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Objectives: Many interventional physiological assessments for retrograde cerebral perfusion (RCP) have been explored. However, the appropriate arterial gas management of carbon dioxide (CO 2 ) remains controversial. The aim of this study is to determine whether alpha-stat or pH-stat could be used for effective brain protection under RCP in terms of cortical cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO 2 ) and distribution of regional cerebral blood flow. Methods: Fifteen anesthetized dogs (25.1 ± 1.1 kg) on cardiopulmonary bypass (CPB) were cooled to 18°C under alpha-stat management and had RCP for 90 min under: (1), alpha-stat; (2), pH-stat: or (3), deep hypothermic (18°C) antegrade CPB (antegrade). RCP flow was regulated for a sagittal sinus pressure of around 25 mmHg. CBF was monitored by a laser tissue flowmeter. Serial analyses of blood gas were made. The regional cerebral blood flow was measured with colored microspheres before discontinuation of RCP. CBF and CMRO 2 were evaluated as the percentage of the baseline level (%CBF, %CMRO 2 ). Results: The oxygen content of arterial inflow and oxygen extraction was not significantly different between the RCP groups. The %CBF and %CMRO 2 were significantly higher for pH-stat RCP than for alpha-stat RCP. The regional cerebral blood flow, measured with colored microspheres, tended to be higher for pH-stat RCP than for alpha-stat RCP, at every site in the brain. Irrespective of CO 2 management, regional differences were not significant among any site in the brain. Conclusions: CO 2 management is crucial for brain protection under deep hypothermic RCP. This study revealed that pH-stat was considered to be better than alpha-stat in terms of CBF and oxygen metabolism in the brain. The regional blood flow distribution was considered to be unchanged irrespective of CO 2 management.

Objective: The purpose of this study is to evaluate the possibility of identifying critical segmental arteries (CSAs) based on Doppler ultrasonographic hemodynamics. Methods: In 18 mongrel dogs, the descending aorta was scanned directly with a 5-MHz linear probe through left thoracotomies and the flow velocities in segmental arteries were measured by pulsed Doppler. The aorta was cross-clamped between Th13 and L1, and flow velocity changes were recorded. According to flow increases, segmental arteries were divided into three groups: arteries with the largest flow increase (L-arteries), arteries with the smallest increase (S-arteries) and other arteries (O-arteries). Animals were divided into three groups. One aortic segment including an L-artery or an S-artery was perfused via a temporary shunt during 30-min aortic cross-clamping distal to the left subclavian artery (Group L or Group S) and neurological outcomes were compared with those of animals without shunting (Group N) after 24 and 48 h. Results: L-arteries had significantly larger flow increases than S- and O-arteries (74.3 ^ 33.8, 20.4 ^ 9.8 and 33.3 ^ 17.8 cm/s, P , 0.01). In Group N, five of the six animals were completely paraplegic (Tarlov Grade 0) and the other was Grade 1. In Group S, four animals were Grade 4 and two were Grade 0 after 24 h. However, two animals showed delayed paraplegia. Therefore, four animals were Grade 0 and two were Grade 4 after 48 h. All animals in Group L were neurologically normal (Grade 4) at both after 24 h (vs. Group N, Pa 0:0013) and 48 h (vs. Group N, Pa 0:0013; vs. Group S, Pa 0:019). Conclusions: Flow responses to aortic cross-clamping differed among segmental arteries and selective perfusion of L-arteries completely prevented paraplegia. Therefore, L-arteries were considered to be CSAs. Hemodynamic measurement of segmental arterial flow using Doppler ultrasonography could be clinically useful for spinal cord protection during thoracoabdominal aortic surgery. q 2001 Elsevier Science B.V. All rights reserved.

Background: Visualization of the left circumflex arteries during off-pump coronary artery bypass grafting (CABG) causes hemodynamic disturbance. We investigated whether right heart mini-pump bypass (RHB), using a centrifugal pump, improved the safety of this procedure by studying the influences of different heart displacement positions, the Trendelenburg maneuver and RHB on hemodynamics. Method: Hemodynamic parameters in eight mongrel dogs (15.5‐20 kg) were continuously monitored at a fixed heart rate of 80 beats/min through a conventional median sternotomy. The posterior descending artery (PDA) and left circumflex artery (LCX) were exposed using an Octopus tissue stabilizer. After evaluating the influence of the Trendelenburg maneuver on hemodynamics, a heparin-coated centrifugal pump without an oxygenator was introduced and the impact of different pump flow volumes was investigated during RHB. Results: LCX exposure caused significant decreases in aortic flow (to 35.1 ^ 12.8%) and arterial mean pressure (to 66.1 ^ 9.3%) compared with baseline (P , 0:001). In contrast to PDA exposure, values remained significantly decreased during the Trendelenburg maneuver. On the contrary, RHB significantly improved the hemodynamic impairments caused by both heart displacement procedures, especially LCX exposure, although 100% pump flow significantly increased left atrial pressure to 131.3 ^ 19.5% (P , 0:01). Conclusion: Exposure of the LCX caused severe hemodynamic deterioration, which was not fully reversed by the Trendelenburg maneuver. In contrast, RHB significantly improved hemodynamics, and therefore this technique can be beneficial for CABG of LCX in the limited cases. q 2000 Elsevier Science B.V. All rights reserved.

Objective: The transseptal superior approach can offer an excellent view of the mitral valve but the incision almost always transects the sinus node artery. The purpose of this study was to evaluate the sinus node function after mitral operation by this approach. Patients and Methods: We reviewed the electrocardiograms of 76 patients who underwent mitral valve operations either via transseptal superior approach or via right lateral atriotomy. Nine patients who maintained the sinus rhythm for more than one year after surgery via the transseptal superior approach were selected for electrophysiological study to evaluate the sinus node function. Results and Conclusions: Postoperative electrocardiographic and electrophysiological studies revealed that the sinus node function after the transseptal superior approach was relatively well maintained for more than one year after the operation. The influence of the transseptal superior approach on the sinus node function in the mid-term postoperative period was apparently mild and did not cause a serious problem. However, some of the patients did show abnormal data in terms of sino-atrial conduction time and intrinsic heart rate. Therefore, further follow-up of the sinus node function is necessary in patients who underwent mitral surgery through the transseptal superior approach.