Retrograde Cerebral Perfusion Does Not Improve NeuropsychometricOutcome After Aortic Surgery

TJ Jones, DK Harrington, CH Wong, M Bonser, A Moss, T Heafield, JRiddoch, and RS Bonser. Cardiothoracic Surgical Unit, University Hos-pital Birmingham, Birmingham, United Kingdom

Introduction. Aortic surgery requiring hypothermic circulatory arrest(HCA) is associated with a high incidence of brain injury. Althoughretrograde cerebral perfusion (RCP) has become a popular adjunctiveprotective technique providing some true reverse brain perfusion, wehave previously demonstrated that this has little metabolic impact. Theaim of this study was to compare neuropsychometric outcome with thetwo techniques.Methods. In a prospective randomized trial, 38 patients requiring electiveaortic arch surgery were allocated to either RCP or HCA alone. Informedconsent and ethics committee approval was obtained. They underwentneuropyschometric testing preoperatively, and 6 weeks and 12 weekspostoperatively using a standard test battery.Results. Eighteen patients underwent HCA and 20 patients underwentRCP. The mean cardiopulmonary bypass, HCA, and RCP durations were169, 30 and 25 minutes, respectively. There were no deaths or neurologicaldeficits. At 6 weeks postoperatively, 75% of the HCA group and 83% of theRCP group had a neuropsychometric deficit (p � 0.58). At 12 weeks, thiswas reduced to 44% and 42%, respectively (p � 0.45). Mean Z scores werecalculated for each group for each test. There was no overall difference inZ test scores, but two tests showed a significantly greater deterioration inRCP patients at 6 weeks (p � 0.03).Conclusions. Although small, this study suggests that RCP does notimprove outcome after aortic arch surgery, and may be detrimental. Itsrole in cerebral protection warrants continued scrutiny.

Arterial Temperature Measurement Inaccuracies in the ExtracorporealCircuit

RG Sutton, MS, CCP, S Jackson, BS, DE Baker BS, CCP, and M Djuric, MA,CCP. Extracorporeal Services, Rush-Presbyterian-St. Luke’s MedicalCenter, Chicago, Illinois

Introduction. Arterial blood temperature greater than 37°C during therewarming phase of cardiopulmonary is associated with postoperativecerebral vascular injury and cognitive dysfunction. The purpose of thisstudy was to determine the accuracy of temperature measurements atvarious points in the arterial line of the extracorporeal circuit.Methods. An in vitro circuit consisting of a heater-cooler, roller pump,membrane oxygenator, arterial line filter, and A-V loop was primed withcrystalloid solution. Backpressure on the arterial line was maintained at150 mm Hg. Temperatures were monitored at the following sites: arterialoutlet of the membrane oxygenator (coupling site), CDI 500 arterial bloodgas shunt sensor, 4 feet distal to the arterial line filter utilizing amyocardial temperature probe, heater-cooler water, and room air. Watertemperatures (25 to 41°C), pump flows (2.5 to 5.5 L/min), and room air (55to 85°F) were varied. Because the temperature probe of the distal site wasin direct contact with the prime, that site was considered the actualtemperature.Results. Data analysis demonstrated a positive correlation between theoxygenator, CDI, and distal temperatures. However, the distal tempera-tures read higher than the oxygenator and CDI temperatures (p � 0.001),with an average difference of 0.99°C and 0.98°C, respectively. In addition,the oxygenator temperature error was correlated with room temperature(p � 0.05).Conclusions. The distal temperature is higher than the arterial membraneoxygenator reading. Therefore, the oxygenator arterial temperature read-ing should not exceed 36°C.

Brain O2 Desaturation Despite Preserved Autoregulation During Cardio-pulmonary Bypass

HL Edmonds, Jr, PhD,1 MH Thomas, MA,1 BL Ganzel, MD, SB Pollock, Jr,MD, SW Etoch, MD, and PA Spence, MD. Departments of Anesthesiologyand Cardiothoracic Surgery, University of Louisville, Louisville, Kentucky

Introduction. We determined the lower limit of autoregulation (LLA)during cardiopulmonary bypass (CPB) using transcranial Doppler (TCD)and regional O2 saturation (rSO2) with spatially resolved near-infraredspectroscopy.Methods. With Internal Review Board-approved informed consent, pres-sure-velocity and pressure-saturation relationships were examined dur-ing 56 CPB cases maintained with 1–2 MAC volatile anesthetic. LLA wasgiven by the intersection of the horizontal and oblique lines formed fromregression of velocity and saturation on pressure [1].Results. Despite TCD and rSO2 evidence of maintained autoregulation,ie, LLA � 45 (40 to 49) mm Hg (mean [95% CI]), a clinically significantrSO2 decline of �25% below baseline occurred in 18 cases.Conclusions. These results question the sensitivity of arterial pressure asan indicator of adequate brain perfusion/oxygenation during nonpulsa-tile CPB. They also help explain the inconsistent association betweenintraoperative blood pressure and later neurocognitive decline.Reference1. J Neurosurg Anesthesiol 1996;8:280–5.

Reduced Postoperative Length of Stay May Result From Using CerebralOximetry Monitoring to Guide Treatment

JC Alexander, Jr, MD, MA Kronenfeld, MD, and GR Dance, CCP. Hacken-sack University Medical Center, Hackensack, New Jersey

Introduction. Renal failure and control nervous system (CNS) events arecauses of morbidity after open-heart surgery (OHS). The objective of thispilot study was to evaluate the incidence of renal failure and postopera-tive CNS events after OHS.Methods. Fifty-four patients were monitored intraoperatively using theINVOS 4100 cerebral oximeter; readings were maintained at levels of 40or greater. Interventions used to increase INVOS readings includedincreased pump flow, elevated perfusion pressures, augmenting CO2levels, and transfusions. The study group was compared with 1,131patients operated on in the prior year who did not have INVOS moni-toring. The demographics of both groups were similar.Results. STS database criteria were used to determine the incidence ofrenal failure and CNS complications, shown below with mortality andlength of stay.

Table 1.

NAverage Age

(years) M/F(%) CABG(%) Valve(%)Study Group 54 65 60/40 67 33Control Group 1,131 67 69/31 70 30

Table 2.

Mortality(%) LOSCNS

Comp(%)Renal

Failure(%)Study Group 1.85 6.81 0 0Control Group 3.89 8.79 4.7 2.5

Interventions required to elevate the INVOS readings were surprisinglyfrequent (�50%). Low readings were relatively easy to correct. Theabsence of CNS and renal problems was reflected in reduced postoper-ative length of stay (LOS).Conclusions. These findings suggest that unappreciated hypoxia reflectedin renal and CNS dysfunction may be responsible for morbidity that ispreventable, resulting in reduced LOS.

S373Ann Thorac Surg OUTCOMES 20012002;73:S366–77 ABSTRACTS