Major Clinical Outcomes in Adults Undergoing Thoracic Aortic Surgery Requiring Deep Hypothermic Circulatory Arrest: Quantification of Organ-Based Perioperative Outcome and Detection of Opportunities for Perioperative Intervention

Bradykinin induces acute kidney injury after hypothermic circulatory arrest through the repression of the Nrf2-xCT pathway

Postoperative acute kidney injury (AKI) is a common complication in patients undergoing deep hypothermic circulatory arrest (HCA); however, its underlying pathogenesis is unclear. In this study, we established a rat cardiopulmonary bypass model and demonstrated that hypothermia during HCA, rather than circulatory arrest, was responsible for the occurrence of AKI. By recruiting 56 patients who underwent surgery with HCA and analyzing the blood samples, we found that post-HCA AKI was associated with an increase in bradykinin. Animal experiments confirmed this and showed that hypothermia during HCA increased bradykinin levels by increasing kallikrein expression. Mechanistically, bradykinin inhibited the Nrf2-xCT pathway through B2R and caused renal oxidative stress damage. Application of Icatibant, a B2R inhibitor, reversed changes in the Nrf2-xCT pathway and oxidative stress damage. Finally, Icatibant reversed hypothermia-induced AKI in vivo. This finding reveals the pathogenesis of AKI after HCA and helps to provide therapeutic strategy for patients with post-HCA AKI.

Whole Body Retrograde Perfusion Combined With Central Aortic Perfusion Strategy in the Repair of Distal Arch Pathology Through a Lateral Thoracotomy

OBJECTIVE

To compare the results of the hypothermic circulatory arrest (HCA) + retrograde whole-body perfusion (RBP) technique with those of deep hypothermic circulatory arrest (DHCA-only) approach.

METHODS

Limited data are available on cerebral protection techniques when distal arch repairs are performed through a lateral thoracotomy. In 2012, the RBP technique was introduced as adjunct to HCA during open distal arch repair via thoracotomy. We reviewed the results of the HCA + RBP technique compared with those of the DHCA-only approach. From February 2000 to November 2019, 189 patients (median age, 59 [IQR, 46 to 71] years; 30.7% female) underwent open distal arch repair via lateral thoracotomy to treat aortic aneurysms. The DHCA technique was used in 117 patients (62%, median age 53 [IQR, 41 to 60] years), whereas HCA + RBP was used in 72 patients (38%, median age 65 [IQR, 51 to 74] years). In HCA + RBP patients, cardiopulmonary bypass was interrupted when systemic cooling achieved isoelectric electroencephalogram; once the distal arch had been opened, RBP was then initiated via the venous cannula (flow of 700 to 1000 mL/min, central venous pressure <15 to 20 mm Hg).

RESULTS

The stroke rate was significantly lower in the HCA + RBP group (3%, n=2) compared with the DHCA-only (12%, n=14) (P=.031), despite longer circulatory arrest times in HCA + RBP compared with the DHCA-only (31 [IQR, 25 to 40] minutes vs 22 [IQR, 17 to 30] minutes, respectively; P<.001). Operative mortality for patients undergoing HCA + RBP was 6.7% (n=4), whereas for those undergoing DHCA-only it was 10.4% (n=12) (P=.410). The 1-, 3-, and 5-year age-adjusted survival rates for the DHCA group are 86%, 81%, and 75%, respectively. The 1-, 3-, and 5-year age-adjusted survival rates for the HCA + RBP group are 88%, 88%, and 76%, respectively.

CONCLUSION

The addition of RBP to HCA in the treatment of distal open arch repair via a lateral thoracotomy is safe and provides excellent neurological protection.

Dendrimer nanoplatforms for veterinary medicine applications: A concise overview

Within the nanoparticle (NP) space, dendrimers are becoming increasingly important in the field of nanomedicine, not only to treat human diseases, but also in veterinary medicine, which represents a new therapeutic approach. Major applications include using dendrimers to tackle highly contagious foot-and-mouth disease virus (FMDV) and swine fever virus (SFV) in pigs, FMDV in cattle, hypothermic circulatory arrest (HCA) in dogs, rabies, and H9N2 avian influenza virus in chickens. As we review here, intramuscular (im) subcutaneous (sc), intravenous (iv), and intraperitoneal (ip) routes of administration can be used for the successful application of dendrimers in animals.

Retrograde inferior vena caval perfusion for total aortic arch replacement surgery: a randomized pilot study

Objectives

Antegrade cerebral perfusion (ACP) under moderate hypothermic circulatory arrest is used during total aortic arch replacement surgery (TARS) in patients with acute type A aortic dissection, but it is associated with high mortality and morbidity. We hypothesized that combining ACP with retrograde inferior vena caval perfusion (RIVP) improves outcomes.

Methods

This pilot study was prospective, randomized, controlled and assessor-blinded. Patients scheduled for TARS were randomly treated with either ACP or RIVP + ACP. The primary outcome was a composite of mortality and major complications including paraplegia, postoperative renal failure, severe liver dysfunction, and gastrointestinal complications. Secondary outcomes included neurological complications, length of intubation and requirement of blood products.

Results

A total of 76 patients were recruited (n = 38 per group). Primary outcome occurred in 23 patients (61%) in the ACP group and 16 (42%) in the RIVP + ACP group (OR: 0.60, 95% CI: 0.21–1.62; p = 0.31). There was a lower incidence of transient neurological deficits in the RIVP + ACP group (26% vs. 58%, OR: 0.26; 95% CI: 0.10–0.67,p = 0.006;). The RIVP + ACP group underwent shorter intubation (25 vs 47 h, p = 0.022) and required fewer blood products (red cells, 3.8 units vs 6.5 units, p = 0.047; platelet: 2.0 units vs 2.0 units, p = 0.023) compared with the ACP group.

Conclusions

RIVP + ACP may be associated with lower incidence of transient neurological deficits, shorter intubation and less blood transfusion requirement than ACP alone during TARS. Multi-center, randomized trials with larger samples are required to determine whether RIVP + ACP is associated with lower rates of mortality and major complications.

Trial registration: Pilot study of a RCT registered in clinicaltrials.gov (NCT03607786), Registered 30 July, 2018—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03607786.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02002-9.

Level of serum soluble lumican and risks of perioperative complications in patients receiving aortic surgery

Objective

Several serum biomarkers have been investigated for their potential as diagnostic tools in aortic disease; however, no study has investigated the association between serum biomarkers and outcomes after aortic surgery. This study explored the predictive ability of serum soluble lumican in postoperative outcomes after aortic surgery.

Methods

In total, 58 patients receiving aortic surgery for aortic dissection or aneurysm at Linkou Chang Gung Memorial Hospital in Taiwan in December 2011–September 2018 were enrolled. Blood samples were collected immediately upon patients’ arrival in the intensive care unit after aortic surgery. The diagnostic properties of soluble lumican levels were assessed by performing receiver operating characteristic (ROC) curve analysis. The confidence interval (CI) of the area under the ROC curve (AUC) was measured using DeLong’s nonparametric method and the optimal cutoff was determined using the Youden index.

Results

The serum soluble lumican level distinguished prolonged ventilation (AUC, 73.5%; 95% CI, 57.7%–89.3%) and hospital stay for >30 days (AUC, 78.2%; 95% CI, 61.6%–94.7%). The optimal cutoffs of prolonged ventilation and hospital stay for >30 days were 1.547 and 5.992 ng/mL, respectively. The sensitivity and specificity were respectively 100% (95% CI, 71.5%–100%) and 40.4% (95% CI, 26.4%–55.7%) for prolonged ventilation and 58% (95% 27.7%–84.8%) and 91.3% (95% CI, 79.2%–97.6%) for hospital stay for >30 days.

Conclusions

The serum soluble lumican level can be a potential prognostic factor for predicting poor postoperative outcomes after aortic surgery. However, more studies are warranted in the future.

NMDA Receptor Antagonism for Neuroprotection in a Canine Model of Hypothermic Circulatory Arrest

BACKGROUND

Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part mediated by activation of the N-methyl-D-aspartate glutamate receptor causing excitotoxicity and neuronal apoptosis. Using a canine model, we hypothesized that the N-methyl-D-aspartate receptor antagonist MK801 would provide neuroprotection and that MK801 conjugation to dendrimer nanoparticles would improve efficacy.

MATERIALS AND METHODS

Male hound dogs were placed on cardiopulmonary bypass, cooled to 18°C, and underwent 90 min of HCA. Dendrimer conjugates (d-MK801) were prepared by covalently linking dendrimer surface OH groups to MK801. Six experimental groups received either saline (control), medium- (0.15 mg/kg) or high-dose (1.56 mg/kg) MK801, or low- (0.05 mg/kg), medium-, or high-dose d-MK801. At 24, 48, and 72 h after HCA, animals were scored by a standardized neurobehavioral paradigm (higher scores indicate increasing deficits). Cerebrospinal fluid was obtained at baseline, eight, 24, 48, and 72 h after HCA. At 72 h, brains were examined for histopathologic injury in a blinded manner (higher scores indicate more injury).

RESULTS

Neurobehavioral deficit scores were reduced by low-dose d-MK801 on postoperative day two (P < 0.05) and by medium-dose d-MK801 on postoperative day 3 (P = 0.05) compared with saline controls, but free drug had no effect. In contrast, high-dose free MK801 significantly improved histopathology scores compared with saline (P < 0.05) and altered biomarkers of injury in cerebrospinal fluid, with a significant reduction in phosphorylated neurofilament-H for high-dose MK801 versus saline (P < 0.05).

CONCLUSIONS

Treatment with MK-801 demonstrated significant improvement in neurobehavioral and histopathology scores after HCA, although not consistently across doses and conjugates.

Anticipating Postoperative Delirium During Burst Suppression Using Electroencephalography

OBJECTIVE

This study develops an electro-encephalography-based method for predicting postoperative delirium early during cardiac surgeries involving deep hypothermia circulatory arrest (DHCA), potentially providing an opportunity to intervene and minimize poor surgical outcome. DHCA is a surgical technique used during cardiac surgeries to facilitate repairs. Deep hypothermia is induced and supplemented by perfusion techniques to protect the brain during circulatory arrest, but concern for cerebral injury still remains.

METHODS

This research studies whether or not monitoring burst suppression, an electrophysiological phenomenon observed during patient cooling and warming, helps in predicting postoperative delirium, a correlate of poor prognosis. A metric called the burst suppression duty cycle (BSDC), akin to burst suppression ratio, is formulated to characterize this electrophysiological activity.

RESULTS

Assuming no complications occur prior to circulatory arrest, delirium diagnoses are correlated with the time elapsed until suppression activity ceases since resuming cardiopulmonary bypass. By comparing against a benchmark the times when BSDC reaches 100%, 15 of 16 cases can be correctly predicted. Similar accuracy can be achieved when querying BSDC progress earlier during warming.

CONCLUSION

Our results show that our BSDC metric is a promising candidate for early detection of postoperative delirium, and motivates further analysis of the causal relationship between postoperative delirium and the procedure transitioning out of circulatory arrest.

SIGNIFICANCE

The developed methodology anticipates incidences of postoperative delirium during rewarming, which potentially provides an opportunity to intervene and avert it.

Retrograde Inferior Vena caval Perfusion for Total Aortic arch Replacement Surgery (RIVP-TARS): study protocol for a multicenter, randomized controlled trial

BACKGROUND

During total aortic arch replacement surgery (TARS) for patients with acute type A aortic dissection, the organs in the lower body, such as the viscera and spinal cord, are at risk of ischemia even when antegrade cerebral perfusion (ACP) is performed. Combining ACP with retrograde inferior vena caval perfusion (RIVP) during TARS may improve outcomes by providing the lower body with oxygenated blood.

METHODS

This study is designed as a multicenter, computer-generated, randomized controlled, assessor-blind, parallel-group study with a superiority framework in patients scheduled for TARS. A total of 636 patients will be randomized on a 1:1 basis to a moderate hypothermia circulatory arrest (MHCA) group, which will receive selective ACP with moderate hypothermia during TARS; or to an RIVP group, which will receive the combination of RIVP and selective ACP under moderate hypothermia during TARS. The primary outcome will be a composite of early mortality and major complications, including paraplegia, postoperative renal failure, severe liver dysfunction, and gastrointestinal complications. All patients will be analyzed according to the intention-to-treat protocol.

DISCUSSION

This study aims to assess whether RIVP combined with ACP leads to superior outcomes than ACP alone for patients undergoing TARS under moderate hypothermia. This study seeks to provide high-quality evidence for RIVP to be used in patients with acute type A aortic dissection undergoing TARS.

TRIAL REGISTRATION

Clinicaltrials.gov, ID: NCT03607786 . Registered on 30 July 2018.

Does the melatonin receptor 1B gene polymorphism have a role in postoperative delirium?

INTRODUCTION

Patients undergoing cardiac surgery are at high risk for postoperative delirium, which is associated with longer hospital and intensive care lengths of stays, increased morbidity and mortality. Because sleep disturbances are common in delirium, melatonin has been an area of interest in the treatment of delirium. The rs10830963 single nucleotide polymorphism of the melatonin receptor 1B gene can cause pathological dysfunction of this receptor and is associated with delayed morning offset of melatonin. We hypothesized patients undergoing aortic cardiac surgery who have the risk genotype of a melatonin receptor 1B polymorphism would have a higher incidence of postoperative delirium.

METHODS

Ninety-eight patients undergoing aortic root or valve surgery underwent analysis for melatonin receptor 1B single nucleotide polymorphism, rs10830963. Using a validated method, CHART-DEL, all charts were retrospectively reviewed and scored for the presence of delirium while blinded to the results of the melatonin receptor 1B gene polymorphism.

RESULTS

Genotyping for melatonin receptor 1B polymorphism was acceptable in 76 subjects of European descent of which 18 (23.7%) had delirium. Four of seven subjects with the risk genotype had delirium versus only 20.3% of subjects without the risk genotype. This carried an odds ratio of 5.2 (1.0, 26.1), p = 0.050.

CONCLUSION

This observation suggests a role of the risk genotype of a melatonin receptor 1B polymorphism in the development of postoperative delirium. These hypotheses generating results warrant further prospective studies in a larger cohort group with delirium, circadian rhythm and melatonin assessments.

Whole body perfusion strategy for aortic arch repair under moderate hypothermia

INTRODUCTION

Aortic arch reconstruction under moderate hypothermia is commonly performed with antegrade cerebral perfusion (ACP) for brain protection; however, hypothermia alone is often solely relied upon for visceral and lower body protection. We investigated whether the addition of simultaneous lower body perfusion to ACP (whole body perfusion - WBP) may ameliorate the metabolic derangements of moderate hypothermic circulatory arrest (MHCA).

METHODS

Between 2008 and 2014, 106 consecutive patients underwent elective or emergent aortic arch surgery with MHCA, with either ACP only (44 patients, 66±12 years, 30% female) or WBP (62 patients, 61±15 years, 31% female). Primary outcomes included 30-day/in-hospital mortality, intensive care unit (ICU) and hospital lengths of stay (LOS) and specific parameters of metabolic recovery.

RESULTS

There were no significant differences between the groups in 30-day/in-hospital mortality (ACP: 3 (6.8%), WBP: 2 (3.2%); p=0.65), stroke (ACP: 1 (2.3%), WBP: 1 (1.6%); p=1.0) or renal failure (ACP: 2 (4.5%), WBP: 1 (1.5%); p=0.57). In the WBP group, we identified a significant reduction in lactate level at ICU admission (ACP 5.5 vs. WBP 3.5 mmol/L; p=0.002), time to lactate normalization (p=0.014) and median ICU length-of-stay (ACP 3 vs. WBP 1 days; p=0.049). There was no difference in post-operative creatinine (ACP: 104, WBP: 107 μmol/L; p=0.66). After multivariable regression adjustment, perfusion strategy no longer remained an independent predictor of ICU discharge time (p=0.09), however, cardiopulmonary bypass time (p=0.02), age (p=0.012) and emergent surgery (p=0.02) were.

CONCLUSIONS

A WBP strategy during aortic arch reconstruction with MHCA may be associated with more rapid normalization of metabolic parameters and reduced ICU length of stay compared to using ACP alone. Further evaluation with a randomized trial is warranted.

Immediate ICU Care for Patients Following Aortic Arch Surgery

Patients undergoing aortic arch surgery are at high risk for stroke, delirium, low cardiac output, respiratory failure, renal failure, and coagulopathy. A significantly higher mortality is seen in patients experiencing any of these complications when compared with those without complications. As surgical, perfusion, and anesthetic techniques improve, the incidence of major complications have decreased. A recent paradigm shift in cardiac surgery has focused on rapid postoperative recovery, and a similar change has affected the care of patients after arch surgery. Nevertheless, a small subset of patients experience significant morbidity and mortality after aortic arch surgery, and rapid identification of any organ dysfunction and appropriate supportive care is critical in these patients. In this article, the current state of postoperative care of the patient after open aortic arch surgery will be reviewed.

Current approach to diagnosis and treatment of delirium after cardiac surgery

Delirium after cardiac surgery remains a common occurrence that results in significant short- and long-term morbidity and mortality. It continues to be underdiagnosed given its complex presentation and multifactorial etiology; however, its prevalence is increasing given the aging cardiac surgical population. This review highlights the perioperative risk factors, tools to assist in diagnosing delirium, and current pharmacological and nonpharmacological therapy options.

Prolonged postoperative respiratory support after proximal thoracic aortic surgery: Is deep hypothermic circulatory arrest a risk factor?

PURPOSE

In addition to the pulmonary risks associated with cardiopulmonary bypass, thoracic aortic surgery using deep hypothermic circulatory arrest (DHCA) may subject the lungs to further injury. However, this topic has received little investigation to date.

MATERIALS AND METHODS

A prospective cohort review was performed on all patients undergoing proximal thoracic aortic surgery with (n = 478) and without (n = 135) DHCA between July 2005 and February 2013 at a single institution. The primary outcome was prolonged postoperative respiratory support (PPRS), defined as any of the following: >1 day of mechanical ventilation at either fraction of inspired oxygen >0.4 and/or positive end-expiratory pressure >5 mm Hg, >2 days of supplemental O2 requirement of at least 2.5 L/min, or discharge with new O2 requirement. Independent risk factors for PPRS were identified using multivariable logistic regression.

RESULTS

Postoperative respiratory support was required in 100 patients (20.9%) with and 30 patients (22.2%) without DHCA (P = .74). Independent predictors of PPRS after proximal aortic surgery included the following: age, diabetes, history of stroke, preoperative creatinine, American Society of Anesthesiologists class 4, redo-sternotomy, total arch replacement, and transfusion requirement. Use of DHCA was not an independent risk factor for PPRS in the entire cohort. Subanalysis of only DHCA patients revealed that longer DHCA times were independently associated with PPRS.

CONCLUSIONS

Prolonged postoperative respiratory support is common after proximal aortic surgery. The use of DHCA was not associated with this complication in the overall cohort, although longer DHCA times were predictive when only the subset of patients undergoing DHCA was analyzed. Knowledge of the risk factors for PPRS after proximal aortic surgery should improve preoperative risk stratification and postoperative management of these patients.

A novel microwave sensor to detect specific biomarkers in human cerebrospinal fluid and their relationship to cellular ischemia during thoracoabdominal aortic aneurysm repair

Thoraco-abdominal aneurysms (TAAA) represents a particularly lethal vascular disease that without surgical repair carries a dismal prognosis. However, there is an inherent risk from surgical repair of spinal cord ischaemia that can result in paraplegia. One method of reducing this risk is cerebrospinal fluid (CSF) drainage. We believe that the CSF contains clinically significant biomarkers that can indicate impending spinal cord ischaemia. This work therefore presents a novel measurement method for proteins, namely albumin, as a precursor to further work in this area. The work uses an interdigitated electrode (IDE) sensor and shows that it is capable of detecting various concentrations of albumin (from 0 to 100 g/L) with a high degree of repeatability at 200 MHz (R(2) = 0.991) and 4 GHz (R(2) = 0.975).

Brain injury in canine models of cardiac surgery

Neuropathology and neurologic impairment were characterized in a clinically relevant canine model of hypothermic (18°C) circulatory arrest (HCA) and cardiopulmonary bypass (CPB). Adult dogs underwent 2 hours of HCA (n = 39), 1 hour of HCA (n = 20), or standard CPB (n = 22) and survived 2, 8, 24, or 72 hours. Neurologic impairment and neuropathology were much more severe after 2-hour HCA than after 1-hour HCA or CPB; histopathology and neurologic deficit scores were significantly correlated. Apoptosis developed as early as 2 hours after injury and was most severe in the granule cells of the hippocampal dentate gyrus. Necrosis evolved more slowly and was most severe in amygdala and pyramidal neurons in the cornu ammonis hippocampus. Neuronal injury was minimal up to 24 hours after 1-hour HCA, but 1 dog that survived to 72 hours showed substantial necrosis in the hippocampus, suggesting that, with longer survival time, the injury was worse. Although neuronal injury was minimal after CPB, we observed rare apoptotic and necrotic neurons in hippocampi and caudate nuclei. These results have important implications for CPB in humans and may help explain the subtle cognitive changes experienced by patients after CPB.

Dendrimer brain uptake and targeted therapy for brain injury in a large animal model of hypothermic circulatory arrest

Treatment of brain injury following circulatory arrest is a challenging health issue with no viable therapeutic options. Based on studies in a clinically relevant large animal (canine) model of hypothermic circulatory arrest (HCA)-induced brain injury, neuroinflammation and excitotoxicity have been identified as key players in mediating the brain injury after HCA. Therapy with large doses of valproic acid (VPA) showed some neuroprotection but was associated with adverse side effects. For the first time in a large animal model, we explored whether systemically administered polyamidoamine (PAMAM) dendrimers could be effective in reaching target cells in the brain and deliver therapeutics. We showed that, upon systemic administration, hydroxyl-terminated PAMAM dendrimers are taken up in the brain of injured animals and selectively localize in the injured neurons and microglia in the brain. The biodistribution in other major organs was similar to that seen in small animal models. We studied systemic dendrimer-drug combination therapy with two clinically approved drugs, N-acetyl cysteine (NAC) (attenuating neuroinflammation) and valproic acid (attenuating excitotoxicity), building on positive outcomes in a rabbit model of perinatal brain injury. We prepared and characterized dendrimer-NAC (D-NAC) and dendrimer-VPA (D-VPA) conjugates in multigram quantities. A glutathione-sensitive linker to enable for fast intracellular release. In preliminary efficacy studies, combination therapy with D-NAC and D-VPA showed promise in this large animal model, producing 24 h neurological deficit score improvements comparable to high dose combination therapy with VPA and NAC, or free VPA, but at one-tenth the dose, while significantly reducing the adverse side effects. Since adverse side effects of drugs are exaggerated in HCA, the reduced side effects with dendrimer conjugates and suggestions of neuroprotection offer promise for these nanoscale drug delivery systems.

Clinical and biochemical outcomes for additive mesenteric and lower body perfusion during hypothermic circulatory arrest for complex total aortic arch replacement surgery

Surgical repair of transverse aortic arch aneurysms frequently employ hypothermia and antegrade cerebral perfusion as protective strategies during circulatory arrest. However, prolonged mesenteric and lower limb ischemia can lead to significant lactic acidosis and end organ dysfunction, which remains a significant cause of post-operative morbidity and mortality. We report our experience with additive warm mesenteric and lower body perfusion (1-3 L/min, 30°C) in addition to continuous cerebral and myocardial perfusion in 5 patients who underwent total aortic arch replacement with trifurcated head vessel re-implantation and distal elephant trunk reconstruction. Concomitant surgical procedures included re-operations (2), aortic root operations (2), coronary artery bypass (2) and descending thoracic aortic replacement (1). Serum lactate levels demonstrated a rapid decline from a peak 9.9±2.6 post circulatory arrest to 3.4±2.0 in the intensive care unit (ICU). The lowest serum bicarbonate levels were 19.3±3.5 mmol/L, intra-operatively, which normalized to 28.4±2.4 mmol/L on return to the ICU. The lowest pH levels were 7.25±0.10, corrected to 7.43±0.04 on return to the ICU. Mean cardiopulmonary bypass and aortic cross-clamp times were 361±104 and 253±85 minutes, respectively. Mean cerebral and lower body circulatory arrest times were 0 (0) and 50±35 minutes, respectively. The mean time required for systemic rewarming was 95±66 minutes. There were no in-hospital mortalities and no patient experienced any neurological, mesenteric, renal or lower limb ischemic complications. Two patients required mechanical ventilation >24 hours, and one patient returned for reoperation for bleeding. Median intensive care unit and total hospital lengths of stay were 5 and 16 days, respectively. Our results suggest early serum lactate clearance, normalization of acidosis, and metabolic recovery when utilizing a simultaneous cerebral perfusion and warm body protection strategy for complex aortic arch surgery. This additive perfusion strategy may attenuate visceral and lower body ischemia that normally develops during periods of deep hypothermic circulatory arrest.

Serum levels of neuron-specific ubiquitin carboxyl-terminal esterase-L1 predict brain injury in a canine model of hypothermic circulatory arrest

OBJECTIVES

Ubiquitin carboxyl-terminal esterase-L1 (UCHL1) is a protein highly selectively expressed in neurons and has been linked to neurodegenerative disease in humans. We hypothesize that UCHL1 would be an effective serum biomarker for brain injury as tested in canine models of hypothermic circulatory arrest (HCA) and cardiopulmonary bypass (CPB).

METHODS

Dogs were exposed to CPB (n = 14), 1 hour of HCA (1h-HCA; n = 11), or 2 hours of HCA (2h-HCA; n = 20). Cerebrospinal fluid and serum were collected at baseline, 8 hours, and 24 hours after treatment. UCHL1 levels were measured using a sandwich enzyme-linked immunosorbent assay. Neurologic function and histopathology were scored at 24 hours, and UCHL1 immunoreactivity was examined at 8 hours.

RESULTS

Baseline UCHL1 protein levels in cerebrospinal fluid and serum were similar for all groups. In serum, UCHL1 levels were elevated at 8 hours after treatment for 2h-HCA subjects compared with baseline values (P < .01) and also compared with CPB dogs at 8 hours (P < .01). A serum UCHL1 level above 3.9 ng/(mg total protein) at 8 hours had the best discriminatory power for predicting functional disability. In cerebrospinal fluid, UCHL1 was elevated in all groups at 8 hours after treatment compared with baseline (P < .01). However, UCHL1 levels in cerebrospinal fluid remained elevated at 24 hours only in 2h-HCA subjects (P < .01). Functional and histopathologic scores were closely correlated (Pearson coefficient, 0.66; P < .01) and were significantly worse in 2h-HCA animals.

CONCLUSIONS

This is the first report associating elevated serum UCHL1 with brain injury. The novel neuronal biomarker UCHL1 is increased in serum 8 hours after severe neurologic insult in 2h-HCA animals compared with CPB animals. These results support the potential for use in cardiac surgery patients and form the basis for clinical correlation in humans.

Acute kidney injury during aortic arch surgery under deep hypothermic circulatory arrest

PURPOSE

The aim of this investigation was to describe the renal outcome and to identify risk factors for acute kidney injury (AKI), as defined by the Acute Kidney Injury Network (AKIN), during aortic arch surgery (AAS) under deep hypothermic circulatory arrest (DHCA).

METHODS

A retrospective and observational study has been performed. One hundred thirty-five patients requiring AAS under DHCA were studied.

RESULTS

Seventy-one patients (52.6%) developed AKI during the postoperative period. A logistic regression analysis identified three independent risk factors for AKI: preoperative hypertension (HT), emergency surgery, and duration of DHCA. Renal replacement therapy (RRT) was required in four patients (3.0%). The postoperative mortality rate among the patients with AKI was 2.8%, which was not statistically different from the rate of 1.6% observed in the non-AKI group (P = 0.62).

CONCLUSIONS

A high incidence of AKI during AAS under DHCA was confirmed. Because AKI is highly associated with aortic surgery, novel approaches for protecting the kidneys other than deep hypothermia are needed. The logistic regression model identified HT, emergency surgery, and duration of DHCA as independent risk factors for AKI.

Hawley H. Seiler Resident Award. Transcriptional profile of brain injury in hypothermic circulatory arrest and cardiopulmonary bypass

BACKGROUND

Little is known about the molecular mechanisms of neurologic complications after hypothermic circulatory arrest (HCA) with cardiopulmonary bypass (CPB). Canine genome sequencing allows profiling of genomic changes after HCA and CPB alone. We hypothesize that gene regulation will increase with increased severity of injury.

METHODS

Dogs underwent 2-hour HCA at 18 degrees C (n = 10), 1-hour HCA (n = 8), or 2-hour CPB at 32 degrees C alone (n = 8). In each group, half were sacrificed at 8 hours and half at 24 hours after treatment. After neurologic scoring, brains were harvested for genomic analysis. Hippocampal RNA isolates were analyzed using canine oligonucleotide expression arrays containing 42,028 probes.

RESULTS

Consistent with prior work, dogs that underwent 2-hour HCA experienced severe neurologic injury. One hour of HCA caused intermediate clinical damage. Cardiopulmonary bypass alone yielded normal clinical scores. Cardiopulmonary bypass, 1-hour HCA, and 2-hour HCA groups historically demonstrated increasing degrees of histopathologic damage (previously published). Exploratory analysis revealed differences in significantly regulated genes (false discovery rate < 10%, absolute fold change > or = 1.2), with increases in differential gene expression with injury severity. At 8 hours and 24 hours after insult, 2-hour HCA dogs had 502 and 1,057 genes regulated, respectively; 1-hour HCA dogs had 179 and 56 genes regulated; and CPB alone dogs had 5 and 0 genes regulated.

CONCLUSIONS

Our genomic profile of canine brains after HCA and CPB revealed 1-hour and 2-hour HCA induced markedly increased gene regulation, in contrast to the minimal effect of CPB alone. This adds to the body of neurologic literature supporting the safety of CPB alone and the minimal effect of CPB on a normal brain, while illuminating genomic results of both.

Preoperative and intraoperative risk factors for prolonged intensive care unit stay after aortic arch surgery

OBJECTIVE

The present study was performed to evaluate preoperative and intraoperative risk factors for prolonged intensive care unit (ICU) stay after aortic arch surgery.

DESIGN

A retrospective study. Prolonged ICU stay was defined as >5 days (120 hours).

SETTING

Cardiovascular operating rooms and the ICU.

PARTICIPANTS

Adults requiring aortic arch surgery with deep hypothermic circulatory arrest plus antegrade selective cerebral perfusion.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

After 11 patients who underwent 1-stage total or subtotal aortic replacement were excluded, 298 patients were enrolled in the study. The average age of patients was 44.9 +/- 10.7 years with male predominance (74.8%). Sixty-one patients (20.5%) stayed longer than 5 days in the ICU. Univariate analyses found age, body mass index, New York Heart Association classification, preoperative serum creatinine, creatinine clearance, emergency, inotropes, cardiopulmonary bypass time, myocardial ischemia time, and fresh-frozen plasma transfused intraoperatively were significantly associated with prolonged ICU stay (p < 0.05). Independent risk factors for prolonged ICU stay were found to be New York Heart Association classification (class III and IV), emergency, inotropes used intraoperatively, and prolonged cardiopulmonary bypass time (p < 0.05).

CONCLUSION

The authors identified 4 preoperative and intraoperative risk factors for prolonged ICU stay. This is helpful to identify patients with increased risk for prolonged ICU stay, implement specific strategies, and allocate medical resources.

Management of neurologic complications of thoracic aortic surgery

Neurologic complications of thoracic aortic surgery are strongly associated with increased morbidity and mortality. Identifying preoperative risk factors for neurologic injury may enable us to refine our perioperative approach, and to lessen or avoid these complications. Methods to identify stroke and spinal ischemia intraoperatively such as neurophysiologic monitoring may enable us to improve outcomes in these patients by immediately instituting measures to improve brain and spine perfusion. The development of both protocols and therapies to treat these complications has allowed us to mitigate and, at times, reverse neurologic injury both intraoperatively and postoperatively.

Fate of the residual distal and proximal aorta after acute type a dissection repair using a contemporary surgical reconstruction algorithm

BACKGROUND

In this study, we evaluated the long-term results of our contemporary, standardized surgical management algorithm for repair of acute type A aortic dissections. Prior reports have analyzed heterogeneous techniques and populations.

METHODS

From 1993 to 2004, 221 consecutive patients underwent repair of acute type A aortic dissection at our aortic center. Hemiarch repair was performed in 97.7% (216 of 221), and total arch in 2.3% (5 of 221). Of these, 72.9% (161 of 221) underwent aortic valve resuspension, and 27.1% (60 of 221) had aortic root replacement.

RESULTS

In-hospital mortality for a primary operation was 12.7% (28 of 221). Actuarial survival was 79.2% at 1 year, 62.8% at 5 years, and 46.3% at 10 years. Significant risk factors for decreased survival included prior stroke, cerebral malperfusion, and length of cardiopulmonary bypass. Freedom from proximal reoperation after aortic valve resuspension was 94.6% at 5 years and 76.8% at 10 years, with cardiac malperfusion as the main risk factor. Freedom from distal reoperation was 87.6% at 5 years and 76.4% at 10 years, with Marfan syndrome, age, and extent of dissection as significant risk factors for reoperation. In-hospital mortality was 18.2% (2 of 11) after proximal reoperation and 31.2% (5 of 16) after distal reoperation.

CONCLUSIONS

We report improved long-term durability of our proximal root repair, with cardiac malperfusion as a significant risk factor. Marfan disease, younger age, and DeBakey type I dissection are risk factors for distal reoperation. To further improve long-term outcome, means to prevent progression of distal aortic disease need to be developed.

Hyperactive delirium and blood glucose control in critically ill patients

Delirium is a common complication of critically ill patients and is often associated with metabolic disorders. One of the most frequent metabolic disorders in intensive care unit (ICU) patients is hyperglycaemia. The aim of this retrospective study of 196 adult ICU patients was to determine if there is an association between hyperactive delirium and blood glucose levels in ICU patients. Hyperactive delirium was diagnosed using the delirium detection score. Blood glucose levels were monitored by blood gas analysis every 4 h. Hyperactive delirium was detected in 55 (28%) patients. Delirious patients showed significantly higher blood glucose levels than non-delirious patients Higher overall complication rates, length of ventilation, ICU stay and mortality rates were seen in the delirium group. In a multivariate analysis, glucose level, alcohol abuse, APACHE II score, complication by hospital-acquired pneumonia and a diagnosis of polytrauma on-admission all significantly influenced the appearance of delirium.

RIFLE criteria for acute kidney injury in aortic arch surgery

OBJECTIVE

The RIFLE criteria are new international consensus definitions for acute kidney injury introduced to facilitate research across disciplines. We identified risk factors for acute kidney injury, renal replacement therapy, and mortality using the RIFLE criteria (RIFLE = risk, injury, failure, loss, end stage) in patients undergoing deep hypothermic circulatory arrest for aortic arch reconstruction.

METHODS

A single-center retrospective cohort study of 267 patients undergoing aortic arch surgery with deep hypothermic circulatory arrest was conducted between July 2001 and October 2005. Known predictors (age, chronic kidney disease, surgery status, redo, diabetes, hypertension, blood transfusion, bypass, and deep hypothermic circulatory arrest time) were used in multivariate logistic regression models for acute kidney injury, renal replacement therapy, and mortality.

RESULTS

Mean age was 64 years (range 23-89 years) with 166 men (62%). Seventy-five (28%) had RIFLE scores of I or F, and 22 (8%) required dialysis. Risk factors for acute kidney injury were hypertension (odds ratio [OR] = 2.17; 95% confidence intervals [CI], 1.14-4.15), chronic kidney disease (OR = 9.04; 95% CI, 1.97-41.59), packed red blood cells greater than 5 units (OR = 2.37; 95% CI, 1.20-4.69), and admission creatinine/Modification of Diet in Renal Disease predicted creatinine ratio greater than 1 (OR = 3.54; 95% CI, 1.95-6.45). Risk factors for mortality were age (per 10 years) (OR = 2.35; 95% CI, 1.35-4.06), AKI (RIFLE class R, I, or F) (OR = 4.60; 95% CI, 1.34-15.77), and cerebrovascular accident (OR = 19.1; 95% CI, 4.96-73.58). Mortality increased with each RIFLE stratification (RIFLE class 0 = 3%, R = 9%, I = 12%, and F = 38%).

CONCLUSIONS

Acute kidney injury as defined according to the RIFLE classification is a risk factor for mortality and will be useful in future studies of renal dysfunction in thoracic aortic surgery.

Significance of malperfusion syndromes prior to contemporary surgical repair for acute type A dissection: outcomes and need for additional revascularizations

OBJECTIVE

The aim of this study was to assess the significance of malperfusion syndromes in patients with acute type A aortic dissection following a contemporary surgical management algorithm and the effects on morbidity, hospital mortality, and long-term survival. We believe that obliteration of the primary tear site with restoration of flow in the true aortic lumen results in decreased need for revascularization of malperfused organ systems.

METHODS

Our operative approach aims at replacing the entire ascending aorta, resuspension of the aortic valve with repair or replacement of the sinus segment, and routine open replacement of the arch under hypothermic circulatory arrest with retrograde cerebral perfusion with obliteration of false lumen at the distal arch/proximal descending thoracic aorta, thus reestablishing normal flow in the descending thoracic true lumen. From January 1993 to December 2004, 221 consecutive patients underwent repair of acute type A aortic dissection at our institution. Data were collected retrospectively and prospectively. Various types of malperfusion syndromes were present in 26.7% of patients. The organ systems with malperfusion were as follows: cardiac, 7.2%; cerebral, 7.2%; ileofemoral, 12.7%; renal, 4.1%; mesenteric, 1.4%; innominate, 5.4%; and spine, 2.2%.

RESULTS

Coronary malperfusion required coronary revascularization in 62.5% of cases. Distal revascularization was needed in 42.9% of patients with ileofemoral malperfusion. Patients with malperfusion were more likely to suffer perioperative myocardial infarction (p<0.001), postoperative coma (p=0.012), delirium (p=0.011), sepsis (p=0.006), acute renal failure (p=0.017), dialysis (p=0.018), and acute limb ischemia (p<0.001). The in-hospital mortality was 30.5% in patients presenting with any malperfusion syndrome while only 6.2% in patients without malperfusion syndrome (p<0.001). Both cardiac (p=0.020) and cerebral malperfusions (p<0.001) were risk factors for in-hospital mortality. The actuarial long-term survival in patients with malperfusion syndrome was estimated by Kaplan-Meier methods to be 67.8%+/-6.1% at 1 year, 54.0%+/-7.0% at 5 years, and 43.1%+/-8.0% at 10 years and for patient without malperfusion 82.7%+/-3.0% at 1 year, 66.3%+/-3.9% at 5 years, and 46.1%+/-6.7% at 10 years (log rank 2.55, p=0.110). Cerebral malperfusion was a significant risk factor for decreased long-term survival (p=0.0002).

CONCLUSIONS

The occurrence of malperfusion in patients with acute type A dissection is associated with significant increased risk of in-hospital mortality and complications. Additional revascularization is generally needed in patients with coronary malperfusion and ileofemoral malperfusion. Patients presenting with cardiac and cerebral malperfusions have a high hospital mortality and preoperative cerebral malperfusion is associated with dismal long-term survival.

Atrial Fibrillation After Aortic Arch Repair Requiring Deep Hypothermic Circulatory Arrest: Incidence, Clinical Outcome, and Clinical Predictors

OBJECTIVE

To delineate the incidence, outcome impact, and clinical predictors of atrial fibrillation (AF) after adult aortic arch repair requiring deep hypothermic circulatory arrest (AAR-DHCA) AIMS: To determine the incidence of AF after AAR-DHCA, to determine whether AF after AAR-DHCA affects mortality or stay in the intensive care unit (ICU), to determine multivariate predictors for AF after AAR-DHCA, and to determine whether aprotinin protects against AF after AAR-DHCA.

STUDY DESIGN

Retrospective and observational.

STUDY SETTING

Single large university hospital.

PARTICIPANTS

All adults undergoing AAR-DHCA in 2000 and 2001.

MAIN RESULTS

The cohort size was 144. Antifibrinolytic exposure was 100%, aprotinin 66% and aminocaproic acid 34%. The incidence of AF was 34.0%. AF was not significantly associated with increased mortality or prolonged ICU stay. Advanced age was a multivariate risk factor for AF. Lower temperature nadir during DHCA was protective against postoperative AF. Aprotinin had no demonstrable effect on AF after AAR-DHCA.

CONCLUSIONS

AF after AAR-DHCA is common but does not independently increase mortality or ICU stay. The risk of AF after AAR-DHCA increases with age but decreases with the degree of hypothermia during DHCA. Aprotinin does not appear to affect the risk of AF after AAR-DHCA.

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.

Renal dysfunction after thoracic aortic surgery requiring deep hypothermic circulatory arrest: definition, incidence, and clinical predictors

OBJECTIVE

The purpose of this study was to evaluate renal dysfunction (RD) after thoracic aortic surgery (TAS) requiring deep hypothermic circulatory arrest (DHCA), to determine the influence of definition on RD after TAS-DHCA, to determine univariate predictors of RD after TAS-DHCA, and to determine multivariate predictors for RD TAS-DHCA. RD was defined in 3 ways: (1) >25% reduction in creatinine clearance, (2) >50% increase in serum creatinine, and (3) >50% increase in serum creatinine with an abnormal peak serum creatinine (>1.3 mg/dL for men and >1.0 mg/dL for women).

STUDY DESIGN

Retrospective and observational.

STUDY SETTING

Single large university hospital.

PARTICIPANTS

All adults requiring TAS-DHCA in 2000 and 2001.

MAIN RESULTS

The cohort size was 144. Antifibrinolytic exposure was 100%: aprotinin 66% and aminocaproic acid 34%. The incidence of RD TAS-DHCA was 22.9% to 38.2%, depending on the definition. The incidence of renal replacement therapy was 2.8%. Multivariate predictors for RD after TAS-DHCA were sepsis, aprotinin exposure, preoperative hypertension, age, and donor exposures.

CONCLUSIONS

Although RD after TAS-DHCA varies substantially because of definition, it is still very common. Its multivariate predictors merit further focused research to enhance perioperative protection of the kidney.