Cerebral metabolic suppression during hypothermic circulatory arrest in humans

An anesthetic experience during open heart surgery in a patient with Budd-Chiari syndrome combined with superior vena cava syndrome: A case report

Budd-Chiari syndrome (BCS) is a rare disorder that arises from obstruction of the hepatic venous outflow tract. BCS causes various clinical status from liver cirrhosis and other systemic diseases that are usually fatal. BCS is caused by hypercoagulability, e.g, arising from malignancy, oral contraceptives, and deficiency of protein S or C. It is not rare that BCS often shows venous thrombosis, including in superior vena cava. We performed a cardiac anesthesia for a 44 year old male with BCS and total superior vena cava syndrome (SVCS) due to the hereditary protein S and C deficiency. Surgical relief of the hepatic outflow stenosis was performed during deep hypothermic circulatory arrest. The patient was managed successfully without conventional intraoperative hemodynamic monitoring such as central venous catheterization, pulmonary artery catheterization, or transesophageal echocardiography due to underlying SVCS and the risk of varix bleeding. After weaning of cardiopulmonary bypass, mild acidosis and hypoxia improved slowly in an intensive care unit. Hypercoagulability was controlled by warfarin during the first postoperative day.

Arterial access through the right subclavian artery in surgery of the aortic arch improves neurologic outcome and mid-term quality of life

BACKGROUND

We have shown that selective antegrade cerebral perfusion improves mid-term quality of life in patients undergoing surgical repair for acute type A aortic dissection and aortic aneurysms. The aim of the study was to assess the impact of continuous cerebral perfusion through the right subclavian artery on immediate outcome and quality of life.

METHODS

Perioperative data of 567 consecutive patients who underwent surgery of the aortic arch using deep hypothermic circulatory arrest have been analyzed. Patients were divided into three groups, according to the management of cerebral protection. Three hundred eighty-seven patients (68.3%) had deep hypothermic circulatory arrest with pharmacologic protection with pentothal only, 91 (16.0%) had selective antegrade cerebral perfusion and pentothal, and 89 (15.7%) had continuous cerebral perfusion through the right subclavian artery and pentothal. All in-hospital data were assessed, and quality of life was analyzed prospectively 2.4 +/- 1.2 years after surgery with the Short Form-36 Health Survey Questionnaire.

RESULTS

Major perioperative cerebrovascular injuries were observed in 1.1% of the patients with continuous cerebral perfusion through the right subclavian artery, compared with 9.8% with selective antegrade cerebral perfusion (p < 0.001) and 6.5% in the group with no antegrade cerebral perfusion (p = 0.007). Average quality of life after an arrest time between 30 and 50 minutes with continuous cerebral perfusion through the right subclavian artery was significantly better than selective antegrade cerebral perfusion (90.2 +/- 12.1 versus 74.4 +/- 40.7; p = 0.015).

CONCLUSIONS

Continuous cerebral perfusion through the right subclavian artery improves considerably perioperative brain protection during deep hypothermic circulatory arrest. Irreversible perioperative neurologic complications can be significantly reduced and duration of deep hypothermic circulatory arrest can be extended up to 50 minutes without impairment in quality of life.

Practical pharmacologic aspects of therapeutic hypothermia after cardiac arrest

Abstract Therapeutic hypothermia has emerged as an effective means of improving neurologic outcomes among cardiac arrest survivors. To achieve optimal results, clinicians must understand and anticipate potential adverse effects of cooling and provide rigorous monitoring and/or pharmacologic interventions as appropriate. Using pharmacotherapy to counter adverse effects of cooling or to treat an intrinsic process under hypothermic conditions requires understanding how hypothermia will influence the clinical effects of the drug, including the drug's pharmacokinetics and pharmacodynamics. The pharmacologic aspects of therapeutic hypothermia in relation to physiology and adverse effects are reviewed.

Neuroprotective effect of diazoxide on brain injury induced by cerebral ischemia/reperfusion during deep hypothermia

OBJECT

The purpose of this study was to determine the effects of diazoxide on apoptosis and the relative mechanisms in a model of brain injury induced by cerebral ischemia/reperfusion (I/R) during deep hypothermia.

METHODS

Three-week-old Sprague-Dawley male rats were randomly and equitably divided into sham-operated group, placebo-treated group and diazoxide-treated group respectively. Specific examination of the regional cerebral blood flow (rCBF) was measured in the three groups continuously during the operation by laser Doppler flowmetry. Terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) was showed DNA fragmentation. The mRNA expressions of cytochrome c and full-length caspase-3 were determined by RT-PCR, while the protein expressions of cytochrome c and cleaved caspase-3 were determined by immunohistochemistry at 1 h, 6 h, 24 h, 72 h and 7 days after I/R, respectively. Cytosolic release of cytochrome c at 24 h after I/R was also confirmed by Western blot.

RESULTS

rCBF was significantly decreased in both of placebo-treated and diazoxide-treated group just after ischemia in the time interval 0-5 min, and had no obvious changes in all the time intervals during the operation. Diazoxide preconditioning significantly decreased the percentage of TUNEL-positive staining cells. The mRNA expressions of cytochrome c and full-length caspase-3 in diazoxide-treated group were significantly decreased. In addition, diazoxide provided a significant reduction in the protein expressions of cytochrome c and cleaved caspase-3.

CONCLUSION

These results suggested that the neuroprotective effects of diazoxide against cerebral I/R injury during deep hypothermia correlated with the reduction of DNA fragmentation, prevention of mitochondrial cytochrome c release and inhibition of caspase-3 activation.

Initial experience of an arterial shunt for bilateral antegrade cerebral perfusion during hypothermic circulatory arrest

PURPOSE

The purpose of this study is to describe an intravessel cerebral shunt that allows perfusion of both cerebral hemispheres through the axillary artery.

DESCRIPTION

The cerebral shunt is a 10-cm to 12-cm long cannula with a lumen for blood perfusion and two balloons, one at each distal end. The proximal balloon is adapted for retaining the proximal end of the catheter in the innominate artery; the second inflatable balloon is adapted for retaining the distal end of the catheter into the left common carotid artery.

EVALUATION

Three consecutive patients received bilateral brain perfusion through the right axillary artery with the use of this cerebral shunt.

CONCLUSIONS

The cerebral shunt allowed bilateral cerebral perfusion as verified with cerebral oximetry in the absence of any evident neurologic dysfunction.

Advances in thoracic aortic surgery: arch replacement with axillary cannulation and thoracic stent grafts

During the past decade, significant advances in thoracic surgery have contributed to a decrease in the morbidity and mortality linked to surgery of the thoracic aorta. Drawing from the experiences at the Quebec Heart Institute, the present article focuses on the improvements in surgery of the aortic arch, mainly the use of the 'arch-first technique' and arterial cannulation through the right axillary artery. Furthermore, advances in the treatment of diseases of the descending aorta using thoracic stent grafts are delineated. The importance of establishing dedicated multidisciplinary teams and follow-up clinics to ensure good outcomes in the treatment of these complex diseases is stressed.

Bench to bedside strategies for optimizing neuroprotection following perinatal hypoxia-ischaemia in high and low resource settings

BACKGROUND

Therapeutic hypothermia gathers impetus in the developed world as a safe and effective therapy for term asphyxial encephalopathy. Although many questions still remain about the optimal application of hypothermic neuroprotection it is difficult to ignore the developing world where the prevalence of asphyxial encephalopathy is much higher. Experimental studies to optimize high tech cooling need to run in parallel with trials to determine the possible benefits of therapeutic hypothermia in low resource settings.

METHODS

We used a validated newborn piglet model of transient HI to determine (i) whether optimal neuroprotection occurs at different temperatures in the cortical and deep grey matter; (ii) the effect of body size on regional brain temperature under normothermia and hypothermia; (iii) the effect of insult severity on the therapeutic window duration; (iv) whether cooling using a water bottle is feasible. In this model hypoxia-ischaemia is induced by reversible occlusion of the common carotid arteries by remotely controlled vascular occluders and simultaneous reduction in the inspired oxygen fraction to 0.12. Intensive care can be administered to the piglet maintaining metabolic and physiological homeostasis throughout the experiment, and cerebral energy metabolism is monitored continuously providing quantitative measures of the HI insult, latent phase and secondary energy failure using phosphorus-31 ((31)P) magnetic resonance spectroscopy (MRS).

RESULTS

(i) The optimal temperature for cooling was lower in the cortex than deep grey matter. (ii) Cerebral temperatures were body-weight dependent: a smaller body weight led to a lower brain temperature especially with selective head cooling. (iii) Latent-phase duration is inversely related to insult severity. (iv) Low tech, simple cooling methods using a water bottle can induce and maintain moderate hypothermia.

CONCLUSIONS

Small shifts in brain temperature critically influence the survival of neuronal cells and body size critically influences brain-temperature gradients - smaller subjects have a larger surface area to brain volume and hence more heat is lost. The clinical implication is that smaller infants may require higher cap or body temperatures to avoid detrimental effects of over-zealous cooling. Latent-phase brevity may explain less effective neuroprotection following severe HI in some clinical studies. "Tailored" treatments which take into account individual and regional characteristics may increase the effectiveness of therapeutic hypothermia in the developed world. Low tech cooling methods using water bottles may be feasible although adequate staffing and monitoring would be required.

Exsanguination cardiac arrest in rats treated by 60min, but not 75min, emergency preservation and delayed resuscitation is associated with intact outcome

Emergency preservation and resuscitation (EPR) is a new approach for resuscitation of exsanguination cardiac arrest (CA) victims to buy time for surgical hemostasis. EPR uses a cold aortic flush to induce deep hypothermic preservation, followed by resuscitation with cardiopulmonary bypass (CPB). We previously reported that 20 min of EPR was feasible with intact outcome. In this report, we tested the limits for EPR in rats. Adult male isoflurane-anesthetized rats were subjected to rapid hemorrhage (12.5 ml over 5 min), followed by esmolol/KCl-induced CA and 1 min of no-flow. EPR was then induced by perfusion with 270 ml of ice-cold Plasma-Lyte to decrease body temperature to 15 degrees C. After 60 min (n=7) or 75 min (n=7) of EPR, resuscitation was attempted with CPB over 60 min, blood transfusion, correction of acid-base balance and electrolyte disturbances, and mechanical ventilation for 2h. Survival, overall performance category (OPC: 1=normal, 5=death), neurological deficit score (NDS), and histological damage score (HDS) were assessed in survivors on day 3. While all rats after 60 min EPR survived, only two out of seven rats after 75 min EPR survived (p<0.05). All rats after 60 min EPR achieved OPC 1 and normal NDS by day 3. Survivors after 75 min EPR achieved best OPC 3 (p<0.05 vs. 60 min EPR). HDS of either brain or individual viscera was not statistically different after 60 versus 75 min EPR, except for kidneys (0+/-0 vs. 1.9+/-1.3, respectively; p<0.05), with a strong trend toward greater injury in all extracerebral organs in the 75-min EPR group (p<0.06). Histological findings were dominated by cardiac lesions observed in both groups and acute renal tubular and liver necrosis in the 75-min EPR group. In conclusion, we have shown that 60 min of EPR after exsanguination CA is associated with survival and favorable neurological outcome, while 75 min of EPR results in significant mortality and neurological damage in survivors. Surprisingly, extracerebral lesions predominated at 75-min EPR group. This model should serve as a screening model both for testing new pharmacological adjuncts to improve survival after exsanguination CA, and for elucidating the underlying mechanisms of ischemia/reperfusion injury.

Hypothermia for neuroprotection after cardiac arrest: mechanisms, clinical trials and patient care

Therapeutic hypothermia is a proven part of cardio-cerebral resuscitation after cardiac arrest as it improves neurologic outcomes after hypoxic brain injury. This article reviews the mechanisms of hypothermic neuroprotection, the clinical trials that support its use after cardiac arrest, as well as the impact of hypothermia on patient management and prognosis. In caring for patients suffering hypoxic brain injury after cardiac arrest, the role of the neurologist is no longer limited to prognosis but is now to become actively involved in clinical management which includes the use of therapeutic hypothermia.

Antegrade selective cerebral perfusion in thoracic aorta surgery: safety of moderate hypothermia

OBJECTIVE

Although antegrade selective cerebral perfusion (ASCP) has been demonstrated to be the best method of protection of brain ischemia during aortic arch surgery, there is no consensus regarding optimal temperature during ASCP. The study analyzed the outcomes of aortic surgery using ASCP at different degree of systemic hypothermia.

METHODS

Between November 1996 and November 2005, 305 patients underwent thoracic aorta surgery using ASCP. Patients were divided into two groups according to the lowest systemic temperature: moderate systemic hypothermia (> or =25 degrees C) was used in 189 patients (group A), and a deeper hypothermia (<25 degrees C) in 116 patients (group B). One hundred and five patients suffered from acute type A aortic dissection.

RESULTS

The extension of aortic replacement was significantly larger in group A, while the average ASCP time was not different between groups (63+/-37.7min group A, 58.6+/-35.6min group B; p=0.314). The 30-day mortality rate was 12.7% in group A and 13.8% in group B (p=0.862). Permanent neurologic deficits occurred in eight patients (2.6%) without significant differences between groups (3.1% group A vs 1.7% group B; p=0.715). Twenty-five patients (8.2%) suffered from temporary neurologic dysfunction (7.9% group A vs 8.6% group B; p=0.833).

CONCLUSIONS

In our experience, ASCP was a safe technique for thoracic aorta surgery allowing complex aortic repairs to be performed with good results in terms of hospital mortality and neurologic outcomes. The fact that there was no difference between the two groups suggests that moderate systemic hypothermia (26 degrees C) appears to be a safe and sufficient tool for brain protection. Moreover, the well known hypothermia-related side effects may be avoided.

Effect of profound hypothermia during circulatory arrest on neurologic injury and apoptotic repressor protein Bcl-2 expression in an acute porcine model

OBJECTIVES

We reported that the neocortex and hippocampus are selectively vulnerable to injury in an acute porcine model of hypothermic circulatory arrest at 18 degrees C. We hypothesize that further cooling to 10 degrees C could reduce neurologic injury in these regions. To further elucidate the mechanisms of neurologic injury and protection, we assessed the expression of the anti-apoptotic protein Bcl-2.

METHODS

Twelve piglets underwent 75 minutes of hypothermic circulatory arrest at 18 degrees C (n = 6) and 10 degrees C (n = 6). After gradual rewarming and reperfusion, animals were put to death and brains were perfusion-fixed and cryopreserved. Regional patterns of neuronal apoptosis after hypothermic circulatory arrest were characterized by in situ DNA fragmentation with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) histochemistry. Bcl-2 protein expression was characterized with immunohistochemistry. Statistical comparisons were made by t test, analysis of variance, and Mann-Whitney U test, as appropriate.

RESULTS

Concentrations of TUNEL(+) cells were significantly lower after profound hypothermia at 10 degrees C compared with 18 degrees C hypothermia in the sensory and motor neocortex and hippocampus (t test, P < .0001; P < .006; P < .006, respectively). Positive Bcl-2 immunostaining was observed only in the motor and sensory neocortex and hippocampus after 18 degrees C hypothermic circulatory arrest. Profound cooling to 10 degrees C resulted in a significant increase in Bcl-2 immunostaining in the motor and sensory cortex as compared with 18 degrees C (Mann-Whitney U test, P < .05).

CONCLUSIONS

Deep hypothermia at 10 degrees C protects the neocortex and hippocampus from insult during hypothermic circulatory arrest as suggested by significantly reduced TUNEL(+) staining in these areas. Although a concomitant increase in Bcl-2 expression was observed in the neocortex at 10 degrees C, it remains unclear whether profound hypothermia deters from neuronal injury by activation of the anti-apoptotic protein Bcl-2.

The safety of moderate hypothermic lower body circulatory arrest with selective cerebral perfusion: A propensity score analysis

OBJECTIVE

There is no common guideline on what temperature should be achieved at the lower body circulatory arrest followed by the initiation of selective cerebral perfusion.

METHODS

Between October 1999 and August 2005, a total of 377 patients underwent repair of the aortic arch with selective cerebral perfusion and hypothermic circulatory arrest at 20 degrees C to 28 degrees C and were divided into two groups: (1) 125 patients with deep lower body circulatory arrest at 20 degrees C to 24.9 degrees C (deep lower body circulatory arrest group) and (2) 252 patients with moderate lower body circulatory arrest at 25 degrees C to 28 degrees C (moderate lower body circulatory arrest group). To compensate for the differences in patient characteristics, we used a propensity score matching analysis, and comparable patients, 92 patients from each group, were identified for final analysis.

RESULTS

There were no significant differences in mortality or morbidity between deep and moderate lower body circulatory arrest, in either the entire study cohort or the propensity-matched cohort. C-reactive protein level 1 day after the operation approached but fell short of significance (108.4 +/- 47.7 mg/L in deep lower body circulatory arrest group and 95.8 +/- 44.2 mg/L in moderate lower body circulatory arrest group, P = .07). The mean temperatures at the initiation of lower body circulatory arrest were 24.1 degrees C +/- 2.2 degrees C in patients who underwent reexploration for bleeding and 24.9 degrees C +/- 1.8 degrees C in patients who did not (P = .025); the difference also reached statistical significance in multivariate analysis (P = .046, odds ratio 0.796).

CONCLUSIONS

Our results suggest that moderate lower body circulatory arrest can be safely performed for aortic arch repair. In fact, postoperative inflammatory response tended to be lower in patients with moderate lower body circulatory arrest than those with deep lower body circulatory arrest, and deep lower body circulatory arrest was a strong risk factor for reexploration for bleeding.

Assessment of Cerebral Oxygen Balance During Deep Hypothermic Circulatory Arrest by Continuous Jugular Bulb Venous Saturation and Near-Infrared Spectroscopy

OBJECTIVE

The purpose of this study was to compare jugular venous bulb saturation (SjvO(2)) and regional cerebral oximetry (rSO(2)) by near-infrared spectroscopy (NIRS) during procedures with deep hypothermic circulatory arrest (DHCA).

DESIGN

Prospective observational study.

SETTING

Academic hospital.

PARTICIPANTS

Patients undergoing aortic reconstructive surgery with DHCA from July 2001 to January 2005.

INTERVENTION

The authors examined cerebral oxygenation by continuous NIRS monitoring and by blood gas analysis of intermittently sampled jugular bulb blood (SjvO(2)). Data were obtained during various stages of the procedure in 29 patients. NIRS measurements were compared with SjvO(2).

MEASUREMENTS AND MAIN RESULTS

NIRS and SjvO(2) trends were similar. Overall, cerebral venous oxygen saturation obtained from NIRS was lower compared with SjvO(2) (p < 0.05), especially during periods of low temperature. The mean correlation between NIRS and SjvO(2) was 0.363, and the individual correlations varied from -0.11 to 0.91. The low mean correlation was because of a high degree of variability in the NIRS data between patients.

CONCLUSION

It was concluded that NIRS does not closely correlate with SjvO(2) in this patient population. Cerebral oximetry measured by NIRS could not replace jugular bulb saturation as an intraoperative marker of adequate metabolic suppression.

Specific bypass conditions determine safe minimum flow rate

BACKGROUND

The purpose of this study is to define a safe minimum flow rate for specific bypass conditions using continuous monitoring with near-infrared spectroscopy and direct observation of the cerebral microcirculation.

METHODS

Two series of experiments (n = 72 in each) were conducted in which piglets were cooled to a temperature of 15 degrees, 25 degrees, or 34 degrees C on cardiopulmonary bypass with hematocrit 20% or 30%, pH-stat management in all, followed by 1 or 2 hours of reduced flow (10, 25, or 50 mL.kg(-1).min(-1)). Animals in series one had a cranial window placed over the parietal cortex to evaluate the microcirculation with intravital microscopy. Plasma was labeled with fluorescein-isothiocyanate-dextran for assessment of functional capillary density (FCD) and microvascular diameter. In series two, near-infrared spectroscopy was utilized to detect tissue oxygenation index (TOI). Outcome measures included histologic and neurologic injury scores.

RESULTS

The TOI during low flow and FCD during rewarming and after weaning from cardiopulmonary bypass were associated with neurologic injury. Failure of FCD to return to baseline during rewarming predicted worse functional and histologic outcome (p < 0.001). Regression analysis indicated that temperature and low-flow rate were multivariable predictors of TOI and FCD during rewarming (p < 0.001).

CONCLUSIONS

Tissue oxygen index derived from near-infrared spectroscopy is a useful real-time monitor for detecting inadequate cerebral perfusion during cardiopulmonary bypass. Minimal safe pump flow rate varies according to the conditions of bypass: using pH stat management and with an hematocrit of either 20% or 30%, a flow rate as low as 10 mL.kg(-1).min(-1) is safe for as long as 2 hours at a temperature of 15 degrees C. However, under the same conditions at 34 degrees C, a flow rate of 10 mL.kg(-1).min(-1) is very likely to be associated with neurologic injury.

High-flow endobronchial cooled humidified air protects non-heart-beating donor rat lungs against warm ischemia

OBJECTIVE

Lungs from non-heart-beating donors for transplantation require protection against warm ischemic damage. Minimally invasive techniques are required to reduce organ damage during the warm ischemic period because invasive surgical procedures are often not feasible at this time. This study investigated the preservative effect of high-flow endobronchial cooled humidified air during warm ischemia in non-heart-beating donor rat lungs.

METHODS

Fourteen animals were divided into a Cooling group (n = 7), which received cooled air/saline spray during a 2-hour warm ischemic period, and a Control group (n = 7), which received no cooling. After ischemia the lungs were reperfused on an isolated lung perfusion apparatus.

RESULTS

Endobronchial temperatures in the Cooling and Control groups were 8 degrees C and 36 degrees C at 10 minutes, and 5 degrees C and 35 degrees C at 20 minutes, respectively (P < .0001). Lung core and surface temperatures in the Cooling group were also lower than those in the corresponding Control group (P < .0001). After reperfusion, pulmonary arterial pressure (P = .003) and peak airway pressure (P = .002) were lower in the Cooling group than in the Control group. Higher pulmonary venous PO2 (P = .02), higher adenosine triphosphate levels (P = .01), and lower wet/dry lung weight ratio (P = .003) were seen in the Cooling group compared with the Control group.

CONCLUSIONS

High-flow endobronchial cooled humidified air can decrease lung temperature and improve post-ischemic pulmonary function and adenosine triphosphate levels in non-heart-beating donor lungs.

Fructose- 1,6-Bisphosphate Supports Cerebral Energy Metabolism in Pigs after Ischemic Brain Injury Caused by Experimental Particle Embolization

BACKGROUND

Fructose-1,6-bisphosphate (FDP) is a high-energy intermediate that enhances glycolysis, preserves cellular adenosine triphosphate stores, and prevents the increase of intracellular calcium in ischemic tissue. Since it has been shown to provide metabolic support to the brain during ischemia, we planned this study to evaluate whether FDP is neuroprotective in the setting of combining hypothermic circulatory arrest (HCA) and irreversible embolic brain ischemic injury.

METHODS

Twenty pigs were randomly assigned to receive 2 intravenous infusions of either FDP (500 mg/kg) or saline. The first infusion was given just before a 25-minute period of HCA and the second infusion immediately after HCA. Immediately before HCA, the descending aorta was clamped and 200 mg of albumin-coated polystyrene microspheres (250-750 mm in diameter) were injected into the isolated aortic arch in both study groups.

RESULTS

There were no significant differences between the study groups in terms of neurological outcome. Brain lactate/pyruvate ratio was significantly lower (P = .015) and brain pyruvate levels (P = .013) were significantly higher in the FDP group compared with controls. Brain lactate levels were significantly higher 8 hours after HCA (P = .049).

CONCLUSION

The administration of FDP before and immediately after HCA combined with embolic brain ischemic injury was associated with significantly lower brain lactate/pyruvate ratio and significantly higher levels of brain pyruvate, as well as lower lactate levels 8 hours after HCA. FDP seems to protect the brain by supporting energy metabolism. The neurological outcome was not improved, most likely resulting from the irreversible nature of the microsphere occlusion.

Short Moderate Hypothermic Circulatory Arrest without Any Adjunctive Cerebral Protection for Surgical Repair of the Ascending Aorta Extending into the Proximal Aortic Arch: Is It Safe?

INTRODUCTION

We have been using only moderate hypothermic circulatory arrest (HCA) for patients with ascending aortic aneurysms extending into the proximal aortic arch if the distal anastomoses seem to be simple and easy. The aim of this study is to evaluate the early and midterm results of the use of moderate HCA without any adjunctive cerebral protection in such patients.

METHODS

Between October 2000 and March 2005, 23 patients with an age range of 39 to 77 years (mean, 59.7 +/- 12.2 years) received surgical repair of the ascending aorta extending into the proximal aortic arch using HCA without any adjunctive cerebral protection. Mean circulatory arrest time was 7.5 +/- 2.0 minutes (range, 2-13 minutes), and mean core temperature at induction of the circulatory arrest was 26.7 +/- 1.4 degrees C (range, 24-30 degrees C).

RESULTS

Operative mortality was 4.3% (1/23) due to unknown cause after successful extubation. Temporary neurological dysfunction was observed in only 1 patient (4.3%), and no persistent neurologic event was observed in any of the patients. One patient died 3 months after the operation due to a mediastinitis. No other cardiac or neurologic event was observed in the 21 surviving patients.

CONCLUSION

Our results suggest that moderate HCA at 26 degrees C to 28 degrees C without any adjunctive cerebral protection within 10 minutes is safe in selected patients.

Antegrade Cerebral Perfusion With a Simplified Technique: Unilateral Versus Bilateral Perfusion

BACKGROUND

Selective antegrade cerebral perfusion has been introduced as a strategy of cerebral protection in operations on the aortic arch with hypothermic circulatory arrest. Several techniques of unilateral and bilateral cerebral perfusion have been described with varying results.

METHODS

Patients underwent either unilateral cerebral perfusion with a cannula in the right subclavian artery or bilateral cerebral perfusion, with an additional cannula in the left carotid artery. A simplified Seldinger-type technique for subclavian artery cannulation was employed. Results were analyzed with multivariable logistic regression analysis and propensity score analysis to adjust for nonrandomized treatment assignment.

RESULTS

Of 65 patients, 17 (26%) had unilateral cerebral perfusion. Mortality was 11% (n = 7); 14% (n = 9) had a stroke. In multivariable analysis, unilateral cerebral perfusion was significantly associated with stroke (odds ratio 6.6 [1.2 to 36]). Age more than 70 years was associated with in-hospital death (odds ratio 12 [1.3 to 113]), and concomitant coronary artery bypass graft surgery was associated with adverse outcome (odds ratio 23 [1.8 to 299]). Balancing variables in a propensity score analysis, stroke remained significantly more common with unilateral brain perfusion (29% versus 0%, p = 0.045). Complications associated with subclavian artery cannulation were encountered in 1 patient (1.5%).

CONCLUSIONS

The described cannulation technique is safe and effective. Bilateral cerebral perfusion is easily achieved and is associated with decreased stroke risk, and should be the preferred brain protection strategy.

A mathematical model of intracranial pressure dynamics for brain hypothermia treatment

Brain hypothermia treatment is used as a neuroprotectant to decompress the elevated intracranial pressure (ICP) in acute neuropatients. However, a quantitative relationship between decompression and brain hypothermia is still unclear, this makes medical treatment difficult and ineffective. The objective of this paper is to develop a general mathematical model integrating hemodynamics and biothermal dynamics to enable a quantitative prediction of transient responses of elevated ICP to ambient cooling temperature. The model consists of a lumped-parameter compartmental representation of the body, and is based on two mechanisms of temperature dependence encountered in hypothermia, i.e. the van't Hoff's effect of metabolism and the Arrhenius' effect of capillary filtration. Model parameters are taken from the literature. The model is verified by comparing the simulation results to population-averaged data and clinical evidence of brain hypothermia treatment. It is possible to assign special model inputs to mimic clinical maneuvers, and to adjust model parameters to simulate pathophysiological states of intracranial hypertension. Characteristics of elevated ICP are quantitatively estimated by using linear approximation of step response with respect to ambient cooling temperature. Gain of about 4.9 mmHg degrees C(-1), dead time of about 1.0 h and a time constant of about 9.8h are estimated for the hypothermic decompression. Based on the estimated characteristics, a feedback control of elevated ICP is introduced in a simulated intracranial hypertension of vasogenic brain edema. Simulation results suggest the possibility of an automatic control of the elevated ICP in brain hypothermia treatment.

Methods of cerebral protection in surgery of the thoracic aorta

During the last decade, a considerable increase in the number of operations on the thoracic aorta has been observed. Although patient's outcomes have improved considerably, this surgery is still associated with significant morbidity and mortality due to neurological complications. Various methods have been proposed and widely used as means to protect the brain from ischemic damage. This review summarizes the principal methods of cerebral protection, describes the advantages and disadvantages of each method and their impact on patient outcomes, and discusses the different surgical techniques proposed to minimize the risk of cerebral injuries.

Depth of delayed cooling alters neuroprotection pattern after hypoxia-ischemia

Hypothermia after perinatal hypoxia-ischemia (HI) is neuroprotective; the precise brain temperature that provides optimal protection is unknown. To assess the pattern of brain injury with 3 different rectal temperatures, we randomized 42 newborn piglets: (Group i) sham-normothermia (38.5-39 degrees C); (Group ii) sham-33 degrees C; (Group iii) HI-normothermia; (Group iv) HI-35 degrees C; and (Group v) HI-33 degrees C. Groups iii through v were subjected to transient HI insult. Groups ii, iv, and v were cooled to their target rectal temperatures between 2 and 26 hours after resuscitation. Experiments were terminated at 48 hours. Compared with normothermia, hypothermia at 35 degrees C led to 25 and 39% increases in neuronal viability in cortical gray matter (GM) and deep GM, respectively (both p < 0.05); hypothermia at 33 degrees C resulted in a 55% increase in neuronal viability in cortical GM (p < 0.01) but no significant increase in neuronal viability in deep GM. Comparing hypothermia at 35 and 33 degrees C, 35 degrees C resulted in more viable neurons in deep GM, whereas 33 degrees C resulted in more viable neurons in cortical GM (both p < 0.05). These results suggest that optimal neuroprotection by delayed hypothermia may occur at different temperatures in the cortical and deep GM. To obtain maximum benefit, you may need to design patient-specific hypothermia protocols by combining systemic and selective cooling.

Hypothermic circulatory arrest is not a risk factor for neurologic morbidity in aortic surgery: A propensity score analysis

OBJECTIVE

Hypothermic circulatory arrest has been an important tool in aortic arch surgery, even though its use has recently been discussed controversially. We sought to clarify the role of hypothermic circulatory arrest as a risk factor for mortality and neurologic morbidity in aortic surgery by using a propensity score-matching analysis.

METHODS

Five hundred eleven patients (60 +/- 13 years, 349 male patients) who underwent replacement of the ascending aorta with (n = 273) or without (n = 238) arch involvement were analyzed by means of multivariate analysis. Using propensity score matching, we identified comparable patient groups: HCA(+) group and HCA(-) group (n = 110 each). For aortic arch replacement, hypothermic circulatory arrest was used with a mean duration of 14 +/- 9 minutes: 12 +/- 7 minutes or 26 +/- 8 minutes for partial or total arch replacement, respectively.

RESULTS

In the entire cohort multivariate analysis identified acute dissection and duration of cardiopulmonary bypass as significant predictors for hospital death. Predictors for stroke were acute dissection, diabetes mellitus, peripheral arterial disease, and concomitant mitral valve surgery, and predictors for temporary neurologic dysfunction were peripheral arterial disease and age. After propensity score matching, the incidence of death (HCA[+]: 0.9% vs HCA[-]: 2.7%), stroke (0% vs 1.8%, respectively), and temporary neurologic dysfunction (15.5% vs 13.6%, respectively) was comparable between the 2 groups. Multivariate analysis identified age, diabetes mellitus, peripheral arterial disease, and concomitant coronary artery bypass grafting as the independent risk factors for temporary neurologic dysfunction.

CONCLUSIONS

In a standard clinical setting (hypothermic circulatory arrest of <30 minutes and nasopharyngeal temperature of <20 degrees C), hypothermic circulatory arrest constitutes no significant risk for mortality or neurologic morbidity and thus appears clinically safe. Patient-related risk factors primarily determine clinical outcome.

Operative Management of Ascending Aortic Dissections

Surgical management has been the established standard of care for acute ascending aortic dissection (Stanford type A or Debakey type I or II) with a worldwide average operative mortality rate of 23% compared with a 1-month mortality rate of 60% with medical management alone. Improving an institution's operative results depends on the establishment of a comprehensive and specialized team integrating their expertise into a protocol-driven system of care delivery specific for aortic dissections. The operative strategies and techniques for repairing aortic dissections should also be standardized within an institution to optimize outcomes. The primary goals of operative repair of ascending aortic dissection are to restore aortic valvular competency and systemic perfusion, to obliterate false-lumen blood flow, and to prevent rupture, myocardial infarction, stroke, and death. The goals, strategies, and expected outcomes for the operative management of acute ascending aortic dissection are presented.

Ischemic preconditioning or heat shock pretreatment ameliorates neuronal apoptosis following hypothermic circulatory arrest

OBJECTIVE

Hypothermic circulatory arrest has been widely used in complex cardiac and aortic surgery. Stroke and/or neurologic injury can occur after prolonged hypothermic circulatory arrest, possibly due to apoptosis. Ischemic preconditioning has been widely used as a neuroprotective tool, but its application in neuronal injury under hypothermic circulatory arrest has never been studied.

METHODS

Forty male New Zealand white rabbits were placed on closed-chest cardiopulmonary bypass, subjected to hypothermic circulatory arrest, and rewarmed to normothermia. Experimental groups were treated with heat shock or ischemic preconditioning before hypothermic circulatory arrest. Hippocampal CA1 neurons were analyzed histopathologically. Apoptosis was confirmed by TUNEL assay and Western blot analysis, and serum S-100beta levels, c-Fos and Bcl-2 antibodies, and caspase-3 and heat shock protein 70 levels were measured.

RESULTS

After 2-hour hypothermic circulatory arrest and 4-hour reperfusion, apoptosis was observed in hippocampal CA1 neurons with elevation of serum S-100beta levels, which could be ameliorated by ischemic preconditioning or heat shock manipulations. TUNEL-positive nuclear expression of caspase-3 increased after hypothermic circulatory arrest (3.08% +/- 0.71%, P <.001) and was diminished with ischemic preconditioning (1.61% +/- 0.42%) and heat shock (1.72% +/- 0.38%) manipulations. Ischemic preconditioning or heat shock manipulations produced diverse patterns of heat shock protein 70, c-Fos, and Bcl-2 protein expression, suggesting that these manipulations provide neuroprotection via different pathways.

CONCLUSIONS

Ischemic preconditioning and heat shock can attenuate hippocampal CA1 neuronal apoptosis after prolonged hypothermic circulatory arrest under cardiopulmonary bypass. The expression of heat shock protein 70 may not play a major role in the first window of ischemic preconditioning-induced neuroprotection.

Interaction of temperature with hematocrit level and pH determines safe duration of hypothermic circulatory arrest

OBJECTIVE

Previous studies have demonstrated that both hematocrit level and pH influence the protection afforded by deep hypothermic circulatory arrest. The current study examines how temperature modulates the effect of hematocrit level and pH in determining a safe duration of circulatory arrest. The study also builds on previous work investigating the utility of near-infrared spectroscopy as a real-time monitor of cerebral protection during circulatory arrest.

METHODS

Seventy-six piglets (9.3 +/- 1.2 kg) underwent circulatory arrest under varying conditions with continuous monitoring by means of near-infrared spectroscopy (hematocrit level of 20% or 30%; pH-stat or alpha-stat strategy; temperature of 15 degrees C or 25 degrees C; arrest time of 60, 80, or 100 minutes). Neurologic recovery was evaluated daily by a veterinarian, and the brain was fixed in situ on postoperative day 4 to be examined on the basis of histologic score in a blinded fashion.

RESULTS

Multivariable analysis of total histologic score revealed that higher temperature, lower hematocrit level, more alkaline pH, and longer hypothermic circulatory arrest duration were predictive of more severe damage to the brain (P <.01). Regression modeling revealed that higher temperature exacerbated the disadvantage of a lower hematocrit level and longer arrest times but not pH strategy. Normalized oxyhemoglobin nadir time, derived from near-infrared spectroscopy, was positively correlated with neurologic recovery on the fourth postoperative day and with total histologic injury score (P <.0001).

CONCLUSION

Hematocrit level and pH, as well as temperature, determine the safe duration of hypothermic circulatory arrest. Near-infrared spectroscopy is a useful real-time monitor of safe duration of circulatory arrest.

Partial Clamping of the Brachiocephalic Trunk for Total Ascending Aorta Replacement without Circulatory Arrest: Early and Midterm Results

BACKGROUND

The aim of this study was to evaluate in elective patients the early and midterm results of partial clamping of the brachiocephalic trunk (BCT) for total ascending aorta replacement (TAAR) without circulatory arrest. Contraindications to the procedure were BCT/aortic arch calcifications and chronic aortic dissection.

METHODS

The right radial artery was cannulated to monitor the systemic pressure after the BCT was partially clamped. A specially designed clamp was applied obliquely to occlude approximately 50% of the BCT and part of the aortic arch. The distal tip of the clamp was positioned in front of the left subclavian artery. From January 2002 to October 2003, 92 patients underwent TAAR. In 62 patients (67.4%), partial clamping of the BCT was used. Twenty of these patients underwent isolated TAAR, 27 underwent aortic valve replacement and TAAR, 11 had a Bentall operation, and 2 had a Cabrol operation. The aortic valve was spared in the remaining 2 patients. The mean (+/- SD) aortic cross-clamping and cardiopulmonary bypass times were 96 +/- 31 minutes and 116 +/- 43 minutes, respectively.

RESULTS

Early mortality was 1.6% (1 patient). No cerebrovascular accidents occurred, demonstrating the safety of the technique. The major complications were acute respiratory insufficiency in 2 cases and acute renal failure in 5. The mean follow-up time was 9.0 +/- 6.5 months. The mean 18- month and event-free survival rate was 96.6% +/- 0.9%.

CONCLUSION

Partial clamping of the BCT for TAAR without circulatory arrest provides good early and midterm clinical results. Aortic arch clamping is not associated with cerebrovascular accidents.

Technical advances in total aortic arch replacement

BACKGROUND

We compared the effects of using hypothermic circulatory arrest (HCA) alone, HCA combined with selective cerebral perfusion (SCP), and use of SCP with a trifurcated graft (T) on outcome after aortic arch repair.

METHODS

One hundred fifty patients, median age 66 years (range, 27 to 85), underwent total arch replacement between 1988 and 2002; 75 were female. We retrospectively compared the results of three patient groups roughly comparable with regard to preoperative risk factors: 45 patients using HCA beginning in 1988; 67 patients using HCA/SCP beginning in 1994; and 38 patients utilizing a trifurcated arch graft in conjunction with SCP through the axillary artery (HCA/SCP/T) since 2000. The groups were well matched with regard to median age (66, 68, and 66 years), urgency (emergent 11%, 13%, 5%; urgent 24%, 9%, 18%; and elective 64%, 78%, 76%), and several other known risk factors (p = not significant).

RESULTS

An adverse outcome-hospital death or permanent stroke-occurred in 14%: in 16% with HCA, in 16% with HCA/SCP, and in 8% with HCA/SCP/T. Transient neurologic dysfunction among patients surviving without stroke was lower with HCA/SCP/T (11%) than with HCA (33%) or HCA/SCP (17%). Mean duration of HCA was 52 +/- 16 minutes with HCA alone versus 45 +/- 10 minutes with HCA/SCP and 31 +/- 7 minutes with HCA/SCP/T (p < 0.0001 for groups HCA and HCA/SCP combined versus HCA/SCP/T). Mean duration of SCP was 57 +/- 25 minutes with HCA/SCP versus 62 +/- 24 minutes with HCA/SCP/T (p = not significant). Comparison of the groups of patients who had comparable preoperative risk factors for adverse outcome showed a trend toward lower adverse outcome and transient neurologic dysfunction rates using HCA/SCP/T; a significant reduction in respiratory (p < 0.001), infectious (p = 0.015) and cardiac (p = 0.005) complications in HCA/SCP/T compared with the earlier groups; and significantly shorter durations of intensive care (p < 0.0001) and hospitalization (p = 0.004).

CONCLUSIONS

Our results suggest that HCA/SCP is superior to HCA alone for preventing cerebral injury during operations on the aortic arch. By further reducing embolic risk as well as duration of HCA, HCA/SCP/T with axillary artery cannulation may be the optimal technique for averting adverse outcomes, reducing complications, and shortening hospital stay after aortic arch repair.

Diabetes and evidence of atherosclerosis are major risk factors for adverse outcome after elective thoracic aortic surgery

BACKGROUND

To predict risk after elective repair of ascending aorta and aortic arch aneurysms, we studied 464 consecutive patients.

METHODS

Adverse outcome (stroke or hospital death) was analyzed in 372 patients who underwent proximal repair and 92 patients who underwent aortic arch replacement from 1986 to the present. Preoperative risk factors with a P value less than.2 in a univariate analysis were entered into a multivariate model, and an equation incorporating independent risk factors was derived separately for proximal aorta and arch surgery.

RESULTS

Age more than 65 years (P =.04), diabetes (P =.02), cause (P =.01), and prolonged total cerebral protection time (duration of hypothermic circulatory arrest and selective cerebral perfusion, P =.001) were significant univariate risk factors for elective proximal aortic repair. Diabetes (P =.005, odds ratio 5.1), atherosclerosis (P =.003, odds ratio 4.0), and dissection (P =.048, odds ratio 2.5) were independent factors. For elective arch surgery, female sex (P =.07), age more than 65 years (P =.04), coronary artery disease (P =.02), diabetes (P =.06), cause (P =.07), and prolonged total cerebral protection time (P =.025) were univariate risk factors. Female sex (P =.05, odds ratio 4.7), coronary artery disease (P =.02, odds ratio 6.5), diabetes (P =.13, odds ratio 4.0), and total cerebral protection time (P =.03, odds ratio 1.02/min) were independent factors. To calculate risk of adverse outcome (P), enter 1 if factor is present, 0 if absent, and estimate total cerebral protection time (in minutes). [equation: see text].

CONCLUSION

In this large series of patients, the presence of diabetes and manifestations of atherosclerosis emerge as extremely important risk factors for adverse outcome after ascending aorta or arch surgery, displacing age. Multivariate equations derived from these data allow more precise calculation of risk for each individual contemplating elective surgery.

The incidence of transient neurologic dysfunction after ascending aortic replacement with circulatory arrest

BACKGROUND

Transient neurologic dysfunction (TND) namely postoperative confusion, delirium, and agitation after aortic operation, particularly after deep hypothermic circulatory arrest (DHCA), remains an underestimated adverse event in the early outcome of these patients. Although no influence on long-term outcome has been reported so far, this entity markedly affects the early outcome and leads to prolonged intensive care unit and hospital stay.

METHODS

Between January 1997 and January 2003, 160 consecutive patients (130 type A dissections [81%] and 30 elective atherosclerotic aneurysms [19%]) had surgical repair with DHCA for a thoracic aortic aneurysm limited to the ascending aorta. From those, 40 patients (25%) underwent DHCA alone, whereas in 13 patients (8%) antegrade cerebral perfusion and in 103 patients (64%) retrograde cerebral perfusion was used for further brain protection.

RESULTS

The overall incidence of TND was 18% (28 of 160) with a significant association between duration of circulatory arrest and the incidence of TND (13.8% in DHCA < 30 minutes versus 37.9% in DHCA > 40 minutes; p < 0.05). Furthermore the severity of TND was directly associated with the duration of circulatory arrest and age. In contrast, however, the use of retrograde cerebral perfusion had no influence on the incidence of TND, (p < 0.05). Intensive care unit stay as well as hospital stay were prolonged in the patients with TND (intensive care unit 14.3 +/- 14.2 days versus 10.8 +/- 13.7 days, p < 0.05; hospital stay 15.6 +/- 10.1 days versus 11.4 +/- 7.9 days, p < 0.05).

CONCLUSIONS

Duration of DHCA, regardless of whether retrograde cerebral perfusion was used, was the most important predictor of the incidence of transient neurologic dysfunction in patients who had replacement of the ascending thoracic aorta. The occurrence of TND leads to impaired functional recovery as well as prolonged intensive care unit and hospital stay.

Bispectral index in a 3-year old undergoing deep hypothermia and circulatory arrest

We report a 3-year-old girl who presented with Scimitar syndrome and underwent hypothermic circulatory arrest for correction of anomalous pulmonary veins and an atrial septal defect. In this case the Bispectral Index (BIS) correlated significantly with the gradual onset of hypothermia and circulatory arrest. However, BIS remained low during the rewarming phase of cardiopulmonary bypass, in spite of adequate pump flows and stable haemodynamics. We postulate that this significant lag in BIS during the rewarming phase of deep hypothermic circulatory arrest may represent neuronal bewilderment or perhaps stunning, and differs from previous studies that show significant increase in BIS during rewarming from mild hypothermia.

Resuscitating hypothermic dogs after 2 hours of circulatory arrest below 6 degrees C

BACKGROUND

Ultraprofound hypothermia may have a place in trauma rescue and resuscitation. We describe resuscitation of dogs after asanguineous perfusion and circulatory arrest of 2 hours at 2 degrees to 4 degrees C.

METHODS

Nine dogs were cooled using a bypass apparatus and their circulating blood replaced with bicarbonated Hextend (Abbott, North Chicago, IL). Perfusion was continued to 2 degrees to 4 degrees C, and 60 mL of 2 mol/L KCl and 20 mL of 50% MgSO(4).7H(2)O were infused intra-arterially, and circulation was arrested for 2 hours. The dogs were then rewarmed, transfused, defibrillated, weaned from bypass, and allowed to awaken. Preoperative and postoperative biochemistry and hematology were compared.

RESULTS

Six dogs recovered fully. One of these dogs died of an infection 2 weeks later. Three other dogs never recovered because of technical or procedural difficulties. Biochemical and hematologic parameters were normal by 3 weeks.

CONCLUSION

Hypothermic blood substitution with Hextend allows resuscitation after 2 hours of ice-cold circulatory arrest in dogs.

Deep hypothermic circulatory arrest and antegrade selective cerebral perfusion during ascending aorta-hemiarch replacement: a retrospective comparative study

OBJECTIVE

We sought to compare the results of ascending aorta-hemiarch replacement by using 2 different methods of cerebral protection in terms of hospital mortality, neurologic outcome, and systemic morbidity and to determine predictive risk factors associated with hospital mortality and neurologic outcome after ascending aorta-hemiarch replacement.

METHODS

Between January 1995 and September 2001, 289 patients (mean age, 62.2 +/- 13.2 years; urgent status, 122/289 [42.2%]) underwent ascending aorta-hemiarch replacement with the aid of antegrade selective cerebral perfusion (161 patients) or deep hypothermic circulatory arrest (128 patients).

RESULTS

Overall hospital mortality was 11.4% (deep hypothermic circulatory arrest group, 13.3%; antegrade selective cerebral perfusion group, 9.9%; P =.375). A logistic regression analysis revealed acute type A dissection (P =.001; odds ratio, 4.3) and age of greater than 70 years (P =.019; odds ratio, 2.5) to be independent predictors of hospital mortality. The permanent neurologic dysfunction rate was 9.3% (deep hypothermic circulatory arrest group, 12.5%; antegrade selective cerebral perfusion group, 7.6%; P =.075). Logistic regression analysis revealed acute type A dissection (P =.001; odds ratio, 6.7) and history of cerebral infarction-transient ischemic attack (P =.038; odds ratio, 3.4) to be independent predictors of permanent neurologic dysfunction. The transient neurologic dysfunction rate was 8.0% (deep hypothermic circulatory arrest group, 7.1%; antegrade selective cerebral perfusion group, 8.7%; P =.530). Acute type A dissection (P =.001; odds ratio, 5.1) was indicated as an independent predictor of transient neurologic dysfunction by means of logistic regression. Renal dysfunction (postoperative creatinine level of >250 micromol/L; deep hypothermic circulatory arrest, 10 [7.8%]; antegrade selective cerebral perfusion, 6 [3.7%]; P =.030), as well as prolonged intubation time (deep hypothermic circulatory arrest, 3.8 +/- 6.3 days; antegrade selective cerebral perfusion, 2.2 +/- 2.5 days; P =.005) were more common in the deep hypothermic circulatory arrest group.

CONCLUSION

The use of antegrade selective cerebral perfusion and deep hypothermic circulatory arrest during ascending aorta-hemiarch replacement resulted in acceptable hospital mortality and neurologic outcome. Reduced postoperative intubation time and better renal function preservation were observed in the antegrade selective cerebral perfusion group.

Surgery for acute type A dissection using antegrade selective cerebral perfusion: experience with 122 patients

BACKGROUND

Antegrade selective cerebral perfusion (ASCP) has proved to be a reliable method of brain protection during surgery of the thoracic aorta, but its use during aortic dissection surgery still remains controversial. In this study, we present our results after the operative repair of acute type A aortic dissections using ASCP and moderate hypothermic circulatory arrest.

METHODS

Between October 1995 and August 2001, 122 patients (76 men, 46 women) underwent repair of acute type A aortic dissection with the aid of ASCP and open distal anastomosis. The average age of the patients was 61 +/- 12 (mean +/- standard deviation). Preoperative complications included cardiac tamponade (n = 34; 27.0%), aortic regurgitation (n = 27; 22.1%), and new neurological deficits (n = 11; 9%).

RESULTS

Stepwise logistic regression revealed preoperative cardiac tamponade (p = 0.018) and new neurological deficits (p = 0.017) to be independent determinants for hospital mortality (19.7%). Permanent neurological complications occurred in 7% of the patients. Independent risk factors for temporary neurological dysfunction (11.2%) included cardiac tamponade (p = 0.019) and preoperative neurological deficits (p = 0.000).

CONCLUSIONS

In our experience, the surgical treatment of acute type A aortic dissection with the aid of ASCP was associated with acceptable hospital mortality and neurologic morbidity rates.

Antegrade selective cerebral perfusion during operations on the thoracic aorta: factors influencing survival and neurologic outcome in 413 patients

OBJECTIVE

We retrospectively analyzed hospital mortality and neurologic outcome after operations on the thoracic aorta with the aid of antegrade selective cerebral perfusion to determine a predictive risk model.

METHODS

Between October 1995 and May 2001, 413 patients (mean age, 63.0 +/- 11.5 years) underwent operations on the thoracic aorta with antegrade selective cerebral perfusion. Indications for surgical intervention were acute type A dissection in 116 (28.1%) patients, degenerative aneurysm in 227 (55.0%) patients, and postdissection aneurysm in 70 (16.9%) patients. One hundred twenty-five (30.3%) patients were operated on urgently; concomitant procedures were performed in 171 (41.4%) patients. Mean cerebral perfusion time was 63.0 +/- 38.7 minutes (range, 16-220 minutes). Preoperative and intraoperative factors were evaluated by means of univariate and multivariate analysis to identify predictors of hospital mortality and neurologic outcome.

RESULTS

The hospital mortality was 9.4%. Stepwise logistic regression revealed urgency status (P =.000; odds ratio, 19.9) and recent history of a recent central neurologic event (P =.004; odds ratio, 8.0) to be independent determinants for hospital mortality. Temporary neurologic dysfunction occurred in 20 (5.1%) patients. Urgency status (P =.005; odds ratio, 7.5), history of a central neurologic event (P =.003; odds ratio, 8.6), and coronary artery bypass grafting (P =.019; odds ratio, 6.0) were independent determinants of temporary neurologic dysfunction. Urgency status (P =.003; odds ratio, 8.6) was the only independent determinant for permanent neurologic dysfunction, and it occurred in 15 (3.7%) patients.

CONCLUSION

Antegrade selective cerebral perfusion is an effective method of brain protection. Cerebral perfusion times of longer than 90 minutes were not associated with an increased risk of hospital mortality or poorer neurologic outcome. Urgency status and recent history of central neurologic events were retained as important risk factors for hospital mortality and neurologic outcome.

Aortic arch replacement using a trifurcated graft and selective cerebral antegrade perfusion

BACKGROUND

Aortic arch aneurysm repair remains associated with considerable mortality and risk of cerebral complications. We present results of a technique utilizing a three-branched graft for arch replacement, deep hypothermic circulatory arrest (HCA), and selective antegrade cerebral perfusion (SCP).

METHODS

Between March 2000 and November 2001, 22 patients (11 female) aged 40 to 77 years (mean 64 +/- 11.2) underwent arch replacement utilizing the trifurcated-graft technique. Serial anastomosis of the branched graft to individual cerebral vessels was carried out during HCA, followed by arch reconstruction during SCP through the graft. All 22 patients had surgery electively. Eight patients (36%) had undergone previous aortic surgery. In 19 patients, arch replacement was part of an elephant trunk procedure; 2 patients had Bentall operations and 1 had isolated arch replacement. Concomitant coronary artery bypass grafting was performed in 6 patients (27%). Mean HCA duration was 30 +/- 6 minutes at a mean temperature of 11.4 +/- 0.8 degrees C. Mean duration of SCP was 52 +/- 18 minutes.

RESULTS

Adverse outcome--death before hospital discharge or permanent stroke or both--occurred in 2 patients (9%). Two patients experienced transient neurologic dysfunction (9%). Two patients (9%) developed renal failure requiring short-term hemodialysis and pulmonary complications occurred in 2 patients.

CONCLUSIONS

Cerebral protection and prevention of atheroembolism remain challenges in aortic arch reconstruction. To reduce neurologic complications we developed an aortic arch reconstruction technique in which a trifurcated graft is anastomosed to the brachiocephalic vessels during HCA, reducing the risk of embolization while minimizing cerebral ischemia by permitting antegrade cerebral perfusion as arch repair is completed.

Increase of intracranial pressure after hypothermic circulatory arrest in a chronic porcine model

OBJECTIVE

An increase in intracranial pressure has been shown to threaten the outcome of patients with ischemic or traumatic brain injury. Its impact on the outcome of pigs undergoing hypothermic circulatory arrest has been evaluated in this study.

DESIGN

Fifty-six pigs underwent a 75-min period of hypothermic circulatory arrest at 20 degrees C. Intracranial pressure, cerebral microdialysis, hemodynamic and metabolic parameters were monitored throughout the experiment. The animals were allowed to survive until the 7th postoperative day and, then, electively killed.

RESULTS

The 7-day survival rate was 60.7%, and among survivors, 20 of them (58.8%) developed brain infarction. A significant increase in intracranial pressure as compared with the baseline level was observed since the end of cooling (p = 0.047) and the difference became larger during all the postoperative intervals (p < 0.0001). Animals that died postoperatively tended to have higher intracranial pressure levels during all the postoperative intervals, but such a difference reached significance only at the 4-h postoperative interval (p = 0.040). The same tendency was observed among animals that survived until the 7th postoperative day and that developed brain infarction or not, but the difference between these two groups did not reach statistical significance. The animals that died or developed postoperatively brain infarction had higher intracranial pressure values postoperatively as compared with those that survived without developing brain infarction and such a difference reached significance at the 2-h (p = 0.015) and 4-h postoperative intervals (p = 0.035). The peak intracranial pressure was 17.2 mmHg (IQR, 13.7-20.8) in animals that died or developed brain infarction and 14.1 mmHg (IQR, 11.8-16.4) in those that survived 7 days without developing brain infarction (p = NS).

CONCLUSION

Intracranial pressure increases significantly after 75 min of experimental hypothermic circulatory arrest and such an increase is associated with a high risk of postoperative death and brain infarction.

Effect of hypothermia on cerebral blood flow and metabolism in the pig

BACKGROUND

The pig has become an increasingly popular model for the study of cerebral protection during cardiothoracic surgery in recent years, but little information is available concerning hypothermic porcine physiology. Because the efficacy of cerebral protection depends largely upon metabolic suppression, we studied cerebral oxygen metabolism at various temperatures using two different methods to assess cerebral blood flow (CBF).

MATERIAL AND METHODS

Twelve pigs (7 to 13 kg) underwent cooling on cardiopulmonary bypass to 8 degrees C as recorded by an electrode placed deep in the parenchyma of the brain. CBF was measured in 6 animals using radioactive microspheres and in the other 6 using fluorescent microspheres. CBF, cerebral oxygen consumption, and cerebral vascular resistance were determined at 37 degrees C, 28 degrees C, 18 degrees C, and 8 degrees C.

RESULTS

Both methods produced very similar data. CBF fell steadily with decrease in temperature to 18 degrees C but failed to drop further with more profound hypothermia. With both groups combined, mean cerebral oxygen metabolism was 2.63 mL/100 g per minute at 37 degrees C. Metabolic activity was 50% of base line values at 28 degrees C, 19% at 18 degrees C, and 11% at 8 degrees C. The Q10 value in the pig--the degree of metabolic suppression achieved by a 10 degrees C drop in temperature--is 2.46 (95% confidence interval 2.1 to 2.9); this value is consistent with similar studies in humans.

CONCLUSIONS

The presence of significant residual metabolic activity at 18 degrees C suggests that this degree of hypothermia may provide incomplete cerebral protection during prolonged interruption of CBF. This study demonstrates that cooling to temperatures below 18 degrees C in the pig can achieve greater metabolic suppression although it may be associated with loss of cerebral autoregulation.

Lamotrigine plus leukocyte filtration as a neuroprotective strategy in experimental hypothermic circulatory arrest

BACKGROUND

Lamotrigine and leukocyte filtration seem to improve cerebral protection during experimental hypothermic circulatory arrest (HCA). This study was performed to evaluate whether their combined use may further improve cerebral protection.

METHODS

Twenty-four pigs undergoing 75-minute period of HCA at 20 degrees C were randomly assigned to receive saline; lamotrigine (20 mg/kg) before HCA (L); or lamotrigine (20 mg/kg) before HCA plus leukocyte filtration before and after HCA (L + LF).

RESULTS

Seven animals (87%) in the L + LF group, 4 (50%) in the L group, and 3 (37%) in the control group were alive on the seventh postoperative day. The median electroencephalogram burst recovery was 94% in the L + LF group (p = 0.024 versus control group), 81% in the L group, and 64% in the control group. Among the surviving animals, the median behavioral scores were 9, 9, and 6 at the seventh day, respectively (p = 0.005 between the L + LF group and the control group). The median histopathologic score was 14 in the L + LF group (p = 0.046 versus control group), 14.5 in the L group (p = 0.062 versus control group), and 21 in the control group.

CONCLUSIONS

Lamotrigine has neuroprotective effect during HCA. The combined use of lamotrigine and LF may further improve the survival outcome.

Involvement of apoptosis in neurological injury after hypothermic circulatory arrest: a new target for therapeutic intervention?

BACKGROUND

This study was undertaken to evaluate the role of apoptosis in neurological injury after hypothermic circulatory arrest (HCA).

METHODS

Twenty-one pigs (27 to 31 kg) underwent 90 minutes of HCA at 20 degrees C and were electively sacrificed at 6, 24, 48, and 72 hours, and at 7, 10, and 12 days after HCA, and compared with unoperated controls. In addition, 3 animals that had HCA at 10 degrees C, and 3 treated with cyclosporine A (CsA) in conjunction with HCA at 20 degrees C, were examined 72 hours after HCA. After selective perfusion and cryopreservation, all brains were examined to visualize apoptotic DNA fragmentation and chromatin condensation on the same cryosection of the hippocampus: fluorescent in situ end labeling (ISEL) was combined with staining with a nucleic acid-binding cyanine dye (YOYO).

RESULTS

In addition to apoptosis, which was seen at a significantly higher level (p = 0.05) after HCA than in controls, two other characteristic degenerative morphological cell types (not seen in controls) were characterized after HCA. Cell death began 6 hours after HCA and reached its peak at 72 hours, but continued for at least 7 days. Compared with the standard protocol at 20 degrees C, HCA at 10 degrees C and CsA treatment both significantly reduced overall cell death after HCA, but not apoptosis.

CONCLUSIONS

The data establish that significant neuronal apoptosis occurs as a consequence of HCA, but at 20 degrees C, other pathways of cell death, probably including necrosis, predominate. Although preliminary results suggest that the neuroprotective effects of lower temperature and of CsA are not a consequence of blockade of apoptotic pathways, inhibition of apoptosis nevertheless seems promising as a strategy to protect the brain from the subtle neurological injury that is associated with prolonged HCA at clinically relevant temperatures.

Retrograde cerebral perfusion as a method of neuroprotection during thoracic aortic surgery

Retrograde cerebral perfusion is commonly used as an adjunct to hypothermic circulatory arrest to enhance cerebral protection during thoracic aortic surgery. This review summarizes a large number of studies that demonstrate a spectrum of beneficial, neutral, and detrimental effects of retrograde cerebral perfusion in humans and experimental animal models. It remains unclear whether retrograde cerebral perfusion provides effective cerebral perfusion, metabolic support, washout of embolic material, and improved neurological and neuropsychological outcome.

Prediction of safe duration of hypothermic circulatory arrest by near-infrared spectroscopy

OBJECTIVE

Hypothermic circulatory arrest is widely used for adults with aortic arch disease as well as for children with congenital heart disease. At present, no method exists for monitoring safe duration of circulatory arrest. Near-infrared spectroscopy is a new technique for noninvasive monitoring of cerebral oxygenation and energy state. In the current study, the relationship between near-infrared spectroscopy data and neurologic outcome was evaluated in a survival piglet model with hypothermic circulatory arrest.

METHODS

Thirty-six piglets (9.36 +/- 0.16 kg) underwent circulatory arrest under varying conditions with continuous monitoring by near-infrared spectroscopy (temperature 15 degrees C or 25 degrees C, hematocrit value 20% or 30%, circulatory arrest time 60, 80, or 100 minutes). Each setting included 3 animals. Neurologic recovery was evaluated daily by neurologic deficit score and overall performance category. Brain was fixed in situ on postoperative day 4 and examined by histologic score.

RESULTS

Oxygenated hemoglobin signal declined to a plateau (nadir) during circulatory arrest. Time to nadir was significantly shorter with lower hematocrit value (P <.001) and higher temperature (P <.01). Duration from reaching nadir until reperfusion ("oxygenated hemoglobin signal nadir time") was significantly related to histologic score (r (s) = 0.826), neurologic deficit score (r (s) = 0.717 on postoperative day 1; 0.716 on postoperative day 4), and overall performance category (r (s) = 0.642 on postoperative day 1; 0.702 on postoperative day 4) (P <.001). All animals in which oxygenated hemoglobin signal nadir time was less than 25 minutes were free of behavioral or histologic evidence of brain injury.

CONCLUSION

Oxygenated hemoglobin signal nadir time determined by near-infrared spectroscopy monitoring is a useful predictor of safe duration of circulatory arrest. Safe duration of hypothermic circulatory arrest is strongly influenced by perfusate hematocrit value and temperature during circulatory arrest.