不同深低温停循环方法对脑组织S-100蛋白表达的影响

目的观察不同深低温停循环方法对脑组织S—100蛋白表达及组织结构的影响。方法将18只实验犬随机分为3组，深低温停循环（deep hypothermic circulatory arrest，DHCA组）组，深低温停循环结合逆行脑灌注（retrograde cerebral perfusion，RCP，DHCA＋RCP组）组，深低温停循环结合顺行性间断脑灌注（intermittent antegrade cerebral perfusion，IACP，DHCA＋IACP组）组。3组犬体外循环开始后将鼻咽温降至18℃，随后停循环90min，开放循环后复温至36℃，随后停机。在停循环前、停循环后45min、90min及开放循环后15min和30min由颈静脉插管留取血液标本进行S-100蛋白含量测定。手术结束时取脑海马组织作透射电子显微镜检查，观察脑组织及神经细胞超微结构的变化。结果3组犬在停循环前颈静脉血S-100蛋白含量差异无统计学意义（P〉0．05），停循环后DHCA组和DHCA＋RCP组S-100蛋白含量较停循环前显著升高（P〈0．01），DHCA＋IACP组S-100蛋白含量停循环前后无显著变化。结论DHCA时间较长时，脑组织会发生缺血缺氧性损伤；RCP对脑组织有一定的保护作用，但易发生脑组织及神经细胞水肿；IACP的脑保护效果较为理想。     

Pediatric physiologic pulsatile pump enhances cerebral and renal blood flow during and after cardiopulmonary bypass

Controversy over benefits of pulsatile flow after pediatric cardiopulmonary bypass (CPB) continues. Our study objectives were to first, quantify pressure and flow waveforms in terms of hemodynamic energy, using the energy equivalent (EEP) formula, for direct comparisons, and second, investigate effects of pulsatile versus nonpulsatile flow on cerebral and renal blood flow, and cerebral vascular resistance during and after CPB with deep hypothermic circulatory arrest (DHCA) in a neonatal piglet model. Fourteen piglets underwent perfusion with either an hydraulically driven dual-chamber physiologic pulsatile pump (P, n = 7) or a conventional nonpulsatile roller pump (NP, n = 7). The radiolabeled microsphere technique was used to determine the cerebral and renal blood flow. P produced higher hemodynamic energy (from mean arterial pressure to EEP) compared to NP during normothermic CPB (13 +/- 3% versus 1 +/- 1%, p < 0.0001), hypothermic CPB (15 +/- 4% versus 1 +/- 1%, p < 0.0001) and after rewarming (16 +/- 5% versus 1 +/- 1%, p < 0.0001). Global cerebral blood flow was higher for P compared to NP during CPB (104 +/- 12 ml/100g/min versus 70 +/- 8 ml/100g/min, p < 0.05). In the right and left hemispheres, cerebellum, basal ganglia, and brainstem, blood flow resembled the global cerebral blood flow. Cerebral vascular resistance was lower (p < 0.007) and renal blood flow was improved fourfold (p < 0.05) for P versus NP, after CPB. Pulsatile flow generates higher hemodynamic energy, enhancing cerebral and renal blood flow during and after CPB with DHCA in this model.     

经上腔静脉逆行灌注脑保护在主动脉瘤手术中的应用

目的　探讨在主动脉瘤手术中应用经上腔静脉逆行灌注的脑保护效果。　方法　 65例主动脉瘤患者分 2组 ,15例采用深低温停循环 (DHCA) ,5 0例经上腔静脉逆行灌注 (RCP)进行脑保护。术中比较 2组患者不同时间颈内静脉的血乳酸含量 ,对部分RCP患者测定了灌注血和回流血的流量分布 ,以及灌注血和回流血的氧含量。　结果　DHCA组停循环时间为 10 0～ 63 0min ,平均(3 5 9± 18 8)min ;RCP组为 16 0～ 81 0min ,平均 (45 5± 17 2 )min。术后至清醒时间DHCA组为4 4～ 9 4h ,平均 (7 1± 1 6)h ;RCP组 2 0～ 9 0h ,平均 (5 4± 2 2 )h。DHCA组手术死亡 3例 ,RCP组死亡 1例 ;术后神经系统并发症DHCA组 3例 (死亡 2例 ,成活 1例 ) ,RCP组 1例 (存活 )。手术总成功率和神经系统并发症发生率RCP组分别为 96%和 2 % ,DHCA组为 67%和 2 0 % (P <0 0 5 )。RCP组再灌注期间颈内静脉血乳酸含量增高幅度低于DHCA组 [(4 4± 0 6)mmol/Lvs (6 2± 0 9)mmol/L ,P <0 0 1],经头臂和下腔静脉血流量测定显示约 2 0 %血液经头臂动脉回流 ,灌注血和回流血氧差9 0 0～ 13 67ml/L ,证实RCP期间脑组织有氧利用。　结论　在主动脉瘤手术中 ,应用RCP可以延长停循环的安全时限 ,是可行的脑保护方法     

Clinical application of retrograde cerebral perfusion for brain protection during surgery of ascending aortic aneurysm--a report of 50 cases

This study was designed to discuss the effects on the brain by different protective methods in ascending aortic aneurysm surgery retrospectively. Two hundred seventy-one surgeries of ascending aortic aneurysm have been done in the past 15 years. There were 65 patients with a dissecting aneurysm of the aortic arch or right arch. To protect the brain, deep hypothermic circulatory arrest (DHCA) combined with retrograde cerebral perfusion (RCP) through superior vena cava (N = 50) and simple DHCA (N = 15) were used during the procedure. Blood samples for lactic acid level from the jugular vein were compared in both groups. Perfusion blood distribution and oxygen content difference between the perfused blood and returned blood were measured in 5 and 10 of RCP patients, respectively. The DHCA time was 35.86 +/- 18.81 min (10 approximately 63 min) and DHCA + RCP time was 45.5 +/- 17.21 min (16 approximately 81 min). The resuscitation time was 7.11 +/- 1.59 h (4.4 - 9.4 h) in DHCA versus 5.43 +/- 2.15 h (2 approximately 9 h) in RCP patients. The operation death rate was 3/15 in DHCA group and 1/50 in RCP patients. Central nervous complication occurred in 3/12 of DHCA patients and 1/49 of RCP patients (p < .01). The overall survival rate was 96% (RCP) versus 67% (DHCA); the central nervous system dysfunction was 20% in DHCA versus 2% in RCP (p < .001). The blood lactic acid level increased significantly after reperfusion in DHCA than that in RCP. The measurement of blood distribution indicated that approximately 2Q% of the perfused blood returned from arch vessels. The difference of oxygen content between perfused and returned blood showed that the oxygen uptake was adequate in RCP group. The application of RCP can prolong the safety duration of circulation arrest. Continuous cerebral perfusion may maintain the brain at a cooler temperature and flush out particulate and air emboli while open anastomosis of the aortic arch to the prosthesis can be safely performed. Therefore, RCP is a preferable method for brain protection in our clinical practices.     

Use of a pH-stat strategy during retrograde cerebral perfusion improves cerebral perfusion and tissue oxygenation

BACKGROUND: Although it is well documented that the use of a pH-stat strategy during hypothermic cardiopulmonary bypass improves cerebral blood flow, an alpha-stat strategy has been almost exclusively used during retrograde cerebral perfusion. We investigated the effects of pH-stat and alpha-stat management on brain tissue blood flow and oxygenation during retrograde cerebral perfusion in a porcine model to determine if the use of a pH-stat strategy during retrograde cerebral perfusion improves brain tissue perfusion. METHODS: Fourteen pigs were managed by an alpha-stat strategy (alpha-stat group, n = 7) or by a pH-stat strategy (pH-stat group, n = 7) during 120 minutes of hypothermic retrograde cerebral perfusion. Retrograde cerebral perfusion was established through the superior vena cava. Brain tissue blood flow and oxygenation were measured continuously with a laser flowmeter and near infrared spectroscopy, respectively. Brain tissue water content was determined at the end of the experiments. RESULTS: During cooling, brain tissue blood flow was significantly higher with use of the pH-stat strategy than with the alpha-stat strategy (86% +/- 10% versus 40% +/- 3% of baseline). During retrograde cerebral perfusion, brain tissue blood flow was also significantly higher (about three times higher) in the pH-stat group than in the alpha-stat group (15% +/- 4% versus 5% +/- 1% of baseline at 60 minutes of retrograde cerebral perfusion). Tissue oxygen saturation appeared to be higher during retrograde cerebral perfusion in the pH-stat group than in the alpha-stat group. Brain tissue blood flow during rewarming remained significantly higher with the use of pH-stat than with the use of alpha-stat. Brain tissue water contents were similar in both groups. CONCLUSIONS: In our pig model, the use of a pH-stat strategy during retrograde cerebral perfusion significantly improves brain tissue perfusion. Therefore, to improve retrograde cerebral blood flow during retrograde cerebral perfusion, it may be preferable to use a pH-stat strategy, rather than an alpha-stat strategy.     

Determination of cerebral blood flow dynamics during retrograde cerebral perfusion using power M-mode transcranial Doppler

BACKGROUND: Retrograde cerebral perfusion (RCP) during profound hypothermic circulatory arrest has been used as an adjunct for cerebral protection for repairs of the ascending and transverse aortic arch. Transcranial Doppler ultrasound has been used to monitor cerebral blood flow during RCP with varying success. The purpose of this study was to characterize cerebral blood flow dynamics during RCP using a new mode of monitoring known as transcranial power motion-mode (M-mode) Doppler ultrasound. METHODS: Data on pump-flow characteristics and patient outcomes were collected prospectively for patients undergoing ascending and transverse aortic arch repair. Retrograde cerebral perfusion during profound hypothermic circulatory arrest was used for all operations. Intraoperative cerebral blood flow dynamics were monitored and recorded using transcranial power M-mode Doppler ultrasound. RESULTS: Between August 2001 and March 2002, we used transcranial power M-mode Doppler ultrasound monitoring for 40 ascending and transverse aortic arch repairs during RCP. Mean RCP time was 32.2 +/- 13.8 minutes. Mean RCP pump flow and RCP peak pressure for identification of cerebral blood flow were 0.66 +/- 0.11 L/min and 31.8 +/- 9.7 mm Hg, respectively. Retrograde cerebral blood flow during RCP was detected in 97.5% of cases (39 of 40 patients) with a mean transcranial power M-mode Doppler ultrasound flow velocity of 15.5 +/- 12.3 cm/s. In the study group, 30-day mortality was 10.0% (4 of 40 patients). The incidence of stroke was 7.6% (3 of 40 patients); the incidence of temporary neurologic deficit was 35.0% (14 of 40 patients). CONCLUSIONS: Transcranial power M-mode Doppler ultrasound consistently demonstrated retrograde middle cerebral artery blood flow during RCP. Transcranial power M-mode Doppler ultrasound can provide optimal RCP with individualized settings of pump flow.     

深低温停循环逆行脑灌注脑组织自由基变化的实验研究

研究深低温停循环（ＤＨＣＡ）与逆行脑灌注（ＲＣＰ）时脑组织自由基的变化。健康杂种犬１４只，随机等分为ＤＨＣＡ组和ＲＣＰ组，在停循环前（Ａ点）、ＤＨＣＡ／ＲＣＰ３０分（Ｂ点）、ＤＨＣＡ／ＲＣＰ６０分（Ｃ点）ＤＨＣＡ／ＲＣＰ９０分（Ｄ眯）和复温再灌注３０分（Ｅ点）取脑皮层ｌｇ，检测丙二醛（ＭＤＡ）和超氧化物歧化酶（ＳＯＤ）水平。结果见两组在Ａ点ＭＤＡ和ＳＯＤ无差别。在Ｂ、Ｃ、Ｄ、Ｅ点，ＤＨＣＡ组ＭＤＡ     

Fundus microvascular flow monitoring during retrograde cerebral perfusion: an experimental study

BACKGROUND: Retrograde cerebral perfusion (RCP) through the superior vena cava was clinically introduced as a supportive technique to protect the brain during deep hypothermic circulatory arrest. This study searched for a direct monitor of cerebral blood flow to evaluate the effect of cerebral perfusion. METHODS: Retinal microvascular perfusions were studied in six piglets using fundus fluorescein angiography (FFA) and color Doppler sonography before cardiopulmonary bypass and retrograde cerebral perfusion during deep hypothermic circulatory arrest. RESULTS: FFA showed initial filling of the fundus venae in 2.5 minutes, and complete filling in 4.5 minutes with partial filling of the arteriae. Arteriae completely filled in 8 minutes, and all of the arteriae and venae filled from 15 to 17 minutes. Color Doppler sonography showed that flow signals were detected in all of the fundus vessels during RCP. CONCLUSIONS: FFA and color Doppler sonography are direct and sensitive methods for observing cerebral blood flow and assessing the effect of cerebral perfusion.     

pH-stat blood gas management provides better cerebral perfusion during deep hypothermic retrograde cerebral perfusion

We performed a retrospective comparative clinical study to evaluate whether pH-stat (n=14) or alpha-stat strategy (n=15) provides better perfusion or oxygen metabolism during hypothermic retrograde cerebral perfusion (RCP). The pH-stat group showed significantly lower superior vena cava (SVC) pressure (21+/-4 versus 27+/-6 mmHg, P<0.0001), apparently lower retrograde cerebral vascular resistance index (7.4+/-2.1 versus 10.1+/-3.8 dynes/s cm(-5) m(-2), P=0.009) but there were no significant differences in RCP flow index, oxygen supply or oxygen extraction between groups. Further studies are necessary to determine which blood gas management is better for RCP, however, pH-stat strategy should be useful in deep hypothermic RCP.     

Cerebral protection during surgery for aortic arch aneurysms.

Surgical repair of aneurysms or dissections involving the transverse aortic arch and the distal aortic arch carries a considerable risk of cerebral complications. Currently, deep hypothermic circulatory arrest (DHCA), moderate hypothermic circulatory arrest or DHCA with selective cerebral perfusion (SCP) and DHCA with retrograde cerebral perfusion (RCP) are used as means to protect the central nervous system. DHCA alone is simple, but the safe time of DHCA is limited. RCP is an alternative technique for cerebral protection that can prolong the safe time of DHCA. SCP offers virtually unlimited time in isolating cerebral circulation. With the improvement of cardiopulmonary bypass (CPB) materials and myocardial preservation, DHCA with SCP is our current preference of an adjunct for cerebral protection, although possible increment of mortality and morbidity associated with a prolonged DHCA and CPB remains to be overcome.     

深低温停循环逆行性灌注脑保护

为评价上腔静脉逆行性灌注对脑保护的效果,对１０余年来的研究成果进行综述。上腔静脉逆行性灌注是深低温停循环环脑保护的辅助手段,已证明在低温状态下,它为脑部提供低流量血流,维持脑部低温状态;提供部分氧和营养物质,运走代谢产物;减少气栓及栓塞的发生,从而延长了深低温度循环脑保护的安全时限,而脑水肿的危险性限制了该方法在临床应用。在脑保护液中加入脑保护药物已取得一定进展,而上腔静脉逆行性灌注中束闭下腔静脉     

Increased pressure during retrograde cerebral perfusion in an acute porcine model improves brain tissue perfusion without increase in tissue edema

BACKGROUND: There is a significant lack of scientific data to support the clinically accepted view that 25 to 30 mm Hg is the maximum safe perfusion pressure during retrograde cerebral perfusion (RCP). This study was designed to investigate whether perfusion pressure greater than 30 mm Hg during RCP is beneficial to the brain during prolonged HCA in an acute porcine model. METHODS: Sixteen pigs underwent 120 minutes of circulatory arrest in conjunction with RCP at a perfusion pressure of either 23 to 29 mm Hg (group L, n = 8) or 34 to 40 mm Hg (group H, n = 8) at 15 degrees C, followed by 60 minutes of normothermic cardiopulmonary bypass. Cortical blood flow and oxygenation were measured continuously with a laser flowmeter and near-infrared spectroscopy, respectively. Tissue water content was measured at the end of the experiments. RESULTS: Brain tissue blood flow was significantly higher in group H than in group L (16.8% +/- 4.1% vs 4.8% +/- 0.9% of baseline, p < 0.01) during RCP. Brain oxygen extraction in group L reached a maximum (approximately 70%) immediately after starting RCP, whereas in group H it increased gradually and reached a maximum at 120 minutes of RCP, indicating a greater supply of oxygen to tissue in group H than in group L. After RCP, the ability of brain tissue to use oxygen was better preserved in group H than in group L, as indicated by tissue oxygen saturation and the deoxyhemoglobin level. There was no significant increase in tissue water content in either group (group H 79.2% +/- 0.3%, group L 79.1% +/- 0.4%) relative to normal control pigs (78.7% +/- 0.1%). CONCLUSIONS: In this acute porcine model, increasing perfusion pressure from 23-29 to 34-40 mm Hg during RCP increases tissue blood flow and provides better tissue oxygenation, without increasing tissue edema. The optimal perfusion pressure for RCP needs to be further investigated.     

Arterial blood gas management in retrograde cerebral perfusion: the importance of carbon dioxide.

OBJECTIVES: Many interventional physiological assessments for retrograde cerebral perfusion (RCP) have been explored. However, the appropriate arterial gas management of carbon dioxide (CO2) 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 (CMRO2), and distribution of regional cerebral blood flow. METHODS: Fifteen anesthetized dogs (25.1+/-1.1 kg) on cardiopulmonary bypass (CPB) were cooled to 18 degrees C under alpha-stat management and had RCP for 90 min under: (1), alpha-stat; (2), pH-stat; or (3), deep hypothermic (18 degrees 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 CMRO2 were evaluated as the percentage of the baseline level (%CBF, %CMRO2). RESULTS: The oxygen content of arterial inflow and oxygen extraction was not significantly different between the RCP groups. The %CBF and %CMRO2 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 CO2 management, regional differences were not significant among any site in the brain. CONCLUSIONS: CO2 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 CO2 management.     

Is Maintenance of Cerebral Hypothermia the Principal Mechanism by which Retrograde Cerebral Perfusion Provides Better Brain Protection than Hypothermic Circulatory Arrest?

OBJECTIVE: Retrograde cerebral perfusion (RCP) provides better brain protection than hypothermic circulatory arrest (HCA) alone. The mechanism by which RCP improves brain protection during circulatory arrest remains unknown. The purpose of the study in pigs was to determine if RCP improves brain protection mainly as a result of its ability to maintain cerebral hypothermia. METHODS: Fifteen pigs were subjected to 120 minutes of HCA alone (HCA group, n = 5), HCA + RCP at perfusion pressures of 23 to 29 mmHg (RCP-low group, n = 5), or at perfusion pressures of 34-40 mmHg (RCP-high group, n = 5) at 15 degrees C, followed by 60 minutes of normothermic cardiopulmonary bypass (CPB). After brain temperature reached 15 degrees C, HCA was initiated with or without RCP. Temperatures in the brain, esophagus, and perfusate/blood were monitored continuously. Brain tissue blood flow was measured continuously using a laser flowmeter. Brain oxygen extraction was calculated from the oxygen contents in arterial and venous blood samples. RESULTS: During cooling and rewarming, the change in temperature was slower in the brain than in the esophagus. A similar degree of spontaneous rewarming (from 15 degrees C to 17/18 degrees C) occurred in the brain during HCA and RCP. This indicates that RCP does not provide better maintenance of cerebral hypothermia during circulatory arrest than HCA alone. The esophageal temperature rose more slowly during RCP than during HCA alone, indicating that RCP maintains better hypothermia in the body. During RCP, the brain extracted oxygen continuously from the blood, indicating that RCP may provide nutrient flow to the brain. CONCLUSION: In an acute pig model, maintenance of cerebral hypothermia does not appear to be the principal mechanism by which RCP provides better brain protection than HCA alone. Retrograde cerebral perfusion provides nutrient flow/oxygen to brain tissue, leading to better brain protection than HCA alone.     

Assessment of arteriovenous blood flow during retrograde cerebral perfusion

OBJECTIVE: This study examined arterial and venous blood flow during retrograde cerebral perfusion (RCP) to quantify what proportion of arterial inflow is not recovered as venous outflow. DESIGN: Prospective. SETTING: Community hospital, university setting, single institution. PARTICIPANTS: Twelve patients undergoing reconstructive aortic arch surgery with profound hypothermic circulatory arrest and RCP. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: RCP arterial inflow and venous outflow measurements were recorded at 2-minute intervals for 10 minutes, averaged, and then compared. Only 44.9%+/-16.3% of RCP inflow returned through the aortic arch. The remainder was not recovered. CONCLUSION: Internal jugular venous valves, sequestration, and shunting may contribute to arterial inflow diversion during RCP.     

Cardiopulmonary bypass for thoracic aortic aneurysm: a report on 488 cases

Our objective was to investigate different cardiopulmonary bypass (CPB) techniques for thoracic aortic aneurysm retrospectively. Four hundred and eighty-eight patients with thoracic aortic aneurysm received surgical treatment. Total CPB was used routinely in 331 cases with ascending aortic aneurysm. When the aneurysm expanded to the aortic arch, brain protection was executed by adopting deep hypothermia circulatory arrest (DHCA) or DHCA combined with retrograde cerebral perfusion (RCP). Selected cerebral perfusion via carotid artery was used in three cases and separated upper and lower body perfusion in five cases. Left heart bypass was adopted for the surgeries of 157 cases with descending aortic aneurysm. In two of the cases, ventricular defibrillation could not be achieved, and then bypass was altered to separated upper and lower body perfusion to acquire satisfactory outcome. In the ascending aortic aneurysm group, DHCA time in the 17 patients was 10-63 minutes (mean 35.58 +/- 18.81 min), and DHCA +/- RCP time in 61 patients was 16-81 minutes (mean 43.43 +/- 17.91 min). Total mortality of aortic aneurysm surgery requiring full CPB was 5.4% (18/331), in which eight patients died in emergency operations. The total mortality of emergency operation was 11.9% (8/67). In the descending aortic aneurysm group, time of left heart bypass was 125.56 +/- 57.28 min, and the total mortality was 7% (11 of 157 patients). Three patients developed postoperative paraplegia. Techniques for extracorporeal circulation for surgery of the aorta are dependent on the nature of the disease and require a flexible approach to meet the specific anatomical challenge. The ability to alter the perfusion circuit to meet unexpected situations should be anticipated and planned for. In this series, we have varied our approach to perfusion techniques as required with acceptable outcome data as compared to the international literature.     

Aortic arch replacement with proximal first technique.

BACKGROUND: Deep hypothermic circulatory arrest (DHCA) without retrograde cerebral perfusion (RCP) has a strict time limit. We modified a surgical technique for anastomosis to shorten the period of DHCA and unilateral cerebral perfusion (UCP). METHODS: Between March 1993 and August 2001, retrospective analysis was done on 23 consecutive patients, who underwent aortic arch replacement with branches. The patients were divided into two groups: DHCA group and UCP group. The DHCA group, in which DHCA alone and without additional cerebral perfusion was performed, comprised of nine patients. Proximal aortic anastomosis was performed first during systemic cooling; then both the brachiocephalic artery and left carotid artery were reconstructed with the branches of the artificial graft during circulatory arrest; thereafter, cerebral and coronary perfusions were resumed. The UCP group, in which DHCA was not used but right hemisphere perfusion during deep hypothermia was performed when the origin of brachiocephalic artery was safely clamped, consisted of 14 patients. RESULTS: Mean time of DHCA was 18.8+/-4.2 minutes and that of right hemisphere perfusion time was 11.0+/-3.8 minutes, respectively. Twenty-one patients survived the surgery (91.3%), and two (8.7%) died during hospitalization. Transient cerebral complication occurred in four patients in the DHCA group and all recovered. Logistic regression analysis revealed that DHCA was the only parameter to significantly influence temporary neurological dysfunction. There was no other significant difference between the two groups. CONCLUSION: With our modified and simple surgical technique for aortic arch repair, we were able to successfully shorten the DHCA time and right hemisphere perfusion time. However, because DHCA was the only parameter to significantly influence temporary neurological dysfunction, some form of continuous cerebral perfusion at deep hypothermia may be a safer method to preserve cerebral function.     

Influence of temperature on tracheal tube cuff pressure during cardiac surgery

BACKGROUND: Lateral wall pressure may cause tracheal injury by affecting tracheal capillary blood flow. Damage to the trachea is less severe when lateral wall pressure exerted by the endotracheal tube cuff does not exceed the mean capillary perfusion pressure of the mucosa. The purpose of this study was to determine the effects of hypothermic and normothermic cardiopulmonary bypass (CPB) on tracheal tube cuff pressure dynamics. METHODS: Twenty-two patients were studied during normothermic CPB (pulmonary artery blood temperature in the CPB period between 36 and 35 degrees C), and 22 patients during hypothermic CPB (pulmonary artery temperature in the CPB period between 32 and 28 degrees C). A Mallinckrodt Medical Lo-Contour Murphy tracheal tube, with high-volume, low-pressure cuff was used without lubricant. Intracuff pressure (ITCP) was recorded at end-expiration before, during and after cardiopulmonary bypass. RESULTS: ITCP measurements were different between groups during CPB at aortic cross-clamping (13.9 +/- 0.8 mmHg in the normothermic group versus 11.3 +/- 0.4 mmHg in the hypothermic group, P < 0.05), and respectively during CPB after aortic declamping (15.3 +/- 0.8 mmHg and 12.6 +/- 0.8 mmHg, P < 0.05) and after CPB at the end of surgery (16.8 +/- 0.7 mmHg and 18.6 +/- 0.3 mmHg, P < 0.05). CONCLUSION: We conclude that the ITCP is higher in normothermic CPB than in hypothermic CPB; however, the clinical significance of this observation needs further investigation.     

Retrograde cerebral perfusion versus selective cerebral perfusion as evaluated by cerebral oxygen saturation during aortic arch reconstruction.

BACKGROUND: Time limits for neuroprotection by retrograde cerebral perfusion (RCP) and selective cerebral perfusion (SCP) in aortic arch aneurysm repair or dissection are undergoing definition. METHODS: Using near-infrared optical spectroscopy, changes in regional cerebrovascular oxygen saturation (rSO2) were compared between the two perfusion methods. RESULTS: Immediately before cardiopulmonary bypass, baseline rSO2 was 63.9%+/-6.9% for the RCP and 66.1%+/-5.3% for the SCP group (no significant difference). As patients were core-cooled to 20 degrees C, rSO2 increased to 73.1%+/-8.8% and 74.1%+/-7.9% in the RCP and SCP groups, respectively. With circulatory arrest, rSO2 suddenly decreased. After starting cerebral perfusion, rSO2 returned to prearrest values in the SCP group but continued decreasing steadily in the RCP group, to levels below baseline after about 25 minutes. At the end of perfusion, rSO2 was 57.4%+/-12.2% for the RCP group and 71.7%+/-6.9% for the SCP group, and the ratio of rSO2 to baseline value was 0.89 for RCP and 1.08 for SCP despite a shorter brain perfusion time for RCP (38.8+/-18.0 versus 103.3+/-43.3 minutes). Three of 5 patients whose ratios of rSO2 to baseline at the end of brain protection were 0.7 or less had neurologic deficits. CONCLUSIONS: Although SCP showed no clinically important time limitation, rSO2 continued to decrease with time during RCP. An rSO2 ratio less than 0.7 could represent a critical lower limit.     

Pharmacologic cerebral capillary blood flow improvement after deep hypothermic circulatory arrest: an intravital fluorescence microscopy study in pigs

BACKGROUND: Despite meticulous investigation of bypass techniques for deep hypothermic circulatory arrest, unfavorable long-term neurologic deficits have been well documented. Our aim was to improve brain perfusion by reducing platelet plugging with a glycoprotein IIb/IIIa inhibitor (eptifibatide) in an experimental model of deep hypothermic circulatory arrest-reperfusion in pigs. METHODS: Two groups of 12 piglets each (eptifibatide group [eptifibatide + unfractionated heparin] vs UFH group [only unfractionated heparin]) underwent 10 minutes of normothermic bypass, 40 minutes of cooling during cardiopulmonary bypass (hematocrit, 30%; cardiopulmonary bypass flow, 100 mL x kg(-1) x min(-1)), 60 minutes of circulatory arrest at 15 degrees C, and a 40-minute rewarming period. Intravital fluorescence microscopy of pial vessels at set intervals was performed. RESULTS: During the cooling period, there was a tendency toward reduced functional capillary density values without statistical significance in both groups. During reperfusion, the eptifibatide group demonstrated a significantly decreased platelet adhesion and aggregation (at 30 minutes of reperfusion: functional capillary density, 104% +/- 3% vs 77% +/- 4% relative to baseline, P = .02; red blood cell velocity, 0.65 vs 0.30 mm/s, P < .004). A more rapid recovery of tissue oxygenation (P < .001) was documented. Furthermore, a significant microvascular permeability reduction was achieved compared with that seen in the UFH group (P < .02). The use of eptifibatide resulted in fewer ultrastructural changes in hippocampal tissue, which is demonstrated by histologic examination. CONCLUSIONS: Platelet plugging reduction with the glycoprotein IIb/IIIa inhibitor eptifibatide improves cerebral capillary blood flow and reduces cerebral ischemia in the setting of deep hypothermic circulatory arrest. Furthermore, significant endothelial cell injury and perivascular edema reduction can be achieved.