Changes of Electroencephalographic Bicoherence during Isoflurane Anesthesia Combined with Epidural Anesthesia

Background: The authors previously reported that, during isoflurane anesthesia, electroencephalographic bicoherence values changed in a fairly restricted region of frequency versus frequency space. The aim of the current study was to clarify the relation between electroencephalographic bicoherence and the isoflurane concentration.

Methods: Thirty elective abdominal surgery patients (male and female, aged 34-77 yr, American Society of Anesthesiologists physical status I-II) were enrolled. After electroencephalogram recording with patients in an awake state, anesthesia was induced with 3 mg/kg thiopental and maintained with oxygen and isoflurane. Continuous epidural anesthesia with 80-100 mg/kg 1% lidocaine was also administered. Using software they developed, the authors continuously recorded the FP1-A1 lead of the electroencephalographic signal and expired isoflurane concentration to an IBM-PC compatible computer. After confirming the steady state of each isoflurane (end-tidal concentration at 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, and 1.5%), electroencephalographic bicoherence values were calculated.

Results: In a light anesthetic state, electroencephalographic bicoherence values were low (generally <= 15.0%). At increased concentrations of isoflurane, two peaks of electroencephalographic bicoherence emerged along the diagonal line (f1 = f2). The peak emerged at around 4.0 Hz and grew higher as isoflurane concentration increased until it reached a plateau (43.8 +/- 3.5%, mean +/- SD) at isoflurane 0.9%. The other peak, at about 10.0 Hz, also became significantly higher and reached a plateau (32.6 +/- 9.2%) at isoflurane 0.9%; at isoflurane 1.3%, however, this peak slightly decreased.     

Dual effect of local anesthetics on the function of excitable rod outer segment disk membrane

The effects of local anesthetics and a divalent cation, Ca2+, on the function of rhodopsin were estimated from the measurements of light-induced proton uptake. The light-induced proton uptake by rhodopsin in the rod outer segment disk membrane was enhanced at lower pH (4) but depressed at higher pHs (6 to 8) by the tertiary amine local anesthetics lidocaine, bupivacaine, tetracaine, and dibucaine. The order of local anesthetic-induced depression of the proton uptake followed that of their clinical anesthetic potencies. The depression of the proton uptake versus the concentration of the uncharged form of local anesthetic nearly describes the same curve for small and large dose of added anesthetic. Furthermore, a neutral local anesthetic, benzocaine, depressed the proton uptake at all pHs between 4 and 7. These results indicate that the depression of the proton uptake is due to the effect of only the uncharged form. It is hypothesized that the uncharged form of local anesthetics interacts hydrophobically with the rhodopsin in the disk membrane. The dual effect of local anesthetics on the proton uptake, on the other hand, suggests that the activation of the function of rhodopsin may be caused by the charged form. There was no significant change in the light-induced proton uptake by rhodopsin when 1 mM of Ca2+ was introduced into the disk membrane at varying pHs in the absence or presence of local anesthetics. This fact indicates that Ca2+ ion does not influence the diprotonating process of metarhodopsin; neither does it interfere with the local anesthetic-induced changes in the rhodopsin molecule.     

Significance of fiberoptic bronchoscopy after pulmonary resection of lung cancer for early detection in second lung cancer

By the end of 1988, seventy five cases after pulmonary resection for lung cancer and one case after pulmonary resection for basal cell hyperplasia were examined with fiberoptic bronchoscopy as postoperative follow up. Endobronchial tumor was detected in 14 cases. In seven cases, endobronchial tumor was located at site far from the surgical bronchial anastomosis. These tumors were suspected as second lung cancer as long as examined by fiberoptic bronchoscopy. Histological type of all of these was squamous cell carcinoma. Re-operations were performed in five cases and two of them were early lung cancer. In 6 cases (13.6%) among 44 cases examined with fiberoptic bronchoscopy after pulmonary resection for central type squamous cell carcinoma, second lung cancer was detected. In the case of central type squamous cell carcinoma, usually the tumor appears to be of same histological type and at same location. Among those cases those who smoke heavily should be separated as high risk group. If this group is followed with fiberoptic bronchoscopy or sputum cytological examination, it is more possible to detect second lung cancer at an early stage.     

Long-term survival after removal of a malignant peripheral nerve sheath tumor originating in the anterior mediastinum

Malignant peripheral nerve sheath tumors (MPNSTs; malignant schwannomas) rarely occur in the anterior mediastinum, and their prognosis is poor. A 75-year-old man was referred to our hospital for examination of an anterior mediastinal tumor. A computed tomography-guided percutaneous needle biopsy revealed only fibrosis. The tumor was completely excised via a median sternotomy with partial resection of the pericardium and right upper lobe of the lung. Thereafter, the tumor was diagnosed as a storiform-pleomorphic type of malignant fibrous histiocytoma. At 1 year after the surgery, a distant metastasis was found in the interlobular space between the right middle and lower lobes. The tumor was completely excised via a right posterolateral thoracotomy. Reexamination of the primary and secondary tumors revealed an MPNST. No recurrence was found up to 5 years after the second surgery without adjuvant chemotherapy or radiation therapy. However, he died from multiple lung metastases after 6 years.     

cGMP and a germ-line signal control body size in C. elegans through cGMP-dependent protein kinase EGL-4

Mechanisms involved in the control of body size are largely unknown. In the nematode C. elegans, several small body size mutants were isolated, and the responsible genes were reported to encode putative components of a TGFbeta signalling pathway. Recently, mutants in the egl-4 gene encoding cGMP-dependent protein kinases were found to have a larger body size, and it was suggested that EGL-4 down-regulates the TGFbeta/DBL-1 pathway. We show that a permeable cGMP analogue 8-Br-cGMP significantly reduces body size of the wild-type but not that of an egl-4 mutant, indicating that cGMP controls body size through EGL-4. Laser ablation of germ-line cells revealed that a germ-line signal and EGL-4 function in the same pathway. Targeted expression of EGL-4 indicates that EGL-4 can function in hypodermis, neurones and intestine both cell-autonomously and cell-nonautonomously to control organ and body size. We propose a signal cascade for the control of body size that involves a germ-line signal, cGMP, G-kinase EGL-4 and DBL-1/TGFbeta pathway. It is interesting that two important pathways involving cGMP and TGFbeta, respectively, are related. Also, the results suggest a novel mechanism for the control of organ and body size in which hypodermis plays a key role