Joung Uk Kim

Effects of S-Nitrosation and Cross-Linking of Hemoglobin on Hypoxic Pulmonary Vasoconstriction in Isolated Rat Lungs

Abstract— Free hemoglobin (Hb) and red blood cells augment hypoxic pulmonary vasoconstriction (HPV) by scavenging nitric oxide (NO). S-nitrosation of Hb (SNO-Hb) may confer vasodilatory properties by allowing release of NO during deoxygenation and/or by interaction with small-molecular weight thiols. Likewise, cross-linking of free Hb may limit its vasoconstrictive effect by preventing abluminal movement of the molecule. We compared the effects of free SNO-Hb and Hb intramolecularly cross-linked at the &bgr;-cysteine 93 residue [Bis(maleidophenyl)-polyethylene glycol2000HbA (Bis-Mal-PEGHb)] to those of free oxyHb on pulmonary artery pressure (PAP), HPV, and exhaled NO (eNO) in isolated, perfused rat lungs. Ventilation of lungs with anoxic gas for 5 minutes reduced perfusate Po2 to 11±1.0 Torr. Addition of SNO-Hb or Bis-Mal-PEGHb (100 &mgr;mol/L) to buffer perfusate increased normoxic PAP and augmented HPV in similar magnitude as free oxyHb, but had no effect on eNO. Addition of the allosteric modulator inositol hexaphosphate to increase Hb P50 and the thiol glutathione (GSH) to allow removal of NO from Hb via transnitrosation to the perfusate did not reduce augmentation of HPV by SNO-Hb or increase eNO. GSH resulted in an ≈50% reduction in perfusate [S-nitrosothiol], in association with an increase in perfusate [metHb]. Free SNO-Hb is a net NO scavenger and pulmonary vasoconstrictor in this model, although thiol-mediated release of NO from SNO-Hb does occur. However, release of NO from SNO-Hb was not influenced by deoxygenation-mediated allosteric changes in Hb across a broad range of oxyHb saturation. Cross-linking of Hb does not limit its pulmonary vasoconstrictor effects.

Protective effect of isoflurane anesthesia on noise-induced hearing loss in mice.

Hypothesis/Objectives: To examine the protective effect of general anesthesia with isoflurane against noise‐induced hearing loss in mice.

The effect of isoflurane, halothane and pentobarbital on noise-induced hearing loss in Mice

BACKGROUND:Ear surgery using mastoid drills can lead to noise-induced hearing loss (NIHL). We investigated whether inhaled anesthetics or pentobarbital could have protective effects on NIHL in mice. METHODS:Mice were exposed to broad band white noise for 3 h per day for 3 consecutive days, with or without anesthesia, using halothane, isoflurane, or pentobarbital. The hearing level of each mouse was analyzed before exposure, and 1 day, 1, 2, and 3 Wk, and 1 mo after noise exposure by measuring auditory brainstem response thresholds. At 1 Wk after noise exposure, the organ of Corti was stained with a fluorescent isothiocyanate-conjugated phalloidin probe and a TUNEL kit. RESULTS:In the unanesthetized control group, the hearing threshold increased to 77.5 ± 8.0 dB hearing level (HL) after noise stimulation. In the pentobarbital, isoflurane, and halothane groups, hearing threshold increased to 62.5 ± 6.3 dB HL, 45.5 ± 9.8 dB HL, and 39.3 ± 6.2 dB HL, respectively, with all anesthetized groups of mice showing significantly preserved hearing compared with the control group (P < 0.05). But, in mice anesthetized with pentobarbital, hearing loss was more severe than in those treated with the inhaled anesthetics (P < 0.05). Hair cell survival was reduced in unanesthetized control mice and somewhat reduced in pentobarbital-treated mice, but largely unaffected in mice treated with inhaled anesthetics. CONCLUSIONS:These findings indicate that, while halothane, isoflurane and pentobarbital could protect mice against NIHL and hair cell damage, inhaled anesthetics were more effective.

Protective effects of propofol against hydrogen peroxide-induced oxidative stress in human kidney proximal tubular cells

Background We investigated the protective effects of propofol in the HK-2 cell line of human kidney proximal tubular cells against hydrogen peroxide (H2O2)-induced oxidative stress. Methods After pretreatment with different concentrations of propofol (0 µM, 10 µM, 25 µM and 50 µM) for 30 minutes, HK-2 cells were exposed to 8 mM H2O2 for 4 hours. Cell death was assessed by measuring the percentage of lactate dehydrogenase (LDH) release and by counting viable cells. The nature of cell death was assessed by doubles-taining cells with fluorescein isothiocyanate-labeled Annexin V and propidium iodide, and then analyzing the cells using flow cytometry. Results After exposure to 8 mM H2O2 for 4 hours, the percentage of LDH release was 45.1 ± 4.2% and the number of viable HK-2 cells was 5.2 ± 6.0%. Pretreatment with propofol suppressed H2O2-induced LDH release in a concentration-dependent manner, reducing the percentage of LDH release to 38.1 ± 5.6%, 33.5 ± 6.3%, and 26.2 ± 3.8% of the controls at 10 µM, 25 µM and 50 µM propofol, respectively. Numbers of viable cells increased following propofol pretreatment, with 11.4 ± 10.9%, 19.5 ± 16.1%, and 32.4 ± 23.3% cell survival rates after pretreatment with 10 µM, 25 µM and 50 µM propofol, respectively. Analyses of flow cytometry showed that the propofol pretreatment decreased the percentage of necrotic and late apoptotic cells. Conclusions Propofol protects HK-2 human kidney proximal tubular cells against H2O2-induced oxidative stress.

Endotracheal intubation by inexperienced trainees using the Clarus Video System: learning curve and orodental trauma perspectives

Background The ideal alternative airway device should be intuitive to use, yielding proficiency after only a few trials. The Clarus Video System (CVS) is a novel optical stylet with a semi-rigid tip; however, the learning curve and associated orodental trauma are poorly understood. Methods Two novice practitioners with no CVS experience performed 30 intubations each. Each trial was divided into learning (first 10 intubations) and standard phases (remaining 20 intubations). Total time to achieve successful intubation, number of intubation attempts, ease of use, and orodental trauma were recorded. Results Intubation was successful in all patients. In 51 patients (85%), intubation was accomplished in the first attempt. Nine patients required two or three intubation attempts; six were with the first 10 patients. Learning and standard phases differed significantly in terms of success at first attempt, number of attempts, and intubation time (70% vs. 93%, 1.4 ± 0.7 vs. 1.1 ± 0.3, and 71.4 ± 92.3 s vs. 24.6 ± 21.9 s, respectively). The first five patients required longer intubation times than the subsequent five patients (106.8 ± 120.3 s vs. 36.0 ± 26.8 s); however, the number of attempts was similar. Sequential subgroups of five patients in the standard phase did not differ in the number of attempts or intubation time. Dental trauma, lip laceration, or mucosal bleeding were absent. Conclusions Ten intubations are sufficient to learn CVS utilization properly without causing any orodental trauma. A relatively small number of experiences are required in the learning curve compared with other devices.

Spinal epidural hematoma related to an epidural catheter in a cardiac surgery patient -A case report-

The addition of thoracic epidural anesthesia to general anesthesia during cardiac surgery may have a beneficial effect on clinical outcome. However, epidural catheter insertion in a patient anticoagulated with heparin may increase the risk of epidural hematoma. We report a case of epidural hematoma in a 55-year-old male patient who had a thoracic epidural placed under general anesthesia preceding uneventful mitral valve replacement and tricuspid valve annular plasty. During the immediate postoperative period and first postoperative day, prothrombin time (PT) and activate partial thromboplastin time (aPTT) were mildly prolonged. On the first postoperative day, he complained of motor weakness of the lower limbs and back pain. An immediate MRI of the spine was performed and it revealed an epidural hematoma at the T5-6 level. Rapid surgical decompression resulted in a recovery of his neurological abnormalities to near normal levels. Management and preventing strategies of epidural hematoma are discussed.

Comparison of the effects of propofol and pentobarbital on hydrogen peroxide-stimulated hepatic SNU761 cells

Background Propofol and barbiturates are both known to protect cells of several organs against ischemia/reperfusion injury, but there are few reports on any possible protective effects on human hepatocytes. We investigated the activities of both agents on human hepatic SNU761 cells under hydrogen peroxide (H2O2)-induced oxidative stress. Methods To determine whether propofol and pentobarbital protect hepatocytes from H2O2-induced toxicity, we used SNU761 cells, a human hepatocellular carcinoma (HCC) cell line. Cells were pretreated with different dosages (1, 10, 50 µM) of propofol or pentobarbital (1, 10, 50, 100, 400 µM) 30 min before H2O2 application. Lactate dehydrogenase (LDH) was measured to assess and quantify cell death. To determine the nature of cell death, treated hepatocytes were doubly stained with fluorescein isothiocyanate (FITC)-labeled Annexin V and propidium iodide (PI), and analyzed by flow cytometry. Results Pretreatment with propofol, but not pentobarbital, suppressed H2O2-induced LDH release. In Annexin V-FITC/PI binding analysis, propofol decreased the number of necrotic and late apoptotic cells, but no significant decreases in such cell numbers were seen when pentobarbital was used. Conclusions Unlike pentobarbital, propofol, at clinical concentrations, protected SNU-761 HCC cells against oxidative stress.

The effect of phenytoin on rocuronium-induced neuromuscular block in the rat phrenic nerve-hemidiaphragm preparation.

Anticonvulsant therapy alters the action of nondepolarizing muscle relaxants. We determined the effects of acute and chronic administration of phenytoin on rocuronium-induced neuromuscular block using the rat phrenic nerve-hemidiaphragm preparation. Rats were divided into 3 groups: a saline control group (n = 10), an acute phenytoin-treated group (n = 30), and a chronic phenytoin-pretreated group (n = 30). Phrenic nerve-hemidiaphragm was dissected, mounted in a bath containing oxygenated Krebs solution, and the nerve was stimulated at supramaximal intensity. Single twitch responses were recorded by physiogram. In the acute phenytoin-treated group, acute effects of phenytoin were determined based on the phenytoin concentration of 1, 10, or 100 μg/mL in the bath. The chronic effects of phenytoin were determined using phrenic nerve-diaphragms from rats pretreated with phenytoin (50 mg/kg/d) for 1, 7, or 28 days. In rats with phenytoin 100 μg/mL in the bath, all concentrations of rocuronium produced twitch depression significantly different from those of other groups (P < 0.05), and the concentration-response curve shifted to the left. In rats with phenytoin 10 μg/mL in the bath, the effective concentrations for 50%, 90%, and 95% twitch depression values were significantly different from those of the control group (P < 0.05). In chronically (28 days) phenytoin-pretreated rats, the concentration-response curve significantly shifted to the right (P < 0.05). These findings show that acute administration of phenytoin augmented the neuromuscular blocking effects of rocuronium, whereas chronic phenytoin treatment causes resistance to the neuromuscular blocking effects of rocuronium in target organs.

Bilateral tension pneumothorax caused by an abrupt increase in airway pressure during cervical spine surgery in the prone position -A case report-

Elevated peak inspiratory airway pressure (PIP) can occur during general anesthesia and is usually easily rectified. In rare circumstances it can lead to potentially fatal conditions such as tension pneumothorax. We report on a 77-year-old male patient admitted for a cervical laminoplasty. The preoperative chest radiograph showed normal findings and there was no medical history of allergy or underlying airway inflammation. Anesthesia induction and maintenance progressed uneventfully. However, 5 minutes after prophylactic antibiotic administration, PIP suddenly increased and blood pressure dropped. The operation was abandoned and the patient was moved to a supine position to perform chest radiography. Cardiac arrest occurred, and cardiopulmonary resuscitation was performed. The radiograph showed bilateral tension pneumothorax. Needle aspiration was immediately performed, and chest tubes were inserted. Ventilation rapidly improved and the vital signs normalized. The patient was discharged without sequelae on postoperative day 36.

Effects of propofol and etomidate on hydrogen peroxide-induced oxidative damage in hepatocyte

BACKGROUND The present investigation was undertaken to evaluate the protective effect of propofol and etomidate against hydrogen peroxide (H2O2) induced oxidative damage in human hepatic SNU761 cells by measuring lactate dehydrogenase (LDH). METHODS The cell line of human hepatocellular carcinoma was grown for 24 hours in dissociated cell culture. They were divided into eight groups: negative control (NC) group with no drug administration, positive control (PC) group with H2O2 250 micrometer and other groups pretreated with propofol (P; 1, 10, 50 micrometer) or etomidate (ET; 1, 10, 50 micrometer) followed H2O2 administration. After 7 hours, cell death was assessed by morphology under the light microscope and quantified by measuring the LDH in the culture media. RESULTS In the light microscopic findings, the intact cells were increased in all three propofol groups compared to group PC. H2O2-induced LDH production was also significantly suppressed in all three propofol groups compared to group PC (P < 0.001). There were no significant differences in the microscopic findings and LDH production between the etomidate groups and group PC. CONCLUSIONS These results suggest that the propofol has protective effect on the hepatocyte against H2O2-induced oxidative stress.