Tamaki Takano

Blood trauma induced by clinically accepted oxygenators.

Hemolysis remains one of the most serious problems during cardiopulmonary bypass (CPB), extracorporeal membrane oxygenation (ECMO), and percutaneous cardiopulmonary support (PCPS). However, the hemolytic characteristics associated with oxygenators are not well defined. A specialized hemolysis test protocol for oxygenators was developed. A comparative study was performed following this protocol to determine the hemolytic characteristics of the clinically available oxygenators during CPB; pressure drop measurements in the blood chamber were also performed. Four oxygenators (Medtronic Affinity, Cobe Optima, Terumo Capiox SX25, and Bard Quantum) were evaluated. Fresh blood from healthy Dexter calves anticoagulated with citrate phosphate dextrose adenine solution was used. The blood flow was fixed at 5 L/min, similar to that used in CPB. The Normalized Index of Hemolysis for Oxygenators (NIHO) has been modified according to the American Society of Testing and Materials (ASTM) standards. The NIH value, which was obtained from the circuit without an oxygenator, was subtracted from the primary NIH value, obtained from the circuit with an oxygenator to eliminate the effects of a centrifugal pump or other artifacts. The NIHO value was the lowest in the Affinity (0.0116 ± 0.0017) and increased from Affinity < Optima (0.0270 ± 0.0038) < Capiox (0.0335 ± 0.0028) < Quantum (0.0416 ± 0.0015 g/100 L). The Optima and Capiox did not demonstrate a significant difference. In addition, this NIHO value has a close relationship to the pressure drop. In conclusion, this new evaluation method is suitable to compare the biocompatibility performance of different types of clinically available oxygenators for CPB usage.

Hemolytic characteristics of oxygenators during clinical extracorporeal membrane oxygenation.

A connection was previously reported between the hemolytic characteristics associated with oxygenators and the pressure drop measurements in the blood chamber under experimental conditions simulating their use in cardiopulmonary bypass. We examined this association during extracorporeal membrane oxygenation (ECMO) conditions. Three oxygenators for ECMO or pediatric cardiopulmonary bypass (Menox EL4000, Dideco Module 4000, and Mera HPO-15H) were evaluated. Fresh blood from healthy Dexter strain calves anticoagulated with citrate phosphate dextrose adenine solution was used. The blood flow was fixed at 1 L/min, similar to that in ECMO. The Normalized Index of Hemolysis for Oxygenators (NIHO) has been modified according to the American Society of Testing and Materials standards, as was previously reported. The NIHO value was the lowest in the Menox (0.0070 ± 0.0009) and increased from Menox to Dideco (0.0113 ± 0.0099) to Mera (0.0164 ± 0.0043); however, there were no significant differences among the oxygenators. This NIHO value has a close correlation to the pressure drop. In conclusion, this evaluation method is also applicable to comparison of the biocompatibility performance of different types of clinically available oxygenators for ECMO.

Development of an antithrombogenic and antitraumatic blood pump: the Gyro C1E3.

The Gyro C1E3 is a centrifugal blood pump. Its antithrombogenic and antitraumatic blood features were demonstrated by prior studies. Based upon these studies, a mass production model of the C1E3 is becoming commercially available. Therefore, this feasibility study was conducted using the mass production models of the Gyro C1E3 for long-term cardiac assist in ex vivo animal experiments. Five healthy calves were used and 15 pump heads were applied for different time periods (Group 1, 30 days; Group 2, 14 days; Group 3, 10 and 7 days; Group 4, 4 days; and Group 5, 2 days). Activated clotting time (ACT) was kept at 200-250 sec. All five calves demonstrated neither abnormal signs nor abnormal blood examination data throughout the experiment. During necropsy, no thromboembolism was found in any downstream organs. Groups 1-4 showed thrombi inside the pump heads while two pumps in Group 5 had no thrombi formations. Bearing deformation or possible wear did not increase after 2 days of pumping. The C1E3 is capable of long-term assist circulation. However, after 2 days of pumping, careful observation is necessary since thrombi may occur inside the pump when ACT is controlled under 250 sec. During the weaning stage or low flow (under 2 L/min), over 250 sec of ACT is recommended to assure the safety of the patient.

Direct detection of red blood cell fragments: a new flow cytometric method to evaluate hemolysis in blood pumps.

Pump induced hemolysis is presently evaluated by measuring plasma free hemoglobin (fHb). However, this method has disadvantages because quantification of fHb depends on hematocrit (HCT) and hemoglobin (Hb) levels. The aim of this work was to devise a hemoglobin independent method, capable of quantifying cell trauma directly by measuring the number of red blood cell (RBC) fragments. Whole blood flow cytometry was used to quantify circulating RBC fragments derived from a roller pump (Sarns, Inc. Model 2 M 6,002) and a centrifugal pump (Gyro C1E3, Kyocera Corp.). The pumps were tested in a mock circuit for 2 hr (5 L/min flow against 100 mm Hg pressure head). Red blood cell fragments were quantified by a phycoerythrin (PE) labeled glycophorin A antibody specific for erythrocytes. Red blood cell fragments were smaller than the intact RBC population and overlapped in size with the platelet population (based on forward- and side-light scattering measurements). For the roller pump, the values for RBC fragments increased from 1,090 ± 260/&mgr;l at 0 min to 14,880 ± 5,900/&mgr;l after 120 min. In contrast, using the centrifugal pump, there was little increase in RBC fragments (from 730 ± 270/&mgr;l at 0 min to 1,400 ± 840/&mgr;l after 120 min). Flow cytometry can be used for the rapid, sensitive, hemoglobin independent evaluation of pump induced RBC trauma.

Surgical Outcomes of Acute Type A Aortic Dissection in Elderly Patients

BACKGROUND Age is still considered a risk factor in the repair of acute type A aortic dissection. Instead of total arch replacement, we performed hemiarch or partial arch replacement with intimal tear exclusion to reduce death in elderly patients and evaluated early-term and midterm outcomes. METHODS From January 2004 to April 2012, 59 patients older than 70 years (mean age, 77.0±4.3 years) underwent emergency operations for acute type A aortic dissection at our institution. We performed hemiarch, partial arch, or total arch replacement, according to the location of the primary entry tear. The characteristics, surgical procedures, and early-term and midterm outcomes of these patients were reviewed. RESULTS We performed hemiarch replacement in 47 patients, partial arch replacement in 4, and total arch replacement in 8. The primary entry site was excluded in 56 of 59 patients (94.9%). In-hospital mortality was 6.8%, and neurologic impairment occurred in 25.4%. We obtained midterm outcomes for 55 of 59 patients, with a mean follow-up period of 43.9±23.7 months. Fourteen patients died, two of these of aortic-related causes. One patient required repeat aortic operation for rupture of a pseudoaneurysm. Follow-up computed tomography imaging was done in 28 of 55 patients during the 12 months after the operation. No significant difference was noted in the increase in maximal aortic diameter between patients with and without residual dissection. CONCLUSIONS In-hospital mortality was 6.8%; relatively low compared with previous reports. Hemiarch and partial arch replacement with entry tear exclusion may reduce deaths associated with acute type A aortic dissection repair in elderly patients, without increasing the risk of reoperation and aortic-related death.

Prosthetic valve endocarditis caused by Staphylococcus capitis: report of 4 cases

Although Staphylococcus capitis is considered to be a rare causative organism for prosthetic valve endocarditis, we report 4 such cases that were encountered at our hospital over the past 2 years. Case 1 was a 79-year-old woman who underwent aortic valve replacement with a bioprosthetic valve and presented with fever 24 days later. Transesophageal echocardiography revealed an annular abscess in the aorto-mitral continuity and mild perivalvular regurgitation. We performed emergency surgery 5 days after the diagnosis of prosthetic valve endocarditis was made. Case 2 was a 79-year-old woman presenting with fever 40 days after aortic valve replacement with a bioprosthesis. Transesophageal echocardiography showed vegetation on the valve, and she underwent urgent surgery 2 days after prosthetic valve endocarditis was diagnosed. In case 3, a 76-year-old man presented with fever 53 days after aortic valve replacement with a bioprosthesis. Vegetation on the prosthetic leaflet could be seen by transesophageal echocardiography. He underwent emergency surgery 2 days after the diagnosis of prosthetic valve endocarditis was made. Case 4 was a 68-year-old woman who collapsed at her home 106 days after aortic and mitral valve replacement with bioprosthetic valves. Percutaneous cardiopulmonary support was started immediately after massive mitral regurgitation due to prosthetic valve detachment was revealed by transesophageal echocardiography. She was transferred to our hospital by helicopter and received surgery immediately on arrival. In all cases, we re-implanted another bioprosthesis after removal of the infected valve and annular debridement. All patients recovered without severe complications after 2 months of antibiotic treatment, and none experienced re-infection during 163 to 630 days of observation. Since the time interval between diagnosis of prosthetic valve endocarditis and valve re-replacement ranged from 0 to 5 days, early surgical removal of the infected prosthesis and an appropriate course of antibiotics were attributed to good clinical outcomes in our cases.

Platelet Function During Cardiopulmonary Bypass Using Multiple Electrode Aggregometry: Comparison of Centrifugal and Roller Pumps

Blood trauma may be lower with centrifugal pumps (CPs) than with roller pumps (RPs) during cardiopulmonary bypass (CPB), because, unlike RPs, CPs do not compress the tubing, and shear stress is considered lower in CPs than in RPs. However, relative platelet function remains unclear. Using multiple electrode aggregometry (MEA), we compared platelet function with CP and RP. Ten swine underwent CPB for 3 h, with five weaned off using CP and five using RP. Platelet function was measured using MEA, as were hemoglobin concentration and platelet count, before sternotomy, after heparin infusion, 30 min and 3 h after starting CPB, after protamine infusion, and 60 min after stopping CPB. Platelet activation was initiated with adenosine diphosphate (ADP), arachidonic acid (AA), and thrombin receptor-activating protein 6 (TRAP). Fibrinogen, platelet factor 4 (PF4), and β-thromboglobin (β-TG) concentrations were measured before sternotomy and 60 min after stopping CPB. In the CP group and using ADP, aggregation was significantly reduced 30 min (P = 0.019) and 3 h (P = 0.027) after starting CPB, recovering to baseline 60 min after CPB was stopped. In the RP group, aggregation was significantly decreased 30 min (P = 0.007) and 3 h (P = 0.003) after starting CPB and after protamine administration (P = 0.028). With AA, aggregation significantly decreased 30 min after starting CPB in both the CP (P = 0.012) and RP (P = 0.016) groups, slightly increasing 3 h after starting CPB and after protamine infusion, and recovering to baseline 60 min after CPB cessation. With TRAP, aggregation in the CP and RP groups decreased 30 min after starting the pump, although changes were not significant; aggregation gradually recovered after 3 h and returned to baseline 60 min after the pumps were stopped. There were no significant differences at all sampling points of MEA. In both groups, fibrinogen, PF4, and β-TG concentrations were similar 60 min after pump cessation and before sternotomy. Platelet function, evaluated with MEA, was lowest 30 min after CPB was started but did not decrease over time in either group. As assessed by MEA, platelet function using CP and RP did not differ significantly. Platelet dysfunction was caused mainly by initial contact with foreign materials and may not be dependent on type of pump.

Tracheo-Bronchial Obstruction and Esophageal Perforation after TEVAR for Thoracic Aortic Rupture.

A 67-year-old man was referred to our hospital for an ascending aortic aneurysm, thoracoabdominal aortic aneurysm and aortic regurgitation. Graft repair of the thoracic aortic arch and aortic valve replacement was given priority and completed, however he developed descending aortic rupture before the second scheduled surgery, and endovascular stent grafting was performed. He subsequently developed tracheobronchial obstruction and esophageal perforation. The patient underwent urgent esophagectomy and enterostomy with continuity later reestablished. However, he died of sepsis 5 months after surgery. Despite the less invasive nature of endovascular treatment, esophageal perforation can nevertheless occur and postoperative vigilance is well warranted.

Innovative Application of Available Stent Grafts in Japan in Aortic Aneurysm Treatment—Significance of Innovative Debranching and Chimney Method and Coil Embolization Procedure

OBJECTIVE We here describe our experience with innovative uses of these devices. PATIENTS AND METHODS We reviewed treatment outcomes of 310 endovascular abdominal aortic repair (EVAR) and 83 thoracic endovascular aortic repair (TEVAR) cases performed between August 2007 and February 2012. We separately assessed results in elderly and high-risk patients who had a novel procedure. This group included 94 patients who underwent EVAR with IIA embolization, 10 patients who had EVAR and a renal artery chimney procedure for a short aortic neck, 20 patients who had two de-branching TEVAR or Chimney method for thoracic aortic aneurysms (TAA) and 3 patients who had debranching TEVAR for thoracic abdominal aortic aneurysms (TAAA). RESULTS Of the 393 patients given stent grafts (SGs), 3 (0.8%) died in the hospital, including 1 patient with pneumonia who underwent EVAR and IIA embolization and 1 patient with a cerebral infarction who had TEVAR. Four patients (4.3%) who were treated with EVAR with internal iliac artery (IIA) embolization presented with residual buttock claudication 6 months postoperatively, and 3 patients (3.2%) had onset of ischemic enteritis; however, in all 7 patients, the condition resolved without additional intervention. In the 10 patients who had EVAR and a renal artery chimney method, the landing zone (LZ) was ≤10 mm, but neither endoleak nor renal artery occlusion was observed perioperatively or during midterm follow-up. Of the 20 patients who had a 2-debranching TEVAR, including 9 in whom the chimney method was used with the LZ in zone 0, 1 (5%) had a residual endoleak. In 3 patients with TAAA, we used SGs to cover 4 abdominal branches and bypassed the visceral artery; the outcomes were good, with all patients being ambulatory at hospital discharge. CONCLUSION Among innovative SGs treatments, the debranching procedure and the chimney method using catheterization and the coil-embolization technique provided good outcomes, as used in addition to surgical procedures. Aortic aneurysm treatment will become increasingly noninvasive with the continuing development of more innovative ways to use the SGs currently available in Japan. (English Translation of Jpn J Vasc Surg 2012; 21: 165-173).

Successful repair of aberrant right subclavian artery aneurysm combined with bicuspid aortic valve through a median sternotomy

We report a case of a successfully repaired aberrant right subclavian artery aneurysm combined with bicuspid aortic valve using a multibranched vascular prosthesis. Approaching solely through a median sternotomy under cardiopulmonary bypass, hypothermic circulatory arrest, and selective cerebral perfusion, we performed a successful single-stage correction by aortic valve replacement, resection of aneurysm, and reconstruction of the right subclavian artery.