Regional low-flow perfusion provides cerebral circulatory support during neonatal aortic arch reconstruction

OBJECTIVE: Because of concerns regarding the effects of deep hypothermia and circulatory arrest on the neonatal brain, we have developed a technique of regional low-flow perfusion that provides cerebral circulatory support during neonatal aortic arch reconstruction. METHODS: We studied the effects of regional low-flow perfusion on cerebral oxygen saturation and blood volume as measured by near-infrared spectroscopy in 6 neonates who underwent aortic arch reconstruction and compared these effects with 6 children who underwent cardiac repair with deep hypothermia and circulatory arrest. RESULTS: All the children survived with no observed neurologic sequelae. Near-infrared spectroscopy documented significant decreases in both cerebral blood volume and oxygen saturations in children who underwent repair with deep hypothermia and circulatory arrest as compared with children with regional low-flow perfusion. Reacquisition of baseline cerebral blood volume and cerebral oxygen saturations were accomplished with a regional low-flow perfusion rate of 20 mL x kg(-1) x min(-1). CONCLUSIONS: Regional low-flow perfusion is a safe and simple bypass management technique that provides cerebral circulatory support during neonatal aortic arch reconstruction. The reduction of deep hypothermia and circulatory arrest time required may reduce the risk of cognitive and psychomotor deficits.     

Neurologic outcome after surgery of the aortic arch: Comparison of deep hypothermic arrest,antegrade and retrograde cerebral perfusion

Introduction Neurologic deficits are still a major complication of aortic arch surgery. We therefore compared cerebral protection by deep hypothermic circulatory arrest (DHCA), antegrade (ACP) and retrograde (RCP) cerebral perfusion. Patients and Method 64 consecutive patients who underwent replacement of the aortic arch for aneurysms or dissections from January 1999 through August 2001 were analysed retrospectively for clinical and neurologic outcome. For DHCA core temperature was lowered to 18°C and was kept between 18 and 24°C in the perfused groups. Selective antegrade cerebral perfusion (ACP) was achieved either via the subclavian artery or the brachiocephalic trunc. Retrograde cerebral perfusion (RCP) was performed via the superior vena cava. Results Indication for surgery was type A acute dissection or ruptured aneurysm in 39 patients, chronic dissection and aneurysm without rupture in 25 patients. Operative procedure was partial arch replacement in 46 patients and total arch replacement in 18 patients. For cerebral protection retrograde cerebral perfusion (RCP) was used in 22 Patients (23±11 min.), ACP in 30 patients (25±19 min.) and DHCA in 14 patients (23±13 min.). Mortality was 17% (11 of 64 patients: ACP 7, RCP 2 and DHCA 2). Neurologic deficits occured in 5%, without differences for groups. Conclusion For this patient cohort, needing comparatively short times for aortic arch reconstruction, a low neurologic complication rate without significant differences for the method of cerebral perfusion was observed.     

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.     

Aortic arch reconstruction without circulatory arrest: Review of techniques,applications, and indications

The majority of neonatal intracardiac repairs can now be performed with the use of low-flow cardiopulmonary bypass. However, aortic arch reconstruction still requires a period of circulatory arrest. Recently, a number of surgeons have reported techniques of limiting or completely avoiding circulatory arrest during arch reconstruction in an attempt to reduce the risk of neurologic injury. Several techniques are currently in use that have been successfully applied during biventricular repair and the Norwood operation for a wide range of aortic arch pathology including hypoplastic or interrupted aortic arch, the hypoplastic left heart syndrome, and its equivalents. These techniques maintain continuous low-flow cerebral perfusion via the innominate artery, directly or indirectly. In the last 2 years at the Montreal Children's Hospital (Montreal, Canada) we have consistently used such techniques for all arch reconstructions, including the Norwood operation, completely avoiding the use of circulatory arrest. These techniques are still in evolution with regard to flow rates, temperature, and safe period of low flow. Although the early results are encouraging, long-term follow-up with respect to neurodevelopmental outcome is essential to help us decide which techniques are optimal. This chapter provides an overview of the currently used techniques allowing cerebral perfusion during aortic arch reconstruction and summarizes our early experience at the Montreal Children's Hospital. Copyright © 2002 by W.B. Saunders Company     

A technique for performing antegrade selective cerebral perfusion without interruption of forward flow or cannula relocation for pediatric aortic arch reconstruction

New technology and advances in extracorporeal bypass circuitry and surgical techniques have drastically improved outcomes in infants with congenital heart defects. Hypothermia with circulatory arrest has fallen out of favor in many institutions over the last decade in part from data implicating even short circulatory arrest times to long-term neurologic sequelae. Implementing continuous cerebral perfusion techniques for aortic arch reconstruction is desirable in ameliorating neurologic complications because long-term survival of complex defects can be more routinely achieved. Many centers have implemented alternative means of alleviating cerebral ischemic periods by incorporating selective antegrade or retrograde cerebral perfusion techniques. The incidence of post-operative neurologic events is low when alternative cerebral perfusion techniques are used. Many techniques used to perform continuous cerebral perfusion involve brief periods of circulatory arrest, usually for perfusion cannula repositioning. Herein we describe a technique for performing continuous antegrade cerebral perfusion without a need to interrupt forward flow.     

Neonatal aortic arch reconstruction avoiding circulatory arrest and direct arch vessel cannulation.

BACKGROUND: Aortic arch reconstruction in neonates routinely requires deep hypothermic circulatory arrest. We reviewed our experience with techniques of continuous low-flow cerebral perfusion (LFCP) avoiding direct arch vessel cannulation. METHODS: Eighteen patients, with a median age of 11 days (range 1 to 85 days) and a mean weight of 3.2 +/- 0.8 kg, underwent aortic arch reconstruction with LFCP. Seven had biventricular repairs with arch reconstruction, 9 underwent the Norwood operation and 2 had isolated arch repairs. In 1 Norwood and 7 biventricular repair patients, LFCP was maintained by advancing the cannula from the distal ascending aorta into the innominate artery. In 8 of 9 Norwood patients, LFCP was maintained by directing the arterial cannula into the pulmonary artery confluence and perfusing the innominate artery through the right modified Blalock-Taussig shunt fully constructed before cannulation for cardiopulmonary bypass. In 2 patients requiring isolated arch reconstruction, the ascending aorta was cannulated and the cross-clamp was applied just distal to the innominate artery. RESULTS: LFCP was maintained at 0.6 +/- 0.2 L x min(-1) x m(-2) for 41.0 +/- 13.9 minutes at 18.5 degrees C +/- 1.1 degrees C. In 10 of the 18 patients, blood pressure during LFCP was 15 +/- 8 mm Hg remote from the innominate artery (left radial, umbilical or femoral arteries). In 8 of the 18 patients, right radial pressure during LFCP was 24 +/- 10 mm Hg. The mean mixed-venous saturation was 79.8% +/- 10% during LFCP. Two patients had preoperative seizures, whereas none had seizures postoperatively. One patient died. CONCLUSIONS: Neonatal aortic arch reconstruction is possible without circulatory arrest or direct arch vessel cannulation. These techniques maintained adequate mixed-venous oxygen saturations with no associated adverse neurologic outcomes.     

Deep hypothermic systemic circulatory arrest and continuous retrograde cerebral perfusion for surgery of aortic arch aneurysm.

From 1987 to February 1991, we have repaired or replaced the aortic arch in ten patients using deep hypothermic systemic circulatory arrest with continuous retrograde cerebral perfusion (CRCP). CRCP can be implemented using the bypass connecting the arterial and venous lines of the extracorporeal circuit to reverse the flow into the superior vena cava cannula after induction of circulatory arrest. CRCP flow required to maintain an internal jugular vein pressure of 20 mmHg ranged from 100 to 500 ml/min. After completion of suturing of the aortic arch graft, air is evacuated retrogradely from the open arch vessels prior to reestablishing the usual arterial return. Two patients died, one from sepsis and the other from liver cirrhosis 1 month postoperatively. CRCP times ranged from 11 to 56 min, and minimal nasopharyngeal temperatures ranged from 16 degrees to 18 degrees C. The difference in oxygen content between the perfused blood and the blood draining from the arch vessels during CRCP most likely reflected the steady-state metabolism of the brain during the deep hypothermic state. This technique offers advantages including the need for dissecting and clamping the arch branches, providing sufficient metabolic support to the brain during deep hypothermia, and eliminating embolism of particulate debris from the aortic arch.     

Direct visualization of minimal cerebral capillary flow during retrograde cerebral perfusion: an intravital fluorescence microscopy study in pigs

BACKGROUND: Retrograde cerebral perfusion (RCP) is used in some centers during aortic arch surgery for brain protection during hypothermic circulatory arrest. It is still unclear however whether RCP provides adequate microcirculatory blood flow at a capillary level. We used intravital microscopy to directly visualize the cerebral capillary blood flow in a piglet model of RCP. METHODS: Twelve pigs (weight 9.7 +/- 0.9 kg) were divided into two groups (n = 6 each): deep hypothermic circulatory arrest (DHCA) and RCP. After the creation of a window over the parietal cerebral cortex, pigs underwent 10 minutes of normothermic bypass and 40 minutes of cooling to 15 degrees C on cardiopulmonary bypass ([CPB] pH-stat, hemocrit 30%, pump flow 100 mL x kg(-1) x min(-1)). This was followed by 45 minutes of DHCA and rewarming on CPB to 37 degrees C. In the RCP group the brain was retrogradely perfused (pump flow 30 mL x kg(-1) x min(-1)) during DHCA through the superior vena cava after inferior vena cava occlusion. Plasma was labeled with fluorescein-isothiocyanate-dextran for assessing microvascular diameter and functional capillary density (FCD), defined as total length of erythrocyte-perfused capillaries per observation area. Cerebral tissue oxygenation was determined by nicotinamide adenine dinucleotide hydrogen (NADH) autofluorescence, which increases during tissue ischemia. RESULTS: During normothermic and hypothermic antegrade cerebral perfusion the FCD did not significantly change from base line (97% +/- 14% and 96% +/- 12%, respectively). During retrograde cerebral perfusion the FCD decreased highly significantly to 2% +/- 2% of base line values (p < 0.001). Thus there was no evidence of significant capillary blood flow during retrograde cerebral perfusion. The microvascular diameter of cerebral arterioles that were slowly perfused significantly decreased to 27% +/- 6% of base line levels during RCP. NADH fluorescence progressively and significantly increased during RCP, indicating poorer tissue oxygenation. At the end of retrograde cerebral perfusion there was macroscopic evidence of significant brain edema. CONCLUSIONS: RCP does not provide adequate cerebral capillary blood flow and does not prevent cerebral ischemia. Prolonged RCP induces brain edema. However, there might be a role for a short period of RCP to remove air and debris from the cerebral circulation after DHCA because retrograde flow could be detected in cerebral arterioles.     

Hypothermic circulatory arrest does not increase the risk of ascending thoracic aortic aneurysm resection.

OBJECTIVE: The purpose of this study was to investigate the safety and efficacy of a period of deep hypothermic circulatory arrest (DHCA) during elective replacement of the ascending thoracic aorta. SUMMARY BACKGROUND DATA: DHCA has been implemented in ascending thoracic aortic aneurysm resection whenever the anatomy or pathology of the aorta or arch vessels prevents safe or adequate cross-clamping. Profound hypothermia and retrograde cerebral perfusion have been shown to be neurologically protective during ascending aortic replacement under circulatory arrest. METHODS: The authors conducted a retrospective analysis of 91 consecutive patients who underwent repair of chronic ascending thoracic aortic aneurysms from 1986 to present. The authors hypothesized that patients undergoing DHCA with or without retrograde cerebral perfusion during aneurysm repair were at no greater operative risk than patients who received aneurysm resection while on standard cardiopulmonary bypass. RESULTS: There were no significant differences in hospital mortality, stroke rate, or operative morbidity between patients repaired on DHCA when compared to those repaired on cardiopulmonary bypass. CONCLUSIONS: DHCA with or without retrograde cerebral perfusion does not result in increased morbidity or mortality during the resection of ascending thoracic aortic aneurysms. In fact, this technique may prevent damage to the arch vessels in select cases and avoid the possible complications associated with cross-clamping a friable or atherosclerotic aorta.     

Results of proximal arch replacement using deep hypothermia for circulatory arrest: is moderate hypothermia really justifiable?

The use of selective cerebral perfusion with warmer temperatures during circulatory arrest has been increasingly used for arch replacement over concerns regarding the safety of deep hypothermic circulatory arrest (DHCA). However, little data actually exist on outcomes after arch replacement and DHCA. This study examines modern results with DHCA for proximal arch replacement to provide a benchmark for comparison against outcomes with lesser degrees of hypothermia. Between July 2005 and June 2010, 245 proximal arch replacements ("hemiarch") were performed using deep hypothermia; mean minimum core and nasopharyngeal temperatures were 18.0 ± 2.1°C and 14.1 ± 1.6°C, respectively. Adjunctive cerebral perfusion was used in all cases. Concomitant ascending aortic replacement was performed in 41 per cent, ascending plus aortic valve replacement in 23 per cent, and aortic root replacement in 32 per cent. Mean age was 58 ± 14 years; 36 per cent procedures were urgent/emergent. Mean duration of DHCA was 20.4 ± 6.2 minutes. Thirty-day/in-hospital mortality was 2.9 per cent. Rates of stroke, renal failure, and respiratory failure were 4.1 per cent (0.8% for elective cases), 1.2 per cent, and 0.4 per cent, respectively. Deep hypothermia with adjunctive cerebral perfusion for circulatory arrest during proximal arch replacement affords excellent neurologic as well as nonneurologic outcomes. Centers using lesser degrees of hypothermia for arch surgery, the safety of which remains unproven, should ensure comparable results.     

The effects of deep hypothermic cardiopulmonary bypass and total circulatory arrest on cerebral blood flow in infants and children

Cardiopulmonary bypass management in infants and children involves extensive alterations in temperature, hemodilution, and perfusion pressure, with occasional periods of circulatory arrest. Despite the use of these biologic extremes of temperature and perfusion, their effects on cerebral blood flow are unknown. This study was designed to examine the relationship of mean arterial pressure and nasopharyngeal temperature to cerebral blood flow during deep hypothermic cardiopulmonary bypass (18 degrees to 22 degrees C) with and without periods of total circulatory arrest. Cerebral blood flow was measured before, during, and after deep hypothermic cardiopulmonary bypass using xenon clearance techniques in 25 children, aged 2 days to 60 months. Fourteen patients underwent repair with circulatory arrest. There was a highly significant correlation of cerebral blood flow with temperature during cardiopulmonary bypass (p = 0.007). During deep hypothermic bypass there was a significant association between cerebral blood flow and mean arterial pressure (p = 0.027). In infants undergoing repair with deep hypothermia alone, cerebral blood flow returned to prebypass levels in the rewarming phase of bypass. However, in patients undergoing repair with circulatory arrest, no significant increase in cerebral blood flow during rewarming or even after bypass was observed (p = 0.01). These data show that deep hypothermic cardiopulmonary bypass significantly decreases cerebral blood flow because of temperature reduction. Under conditions of deep hypothermia, cerebral pressure-flow autoregulation is lost. This study also demonstrates that cerebral reperfusion after deep hypothermia is impaired if the patient is exposed to a period of total circulatory arrest.     

Low-flow perfusion via the innominate artery during aortic arch operations provides only limited somatic circulatory support.

BACKGROUND: Aortic arch operations in pediatric patients using low-flow perfusion techniques have been standardized to a certain degree, but some of the often-stated beneficial effects have never been proven. Especially, the existence or efficacy of any subdiaphragmal perfusion still remains unclear. METHODS: Twenty-six newborn male piglets (10-15 kg) underwent aortic arch surgery under general anesthesia using either low-flow perfusion via the innominate artery (LF, 30 ml/(kg min), 25 degrees C, n=12) or conventional deep hypothermic circulatory arrest (DHCA, 20 degrees C, n=14). Cortical somatosensory-evoked potentials (SSEPs), carotid, and subdiaphragmal blood flows were measured. The animals of both groups have been randomized to either pH-stat or alpha-stat management on cardiopulmonary bypass (CPB). RESULTS: During low-flow perfusion via the innominate artery only negligible flows of maximum 1-3 ml/min in the femoral arteries were detected, whereas the right carotid artery flow doubled. During reperfusion, serum-lactate and aspartate amino-transferase (AST) levels were significantly higher compared to the circulatory arrest group, whereas alanine amino-transferase (ALT), gamma-glutamyl transpeptidase (gamma-GT), AP, and creatinine did not show any significant differences. Cortical SSEP returned to preoperative values in all but two low-flow animals. There was no return of SSEP in all piglets operated under deep hypothermic circulatory arrest (p<0.01). CONCLUSION: Compared to DHCA, low-flow perfusion via the innominate artery provides superior neuroprotection despite higher tissue temperatures. Although collateral blood flow via the subclavian artery and the circulus arteriosus willisii has often been presumed, only 'trickle-flow' with some protective potential was detectable in the femoral arteries during low-flow perfusion. Origin of elevated lactate and AST levels seems to be the lower limbs.     

Aortic arch reconstruction using regional perfusion without circulatory arrest.

OBJECTIVES: Deep hypothermic circulatory arrest during repair of aortic arch anomalies may induce neurological complications or myocardial injury. Regional cerebral and myocardial perfusion may eliminate those potential side effects. METHODS: From March 2000 to March 2002, 48 neonates or infants with complex arch anomaly were operated on using the regional perfusion technique. Thirty-three patients were male and the median age was 24 days (range 5-301 days). Preoperative diagnosis consisted of coarctation or interruption of the aorta associated with ventricular septal defect (group I, n = 26) and arch anomaly with complex intracardiac defects such as hypoplastic left heart syndrome or its variants (group II, n = 22). Arterial cannula was inserted through the innominate artery and the flow rate was regulated to about 50-100 ml/kg per min during regional perfusion. Simultaneous myocardial perfusion was maintained using a Y-connected infusion line. Cardioplegia was applied during intracardiac repair. RESULTS: Cardiopulmonary bypass and aortic cross-clamp times were 154 +/- 49 and 39 +/- 34 min, respectively. Temporary circulatory arrest for intracardiac procedures was performed in eight patients. However, the mean arrest time was minimized (range 1-18 min). The descending aorta clamping time was 33 +/- 16 min. Operative mortality rates in each group were 0 and 18.2% (0/26 and 4/22). Late mortality rates were 0 and 11.1% (0/26 and 2/18) during 9.1 months of follow-up. Complications consisted of low cardiac output in eight cases, transient neurological problems in two cases, and transient renal insufficiency in two cases, respectively. CONCLUSIONS: Regional perfusion is feasible and can be used with acceptable results. It may reduce potential complications following aortic arch reconstruction using circulatory arrest. However, repair of aortic arch in the patients with complex intracardiac defects still imposes a significant rate of mortality and morbidity.     

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。     

Experience with the Norwood procedure without circulatory arrest.

OBJECTIVE: We evaluated a new cardiopulmonary bypass technique that allowed complete avoidance of circulatory arrest and deep hypothermia in the Norwood procedure for hypoplastic left heart syndrome. METHODS: A total of 10 patients were included in this study. The arterial line of the cardiopulmonary bypass circuit was divided in two in a Y shape; one branch was used for cerebral perfusion through the innominate artery and the other for lower body perfusion through the cannula inserted into the descending thoracic aorta. Moderate hypothermia (29 degrees C-31 degrees C rectal temperature) and high pump flow (150-180 mL. kg(-1). min(-1)) were used. A valveless conduit between the right ventricle and the pulmonary artery was used in 6 patients as an alternative pulmonary blood source to a conventional Blalock-Taussig shunt (n = 4). RESULTS: Circulatory arrest was completely avoided throughout the operation in all cases, and no complications from the new cardiopulmonary bypass technique were seen. Early deaths occurred in 3 cases. Neurologic deficits were not seen among the survivors, and the postoperative course was stable and uneventful, including satisfactory renal function. CONCLUSIONS: The Norwood procedure for hypoplastic left heart syndrome was successfully accomplished with complete avoidance of circulatory arrest by means of cerebral perfusion through the innominate artery combined with cannulation of the descending aorta. A conduit between the right ventricle and the pulmonary artery seems an excellent alternative pulmonary blood source, although right ventricular function needs to be carefully monitored.     

Comparative analysis of alpha-stat and pH-stat strategies with a membrane oxygenator during deep hypothermic circulatory arrest in young pigs

Using young pigs, this study compared the strategies of alpha-stat and pH-stat during deep hypothermic circulatory arrest (DHCA) for the cooling time of brains during the induction of hypothermia and rewarming time with cardiopulmonary bypass (CPB); the cerebral perfusion rate and metabolism rate, and the ratio of these 2 rates; and the extent of the cerebral edema development after circulatory arrest. Fourteen young pigs were assigned to 1 of 2 strategies of gas management. Cerebral blood flow was measured with a cerebral venous outflow technique. With CPB, core cooling was initiated and continued until the nasopharyngeal temperature fell below 20 degrees C. The flow rate was set at 2,500 ml/min. Once the temperature reached below 20 degrees C, the animals were subjected to DHCA for 40 min. During the cooling period, the acid-base balance was maintained using either alpha-stat or pH-stat strategy. After DHCA, the body was rewarmed to the normal body temperature. The animals then were sacrificed, and we measured the brain water content. The cerebral perfusion and metabolism rates were measured before the onset of CPB, before cooling, before DHCA, 15 min after rewarming, and upon the completion of rewarming. The cooling time was significantly shorter with alpha-stat than with pH-stat strategy while no significant differences were observed in the rewarming time between groups. Also, no significant differences were found in cerebral blood flow volume, metabolic rate, or flow/metabolic rate ratio between groups. In each group, the cerebral blood flow volume, metabolic rate, and flow/metabolic rate ratio showed significant differences in body temperature. Brain water content showed no significant differences between the 2 groups. In summary, this study found no significant differences between alpha-stat and pH-stat strategies, except in the cooling time. The cooling time was rather shorter with the alpha-stat than with the pH-stat strategy.     

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     

Novel cerebral physiologic monitoring to guide low-flow cerebral perfusion during neonatal aortic arch reconstruction

OBJECTIVE: This study was undertaken to describe the combined measurement of cerebral blood flow velocity and cerebral oxygen saturation as a guide to bypass flow rate for regional low-flow perfusion during neonatal aortic arch reconstruction. METHODS: Data were prospectively collected from 34 patients undergoing neonatal aortic arch reconstruction with regional low-flow perfusion. Cerebral oxygen saturation and blood flow velocity were measured by near-infrared spectroscopy and transcranial Doppler ultrasonography, respectively, throughout cardiopulmonary bypass. After cooling to 17 degrees C to 22 degrees C, baseline values of cerebral oxygen saturation and blood flow velocity were recorded during full-flow bypass. Regional low-flow perfusion was instituted for aortic arch reconstruction, and bypass flow rate was adjusted to maintain cerebral oxygen saturations and blood flow velocities within 10% of baseline recorded during cold full-flow bypass. Cerebral oxygen saturations and blood flow velocities were recorded again after repair during full-flow hypothermic bypass. Bypass flow during regional low-flow perfusion was recorded, as were arterial pressure and blood gas data. One-way repeated measures analysis of variance was used to determine differences in values during regional low-flow perfusion relative to baseline and after perfusion. RESULTS: A mean bypass flow of 63 mL/(kg x min) was required to maintain cerebral oxygen saturations and blood flow velocities within 10% of baseline. Mean arterial pressure had a poor correlation with the required bypass flow rate (r(2) = 0.006 by linear regression analysis). Fourteen of 34 patients had a cerebral oxygen saturation of 95% during regional low-flow perfusion, placing them at risk for cerebral hyperperfusion if the cerebral oxygen saturation had been used alone to guide bypass flow. Pressure was detected in the umbilical or femoral artery catheter (mean 12 mm Hg) in all patients during regional low-flow perfusion. CONCLUSIONS: Cerebral blood flow velocity, as determined by transcranial Doppler ultrasonography, adds valuable information to cerebral oxygen saturation data in guiding bypass flow during regional low-flow perfusion. Its most important use may be prevention of cerebral hyperperfusion during periods with high near-infrared spectroscopic saturation values.     

Cerebral metabolism during deep hypothermic circulatory arrest vs moderate hypothermic selective cerebral perfusion in a piglet model: a microdialysis study

Background: Few data exist regarding antegrade selective cerebral perfusion (ASCP) and its application in newborn and juvenile patients. Clinical data suggest ASCP alone to be superior to deep hypothermic circulatory arrest (DHCA); however, the effects of moderate hypothermia during ASCP on cerebral metabolism in this patient population are still unclear. Methods: After obtaining the approval from animal investigation committee, 16 piglets were randomly assigned to circulatory arrest combined with either ASCP at 27°C or DHCA at 18°C for 90 min. Cerebral oxygen extraction fraction (COEF) from blood as well as cerebral tissue glucose, glycerol, lactate, pyruvate, and the lactate/pyruvate ratio (L/P ratio) by microdialysis were obtained repeatedly. Results: COEF was lower during cooling and rewarming, respectively, in the DHCA18 group compared to the ASCP27 group (30 ± 8 vs 56 ± 13% and 35 ± 6 vs 58 ± 7%, respectively). Glucose decreased in both the DHCA18 and ASCP27 groups during the course of cardiopulmonary bypass (CPB), but were higher in the ASCP27 group during ASCP, compared to the DHCA18 group during circulatory arrest (0.7 ± 0.1 vs 0.2 ± 0.1 mm ·l^?1, P < 0.05). Pyruvate was higher (ASCP27 vs DHCA18: 53 ± 17 vs 6 ± 2 μm ·l^?1, P < 0.05), and the L/P ratio increased during circulatory arrest in the DHCA18 group, compared to the selective perfusion phase of the ASCP27 group (DHCA18 vs ASCP27: 1891 ± 1020 vs 70 ± 28, P < 0.01). Conclusions: In this piglet model, both cerebral oxygenation and microdialysis findings suggested a depletion of cerebral energy stores during circulatory arrest in the DHCA18 group, compared to selective cerebral perfusion combined with circulatory arrest in the ASCP27 group.     

Similar Cerebral Protective Effectiveness of Antegrade and Retrograde Cerebral Perfusion During Deep Hypothermic Circulatory Arrest in Aortic Surgery: A Meta‐Analysis of 7023 Patients

In aortic arch surgery, deep hypothermic circulatory arrest (DHCA) combined with cerebral perfusion is employed worldwide as a routine practice. Even though antegrade cerebral perfusion (ACP) is more widely used than retrograde cerebral perfusion (RCP), the difference in benefit and risk between ACP and RCP during DHCA is uncertain. The purpose of this meta‐analysis is to compare neurologic outcomes and early mortality between ACP and RCP in patients who underwent aortic surgery during DHCA. PubMed, EMBASE, and the Cochrane Library were searched using the key words “antegrade,” “retrograde,” “cerebral perfusion,” “cardiopulmonary bypass,” “extracorporeal circulation,” and “cardiac surgery” for studies reporting on clinical endpoints including early mortality, stroke, temporary neurologic dysfunction (TND), and permanent neurologic dysfunction (PND) in aortic surgery requiring DHCA with ACP or RCP. Heterogeneity was analyzed with the Cochrane Q statistic and I² statistic. Publication bias was tested with Begg's funnel plot and Egger's test. Thirty‐four studies were included in this meta‐analysis, with 4262 patients undergoing DHCA + ACP and 2761 undergoing DHCA + RCP. The overall pooled relative risk for TND was 0.722 (95% CI = [0.579, 0.900]), and the z‐score for overall effect was 2.9 (P = 0.004). There was low heterogeneity (I² = 18.7%). The analysis showed that patients undergoing DHCA + ACP had better outcomes than those undergoing DHCA + RCP in terms of TND, while there were no significant differences between groups in terms of PND, stroke, and early mortality. This meta‐analysis indicates that DHCA + ACP has an advantage over DHCA + RCP in terms of TND, while the two methods show similar results in terms of PND, early mortality, and stroke.