• Journal of Chest Surgery
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• v.23 no.2
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• pp.268-274
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• 1990

Bleeding after cardiopulmonary bypass remains a cause for concern, requiring reexploration of the chest in approximately 3 percent of patients who have had operations on the heart. We examined the possibility that this problem might be alleviated by desmopressin acetate [DDAVP], synthetic vasopressin analogue that lacks vasoconstrictor activity. In a prospective, randomized trial, we studied the effect of intraoperative desmopressin acetate in 20 patients [the treated group 10 patients and the control group 10 patients] undergoing various cardiac operations requiring cardiopulmonary bypass. The result showed that the early postoperative [during first 24hrs] and mean postoperative blood loss [first 3 days] of the treated group were significantly reduced than the control group[447\ulcorner199ml in the treated group versus 746\ulcorner199ml in the treated group versus 746\ulcorner295 ml in the control group, p=0.014; mean\ulcornerstandard deviation and 675\ulcorner276 ml in the treated group versus 1006\ulcorner303 ml in control group, p=0.019]. The mean red-cell transfusion in first 3days were reduced in the treated group than the control group [3.3\ulcorner1.7 units vs 4.9\ulcorner1.7units, P=0.051]. There were no untoward side effects of desmopressin acetate. We conclude that the administration of desmopressin acetate can be recommended to reduce blood loss and blood conservation in patients undergoing cardiac operations.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1698-1711
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• 2024

Heat pipe cooled reactors have gained attention as a potential solution for nuclear power generation in space and deep sea applications because of their simple design, scalability, safety and reliability. However, under complex operating conditions, a control strategy for variable load operation is necessary. This paper presents a two-dimensional transient characteristics analysis program for a heat pipe cooled reactor and proposes a variable load control strategy using the recuperator bypass (CSURB). The program was verified against previous studies, and steady-state and step-load operating conditions were calculated. For normal operating condition, the predicted temperature distribution with constant heat pipe temperature boundary conditions agrees well with the literature, with a maximum temperature difference of 0.4 K. With the implementation of the control strategy using the recuperator bypass (CSURB) proposed in this paper, it becomes feasible to achieve variable load operation and return the system to a steady state solely through the self-regulation of the reactor, without the need to operate the control drum. The average temperature difference of the fuel does not exceed 1 % at the four power levels of 70 %,80 %, 90 % and 100 % Full power. The output power of the turbine can match the load change process, and the temperature difference between the inlet and outlet of the turbine increases as the power decreases.

• Journal of Korean Society of Disaster and Security
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• v.12 no.1
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• pp.57-66
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• 2019

One of the most serious problems with concrete small dams or barriers installed in small/median rivers is the deposit of sediments, especially, in Korea. An effective way to discharge such sediments to downstream is to construct a bypass pipe under the river bed. However, efficiency may become lowered if ripraps are entered into the bypass pipe. Therefore, in this study, we derived the threshold condition for the exclusion of ripraps from the bypass pipe using 3D numerical analysis. Upstream flow of the small dam was assumed to be stationary, and the energy concept was applied to the control volume containing the bypass pipe and its periphery. As a result, when the ratio of the water level difference between upstream and downstream to the diameter of the riprap was approximately equal to 1.2, the threshold condition for exclusion of the stones or riprap from the bypass pipe was affirmatively determined. If the characteristics of the adsorptive sediment adversely affecting the river environment in the future would be taken into account, results from this study are expected to put to practical use in the management of concrete small dam with bypass pipe system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.12
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• pp.782-790
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• 2011

Typical temperature control methods of a cooler for machine tools are hot-gas bypass and compressor variable speed control. The hot-gas bypass system has been widely used to control the cooler temperature in many general industrial fields. On the contrary, the compressor variable speed control is focused on special fields such as aerospace and high precision machine tools which need high precision control. The variable speed control system usually has two control variables such as target temperature and superheat. In other words, the variable speed control system is basically multi-input multi-output(MIMO) system. In spite of MIMO system, the proportional integral derivative(PID) feedback control methodology that based on single-input single-output (SISO) system is generally used for designing the variable speed control system. Therefore, it is inevitable to describe transfer functions for dynamic behaviors of every controlled variables and decide the PID gains with tremendous iteration process. Moreover, the designed PID gains do not provide optimum system performances. To solve these problems, high performance controller design method based on a state space model is suggested in this paper. An optimum controller is designed to minimize both control errors and energy inputs. This method was more simple to describe dynamic behaviors and easier to design the cooler controller which is MIMO system.

• Journal of Chest Surgery
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• v.23 no.3
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• pp.482-487
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• 1990

The leading cause of death in patients with chronic renal failure is cardiovascular diseases. The problems relevant to cardiac surgery in these patients are occurring more frequently with a growing number of patients at risk. Among these, important risk factors related to uremic patients undergone open heart surgery are fluid and electrolytes imbalance, coagulopathy, increased susceptibility to infection. Since 1968 when Lansing and colleagues reported the first successful aortic valve replacement in patients with chronic renal failure and infective endocarditis, there have been increasing reports of the cardiopulmonary bypass surgery in chronic renal failure patients with acceptable perioperative morbidity and mortality From Jan. 1988 to Nov. 1989 we have experienced four uremic patients necessitating open heart surgery ; one needing a coronary artery bypass graft and the other 3 needed cardiac valve replacement. Based on our observations we would like to suggest followings 1]Intraoperative ultrahemofiltration during C-P bypass thought to be an excellent means for the control of hyperkalemia and fluid balance. 2] The immediate postoperative application of peritoneal dialysis instead of hemodialysis is beneficial in controlling fluid and electrolyte imbalance. 3]The cause of one early postoperative death was not associated to renal failure, rather it was the result of an accidental rupture in the right ventricular wall.

• Journal of Chest Surgery
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• v.34 no.6
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• pp.454-464
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• 2001

Background: It has been recognized that systemic inflammatory reaction and oxygen free radical formed by activated leukocyte in the procedure of cardiopulmonary bypass(CPB) frequently produce postoperative cardiac and pulmonary dysfunction. The purpose of this study was to evaluate the efficacy of leukocyte-depleting filters in the cardiopulmonary bypass circuit for patients undergoing open heart surgery(OHS). Material and method: The study involved 15 patients who underwent OHS with a Leukoguard-6 leukocyte filter placed in the arterial limbs of the bypass circuit(filter group, n=15) and 15 patients who did not have the filter(control group, n=15). We analyzed the differences between the groups in intraoperative changes of peripheral blood leukocyte and platelet counts, pre- and postbypass changes of malondialdehyde(MDA), troponin-T(TnT), 5'-nucleotidase(5'-NT) in coronary sinus blood, spontaneous recovery rate of heart beat after CPB, pre-and postoperative cardiac index(Cl) and pulmonary vascular resistance(PVR), and the amounts of postoperative bleeding and sternal wound complication. Result: During CPB, total leukocyte count of the filter group(9,567$\pm$ 842/㎣) was significantly less than that of the control group(13,573+1,167/㎣) (p<0.01), but there was no significant difference in platelet count between the groups. Postoperative levels of MDA(3.78+0.32 $\mu$mol/L vs 5.86+0.65 $\mu$mo1/L, p<0.01), TnT(0.40$\pm$0.04 ng/mL vs 0.59$\pm$0.08 ng/mL, p<0.05) and 5'-NT(3.88$\pm$0.61 U/L vs 5.80$\pm$0.90 U/L, p<0.05) were all significantly lower in the filter group than the control group. Postoperative Cl was higher in the filter group than the control group(3.26$\pm$0.18 L/$m^2$min vs 2.75$\pm$0.17 L/$m^2$/min, p=0.05). PVR of the filter group was lower than that of the control group(65.87$\pm$7.59 dyne/sec/cm$^{5}$ vs 110.80+12.22 dyne/sec/cm$^{5}$ , p<0.01). Spontaneous recovery rate of heart beat in the filter group was higher than that in the control group(12 patients vs 8 patients, p<0.05). Postoperative wound infection occurred in one case in the filter group and 4 case in the control group(p<0.05). Postoperative 24 hour blood loss of the filter group was more than that of the control group (614$\pm$107 mL vs 380+71 mL, p=0.05).

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.643-647
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• 1986

A new type of motor-driven Total Artificial Heart (TAH) system with rolling-ball mechanism has been developed. To test its performance as a Left Ventricular Assist Device (LVAD), LVAD is controlled to bypass blood for impaired heart triggered by the R-wave in ECG. Results of the test with a Mock Circulation System (MCS) and an animal experiment with a dog are also included. More powerful system using a brushless DC motor has been developed and its control scheme is represented.

• Journal of Chest Surgery
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• v.32 no.6
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• pp.518-524
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• 1999

Background: This study has proven the effect of modified ultrafiltration(MUF) performed after the cessation of cardiopulmonary bypass in pediatric patients who underwent open heart surgery. Material and Method: From Jan. to Dec. 1997, modified ultrafiltration was performed after cardiopulmonary bypass in 50 infants with cyanotic heart disease and the results were compared to the control group of 50 patients with cyanotic heart disease in whom modified ultrafiltration was not used. Changes of hematocrit, central venous pressure, systolic and diastolic pressure, heart rate and body weight were compared. Result: Age and body weight were not different(p=0.38, p=0.46). Disease categories were similar. Average filtering volume was 60.0$\pm$29.2cc/kg for 7.0$\pm$2.4minutes of filtration. Mean hematocrit after filtration(MUF=36.1%, control=26.4%, p=0.001) was higher in the MUF group. Systolic (p=0.0001) and diastolic blood pressure(p=0.0001) were observed to increase more and the central venous pressure(p=0.02) and the heart rate(p=0.02) were lower after filtration in the MUF group. Conclusion: This study demonstrated that modified ultrafiltration after cardiopulmonary bypass was a technically feasible option to improve the post-surgical course through the effective hemoconcentration, hemodynamic improvements, and body water control.

• Journal of Chest Surgery
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• v.46 no.1
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• pp.22-26
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• 2013

Background: Constrictive pericarditis after coronary artery bypass surgery has been known to affect cardiac output by limiting diastolic ventricular filling. We aimed to assess the influence of postoperative constrictive physiology on the early outcomes of patients undergoing off-pump coronary artery bypass grafting (OPCAB). Materials and Methods: Between January 2008 and July 2011, 903 patients underwent an isolated OPCAB and postoperative transthoracic-echocardiography. The patient cohort was classified into two groups: group A, constrictive physiology and group B, control group without constrictive physiology. Early outcomes were analyzed between the two groups. Results: Of the total 903 patients, group A consisted of 153 patients (16.9%). The amount of blood loss in group A during the postoperative 24 hours was greater than that of group B, but this was not statistically significant (p=0.20). No significant differences were found in the mortality rates (group A, 0.6%; group B, 1.4%; p=0.40) and 30-day major adverse cardiac and cerebrovascular events (MACCEs; group A, 3.3%; group B, 6.1%; p=0.42). Conclusion: Postoperative constrictive physiology does not affect 30-day MACCEs or other major complications after OPCAB. The results of this study suggest that patients with early postoperative constrictive physiology do not need medical or surgical treatment, and that conservative care is sufficient.

• Journal of Chest Surgery
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• v.43 no.5
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• pp.534-537
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• 2010

A twenty six year old man was admitted to our clinic for bleeding from a venous ulcer of the left leg. His left femoral vein had been ligated for bleeding control after a traffic accident that happened when he was 5 years old. He had a varicose vein, stasis dermatitis, and a venous ulcer on his left leg. To shunt left femoral venous return to the right femoral vein, we did a crossover bypass with arteriovenous fistula using the right greater saphenous vein. To get good patency of the arteriovenous fistula, the bypass graft was closed 6 weeks after the initial operation. He maintained his left leg circumference relatively well for 6 months after the operation. We report the case of a patient who had a vein crossover bypass for a chronic femoral vein ligation.