Kazufumi Okamoto

Osaka Prefecture Senshu Critical Care Medical Center, Ōsaka, Ōsaka, Japan

Are you Kazufumi Okamoto?

Claim your profile

Publications (52)93.72 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: During nitric oxide (NO) inhalation therapy, toxicity may be produced by the reactive metabolite nitrogen dioxide (NO2). The purpose of the present study was to determine the NO2 concentration in a NO inhalation system used for respiratory failure in children at relatively low concentrations of NO (< 20 ppm). The production of NO2 in the NO inhalation system using the Servo Ventilator 900C connected to the test lung under each of 30 combinations of NO concentrations (0, 4, 8, 12, 16, and 19 ppm) and inspired oxygen (O2) concentrations (21, 40, 60, 80, and 100%). Pressure controlled ventilation was used with a respiratory rate of 20 breaths/min. NO and NO2 measurements were obtained on the inspiratory side of the Y-piece connected to the test lung. At a given NO level, increases in the concentration of inspired O2 resulted in increases in the concentration of NO2 produced, as did increases in the amount of NO at a given concentration of O2. The mean NO2 concentration at the inspiratory site of the Y-piece did not exceed 0.05 ppm (the limit of NO2 as an outdoor air pollutant in the United States) when the NO concentration did not exceed 8 ppm, regardless of the O2 concentration. NO inhalation therapy for children with severe respiratory failure using the Servo Ventilator 900C can be performed safely when the concentration of NO does not exceed 8 ppm.
    No preview · Article · Jan 2011 · Pediatrics International
  • [Show abstract] [Hide abstract]
    ABSTRACT: Apoptosis may play an important role in the development of systemic inflammatory response syndrome (SIRS) and progression to multiple organ dysfunction syndrome (MODS). To quantify the extent of apoptosis in these morbidities, we developed a sandwich ELISA system to measure serum cytochrome c (cyt-c) levels and we investigated the prognostic significance of cyt-c concentration in SIRS/MODS patients. Cyt-c concentrations in patients with SIRS (n=53) with or at risk for MODS were measured and compared with those of control subjects (n=14). Cyt-c concentrations in SIRS/MODS patients increased (0.24-210 ng/ml), whereas those in control subjects were under detection limits (0.1 ng/ml). Cyt-c concentrations in non-survivors increased significantly compared with those in survivors both on the day of admission and on the fifth hospital day. A significant positive correlation was found between cyt-c concentration and two representative organ dysfunction scores, APACHE II and multi-organ failure (MOF) score. Cyt-c concentrations increased earlier than MOF score during the exacerbation phase and rapidly decreased during the convalescence phase in a survivor, but the level continued to be high in a non-survivor. Determination of serum cyt-c concentrations may be useful to assess the severity of organ dysfunction and to predict the prognosis of SIRS/MODS patients.
    No preview · Article · May 2004 · Clinica Chimica Acta
  • [Show abstract] [Hide abstract]
    ABSTRACT: Since NO was identified as effective in treatments involving endothelium-derived relaxing factor in 1987, inhalation of NO (iNO) has been widely used in the medical treatment of acute respiratory distress syndrome, acute lung injury, high blood pressure, and other related illnesses. Current iNO systems usually include a gas cylinder of N2 with a high concentration of NO. This system has an inherent risk of generating nitric dioxide (NO2) if leaked NO mixes with air. NO2 is thought to be toxic to the lungs. Therefore, a system that does not include storage of NO is very desirable for administering iNO. In this paper, Prototype of On-site NO generator, which includes a discharge reactor, a NO2-NO catalyst, a charcoal and a particle filter, is developed for animal experiments.
    No preview · Article · Jan 2004 · IEEJ Transactions on Electronics Information and Systems
  • [Show abstract] [Hide abstract]
    ABSTRACT: Host response to infection and other forms of tissue injury have been termed systemic inflammatory response syndrome (SIRS). This inflammatory response can frequently be accompanied by oxidative injury in one or more organ systems in the body. The objective of this report was to clarify the possible role of oxidative stress in the development of multiple organ failure (MOF) in patients with SIRS. Prospective clinical study. Intensive care unit in a university hospital. A total of 214 consecutive patients (mean age, 57.1 +/- 17.4 yrs; range, 13 to 84 yrs; 148 men and 66 women). At the time of admission, 139 patients fulfilled the clinical criteria for SIRS. None. We measured plasma concentrations of thiobarbituric acid reactant substances (TBARS), as an index of oxidative stress, every day from the point of admission to the intensive care unit until discharge or death. Furthermore, all variables of the SIRS score and the Sequential Organ Failure Assessment score were collected every day. At the time of admission, plasma TBARS concentrations in SIRS patients with MOF were significantly higher than those in SIRS patients without MOF (2.3 +/- 0.9 vs. 1.9 +/- 0.6 nmol/mL, p <.01), and there was a significant correlation between plasma TBARS concentration and Sequential Organ Failure Assessment score (r2 =.18, p <.001). Furthermore, the duration of SIRS persistence was significantly associated with the percentage increase in plasma TBARS concentration during SIRS persistence in those patients in whom the duration of SIRS was confirmed (r2 =.73, p <.001). The duration of SIRS was significantly higher in patients who developed MOF than in patients who did not develop MOF (6.9 vs. 3.2 days, p <.001). The percentage increase in plasma TBARS concentration during SIRS was also significantly higher in patients who developed MOF than in patients who did not develop MOF (57.1% vs. 15.8%, p <.001). It can be concluded that processes of oxidative stress in connection with continued SIRS may promote the development of MOF.
    No preview · Article · Apr 2003 · Critical Care Medicine
  • Takao Namihira · Sunao Katsuki · Hidenori Akiyama · Kazufumi Okamoto
    [Show abstract] [Hide abstract]
    ABSTRACT: Nitric monoxide (NO) is increasingly being used in medical applications. Current applications use a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially dangerous, given the possibility of an accidental leak of NO from the cylinder. The presence of NO in air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore on-site generation of NO would be very desirable to treat patients with acute respiratory distress syndrome and other related illnesses. Recently, pure NO was generated using a pulsed arc discharge in dry air with an NO2-NO converter and charcoal. The concentration of NO was easily controlled by controlling pulse repetition rate and gas flow rate. This system is already under investigation in an animal experiment.
    No preview · Article · Jan 2003 · Journal of Plasma and Fusion Research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nitric monoxide (NO) is increasingly being used in medical applications. Currently, a gas cylinder of N<sub>2</sub> mixed with a high concentration of NO is used. This arrangement is potentially risky due to the possibility of accidental leak of NO from the cylinder. The presence of NO in air leads to the formation of nitric dioxide (NO<sub>2</sub>), which is toxic to the lungs. Therefore, an on-site generation of NO would be very desirable for patients with acute respiratory distress syndrome and other related illnesses. We have recently reported on the production of NO using a pulsed arc discharge. In the present work, the discharge reactor was made simpler and smaller. NO was generated using a pulsed arc discharge in dry air and in mixtures of oxygen and nitrogen. The composition of the gas mixture after treatment with an arc discharge followed by exposure to heated molybdenum was 540 ppm of NO, 48 ppm of NO<sub>2</sub>, and the balance dry air at 0.1 MPa and 300 ± 3 K. No ozone was detected at the outlet of the system by UV absorption. The density of the brass particles emitted from the electrodes, which had diameters over 0.3 μm, was less than 1.39 μg/L. A filter could readily capture and thus remove the brass particles.
    Full-text · Article · Nov 2002 · IEEE Transactions on Plasma Science
  • [Show abstract] [Hide abstract]
    ABSTRACT: Inverse ratio ventilation (IRV) is a ventilatory technique that uses an inspiratory to expiratory ratio (I:E) greater than 1:1. We studied the effects of mechanical ventilation with an I:E of 1:3, 1:1, and 2:1 on arterial oxygenation in 10 patients with sepsis-associated acute respiratory distress syndrome (ARDS). At each I:E, patients received 0 and 4 ppm of inhaled nitric oxide (INO) in random order for 30 min. Respiratory and cardiovascular parameters were measured. Of the 10 patients studied, 7 responded to IRV and 3 did not. An increase in the I:E and the addition of INO significantly improved arterial oxygenation in the responders (p < 0. 0001 and p < 0.006, respectively). The combination of an increase in the I:E and INO had an additive effect on arterial oxygenation. The combined use of IRV and INO is a more effective method of avoiding hypoxemia than either INO or IRV alone.
    No preview · Article · Nov 2000 · Artificial Organs
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The dynamic aspects of circulating cytokines and cytokine modulators and their relationship with development of multiple organ failure (MOF) in patients with acute pancreatitis were analyzed. All cytokine and C-reactive protein levels in the circulation were higher than those in the MOF group. In particular, plasma concentrations of soluble tumor necrosis factor receptors (sTNF-RI and sTNF-RII) were significantly higher in patients with MOF than in those without even at admission. Furthermore, plasma concentrations of sTNF-Rs and interleukin-1 (IL-1) receptor antagonist (IL-1ra) were much higher than those of their counterparts, TNF-α and IL-1β, respectively. These results suggest that the plasma concentrations of sTNF-Rs are useful predictors for the development of MOF, and actions of TNF-α and IL-1β could be regulated by their modulators (soluble receptor and receptor antagonist, respectively) in the pathologic condition of severe acute pancreatitis.
    Full-text · Article · Jul 2000 · Pancreas
  • [Show abstract] [Hide abstract]
    ABSTRACT: We studied the combined effects of inhaled nitric oxide (INO) and positive end expiratory pressure (PEEP) during mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). Eleven patients received 0 and 4 parts per million of INO in random order for 30 min at PEEP levels of 0, 5, and 10 cm H2O. Respiratory and cardiovascular parameters were measured. The addition of INO and PEEP significantly improved arterial oxygenation (p < 0.005 and p < 0.0001, respectively). The combined effect of INO and PEEP on arterial oxygenation was remarkable during 10 cm H2O PEEP. There was synergistic effect on arterial oxygenation by combining INO and 10 cm H2O PEEP. The present study showed that the combination of INO and 10 cm H2O PEEP enhanced arterial oxygenation in patients with ARDS.
    No preview · Article · May 2000 · Artificial Organs
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nitric monoxide (NO) is widely used in medical treatment of acute respiratory distress syndrome (ARDS). The production of NO is of interest to the medical community. In the present work, NO is generated by pulsed discharges between two rod electrodes in a mixture of nitrogen and oxygen. An arc discharge having a temperature of about 10000 K was produced, which was sufficient to generate NO. Some of the important parameters affecting the production of NO have been investigated. These include the percentage of O<sub>2</sub> (6-94%) in the mixture of Na and O<sub>2</sub>, the energy of the discharge (0.5-12 J/pulse), the pulse repetition rate (0.54.5 pps) and the flow rate (1.35-5.4 l/min) of the gas mixture. NO<sub>2</sub> produced in the discharge was successfully changed to NO using a heated molybdenum tube, NO<sub>2</sub> must be extracted from the gas before clinical inhalation. The concentration of ozone was completely eliminated by bubbling the gas mixture through water. A maximum of NO and a minimum of NO<sub>2</sub> concentrations were generated when the proportion of O<sub>2</sub> in the gas mixture was in the range of 20-27%. The concentrations of NO and NO<sub>2</sub> increased with increasing pulse repetition rate and with decreasing flow rate of the mixture. In all cases, No<sub>2</sub> was effectively removed using a heated molybdenum tube
    Full-text · Article · Mar 2000 · IEEE Transactions on Plasma Science

  • No preview · Article · Jan 2000 · Nihon Shuchu Chiryo Igakukai zasshi
  • [Show abstract] [Hide abstract]
    ABSTRACT: To determine whether oxygen consumption VO2), CO2 production, and resting energy expenditure (REE) in critically ill patients differ in varying grades of systemic inflammatory response syndrome (SIRS). Prospective, clinical study. Intensive care unit at a university hospital. Twenty-six critically ill patients requiring mechanical ventilation. None. A total of 100 metabolic measurements were performed. The grade of SIRS and the Acute Physiology and Chronic Health Evaluation II score were evaluated at the time of the metabolic cart study. VO2 and REE differed among the groups inadequate for SIRS (non-SIRS), with SIRS without infection (nonseptic SIRS), and with SIRS with infection (septic SIRS) (125 +/- 37 mL/min/m2 and 855 +/- 204 kcal/day/m2, 135 +/- 33 mL/min/m2 and 948 +/- 214 kcal/day/m2, and 166 +/- 55 mL/min/m2 and 1149 +/- 339 kcal/day/m2, respectively; p < .005). Patients with septic SIRS had higher VO2 and REE than patients with non-SIRS and nonseptic SIRS. VO2 and REE differ among groups of patients with non-SIRS, nonseptic SIRS, and septic SIRS. Patients with septic SIRS have higher VO2 and REE than patients with non-SIRS or nonseptic SIRS. The present study shows that classifying patients into three grades (non-SIRS, nonseptic SIRS, and septic SIRS) is a valid predictor of metabolic stress in critically ill patients.
    No preview · Article · Oct 1999 · Critical Care Medicine
  • [Show abstract] [Hide abstract]
    ABSTRACT: We studied the pharmacokinetics of ceftazidime in 3 critically ill patients undergoing continuous hemodiafiltration (CHDF). Blood samples were obtained from both the arterial and venous sites of the CHDF system 0, 1, 2, 4, 6, and 12 h after the start of ceftazidime administration. Pharmacokinetic variables were calculated by fitting individual concentration-time curves to a two-compartment open model. The elimination phase half-life was 6.86 h, and the total elimination rate constant was 0.17 h(-1). Six hours after the start of administration, the ceftazidime concentration in the arterial site decreased from the peak level of 77.5+/-31.4 (mean+/-standard deviation [SD]) microg/ml to 26.2+/-2.5 microg/ml. The ceftazidime concentration examined in 2 cases decreased to 14.7+/-5.8 microg/ml after 12 h. The results suggested that ceftazidime should be administered at 1 g/day in patients with severe infection during CHDF.
    No preview · Article · Mar 1999 · Artificial Organs
  • [Show abstract] [Hide abstract]
    ABSTRACT: The relationships between oxygen delivery (DO2), oxygen consumption (VO2), and the extraction rate (ER = VO2/DO2 x 100) in patients undergoing cardiopulmonary bypass (CPB) may differ from the normal physiologic state due to the oxygen debt acquired during CPB. Blood gas analysis and hemodynamic parameters were repeatedly measured for the determination of DO2 and VO2 in 40 patients undergoing CPB, every 8 h during the first 48 h postoperatively. As a control, 20 patients who had suffered acute myocardial infarction (AMI) were also studied using the same protocol. In the CPB group, a regression analysis showed that VO2 was significantly dependent on DO2, even within the physiologic range of DO2 (>500 ml/min per m2); VO2 = 121.4 + 0.0844 x DO2 (r = 0.254, P = 0.023). Conversely, in the AMI group, no such supply-dependent consumption was observed within the same range of DO2. At an ER of 30%, which is the optimal value in general, the DO2 of the CPB group was 575 ml/min per m2 and that of the AMI group was 493 ml/min per m2. All these results suggest that patients undergoing CPB need a much higher oxygen supply to recover from the oxygen debt acquired during open heart surgery.
    No preview · Article · Feb 1999 · Surgery Today
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present three cases treated with hyperbaric oxygenation therapy (HBO) for prolonged jaundice after hepatectomy. Case 1 : A 65-year-old man underwent right lobectomy for cancer of the gallbladder. After the operation, jaundice was prolonged and his total bilirubin rose to 18.1mg/dl. HBO was performed thirteen times, and his total bilirubin decreased to 5.4mg/dl. Case 2 : A 69-year-old man underwent right lobectomy for bile duct cancer. His total bilirubin increased to 19.3mg/dl. HBO was performed sixteen times and his total bilirubin decreased to 3.3mg/dl. Case 3 : A 64-year-old man underwent electrohydraulic lithotripsy for his remnant intrahepatic stone after hepatectomy of his cirrhotic liver. His total bilirubin increased with each lithotripsy treatment. HBO was commenced and his total bilirubin temporarily decreased to 11.5mg/dl from 21.1mg/dl, but finally increased again due to severe cholangitis, which caused fatal liver failure. Therefore HBO was not effective for jaundice in the patient with a cirrhotic liver and without a functional reserve. However, prolonged jaundice after hepatectomy of a non-cirrhotic liver was successfully treated with HBO.
    No preview · Article · Jan 1999 · Nippon Shokaki Geka Gakkai zasshi

  • No preview · Article · Jan 1999 · Nihon Kyukyu Igakukai Zasshi
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the influence of body temperature during cardiopulmonary bypass (CPB) on postoperative systemic metabolism, 32 patients undergoing elective cardiac surgery were randomly assigned to either hypothermia (n = 16) or normothermia (n = 16). Serial hemodynamic parameters and blood samples were obtained after surgery. CPB and operation times were significantly shorter and the platelet reduction ratio during CPB [ = (platelets before CPB-platelets after CPB)/platelets before CPB] was significantly lower in normothermic patients than in hypothermic patients. The platelet reduction ratio was dependent on the minimum rectal temperature during CPB, the operation time, and the CPB time. In the early postoperative period, hypothermic patients had abnormally high systemic vascular resistance and a reduced cardiac index compared with the normothermic patients. There were no differences between 2 groups in postoperative hepatic and renal functions, changes in oxygen consumption, arterial-venous PCO2 or arterial-venous pH gradient. This study suggested a beneficial influence of normothermic CPB on postoperative hemodynamics. Normothermic CPB was not associated with adverse effects on postoperative metabolic recovery.
    No preview · Article · Mar 1998 · The Japanese Journal of Thoracic and Cardiovascular Surgery
  • [Show abstract] [Hide abstract]
    ABSTRACT: In a newborn requiring cardiopulmonary resuscitation because of hypoxemia due to sepsis (oxygenation index > 40), inhalation of nitric oxide (NO) in a concentration of 16 p.p.m. improved oxygenation and restored spontaneous circulation. Cannulation for extracorporeal membrane oxygenation (ECMO) then was performed safely under NO inhalation. ECMO was discontinued on day 7, and on day 14 the infant was extubated. During follow-up examination at 5 months of age no neurological abnormalities were found. This case shows the usefulness of combining inhaled NO and ECMO.
    No preview · Article · Feb 1998 · Acta paediatrica Japonica; Overseas edition
  • [Show abstract] [Hide abstract]
    ABSTRACT: Extracorporeal life support (ECLS) was used to treat three patients with near-fatal status asthmaticus who did not respond to aggressive medical therapies and mechanical ventilation under controlled permissive hypercapnia. ECLS was instituted in patient 1 because PaCO2 was excessively high and pH was excessively low, in patient 2 because hypoxemia and shock were not responsive to treatment, and in patient 3 because of sustained severe hypotension. ECLS supported adequate gas exchange until pulmonary function improved, diminishing the need for mechanical ventilation and preventing pulmonary complications. Pulmonary dysfunction improved markedly after only 21 to 86 hours of ECLS. Aggressive medical treatments were continued during ECLS. Our findings indicate that ECLS is a useful method for preventing death in patients with near-fatal status asthmaticus.
    No preview · Article · Nov 1997 · American Journal of Emergency Medicine
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nitric oxide (NO) inhalation and high frequency oscillatory ventilation (HFOV) has been indicated in infants with severe respiratory failure. The purpose of the present study was to evaluate the safety of an NO inhalation system with HFOV in terms of nitrogen dioxide (NO2) production. The NO inhalation system consisted of a high frequency oscillatory ventilator, a neonatal circuit and a test lung. The NO concentration was changed from 0 to 19 p.p.m. At each level of NO, the oxygen (O2) concentration was changed from 21 to 100%. The NO and NO2 concentrations were measured with a chemiluminescence analyzer using a molybdenum converter. The NO2 concentration was increased when either the O2 or the NO concentration was increased. The interposition of the endotracheal tubes increased NO2 concentrations at 4 p.p.m. NO. The high stroke volume and high mean airway pressure produced a significant increase in NO2 production at 4 p.p.m. NO. The increase in NO2 production was prevented by placing a one-way valve at the joint of the NO gas line to the inspired limb. It was concluded that the NO inhalation system with HFOV can be safely used when a one-way valve is placed at the joint of the NO gas line to the inspired limb and when inhaled NO is at a relatively low concentration.
    No preview · Article · May 1997 · Acta paediatrica Japonica; Overseas edition

Publication Stats

608 Citations
93.72 Total Impact Points

Institutions

  • 2011
    • Osaka Prefecture Senshu Critical Care Medical Center
      Ōsaka, Ōsaka, Japan
  • 2004
    • Shinshu University
      Shonai, Nagano, Japan
  • 1981-2000
    • Kumamoto University
      • • School of Medicine
      • • Department of Anesthesiology
      • • Department of Aggressology and Critical Care Medicine
      Kumamoto, Kumamoto, Japan