Conference...
 References
 
This study shows that differential brain cooling is possible while maintaining a warm body perfusion. A 3 °C differential was achieved in all the study patients and a 5 °C differential in the majority.

Adverse neurological outcomes continue to be a major cause of mortality and morbidity following cardiac surgery. The incidence of type I brain injury or ‘stroke’ following cardiac surgery has been reported to be approximately 3% [1]. The incidence of adverse neurological outcomes is related to age, in patients <50 years the incidence is 1% while in patients >75 years it dramatically increases.[20]. Besides resulting in an increased mortality there is increased morbidity and an extra use of resources [1]. The other more subtle adverse neurological outcome is post-operative cognitive dysfunction with has a reported incidence of 22.5% in the early post-operative period [21] that can persist.

The exact aetiology of CPB associated neurological morbidity and mortality remains unclear. It is probably multi-factorial resulting from the interactions of a variety of mechanisms including, alterations in blood flow, activation of inflammatory processes and micro or macro emboli [4]. Emboli have been detected in the cerebral and retinal circulation during cardiac surgery [22]. There is an increase in the number of emboli during specific interventions and an association has been made between embolic numbers and post-operative injury [23,24].

Hypothermia is a widely used neuroprotective adjunct and may protect the brain by a variety of complex mechanisms which include: reducing cerebral oxygen consumption; reducing cerebral blood flow leading to a decrease in the embolic load; decreased excitatory transmitter release; reduced alterations in ion influx; reduced vascular permeability, oedema and blood–brain barrier disruption. In addition hypothermia decreases experimental brain infarct size associated with reversible transient ischaemic events [25].

Until the early 1990's CPB was routinely conducted using moderate hypothermia (28–32 °C). However, following successful reports of normothermic CPB [5] there was an increased use of warm heart surgery techniques. Normothermic bypass has been shown to have various systemic advantages including increased cardiac output [6], improved myocardial function [7], reduced bleeding complications [8], shorter time to extubation and length of hospital stay. However, along with these advantages, there have been reports of increased incidence of adverse neurological events in warm bypass groups [9,10]. Therefore the development of a strategy which allows hypothermia to the brain and normothermia to the body could be beneficial.

The dual channels of CobraTM Catheter isolate brain and corporeal perfusion and achieve cerebral hypothermia. To our knowledge this study is the first randomized clinical study to examine the temperature efficacy of this technology in humans. All routine cardiac procedures namely coronary artery bypass surgery, valve surgery or combined valve and coronary surgery patients were included to establish the applicability of this technique to a range of cardiac procedures. The main study end points were to establish the safety and effectiveness of the technique in maintaining a temperature differential during CPB. The study was therefore powered to detect a temperature difference between the brain and the body while observing the jugular bulb and mixed venous saturations as indicators of adequacy of perfusion (Fig. 6) .



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  		Fig. 6. Jugular bulb (SJVO2) and mixed venous saturations (SVO2) in the Cobra and control group (std) during the procedure. Time points represent (1) Pre-bypass, (2) At aortic cross-clamp placement, (3) 25 min after cross-clamp placement, (4) 40 min after cross-clamp placement, (5) At removal of all aortic clamps (including partial occlusion clamps) and (6) 30 min post-final clamp release.

 
Such differential perfusion might also reduce the brain embolic load via three mechanisms [12]. First, induction of cerebral hypothermia may reduce actual brain blood flow, second, the aortic baffle may direct blood and emboli originating in the heart or proximal aorta to the distal aorta (Fig. 2) and third, the design of the cannula maintain a relatively higher arch flow compared to the corporeal flow. This allows excessive blood to flow from the arch circulation over the non-occlusive baffle to the corporeal circulation. Cook et al. demonstrated in animal models that the flow segmentation reduced the embolic load to the brain by 80–90% [12]. However, we did not detect any reduction in embolic load in humans. On the basis of this study, much larger studies would be required to assess efficacy in this area.

Re-warming at the end of routine hypothermic bypass procedures may sometimes lead to inadvertent hyperthermia and this could be deleterious to the brain [10]. The use of this novel cannula, maintains the body at normothermia during CPB and thus, there is no need to actively re-warm the patient prior to discontinuation of CPB. Immediately prior to removal of the aortic cross clamp, active cooling of the blood passing to the head and neck vessels is stopped. The cerebral circulation is still cold at the time of cross clamp removal and subsequently the brain re-warms passively as the corporeal and the cerebral circulations mix. This avoids the potential for cerebral hyperthermia created by active re-warming. This phenomenon accounts for the lower blood temperature on arrival in intensive care observed in the differential cooling group and may also explain the longer extubation times in this group (15.9 vs 10.9 h) although this did not reach statistical significance (P=0.2).

We did not observe any difference in the clinical or neuropsychometric outcomes but acknowledge that the sample size was small. A large multi-centre trail is currently underway to address this. Hospital length of stay was shorter in the Cobra group but in a small study, with a heterogeneous population, this finding should be viewed with caution.

An important concern with any endo-aortic device is whether the device can be accurately and safely deployed without aortic injury. In this study, satisfactory positioning was achieved and confirmed without difficulty and no complications arose from the insertion or withdrawal of the cannula. In laboratory animal studies, the entire perimeter of the baffle does not contact the aortic wall [12] but this safety aspect needs to be confirmed in clinical practice. As the risk of athero-embolism due to device deployment would intuitively be greatest in the severe grade 4 atheromatous aortas, these were excluded from this study. Severe atherosclerosis was detected in about 7% of our initial recruitment patient population.

It is possible to establish and maintain a 3–5 °C temperature differential between the brain and the body in patients undergoing cardiopulmonary bypass. A much larger study is required to establish whether this effect translates into clinical benefit.


   Acknowledgments
 
We thank Cardeon Corporation®, Cupertino, USA for supporting this study and Dr P. Nightingale, Department of Medical Statistics, University of Birmingham, UK for his advice and support. We are grateful to the perfusion, technical and nursing staff at Queen Elizabeth University Hospital for their co-operation.

Funding: This independent trial was funded by an educational grant from Cardeon Corporation®, USA.

Conflict of interest: The study was investigator initiated with corporate financial support. No co-author has received other corporate support related to the study or has a pecuniary interest in the device studied.


   Footnotes
 
Presented at the joint 17th Annual Meeting of the European Association for Cardio-thoracic Surgery and the 11th Annual Meeting of the European Society of the Thoracic Surgeons, Vienna, Austria, October 12–15, 2003.

1 See Appendix A. Back


   Appendix A. Study group
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Appendix A. Study group
Appendix B. Conference...
 References
 
The study group included the following individuals as co-authors:

Stephen J Rooney FRCS
Domenico Pagano MD, FRCS
Timothy R Graham FRCS
Ashesh Buch MRCP
Peter Townsend FRCA
David Green FRCA
David W Riddington FRCA

Department of Cardiac Surgery, Queen Elizabeth Hospital, University Hospital NHS Trust, Birmingham B15 2TH, UK.


   Appendix B. Conference discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Appendix A. Study group
 Appendix B. Conference...
References
 
Dr V. Kucera (Prague, Czech Republic): It's a very interesting study. But what I was concerned is the arterial cannula, because the flow is divided into four jets. Can you always know about the stream of the jets to the carotid artery and don't you think that the jet could damage the artery wall?

Dr Kaukuntla: That was the reason why we looked at the middle cerebral artery embolic HITS. And then we did not find any difference in the number of HITS in both the groups. There was a tendency for lesser amount of emboli in the group, which had the Cobra cannula. The two time frames when there is an increased risk of emboli due to the cannula are when the cannula goes in itself and the baffle is inflated and the other time is when the cannula is taken out. We found no increased incidence of any emboli at those two time points.

Dr D. Chambers (London, UK): I had a question about a minor aspect of your study and that's the embolic count. We heard earlier this morning that patients on-bypass tend to have very much higher emboli counts than off-pump patients, and yet you're seeing the same sort of emboli counts as off-pump patients. Do you have an explanation for that?

Dr Kaukuntla: One very important issue will be about the methodology used. It has now been recognized that there is some amount of difference between the embolic counts registered, depending upon which particular instrument you're using. What we used was the Multi-Dop by DWL Germany. From memory, I think it was a different machine, which was used in the other group. For our group, it was just the comparison between the two patient groups; and therefore, it did not really matter to us as to how our counts reflected when compared to other methodologies.

Dr R. Williams (Birmingham, UK): It's not in the abstract. Could you just recap on the neuropsychological outcomes. And as regards other neurological adverse outcomes, I know it's too early and it's too small, but do you get a feeling there will be a real advantage with this? Because if so, it will be a very useful adjunct.

Dr Kaukuntla: There were no overt neurological events seen in any of the patients, in either groups with a total number of 60 patients. With regards to the neuropsych outcomes, again, I have to reiterate that this was a very small group. We did not find any difference in the neurocognitive decline either at 1 week, 3 weeks or at 8 weeks in the two groups. This could either mean that there is no change or the change is not detectable in a small sample size. And we do accept that that is a shortcoming of this small trial. A multi-centre trial is underway to address this question.


   References
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Appendix A. Study group
 Appendix B. Conference...
 References
 

  1. Roach G.W., Kanchuger M., Mangano C.M., Newman M., Nussmeier N., Wolman R., Aggarwal A., Marschall K., Graham S.H., Ley C. Adverse cerebral outcomes after coronary bypass surgery. Multicenter Study of Perioperative Ischemia Research Group and the Ischemia Research and Education Foundation Investigators. N Engl J Med 1996;335:1857-1863.[Abstract/Free Full Text]
  2. Wolman R.L., Nussmeier N.A., Aggarwal A., Kanchuger M.S., Roach G.W., Newman M.F., Mangano C.M., Marschall K.E., Ley C., Boisvert D.M., Ozanne G.M., Herskowitz A., Graham S.H., Mangano D.T. Cerebral injury after cardiac surgery: identification of a group at extraordinary risk. Multicenter Study of Perioperative Ischemia Research Group (McSPI) and the Ischemia Research Education Foundation (IREF) Investigators. Stroke 1999;30:514-522.[Abstract/Free Full Text]
  3. McKhann G.M., Goldsborough M.A., Borowicz L.M., Jr, Selnes O.A., Mellits E.D., Enger C., Quaskey S.A., Baumgartner W.A., Cameron D.E., Stuart R.S., Gardner T.J. Cognitive outcome after coronary artery bypass: a one-year prospective study. Ann Thorac Surg 1997;63:510-515.[Abstract/Free Full Text]
  4. Rees K., Beranek-Stanley M., Burke M., Ebrahim S. Hypothermia to reduce neurological damage following coronary artery bypass surgery. Cochrane Database Syst Rev 2001(1):CD002138.
  5. Lichtenstein S.V., Ashe K.A., el Dalati H., Cusimano R.J., Panos A., Slutsky A.S. Warm heart surgery. J Thorac Cardiovasc Surg 1991;101:269-274.[Abstract]
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