Biomedical subjects

N Shiiya

Publications and source records attributed to N Shiiya.

96 records · Page 6Linked to original sources

PubMedDate not supplied

Partial cardiopulmonary bypass in rats for evaluating ischemia-reperfusion injury.

The authors developed a miniaturized partial cardiopulmonary bypass model in rats by using membrane oxygenators. Sprague-Dawley rats underwent general anesthesia and tracheostomy for ventilation. Partial cardiopulmonary bypass was carried out through the jugular cannula (18 gauge) for venous blood drainage and through the femoral arterial cannula (24 gauge) at a flow of 50 ml/kg/min. Membrane oxygenators used in this study maintained arterial oxygen tensions (PaO2) at 300-500 mmHg and carbon dioxide tensions (PaCO2) at 25-35 mmHg, with a gas mixture of 95% O2 + 5% CO2 (n = 7) for at least 2 hr of bypass circulation. To test the feasibility of this system for investigation of ischemia-reperfusion injury, hypoxic challenges with gas mixtures of different oxygen concentrations were examined. After equilibration of the bypass circulation for 1 hr, the following gases were tested for 15 min: Group I, 95% air + 5% CO2 (FiO2 = 0.21, n = 5); Group II, 10% O2 + 5% CO2 + 85% N2 (FiO2 = 0.1, n = 5); and Group III, 95% N2 + 5% CO2 (FiO2 = 0, n = 5). Equilibrated PaO2 values after challenge with these gases for 15 min were as follows: Group I: 89.6 +/- 3.7, Group II: 53.8 +/- 1.4, Group III: 25.6 +/- 2.0 mmHg (p < 0.01 between Groups I and II, I and III, II and III; p < 0.01 vs. prehypoxic PaO2 values in all groups). PaO2 values returned to the previous level within 15 min after return to the standard gas mixture (95% O2 + 5% CO2) supply. This system provided stable cardiopulmonary bypass in rats for at least 2 hr and may be useful for investigation of ischemia-reperfusion injury.

Analysis of Variance↗

PubMedDate not supplied

Near infrared spectrophotometry reflects cerebral metabolism during hypothermic circulatory arrest in adults.

Near-infrared spectrophotometry (NIRS) is assumed to reflect cerebral oxygenation during hypothermic circulatory arrest (HCA). However, the rationale for the use of NIRS as a marker of cerebral metabolism remains to be elucidated. We examined whether cerebral oxygenation measured by NIRS correlated with cerebral metabolic function assessed by cerebral oxygen extraction ratio (OER) during HCA in adults. NIRS was continuously monitored in 14 patients undergoing thoracic aortic surgery using HCA (17.9 +/- 2.9 degrees C esophageal temperature at HCA onset). Jugular venous oxygen saturation and OER were also monitored. OER was significantly reduced from 37.3 +/- 7.2% at the onset of cardiopulmonary bypass to 13.6 +/- 6.2% at the onset of HCA (p < 0.0001). A linear decrease in oxygenated-hemoglobin (oxy-Hb) and increase in deoxygenated-hemoglobin (deoxy-Hb) were found during HCA, which returned to baseline levels after rewarming. The rate of decrease in oxy-Hb and increase in deoxy-Hb were -0.63 +/- 0.45 and 0.51 +/- 0.30 (10(-5) OD/cm per sec), respectively, both of which significantly correlated with OER at the onset of HCA (R2=0.739 and 0.633; p < 0.0001 and p = 0.0007, respectively). NIRS may serve as a reliable diagnostic modality for monitoring cerebral metabolism during aortic surgery using HCA.

Adult↗

PubMedDate not supplied

Effects of Hemopump support on left ventricular unloading and coronary blood flow.

The effects of the Hemopump (HP) on left ventricular (LV) and coronary hemodynamics, with and without myocardial ischemia, were studied in an acute, anesthetized, open-chest dog preparation (n = 6). Coronary blood flow velocity in the left circumflex was assessed with an intracoronary Doppler catheter. Measurements were made at two pump speeds (minimal = HP1 and maximal = HP7) before coronary ligation (control), after ligation of the LAD (ischemia), and after induction of cardiac failure by multiple ligations of the diagonal branches (failure). Changing from HP1 to HP7 resulted in 1) Increased total cardiac output in ischemia and failure; 2) Increased mean aortic pressure and systemic vascular resistance in control, ischemia, and failure; 3) Decreased LV external work (LV systolic pressure X stroke volume) in control, ischemia, and failure; 4) Decreased LV end diastolic pressure in ischemia; 5) Decreased LV systolic pressure and pressure-rate product in failure; and 6) Increased coronary blood flow/O2 demand ratio in failure. Hemopump support reduced O2 demand by LV decompression, and improved blood flow/O2 demand ratio in the nonoccluded coronaries of ischemic, failing hearts.

Animals↗

PubMedDate not supplied

The real impact of mechanical bridge strategy in patients with severe acute infarction.

Results obtained in the past 3 years in patients referred with acute myocardial infarction (AMI) and cardiogenic shock for a mechanical bridge to urgent transplantation permit one to assess the real impact of the present strategy in clinical practice. Ten patients (mean age = 49) were admitted in serious condition (CI = 1.8 +/- 0.2 L/min/m2, PCWP = 28 +/- 6 mmHg, systolic aortic pressure = 88 +/- 20 mmHg, urine output 11 +/- 20 ml/hr) and were treated by maximal sympathomimetic support and i.v. enoximone. Two had to be implanted with a total artificial heart (TAH) and one with a left ventricular assist device (LVAD) for recurrent fibrillation despite hemodynamic improvement, within 8 hr. Two have received transplants and are living well after 20 months. Seven who initially improved markedly have been listed as urgent transplant candidates: two of these have been successfully transplanted, and three died suddenly after 6, 25, and 45 days, respectively. One has undergone successful coronary surgery. One patient (age 62, diabetic) was secondarily rejected for a transplant and died. This experience clearly shows that despite initial spectacular hemodynamic improvement, which was due to optimized medical management, death rate before transplant because of sudden ventricular fibrillation remains unacceptably high. This should prompt early mechanical support, with less invasive systems, in patients with AMI.

Adult↗

PubMedDate not supplied

Hemopump ventricular support for patients undergoing high risk coronary angioplasty.

Prophylactic implantation of a Hemopump (Johnson and Johnson, Skillman, NJ) has been evaluated in nine patients selected for high risk coronary angioplasty. They were unstable patients, refractory to maximal pharmacology, with indications for revascularization, but contraindications for surgery such as low ejection fraction and lack of material for bypass. In all, the target lesion was located on the last patent vessel. The pump was inserted under local anesthesia, without any graft. A specially designed occluder permitted avoidance of retrograde bleeding during implantation. The bypass flow ranged from 2.5 to 3.2 L/min, and permitted a rise in cardiac index from 2.05 to 2.55 L/min/m2, with a drop in capillary wedge pressure from 13 (7-18) to 10 (7-13) mmHg. During balloon inflation, no electrocardiographic changes were observed, because only minor ventricular arrhythmias occurred. No significant hemolysis was seen (plasma free hemoglobin less than 10 mg/dl in all) after 2 hr of pumping. The only limitation of the technique appears to be difficulty at the time of implantation from narrow, stenosed, or tortuous iliofemoral arteries (3 patients). This experience strongly supports the benefit of temporary left ventricular Hemopump support in high-risk situations and clearly shows the need for a smaller pump.

Aged↗

PubMedDate not supplied

A lactobionate-based extracellular-type solution for donor heart preservation.

The University of Wisconsin solution, which contains the impermeant lactobionate and has an intracellular-type electrolyte composition, has been shown to improve donor heart preservation. Because a deleterious effect of the intracellular-type solutions has been reported, we evaluated a new lactobionate-based extracellular-type solution, by comparing it with University of Wisconsin solution and a crystalloid cardioplegic solution in 45 rabbit hearts. Hearts were arrested by infusion of these solutions and immersed in the same solution (lactobionate-based extracellular-type solution, University of Wisconsin solution) or in the lactated Ringer's solution (crystalloid cardioplegic solution) for 6 hours at 4 degrees C. A Langendorff circuit was used for reperfusion. Left ventricular compliance was better preserved with both lactobionate-based solutions than with the crystalloid cardioplegic solution. Adenosine triphosphate was best preserved with the lactobionate-based extracellular-type solution after arrest and after reperfusion, whereas reperfusion arrhythmias were less marked with the University of Wisconsin solution. These results suggest that lactobionate plays an important role in the preservation of ventricular compliance and that the lactobionate-based extracellular-type solution is preferable for adenosine triphosphate preservation. Further study will be required to assess the factors predisposing to reperfusion arrhythmias.

Adenine↗