Angle-resolved photoemission spectroscopy of the antiferromagnetic superconductor Nd1.87Ce0.13CuO4: anisotropic spin-correlation gap, pseudogap, and the induced quasiparticle mass enhancement.

We performed high-resolution angle-resolved photoemission spectroscopy on Nd1.87Ce0.13CuO4, which is located at the boundary of the antiferromagnetic (AF) and the superconducting phase. We observed that the quasiparticle (QP) effective mass around (pi,0) is strongly enhanced due to the opening of the AF gap. The QP mass and the AF gap are found to be anisotropic, with the largest value near the intersecting point of the Fermi surface and the AF zone boundary. In addition, we observed that the QP peak disappears around the Néel temperature (TN) while the AF pseudogap is gradually filled up at much higher temperatures, possibly due to the short-range AF correlation.

Square vortex lattice at anomalously low magnetic fields in electron-doped Nd1.85Ce0.15CuO4.

We report here on the first direct observations of the vortex lattice in the bulk of electron-doped Nd1.85Ce0.15CuO4 single crystals. Using small-angle neutron scattering, we have observed a square vortex lattice with the nearest neighbors oriented at 45 degrees from the Cu-O bond direction, which is consistent with theories based on the d-wave superconducting gap. However, the square symmetry persists down to unusually low magnetic fields. Moreover, the diffracted intensity from the vortex lattice is found to decrease rapidly with increasing magnetic field.

Commensurate spin dynamics in the superconducting state of an electron-doped cuprate superconductor.

We report neutron scattering studies on two single crystal samples of the electron-doped (n-type) superconducting (SC) cuprate Nd2-xCexCuO4 (x=0.15) with T(c)=18 and 25 K. Unlike the hole-doped (p-type) SC cuprates, where incommensurate magnetic fluctuations commonly exist, the n-type cuprate shows commensurate magnetic fluctuations at the tetragonal (1/2 1/2 0) reciprocal points both in the SC and in the normal state. A spin gap opens up when the n-type cuprate becomes SC, as in the optimally doped p-type La2-xSrxCuO4. The gap energy, however, increases gradually up to about 4 meV as T decreases from T(c) to 2 K, which contrasts with the spin pseudogap behavior with a T-independent gap energy in the SC state of p-type cuprates.

[Persistent neurological deficit and adhesive arachnoiditis following spinal anesthesia with bupivacaine containing preservatives].

A 75 year-old female with osteoarthritis of bilateral knee joints was scheduled for right total knee replacement. Her medical history included coronary artery disease, bronchial asthma, and previous surgery of lumbar laminectomy, but she had no neurological deficit before the operation. A 22-gauge spinal needle was inserted at the L 4-5 level and 4 ml of 0.5% bupivacaine with preservatives (Marcain 0.5%) was administered. The sensory block level was noted to L 1 and motor blockade of bilateral feet was achieved within 10 minutes. Anesthesia and operative courses were uneventful for 1.5 hours, and she complained severe low back pain but she could not move her thigh. Eight hours after administration of the anesthetic, her low back pain improved but the anesthetic effects showed no improvement. MRI showed no abnormality of the spinal cord on the following day, but her sensory loss level to L 1 and flaccid paralysis of bilateral lower extremities continued. Myelogram showed inflammation of cauda equina on the fourth day after the operation. She suffered from hydrocephalus two months later and MRI utilizing gadolinium as a contrast medium was consistent with a diagnosis of adhesive arachnoiditis of thoracolumbar region. Her neurological deficit showed no improvement for two years.

[Permanent paraplegia following epidural and general anesthesia: two case reports].

Case-1: A 72-year-old woman with no past neurological history was scheduled for a rectum resection under general combined with epidural anesthesia. An epidural catheter was introduced at T11-12 interspace without any difficulties. During the operation, she had hypotensive episode needing dopamine, but waked up from anesthesia without any event. When she became alert, she complained muscle weakness and loss of sensation in both lower extremities. On the day after surgery, she became quadriplegic and completely insensitive under Th4 level, but her MRI of the spine showed no abnormal findings. A month after the operation, her MRI showed diffuse spinal degeneration below C4 level and she had flaccid paralysis below Th1 with complete sensory loss below Th7 level. Case-2: A 62-year-old man with no past neurological history was scheduled for gastrectomy under general combined with epidural anesthesia. An epidural catheter was placed via T12-L1 without any difficulty. Operative course was uneventful and awakening from anesthesia was normal. He showed muscle weakness and hypesthesia of lower extremities two hours after the operation, and we stopped continuous injection of epidural anesthesia. His paralysis became worse but MRI of his spine showed no abnormality on the day after the operation. He became complete flaccid paralytic and had complete sensory loss below T7 level. The MRI examination two weeks after the operation showed degeneration below middle thoracic spinal cord. His neurologic symptoms have not improved for two years. The etiology of neurologic deficits of these two case is not obvious although the relation between epidural anesthesia and neurologic symptoms was most likely.

Thyrotropin-releasing hormone produces different hemodynamic effects in vegetative and brain-dead patients.

To define a mechanism for the pressor effects of thyrotropin-releasing hormone (TRH), we evaluated changes in mean blood pressure (MBP) when a synthetic form of TRH (0.1 mg/kg, i.v.) was injected into two types of comatose patients: vegetative and brain dead. The patients in the vegetative group (n = 7, age 58 +/- 6) retained spontaneous respiration and brainstem function, whereas the brain-dead (BD) patients (n = 7, age 68 +/- 4) lacked these functions. In the vegetative group, TRH caused significant increases in MBP (from 91 +/- 8 mm Hg to 110 +/- 10 mm Hg) at 2 min after the injection [p < 0.05, analysis of variance (ANOVA) with a Scheffé F-test]. In contrast, five of the seven BD patient showed no alterations in the measured parameter in response to the TRH injection. However, the remaining two BD patients, who had spinal reflexes, exhibited an elevation in MBP. In such BD patients, baroreceptor reflex function was virtually absent, suggesting that the blood pressure regulation mediating through the baroreceptor reflex system might be abolished. These results indicate that in comatose patients, the hemodynamic effects of TRH may differ depending on impairments in the central nervous system; the results support previous reports indicating a mediation of the central sympathetic nervous system in the development of pressor effects of TRH. Furthermore, because brain-dead patients with spinal reflexes showed hypertensive responses to TRH, there is a possibility that these responses may have resulted from an activation of TRH receptors in the spinal cord.

[Changes in heart rate during and after enflurane-nitrous oxide anesthesia].

Changes in heart rate of 21 patients who received enflurane-nitrous oxide anesthesia were studied. They had no cardiac, pulmonary, nervous system and endocrine diseases. We measured coefficient of variation of R-R intervals (CV) and power spectrum of heart rate fluctuation in 6 periods, (1) control phase (the day before operation), (2) during operation under enflurane-nitrous oxide anesthesia, (3) ten minutes after endotracheal extubation, (4) sixty minutes after arrival in the recovery room, (5) the next morning and (6) the next evening. The patients who were 15-25 years old, showed larger value of CV and larger power of low frequency component (0.03-0.1 Hz, LFC) as well as high frequency component (0.2-0.45 Hz, HFC) compared with patients who were 40-50 years old during control phase. They showed a significant decrease of CV, LFC and HFC in period (2), (3) and (4) but not in (5) and (6). These evidences show that autonomic nervous system is impared after enflurane-nitrous oxide anesthesia until the next morning.

[Anesthesia for surgical intervention in recurrent pneumothorax in a patient with one lung].

A 56 year old man was scheduled for partial resection of the right lung because of many spontaneous pneumothorax episodes. He had received left pneumonectomy for pulmonary tuberculosis and his respiratory function was severely depressed. During anesthesia, pulse oximetry, pulmonary arterial pressure monitoring, pulmonary arterial oximetry in addition to ordinary systemic arterial pressure and electrocardiogram monitoring were performed. Anesthesia was maintained with fentanyl and enflurane, and nitrous oxide was added after thoracotomy. During thoracotomy SpO2 and SVO2 dropped transiently, but intraoperative course was uneventful except an episode of paroxysmal atrial tachycardia. A successful satisfactory anesthetic management of this case depended on the cooperation between anesthesiologist and surgeon, and the appropriate monitoring especially of SVO2 was helpful.

[Anesthetic management of a patient with dermatomyositis--clinical observation of the effect of muscle relaxants].

A 58 year old woman suffering from dermatomyositis underwent elective surgery for spinal caries. Concerning the anesthetic management of patient suffering from dermatomyositis, there is little information on the appropriate use of muscle relaxants. It is generally suspected that the patient is sensitive to nondepolarizing muscle relaxants. Anesthesia was with oxygen-nitrous oxide and fentanyl. Pancuronium 6 mg was given intravenously after awake intubation and an additional dose of 2 mg was given after 7.3 hours. During anesthesia neuromuscular function was monitored by neuromuscular transmission monitor (Datex Relaxograph). Duration of neuromuscular block was defined as the time for the twitch height to recover from total paralysis to 25% of the control value. Duration in this patient was 3.1 hours and this was longer as compared with the values of 1.1-1.8 hours obtained in 7 control patients. It is suggested that a usual dose of muscle relaxants results in a relatively higher effect in the patients with dermatomyositis because of their diminished muscle mass. The anesthetist should be careful in using muscle relaxants. The muscle relaxants should be given to such a patient with monitoring closely the neuromuscular function using a neuromuscular transmission monitor.

Detection of air embolism by transesophageal echocardiography.

In this study transesophageal echocardiography was utilized for detecting air embolism in dogs in the supine position and in patients undergoing neurosurgery in the sitting position. In dogs, the threshold dose of venous air for detection was determined using either a bolus injection or continuous infusion of air via the jugular vein for up to three minutes. The ability to detect air in the aorta also was determined by a bolus injection into the left ventricular via an arterial catheter. For venous injection of air, the threshold dose by bolus was 0.02 ml/kg. When given by infusion, air could be detected in all cases by both contrast echocardiogram and Doppler sound changes at the rate of 0.05 ml . kg-1 . min-1. When air was injected into the left ventricle, the threshold dose was 0.001 ml/kg using contrast echocardiogram. In the clinical evaluation, air was clearly demonstrated in five of six patients by transesophageal echocardiogram along with appropriate changes in Doppler sounds, pulmonary artery pressure, and end-tidal carbon dioxide concentration. Our results suggest that transesophageal echocardiography may be a more sensitive and accurate method for detecting venous air embolism than other commonly used monitors for patients undergoing neurosurgical procedures in the sitting position. This device may also be able to detect air in the aorta in patients experiencing paradoxical air embolism during surgery due to intracardiac or pulmonary shunts.