Differential perfusion: a new technique for isolated brain cooling during cardiopulmonary bypass

Neuroprotection in cardiac surgery

This article reviews past and present neuroprotective efforts and outlines a framework for the future development of techniques for neuroprotection during cardiac surgery.

Effectiveness of the Cobra aortic catheter for dual-temperature management during adult cardiac surgery

OBJECTIVES

In animals the Cardeon Cobra catheter (Cardeon Corp, Cupertino, Calif) allows independent control of aortic arch and descending aortic temperatures and profoundly reduces cerebral embolization during bypass. This investigation describes the first clinical use of the device during adult cardiac surgery. The purpose of the study was to confirm that the Cobra catheter delivers adequate cerebral and systemic perfusion while providing simultaneous cerebral hypothermia and systemic normothermia during cardiopulmonary bypass.

METHODS

In a prospective multicenter study the Cobra aortic catheter was placed in 20 adults undergoing cardiopulmonary bypass. Arch and corporeal temperatures, bypass flows, and arterial blood pressures were recorded intraoperatively. Jugular bulb and mixed venous oxygen saturation was used to assess the adequacy of cerebral and systemic perfusion.

RESULTS

Surgeons at 3 institutions placed the Cobra catheter in patients undergoing coronary artery bypass grafting (n = 13), valve (n = 3), and combined valve-bypass (n = 4) operations. Mean total bypass flows of 2.1 +/- 0.2 L x min(-1) x m(-2) maintained mean arterial pressures in arch and descending aortic circulations of greater than 55 mm Hg. A mean differential of 4.3 degrees C between arch and descending aortic temperatures was established before crossclamp application, and a mean maximum temperature differential of 7 degrees C was established during bypass. A 2.4 degrees C temperature differential was maintained at crossclamp removal. Cerebral and systemic venous oxygen saturation remained greater than 65% during bypass.

CONCLUSIONS

The Cobra device met all expectations for an arterial cannula with adequate perfusion to the arch and corporeal circulations. Dual perfusion with the Cobra catheter allows for independent temperature control during cardiopulmonary bypass with simultaneous cerebral hypothermia and systemic normothermia.

Best Practice for Cardiopulmonary Bypass in the High-Risk Elderly Patient

The management of cardiopulmonary bypass has evolved over the last 50 years resulting in a largely consistent approach to both adult and pediatric perfusion. Very little has been written or prospectively researched on the best practice for cardiopulmonary bypass in the high-risk elderly patient, despite the challenge this patient cohort presents compared to the general adult population and the rapidly increasing number of such patients undergoing cardiac surgery. We propose a framework for perfusion strategies for the high-risk elderly patient from our current understanding of cardiopulmonary bypass. It should stimulate discussion for a consensus on perfusion strategies for the elderly and encourage further research into perfusion variables as they relate to the outcome of patients of advanced age.

Reduction in brain embolization using the Aegis aortic cannula during bypass in swine

BACKGROUND

Cerebral embolization during cardiopulmonary bypass (CPB) is an important cause of neurologic injury. This study determined whether a new aortic cannula (Cardeon Aegis) could substantially reduce brain embolization in a swine CPB model.

METHODS

Fourteen 70-kg pigs underwent normothermic CPB, 7 animals with the Aegis device and 7 with a control cannula. Cerebral blood flow was determined using 15-microm fluorescent microspheres before bypass and twice during CPB. After the second bypass CBF measurement, animals were embolized with 120,000 78-microm fluorescent microspheres at normothermia. At the end of the experiment the brain, eyes, kidneys, myocardium, and small bowel were removed and the microspheres isolated.

RESULTS

Cerebral blood flow was equivalent between groups before bypass and during both bypass periods. While the two groups were equivalent with regard to pump flow, temperature, hemoglobin, and PaCO2, use of the Aegis cannula markedly reduced embolization to three of four brain regions. Deployment of the baffle reduced total brain embolization by 91% from a mean of 22 +/- 21 emboli per gram in the control animals to 2 +/- 6 emboli per gram in animals receiving the Aegis device.

CONCLUSIONS

Cerebral blood flow with the Aegis device is equal to or greater than that observed under nonbypass conditions and that seen with conventional aortic cannulas. However, cerebral embolization is profoundly reduced by use of the Aegis device. The application of this cannula may reduce postcardiac surgical neurologic injury.

Use of the Cobra catheter for targeted temperature management during cardiopulmonary bypass in swine

BACKGROUND

The purpose of this investigation was to determine whether temperatures of the aortic arch and descending aortic circulations could be controlled independently during cardiopulmonary bypass with a cannula possessing an endoaortic baffle (Cobra; Cardeon, Cupertino, Calif).

METHODS

After Institutional Animal Care and Use Committee approval, 12 pigs weighing 60 kg were started on bypass through a sternotomy. A dual-lumen endoaortic cannula with a deployable baffle was used for arterial cannulation. Bypass was initiated at 37 degrees C, and control measurements were obtained. The baffle was then inflated with saline solution, segmenting blood flow along the greater and lesser curvatures of the aortic arch. Parallel heat exchangers were used to independently control temperature of the arch and descending aortic perfusates. Cerebral and systemic temperatures were recorded continuously.

RESULTS

During cardiopulmonary bypass, mean flow and arterial pressure were maintained at 2.4 to 2.6 L x min(-1) x m(-2) and 60 to 70 mm Hg, respectively. With aortic flow distributed by the baffle, a 5 degrees C temperature differential between brain (30 degrees C) and body (35 degrees C) was established in a mean of 5 +/- 2 minutes. Mean brain and corporeal temperatures of 27 degrees C and 35 degrees C were then maintained over 60 minutes. Relative to control, internal jugular and inferior vena cava oxygen saturations increased during targeted temperature control with the device.

CONCLUSIONS

The Cobra cannula allows for independent control of brain and body temperature while providing satisfactory hemodynamics. Application of this temperature management strategy may offer cerebral protection and the advantages of warm systemic bypass temperature.

Comparing dual-stream and standard cardiopulmonary bypass in pigs

BACKGROUND

Dual-stream (DS) and standard cardiopulmonary bypass (CPB) were compared.

METHODS

A DS catheter inserted into the distal ascending aorta across the arch pumps blood through an upper lumen (maximum 2.25 L/min) directed by a bloodstreaming baffle toward the arch vessels. A separate lower lumen pumps blood (maximum 3.75 L/min) into the aorta caudad to the inflated baffle. The baffle is flat and horizontal along the catheter. When the baffle is collapsed the heart or both lumens may perfuse all organs. For 30 minutes 8 randomized CPB pigs had corporeal cooling to 32 degrees C and for 30 minutes had rewarming to 36 degrees C. Eight randomized DS pigs had 25 degrees C upper lumen cooling for 60 minutes. Lower lumen blood flow was streamed at 32 degrees C for 30 minutes, then rewarmed to 36 degrees C for 30 minutes.

RESULTS

The change in relative lower lumen to brain blood flow as determined by brain-counted microspheres (15 micron) injected into the ascending aorta was less for DS brains than controls during full flow (DS 63.4+/-129.5 versus CPB 2,585.4+/-250.8, p < 0.001), and when injected into the ejecting-heart left atrium just after weaning off only lower lumen blood flow (DS 250.8+/-297.3 versus CPB 1,159.1+/-782.3, p < 0.001). DS brain temperatures were lower at an equal pump-off core temperature of 36 degrees C+/-0.5 degrees C (DS 31.6 degrees C+/-3.2 degrees C versus CPB 36.5 degrees C+/-1.7 degrees C, p < 0.025). Jugular O2 saturations were not different.

CONCLUSIONS

DS-CPB prioritizes pump-filtered separate cold blood flow to the brain over a blood-streaming baffle to wash away potentially surgery related air and particulate matter arising from the heart or ascending aorta.

Profound reduction in brain embolization using an endoaortic baffle during bypass in swine

BACKGROUND

Cerebral embolization during cardiopulmonary bypass is an important cause of neurologic injury. This study determined whether an endoaortic baffle catheter (Cardeon Cobra Catheter; Cardeon Corporation, Cupertino, CA) could substantially reduce cerebral embolization in a swine cardiopulmonary bypass model.

METHODS

Sixteen 60 kg pigs underwent cardiopulmonary bypass; 8 animals with the Cobra baffle (Cardeon Corporation, Cupertino, CA) deployed, and 8 with the same cannula without baffle deployment. The animals were embolized with 72,000 fluorescent microspheres (97 to 100 microm) at normothermia. At the end of the experiment, the brains were removed and microspheres were isolated from eight regions.

RESULTS

During embolization, the two groups were equivalent with regard to pump flow, mean arterial pressure, temperature, Hgb and PaCO2. Deployment of the Cobra baffle reduced embolization to every brain region. Deployment of the baffle reduced total brain embolization by 89%. There was a mean of 61+/-60 emboli per gram in the control animals and 7+/-24 emboli per gram in those animals in which the baffle was deployed.

CONCLUSIONS

Cerebral embolization is profoundly reduced by use of the Cobra baffle aortic cannula. The application of this device may reduce postcardiac surgical neurologic injury.

Attenuation of neurologic injury during cardiac surgery

Neurologic injury after cardiac surgery can be divided into type I, including clinically apparent stroke, seizures stupor, or coma, and much more occurring type II injury, including intellectual deterioration, memory deficit, or seizures. Cerebral embolization is demonstrably etiologic in many such cases, and several new aortic cannulas are being introduced that are aimed at capturing or diverting potential cerebral emboli. No outcome data are yet available. Several potentially cerebroprotective pharmacologic therapies including thiopental, propofol, and nimodipine, have been assessed clinically but, generally, the results have been poor. Meta-analysis of the large North American aprotinin database of prospective, randomized, placebo-controlled clinical trials is suggestive of a cerebroprotective potential associated with high-dose aprotinin administration.

Beating heart surgery or conventional CABG: are neurologic outcomes different?

Although there has been much debate about the causes of neurologic complications associated with coronary artery bypass grafting (CABG), there is good evidence linking such complications with some of the pathophysiologic changes associated with use of conventional cardiopulmonary bypass (CPB). Several studies indicate that it is possible to significantly lower risk of stroke and other central nervous system (CNS) morbidity in patients undergoing CPB for CABG by application of selected techniques and equipment modifications. The resurgence of interest in coronary revascularization by using beating heart surgery (BHS) offers a unique opportunity to evaluate neurologic outcome independent of CPB. Currently, BHS would appear to significantly reduce morbidity in the elderly and to decrease the costs and resource use in coronary revascularization patients. It is hoped that by understanding the mechanisms of CNS injury associated with CABG, techniques can be developed to decrease the risk of neurologic injury associated with coronary revascularization, whether or not CPB is used. Definitive conclusions regarding outcomes after best practice CPB or BHS await large-scale, risk-stratisfied multicenter trials.

Approaches to reduce neurologic complications during cardiac surgery

As outcome measures of cardiac surgery are carefully analyzed, neurologic outcomes are a prominent determinant of overall outcome. Sensitive measures of pre- and postoperative neuropsychologic performance and intraoperative emboli reveal a risk group of patients at an advanced age, with severe generalized atherosclerosis who require cardiac surgery. By using the results of observational studies, we have developed a protocol that uses innovative intraoperative techniques to minimize injury and thus improve outcome.

Transesophageal echocardiographic imaging of a new aortic cannula for differential perfusion during cardiopulmonary bypass

We describe the use of echocardiographic imaging to assist in the placement of an aortic cannula that provides differential perfusion of the arch and descending aorta during cardiac surgery in adults.