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Biomedical subjects

K Neya

Publications and source records attributed to K Neya.

16 recordsLinked to original sources
PubMed2006

Hemodynamic effects of dexmedetomidine in patients after cardiac surgery.

AIM: Dexmedetomidine hydrochloride (Prece-dex(R)) is a potent and highly selective central a2-adrenoreceptor agonist. Dexmedetomidine has recently been approved as a new sedative drug, however, its hemodynamic effects on patients just after cardiac surgery has not been established. METHODS: Nineteen patients (14 males and 5 females) who underwent elective cardiovascular surgery were included in this study. The mean age of the patients was 65 years. Coronary artery bypass grafting was performed in 8 patients, aortic valve surgery in 5, mitral valve plus radiofrequency Maze surgery in 3, graft replacement of the ascending aorta in 2 and double valve replacement in 1. After surgery, dexmedetomidine was continuously infused for 3 h in total at a rate of 0.8 mg/kg/h for the initial 1 h and followed by 0.4 mg/kg/h. RESULTS: All patients were well sedated during dexmedetomidine infusion. Dexmedetomidine infusion induced a decrease in systemic blood pressure and systemic vascular resistance index. Heart rate, stroke index, central venous pressure, pulmonary artery pressure and pulmonary artery resistance index remained unchanged. Mixed venous oxygen saturation significantly decreased and arterio-venous O2 content difference increased after the beginning of dexmedetomidine infusion. CONCLUSIONS: Continuous dexmedetomidine infusion did not influence the hemodynamic condition except for the vaso-dilating effect, thus dexmedetomidine was considered to be a viable sedative drug after cardiac surgery.

Journal Article↗
PubMed2002

[A case of ischemic dilated cardiomyopathy, mitral regurgitation and congestive heart failure successfully treated by Batista operation, coronary artery bypass grafting and mitral valve replacement; usefulness of myocardial scintigraphy].

A 75-year-old man diagnosed as having ischemic dilated cardiomyopathy, congestive heart failure and mitral regurgitation underwent left ventricle volume reduction operation (Batista), coronary bypass grafting and mitral valve replacement because myocardial infarction had developed at lateral, inferior and small area of apex wall, not at interventricular septum. Left ventricular endodiastolic volume index and left ventricular endosystolic volume index decreased from pre-operative values of 155, and 128 ml/m2 to post-operative values of 113, and 82 ml/m2, respectively. Left ventricular ejection fraction increased from a pre-operative value of 17% to a post-operative value of 27%. This evaluation was performed by myocardial scintigraphy (quantitative gated spect: QGS). This method was bloodless and useful for determination of indication of left ventricle volume reduction surgery including Batista operation and pre- and post-operative evaluation of this type of surgery. Today, Batista operation is, generally speaking, performed for non-ischemic dilated cardiomyopathy. In this case, however, Batista operation was applied to ischemic dilated cardiomyopathy and was very effective.

Aged↗
PubMed2001

Chemical sensor based on nonlinearity: principle and application.

Novel chemical sensors based on a time-dependent nonlinear response are reviewed. The strategy is to artificially mimic information transduction in living organisms. In taste and olfaction, information of chemical structure and concentration is transformed into nervous impulses in the nervous cell, i.e., time-dependent multi-dimensional information. Because the excitation and pulse generation in the nervous cell are typically nonlinear phenomena, it may be worthwhile to utilize the nonlinearity as the multi-dimensional information for molecular recognition. The principle of a "nonlinear" sensor is that a sinusoidal modulation is applied to a system, and the output signal is analyzed. The output signal of the sensor is characteristically deformed from the sinusoidal input depending on the chemical structure and concentration of the chemical stimuli. The characteristic nonlinear responses to chemical stimuli are discussed in relation to the kinetics of chemical compounds on the sensor surface. As a practical application, we introduced electrochemical sensors based on the differential capacitance, semiconductor gas sensors under the application of sinusoidal temperature or diffusion change, and a chemical sensor based on the spatio-temporal information. We demonstrated that mutli-dimensional information based on nonlinearity can provide quite useful information for the analysis of chemical species, even in the presence of another analyte or an interference with a single detector.

Artificial Organs↗
PubMed1995

Experimental ablation of outflow tract muscle with a thermal balloon catheter.

BACKGROUND: Pulmonary balloon valvuloplasty has been performed in selected patients with tetralogy of Fallot as an alternative to surgical palliation; this technique is limited, however, by the fact that the balloon has little effect on the dynamic, muscular contribution to outflow tract obstruction. In an experimental model, we used a new thermal balloon catheter to ablate right ventricular outflow tract muscle. We evaluated the acute efficacy and muscle ablation parameters of this technology and its effects after myocardial healing. METHODS AND RESULTS: A prototype electrolyte-filled balloon catheter, heated by radiofrequency energy, was constructed. Studies were conducted to determine the optimum electrolyte solution needed to minimize balloon heating time with an unmodified, commercially available radiofrequency generator. In vivo ablations of right ventricular outflow tract muscle with the thermal balloon were performed in lambs that were divided into three groups (n = 5 each) according to the duration of thermal energy delivery (20, 40, and 60 seconds, respectively). Ablated lesion volume increased (460 +/- 63 to 1156 +/- 256 mm3) as the energy delivery time increased (20 to 60 seconds) and was correlated with delivered energy, temperature integral, and maximum epicardial surface temperature (r = .85, .82, and .72, respectively). All five lesions in the 60-second group showed an acute decrease of the wall thickness. Additional in vivo ablations were performed in 6 animals in which survival studies showed muscle thinning, healing by fibrosis, and no evidence of aneurysm formation. CONCLUSIONS: Thermal energy can be used with a balloon catheter delivery system to ablate myocardium. This study suggests that this energy delivery technology might be useful for relief of muscular outflow tract obstruction and that further studies are warranted.

Animals↗
PubMed1995

Norepinephrine infusion following cardiopulmonary bypass: effect of infusion site.

The placement of left atrial catheters following cardiopulmonary bypass (CPB) allows accurate monitoring of left ventricular filling pressures, as well as access for the infusion of vasoactive drugs. While the left atrial administration of norepinephrine (NE) is thought to provide higher systemic arterial NE levels while minimizing any pulmonary vasoconstriction, no study critically compares central venous and left atrial NE infusion following cardiopulmonary bypass. A canine model was used to compare central venous and left atrial NE infusion at three dosages (0.2, 0.4, and 0.6 microgram/kg/min) both prior to CPB and following 2 hr of hypothermic CPB at 27 degrees C. Prior to CPB, there was no difference in the hemodynamic efficacy of central venous and left atrial NE infusion at any dosage. The pulmonary circulation metabolized 16-29% of circulating NE. Only at the 0.2 microgram/kg/min dose was there a difference in the arterial NE level between central venous (3474 +/- 486 pg/ml) and left atrial (5504 +/- 751 pg/ml, P = 0.019) NE administration. Above this dose, no difference in the arterial NE level was identified. Following 2 hr of CPB, the pulmonary endothelium metabolized a significantly higher percentage of circulating NE (35-42%). Despite this increased extent of pulmonary metabolism, there was no difference in the hemodynamic efficacy or the resulting arterial NE level of central venous and left atrial NE infusion at a given dose. In conclusion, the results demonstrate: (1) increased pulmonary NE uptake following CPB, and (2) no difference in hemodynamic efficacy between central venous and left atrial NE infusion over a wide range of three doses in a model with normal lungs.

Animals↗
PubMed1995

Limitations of the efficacy of hemoglobin-based oxygen-carrying solutions.

Improvements in hemoglobin-based oxygen-carrying (HBOCs) solutions have overcome the toxicities that plagued earlier efforts. However, limitations of the efficacy of HBOCs are emerging. The potential limitations of an HBOC were studied in an ovine model (n = 6) of exchange transfusion. Hemodynamic, oxygen transport, and hemoglobin kinetic parameters were examined during isovolumic blood exchange to a final hematocrit of 3.2 +/- 0.7% and a plasma hemoglobin concentration of 8.1 +/- 0.4 g/dl while sheep were awake and breathing room air. However, the infusion of HBOC was associated with immediate increases in systemic and pulmonary arterial pressures. Despite hemodilution with HBOC, systemic and pulmonary vascular resistance increased 43.9% (P < 0.001) and 204.2% (P < 0.001), respectively, after HBOC infusion. After blood exchange, the plasma hemoglobin level exhibited a circulatory half-life of 52.7 +/- 18.0 h. The formation of methemoglobin was significant, accounting for 33.0 +/- 7.1% of the total circulating plasma hemoglobin at 24 h; the half-life of HBOC capable of carrying oxygen was 30.1 +/- 5.4 h. This relatively short period of oxygen-carrying efficacy and the observed vasoconstriction properties may constrain the potential applications of HBOC solutions.

Animals↗
PubMed1994

Reduction in experimental pericardial adhesions using a hyaluronic acid bioabsorbable membrane.

Various materials have been suggested for pericardial closure following cardiac surgery to limit postoperative adhesion formation. Unfortunately, these devices have caused difficulties with infection, calcification, and epicardial scar formation. A bioabsorbable membrane with a short in-vivo persistence time, acting as a barrier to adhesion formation until mesothelial healing occurs, might obviate many of these problems. We examined the efficacy of a bioabsorbable membrane containing hyaluronic acid in the prevention of experimental pericardial adhesions; hyaluronic acid solutions have been shown experimentally to reduce adhesions following abdominal, orthopedic and cardiac surgery. Eleven dogs underwent sternotomy and pericardiotomy followed by 2-h protocol of desiccation and abrasion of pericardial and epicardial surfaces. In five dogs, the epicardial surfaces were covered with the test material, followed by pericardial and sternotomy closure. Six dogs served as controls. All animals underwent resternotomy 8 weeks after surgery; intrapericardial adhesions were graded on a severity scale (0-4). The test animals (mean adhesion score 1.4 +/- 0.5) had either no adhesions or filmy, avascular adhesions easily taken down with blunt dissection. In contrast, dense adhesions were found in the control animals (mean score 3.2 +/- 0.4), frequently obscuring tissue planes and epicardial anatomy. Use of the bioabsorbable membrane significantly reduced adhesion formation (test vs control, P < 0.001, Mann-Whitney test). We conclude that a hyaluronic acid membrane reduces postoperative pericardial adhesions in this canine model, and that the use of a bioabsorbable barrier in the prevention of pericardial adhesions warrants further investigation.

Animals↗
PubMed1994

Prevention of postoperative pericardial adhesions with a hyaluronic acid coating solution. Experimental safety and efficacy studies.

Postoperative pericardial adhesions complicate reoperative cardiac procedures. Topical application of solutions containing hyaluronic acid have been shown to reduce adhesions after abdominal and orthopedic surgery. The mechanism by which hyaluronic acid solutions prevent adhesion formation is unknown but may be due to a cytoprotective effect on mesothelial surfaces, which would limit intraoperative injury. In this study, we tested the efficacy and safety of hyaluronic acid coating solutions for the prevention of postoperative intrapericardial adhesion formation. Eighteen mongrel dogs underwent median sternotomy and pericardiotomy followed by a standardized 2-hour protocol of forced warm air desiccation and abrasion of the pericardial and epicardial surfaces. Group 1 (n = 6) served as untreated control animals. Group 2 (n = 6) received topical administration of 0.4% hyaluronic acid in phosphate-buffered saline solution at the time of pericardiotomy, at 20-minute intervals during the desiccation/abrasion protocol, and at pericardial closure. The total test dose was less than 1% of the circulating blood volume. Group 3 (n = 6) served as a vehicle control, receiving phosphate-buffered saline solution as a topical agent in a fashion identical to that used in group 2. At resternotomy 8 weeks after the initial operation, the intrapericardial adhesions were graded on a 0 to 4 severity scale at seven different areas covering the ventricular, atrial, and great vessel surfaces. In both the untreated control (group 1, mean score 3.2 +/- 0.4) and vehicle control (group 3, mean score 3.3 +/- 0.2) animals, dense adhesions were encountered. In contrast, animals treated with the hyaluronic acid solution (group 2, mean score 0.8 +/- 0.3) characteristically had no adhesions or filmy, transparent adhesions graded significantly less severe than either the untreated control (group 2 versus group 1, p < 0.001) or vehicle control (group 2 versus group 3, p < 0.001) animals. In separate experiments, six baboons were infused with 0.4% hyaluronic acid in phosphate-buffered saline solution in volumes equivalent to 2.5%, 5%, and 10% of the measured circulating blood volume. The 2.5% and 5% infusions had no effect on the parameters measured; infusion of the 10% volume produced transient hemodynamic, coagulation, and gas exchange abnormalities. Hyaluronic acid solutions are efficacious in the prevention of pericardial adhesions in this model, and they appear safe in doses five times the amount needed to prevent adhesions. Further studies investigating the mechanism by which these solutions prevent adhesions, their optimal dose and method of application, and documentation of their safe use in humans are warranted.

Animals↗
PubMed1993

Reduction of reperfusion injury by recombinant human superoxide dismutase administered intravenously just prior to reperfusion.

The reduction of reperfusion injury by intravenous administration of recombinant human superoxide dismutase (r-hSOD) was evaluated in a dog model. Two hours of left anterior coronary artery clamping were followed by 30 min of partial reperfusion and 30 min of full reperfusion. In the SOD group, r-hSOD (100,000 U/kg) was given intravenously 5 min before reperfusion. Measured left ventricular (LV) segments were classified thermographically by temperature drop into central (> or = 2 degrees C) and marginal (< 2 degrees C) areas. The regional LV functions were evaluated by percentages of both segmental (%SS) and active (%AS) shortening. In the central area, the %SS values after reperfusion were -9% in the control group and -3% in the SOD group (p < 0.05). The respective %AS values were 6 and 29% (p < 0.01). In the marginal area, both groups had %SS values of -3% and respective %AS values of 34 and 22% (all not significant) after reperfusion. In the central area, there was significantly better LV function recovery in the SOD group than in the control group.

Animals↗
PubMed1993

[Effect of intravenous recombinant human superoxide dismutase on reducing reperfusion injury].

This study was performed to evaluate effects of recombinant human superoxide dismutase (r-hSOD) administered intravenously just prior to reperfusion on reduction of reperfusion injury by using regional left ventricular function recovery in quantitatively controlled reperfusion model. Mongrel dogs underwent 2 hours of left anterior coronary artery clamping followed by 30 minutes of partial reperfusion (25% of control flow) and 30 minutes of full reperfusion (full opening of occluder). Regional left ventricular functions: % segmental shortening (%SS), % active shortening (%AS) = systolic shortening/total shortening, were evaluated during reperfusion. Dogs were divided into 2 groups, Control group and SOD group: r-hSOD was administered 100,000 Unit/kg in bolus intravenously before reperfusion. Measured left ventricular segments were classified by temperature drop in thermography into the central (> or = 2 degrees C) and the marginal (< 2 degrees C) ischemic zones. In the central ischemic zone, the values of %SS before left anterior descending coronary artery clamping were 11% and 12% in Control and SOD groups, respectively. Just after occlusion of coronary artery, %SS dropped down to the range of -5% to -7% and kept the same level during ischemia. After partial reperfusion, there was no significant difference of %SS between Control and SOD groups, however, after full reperfusion, %SS of SOD group showed better improvement than that of Control group (p < 0.05). As for %AS in the central ischemic zones, the same tendency was present. In the marginal ischemic zone, the values of %SS went down when left anterior descending coronary artery was occluded.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Outcome of Stanford type B acute aortic dissection.

BACKGROUND: The optimal timing of surgery in patients with Stanford type B aortic dissection remains controversial. This report reviews retrospectively early and long-term outcomes of patients with Stanford type B acute aortic dissections at our institute. METHODS AND RESULTS: From April 1979 through January 1991, 75 patients were diagnosed with Stanford type B aortic dissection, and 58 of them were hospitalized within 2 weeks from onset. They were treated initially as follows: emergent surgery was performed in 13 patients for rupture or impending rupture, and the remaining 45 were treated medically. In the former group, nine patients (69%) died; in the latter, eight (18%) needed surgery because of enlargement or rupture of the aneurysm in the follow-up period, and only one of these (13%) died. Of the other 37 patients treated medically, three (8%) died within 2 weeks and seven died (19%) in the chronic phase, four of them from rupture. Among 42 discharged patients initially treated medically, rupture occurred in 11.9% (five of 42). CONCLUSIONS: In acute-phase cases, surgical mortality is so high that medical treatment is preferable unless there are major complications. However, even in patients who had undergone successful initial medical treatment, expansion of the aneurysm, requiring surgery, often occurred. If careful observation reveals any sign of expansion, because elective surgery can be performed at low risk, it should be considered as soon as possible before a rupture develops.

Actuarial Analysis↗
PubMed1992

Intraoperative echocardiography for diagnosis and treatment of aortic dissection. Utility of color flow mapping for surgical decision making in acute stage.

In the past eight years until July 1992, 92 patients were admitted in the acute state of aortic dissection within two weeks from the onset of symptoms. 41 were diagnosed as Stanford type A and 51 were type B by transthoracic and transesophageal echography, computer tomography, and surgery. Sensitivity of transesophageal echography to detect the intimal flap and the false lumen was 97.6% in patients with Stanford type A and 100% in patients with Stanford type B. The surgical decision making has been mostly depending on the transesophageal echographic diagnosis. When the intimal flap was detected in the ascending aorta (Stanford type A) surgery was performed in emergency regardless of any evidence of rupture, cardiac tamponade, and severe aortic regurgitation. When the aortic dissection was detected only in the descending aorta (Stanford type B) the main course of therapeutic strategy in our institute was medical treatment. Surgery was performed on 37 patients of type A and nine patients of type B with mortality of 18.9% and 55.5% respectively. Four patients of type A and 42 patients of type B were treated medically with a mortality of 75.0% and 2.2% respectively. The relatively large leakages from the anastomosis of the aortic clamp site were repaired secondarily in two patients, and fenestration of the superior mesenteric artery was performed on one patient due to ischemia of the small intestine depending on the intraoperative direct scanning of color flow mapping. Coronary artery involvement of dissection was strongly suspected in two patients by intraoperative transesophageal echography and aortocoronary bypass grafting was performed on these patients. Perfusion problems was encountered in five of 37 patients with type A aortic dissection (13.5%) during cardiopulmonary bypass. Intraoperative transesophageal echography could clearly detect the hemodynamic changes in the descending aorta resulting from inadequate perfusion which was useful for the management of perfusion control during cardiopulmonary bypass. Secondary repair of the aortic arch was required due to ischemia of the aortic arch vessels in two patients after the primary surgery. The extension of the dissection into the aortic arch vessels can be promptly diagnosed with the combination of transesophageal echography and transcutaneous echography. In conclusion, transesophageal Doppler echography is the most rapid diagnostic tool for decision making in acute aortic dissection, and intraoperative transesophageal echo can provide useful information to resolve the perfusion difficulties during cardiopulmonary bypass.(ABSTRACT TRUNCATED AT 400 WORDS)

Acute Disease↗
PubMed1991

[Successful surgical treatment of total anomalous pulmonary venous connection (supracardiac Ib type) showing an unusual shape of the pulmonary veins in an infant].

An experience of a 9-month-old infant with Darling's type Ib of total anomalous pulmonary venous connection is presented. In this case, the left pulmonary vein traveled horizontally behind the atrium, entered the right thoracic cavity and drained into the SVC together with the right lower, middle and upper pulmonary veins. The patient was treated with repair using Gersony-Malm's method and plasty of SVC because of the stenosis of the common pulmonary vein's entrance to the SVC. Her postoperative course was uneventful, and the result was satisfactory. To our knowledge, our case is the first successful correction not associated with other complex cardiac anomalies in the world.

Female↗
PubMedDate not supplied

Hemoglobin based oxygen carrying solution stability in extracorporeal circulation: an in vitro evaluation and implications for clinical use.

This study evaluated the stability of a hemoglobin based oxygen carrying (HBOC) solution during extracorporeal circulation. HBOC solution was diluted 1:1 with normal saline, 2 L of the resulting solution was oxygenated in either a bubble oxygenator (n=5) or membrane oxygenator (n=5), and it was placed in extracorporeal circulation at a rate of 2 L/min for 5 hr at 37 degrees C. To assess the effect of added human blood, 500 ml of fresh human whole blood was added to 1.5 L of diluted HBOC solution, and circulated as described. Methemoglobin level, hemoglobin integrity (percent of HBOC solution tetramer), and oxygen affinity (PO2 at 50% hemoglobin saturation) were measured. Extracorporeal circulation using the bubble oxygenator slightly altered (<1%) hemoglobin integrity compared with controls. Oxygen affinity decreased during extracorporeal circulation with both the membrane and bubble oxygenators; there was no significant difference between the oxygenators. Methemoglobin formation in controls and in extracorporeal circulation with either oxygenator was significant, with a slight advantage of the membrane compared with the bubble oxygenator; however, the presence of blood significantly decreased the rate of methemoglobin formation. In the presence of blood, HBOC solution remains structurally stable and efficacious for oxygen delivery during extracorporeal circulation.

Blood↗
PubMedDate not supplied

Effect of cardiopulmonary bypass and calcium administration on the splanchnic circulation.

Gastrointestinal complications following cardiopulmonary bypass (CPB) are associated with high mortality rates. The identification of prolonged CPB time and calcium administration as independent predictors of gastrointestinal complications suggests decreased splanchnic perfusion as a possible mechanism. To test this hypothesis, we evaluated splanchnic organ perfusion during CPB and after calcium chloride administration. Mongrel dogs were studied under anesthesia and were cannulated for bypass. CPB was begun at 37 degrees C, and the heart was fibrillated and vented. After 30 min, CPB temperature was reduced to 25 degrees C for 1 h with the heart arrested through cold crystalloid cardioplegia. After rewarming to 37 degrees C for 30 min, the heart was cardioverted, and CPB was weaned off. Calcium chloride (10 mg/kg) or saline was administered. Organ blood flow was determined with radiolabeled microspheres at baseline, during CPB, and after weaning from CPB. Splanchnic organ blood flow did not decrease during any phase of CPB. Calcium chloride administration after CPB had no effect on splanchnic organ blood flow. While gastrointestinal injury may result from CPB, this study suggests that the mechanism of injury is not decreased by splanchnic organ perfusion during bypass. While calcium chloride can cause pancreatic injury, the responsible mechanism is not calcium-induced hypoperfusion.

Animals↗