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Biomedical subjects

Y Shiokawa

Publications and source records attributed to Y Shiokawa.

At least 55 records · Page 3Linked to original sources
PubMed1998

Delayed cyst formation after radiosurgery for cerebral arteriovenous malformation: two case reports.

Two patients who underwent gamma knife radiosurgery for ruptured cerebral arteriovenous malformations (AVM) developed cystic lesions at 78 and 111 months after undergoing treatment. Both patients presented initially with intracerebral hemorrhage. In one patient, the cystic lesion was discovered during routine follow-up imaging and clinical examination revealed homonymous hemianopsia; the second patient presented with seizure and the lesion was identified more than 9 years after radiosurgery. One patient underwent resection of the nidus and histologic analysis of the resected specimen showed vessels in various stages of obliteration. The present paper discusses the possible mechanism for the delayed development of cystic lesions, and the possibility that radiation-induced vascular changes may continue in a nidus even when angiography shows complete obliteration of the nidus.

Adult↗
PubMed1998

Prostaglandin E1 antagonizes hypoxic pulmonary vasoconstriction but reduces systemic blood pressure in dogs.

OBJECTIVE: To investigate whether prostaglandin E1 (PGE1) directly inhibits hypoxic pulmonary vasoconstriction in dogs. DESIGN: Prospective, longitudinal study. SETTING: University research laboratory. SUBJECTS: Six mongrel dogs in vivo. INTERVENTIONS: The left thorax of anesthetized and ventilated dogs was opened and the left lower lobe was separately ventilated. The tip of the thermodilution pulmonary artery catheter was introduced into the left lower lobe pulmonary artery. The left lower lobe was ventilated with hyperoxic (95% oxygen and 5% CO2) or hypoxic (95% nitrogen and 5% CO2) gas. By manipulating the occluders placed on both pulmonary arteries, blood flow in the left lower lobe was regulated. Continuous pressure-flow plots for the left lower lobe were then obtained. MEASUREMENTS AND MAIN RESULTS: Measurements included continuous pressure-flow plot generation, thermodilution cardiac output and blood flow in the left lower lobe, and blood gas analysis. Alveolar hypoxia of the left lower lobe caused blood flow in the left lower lobe to decrease from 371.8 +/- 63.4 to 95.0 +/- 23.4 mL/min and shifted the pressure-flow plot to the right, with a decreased slope and with an increase in the pressure-axis intercept. Subsequently, systemic venous infusion of PGE1 at a rate of 0.3 microg/kg/min had no effect on the pressure-flow plot configuration, blood flow in the left lower lobe, pulmonary vascular resistance, systemic vascular resistance, and PaO2. However, there was a decrease in the pressure-axis intercept of the pressure-flow plot. Infusion of PGE1 at a rate of 3.0 microg/kg/min (high-dose) during hypoxia reduced pulmonary vascular resistance and systemic vascular resistance by 19% and 25%, respectively, and returned the pressure-flow plot toward normal while blood flow in the left lower lobe increased to 122.6 +/- 21.0 mL/min. Consequently, PaO2 decreased from 270 +/- 31 to 144 +/- 32 torr (36.0 +/- 4.1 to 19.2 +/- 4.3 kPa). CONCLUSION: High-dose PGE1 essentially inhibits hypoxic pulmonary vasoconstriction, at the expense of a deterioration in pulmonary gas exchange and systemic blood pressure in dogs.

Alprostadil↗
PubMed1998

[Anesthetic management of a patient with dilated cardiomyopathy using olprinone].

A 51-year-old man with dilated cardiomyopathy, who had been treated with medication for five years, was scheduled for abdomioperineal resection of the rectum. Preoperative echocardiography demonstrated left ventricular dilation and hypertrophy, with an ejection fraction of 0.34. Anesthesia was induced with ketamine 40 mg and fentanyl 0.5 mg intravenously. Endotracheal intubation was facilitated by administration of vecuronium 10 mg. Anesthesia was maintained with nitrous oxide-oxygen-sevoflurane and fentanyl. In order to regulate myocardial contractility and after-load, use of a phosphodiesterase III inhibitor was considered, although phosphodiesterase III inhibitors are known to induce arrhythmias, which should be avoided in dilated cardiomyopathy patients. We chose olprinone, because its inotropic action is not associated with arrhythmogenecity. Before infusing olprinone, cardiac output was 4.5 l.min-1 and systemic vascular resistance was 1306 dynes.sec.cm-5. When olprinone was continuously infused for one hour, cardiac output increased to 5.2 l.min-1 and systemic vascular resistance decreased to 958 dynes.sec.cm-5. Some premature ventricular contractions occurred, but they were easily controlled by administration of 50 mg lidocaine. These clinical data demonstrate that olprinone enhanced myocardial contractility, and decreased after-load and arrhythmogenecity in a dilated cardiomyopathy patients. In conclusion, olprinone is useful in the perioperative cardiovascular management of surgical patients with dilated cardiomyopathy.

Anesthesia↗
PubMed1998

[A case of ruptured P4 segment aneurysm of the posteior cerebral artery: therapeutic pitfalls encountered when dealing with the multiple intracranial aneurysms].

A P4 segment aneurysm of the posterior cerebral artery has rarely been described. A case of ruptured P4 segment aneurysm, which re-ruptured after clipping procedure for unruptured internal carotid artery aneurysm, was reported. A 57-old-man had sudden onset of severe headache and vomiting and was transferred to our hospital. CT scan on admission showed diffuse subarachnoid hemorrhage dominantly extending to the tentorial surface and the occipital interhemispheric tissue. Four-vessel angiography demonstrated a right internal carotid-posterior communicating artery junction aneurysm, and its neck clipping was performed on day 5. Intraoperative inspection of the whole appearance of the aneurysm was difficult because of the aneurysm existing on the ventral portion of the internal carotid artery and definite diagnosis of the bleeding source was not obtained. On day 23, he complained of severe headache and restricted vision and CT scan showed intracerebral hematoma in the left occipital lobe with intraventricular hemorrhage. The angiograms and CT scan on admission were reexamined, and another aneurysm on the left parieto-occipital artery (P4 segment) was retrospectively identified. The ruptured P4 segment aneurysm was obliterated via the interhemispheric approach and the patient enjoyed an uneventful postoperative course. When a thick subarachnoid hemorrhage distributed in the occipital interhemispheric fissure, quadrigeminal cistern, and ambient cistern is encountered, the existence of a possible P4 segment aneurysm should be suspected. Correct initial diagnosis and definite treatment of the ruptured lesion in the acute stage is essential in dealing with SAH-patient with multiple aneurysms. When they are unruptured lesions at a common aneurysm site, the existence of an unusually located aneurysm should not be overlooked as the possible source responsible for symptoms.

Aneurysm, Ruptured↗
PubMed1998

[Pretreatment with magnesium sulphate enhances vecuronium-induced neuromuscular block].

The interaction between magnesium sulphate (MgSO4) and vecuronium was investigated during isoflurane-nitrous oxide-oxygen anesthesia. Neuromuscular function was evaluated by recording the single twitch of the abductor policis muscle. Anesthesia was induced with thiamylal followed by injection of vecuronium. The effects of pretreatment with MgSO4 (20 or 40 mg.kg-1) on the potency of vecuronium were compared with observations in patients without MgSO4 pretreatment (control). We also examined the serum concentration of magnesium ions after administration of MgSO4. We found that the neuromuscular effect of vecuronium was not influenced by pretreatment with MgSO4 20 mg. On the contrary, the onset time of vecuronium was decreased and the duration of action until 25% recovery was increased by pretreatment with MgSO4 40 mg. The serum concentration of magnesium ions after administration of MgSO4 40 mg was significantly higher than that after 20 mg. We conclude that pretreatment with MgSO4 40 mg but not 20 mg enhances vecuronium-induced neuromuscular block.

Adult↗
PubMed1997

The left ventricular outflow tract in atrioventricular septal defect revisited: surgical considerations regarding preservation of aortic valve integrity in the perspective of anatomic observations.

OBJECTIVE: The anatomy of the left ventricular outflow tract in hearts with atrioventricular septal defect has been widely investigated, but controversies remain regarding detailed aspects of left ventricular outflow tract anatomy in the perspective of operative techniques to either prevent or relieve outflow tract obstruction. METHODS: We investigated 29 postmortem hearts with an atrioventricular septal defect. Measurements were taken of the circumferences and of the widths of the components that make up the outflow tract, that is, the interventricular septum, the superior bridging leaflet, the left ventricular free wall, and the length of the tendinous cords. RESULTS: The circumference of the left ventricular outflow tract immediately underneath the aortic valve was not different from that at the middle part of the outflow tract. Hearts with the partial type defect, characterized by separate atrioventricular orifices, had a smaller outflow tract than those with the complete variety. Although the anatomic constituents that contribute to left ventricular outflow tract obstruction are complex, this study showed that a reduced width of the interventricular septum was most intimately related to narrowing immediately underneath the aortic valve. Obstruction at the middle part of the left ventricular outflow tract was largely caused by reduced width of the interventricular septum together with short tendinous cords. CONCLUSIONS: On the basis of these observations, we recommend detailed investigation of the anatomy of the left ventricular outflow tract immediately underneath the aortic valve, before surgical attempts to relieve outflow tract obstruction, because in some procedures the integrity of the aortic valve will be at stake.

Aortic Valve↗
PubMed1997

Ruptured dissecting aneurysm as a cause of subarachnoid hemorrhage of unverified etiology.

BACKGROUND AND PURPOSE: The clinical features of "aneurysmal" subarachnoid hemorrhage (SAH) of angiographically unverified etiology were reviewed to clarify the incidence and natural history of dissecting aneurysms as the hemorrhagic source of SAH. METHODS: We reviewed 30 patients with SAH of unverified etiology in whom initial CT scan showed a diffuse or anteriorly distributed subarachnoid blood clot. Ten of the patients had stenotic or occlusive lesions (SOCL) on initial angiography, and these were the main focus of this study. RESULTS: Among the 10 patients with SOCL on initial angiography, the lesions were located on the anterior circulation in 6 and on the posterior circulation in 4. Ruptured dissecting aneurysms were confirmed by exploratory surgery or autopsy in 6 patients. Subsequent rupture occurred in 6 of the 10 patients (60%), and all 6 of these patients died as a result. CONCLUSIONS: The incidence (6/30) of dissecting aneurysms as the cause of SAH of unverified etiology was unexpectedly high, especially when initial angiography disclosed SOCL (6/10). The moribund patients with SOCL showed a high rate of rebleeding, and the untreated recurrent hemorrhages were fatal. Further MRI study is indicated for these patients to demonstrate the intramural hematoma. Compared with the devastating mortality caused by the subsequent ruptures, the extent of surgical morbidity was minor. Surgical intervention could therefore be justified when the following neuroradiological findings are present: (1) SOCL evident on angiography, (2) distribution of SAH on CT compatible with the location of the SOCL, and (3) intramural hematoma on MRI in the same region as the SOCL.

Adult↗
PubMed1997

Intracranial vascular stenosis and occlusion: MR angiographic findings.

PURPOSE: To investigate whether obtaining axial source images from three-dimensional Fourier transform (3DFT) time-of-flight MR angiography improves the detection of intracranial vascular stenosis and occlusion if added to maximum-intensity projection (MIP) images. METHODS: The angiograms of 103 patients who had MR angiography for evaluation of possible intracranial vascular disease were reviewed retrospectively in a quantitative and nonquantitative fashion. Diameters of vessels on MR angiograms were measured quantitatively by two reviewers using a magnifying loupe and compared with the results from conventional angiograms. Degrees of stenoocclusive disease were categorized into five classes; an artery with stenosis of 50% or greater was considered to be diseased. Another five observers also reviewed the MIP images with and without source images in a blinded fashion by means of nonquantitative visual inspection. RESULTS: In all, 23 stenoocclusive lesions of 50% or greater were available for review. In the quantitative analysis, with MIP images alone, 14 (78%) of 18 moderate and severe stenoses and four (80%) of five occlusions were identified correctly. The addition of the source images increased the sensitivity to 100% for moderate and severe stenoses and to 100% for occluded vessels. In the visual inspection study, however, no statistically significant differences were found between interpretations of MIP images alone and those of MIP images in combination with source images. CONCLUSION: In the quantitative study, interpretation of source images rather than MIP images reduced the tendency to overestimate stenosis seen with MR angiography and improved the sensitivity for detecting stenosis of 50% or greater. There was a discrepancy between the quantitative study and visual inspection. Experienced observers had a tendency to underestimate the degree of stenosis.

Adult↗
PubMed1996

Selective cerebral perfusion technique during aortic arch repair in neonates.

We describe selective cerebral perfusion techniques for repair of the aortic arch in neonates. These techniques may help protect the brain from ischemic injury caused by a cessation of cerebral perfusion for aortic arch reconstruction in patients with hypoplastic left heart syndrome or interrupted aortic arch.

Aorta, Thoracic↗
PubMed1996

Effect of folding on the optical quality of soft acrylic intraocular lenses.

PURPOSE: To assess the effect of folding procedures on modulation transfer function (MTF) and resolving power (RP) in soft acrylic intraocular lenses (IOLs). SETTING: Faculty of Engineering, Chiba University, Chiba, Japan. METHODS: Folding procedures and other manipulations were performed on +18.0 diopter soft acrylic lenses (MA60BM, AcrySof, Alcon Surgical). The IOLs were then immersed in the water chamber of a model eye and MTF and RP under veiling glare light measured. The optical surfaces of the IOLs were examined microscopically. RESULTS: After the IOLs had been folded for 30 seconds, MTF recovered 8 and 6 minutes after unfolding in 20 degrees C 37 degrees C balanced salt solution, respectively. Prolonged folding of 10, 20, and 60 minutes did not affect the final MTF, which was measured 30 minutes after unfolding. However, RP deteriorated after the 60 minute folding. Optic damage was observed after the 20 and 60 minute foldings. Neither parameter changed after the IOLs were tightly folded for 30 seconds; however, both deteriorated slightly after the IOLs were tightly folded for 5 minutes, and minor damage was seen on the optics. With fewer than 10 artificial linear cracks in the central 3 mm of the optic, MTF was not affected; with 20 or fewer, RP was not affected. After forceps pressure on the central optic, MTF recovered within 6 minutes. CONCLUSION: The optical quality of soft acrylic IOLs are not easily affected unless extreme nonphysiological manipulations are applied.

Acrylates↗
PubMed1996

Trigeminal afferents and brainstem centers involved in the occurrence of cerebral vasospasm.

Cisternal injections of blood in the rat and squirrel monkey produce an angiographically demonstrable biphasic vasospasm with a maximal late spasm at two days in the rat and six days post-subarachnoid hemorrhage (SAH) in the monkey. The SAH induces a decrease in cerebral blood flow of about 25% and a corresponding increase in glucose uptake of between 30% and 50%. In about half of the animals low-flow areas were noted in the cortex and the basal ganglia with a corresponding marked increase in glucose uptake. Lesioning of the A2-nucleus, its ascending pathway or the median eminence prevents the occurrence of spasm. Similarly, treatment with a substance P antagonist or gammaglobulin against substance P prevents or significantly reduces the degree of spasm. A unilateral post-ganglionic trigeminal lesion causes an ipsilateral constriction of the cerebral arteries of 27%, while a preganglionic lesion does not affect the baseline diameter. A pre- or post-ganglionic trigeminal lesion induces an increase in glucose uptake globally of about 50% without influencing cerebral blood flow. Following SAH the decrease in blood flow in both groups of lesioned animals is similar to that seen in controls. After SAH there is no further change in glucose uptake in the animals with a preganglionic lesion, while in the post-ganglionically lesioned animals there is an additional increase in glucose uptake of about 50% as compared to controls or the animals with a preganglionic lesion.

Afferent Pathways↗
PubMed1996

The effect of thoracic epidural anesthesia on hypoxic pulmonary vasoconstriction in dogs: an analysis of the pressure-flow curve.

The aim of the present study was to examine whether hypoxic pulmonary vasoconstriction (HPV) is preserved during one-lung ventilation combined with thoracic epidural anesthesia (TEA) in dogs. Using a separately ventilated left lower lobe (LLL) in situ, the pressure-flow (P-Q) curve was obtained. The HPV response was assessed by the shift of the P-Q curve, changes in blood flow diversion rate (FDR) and decrease in PaO2 during hypoxic gas ventilation of LLL. In the control group (n = 7), the shift of P-Q curve, changes in FDR, and decrease in PaO2 remained constant during four consecutive hypoxic stimulations. In the TEA group (n = 6), the P-Q curve shifted to the left during hyperoxia, but the magnitude of the shift during hypoxia was unchanged. FDR and decrease in PaO2 were significantly reduced compared with baseline values (P < 0.05 with analysis of variance). TEA reduced heart rate, cardiac output, mean arterial pressure, mean pulmonary arterial pressure, and mixed venous oxygen tension. Our results suggest that TEA did not affect the primary pulmonary vascular tone at baseline or during lobar hypoxia, but enhanced the diversion of blood flow and arterial blood oxygenation during lobar hypoxia. This enhanced HPV response probably reflects hemodynamic changes, such as decreased cardiac tension, due to sympathetic nerve activity blockade by TEA.

Analysis of Variance↗
PubMed1996

Thromboxane synthetase inhibitor ameliorates delayed neuronal death in the CA1 subfield of the hippocampus after transient global ischemia in gerbils.

Thromboxane A2 accumulates in the hippocampus after global ischemia and may play a key role in postischemic hypoperfusion. Thromboxane synthetase inhibitor (OKY-046) inhibits the accumulation of thromboxane A2 and promotes prostacycline production. Therefore, we set out to determine whether the inhibition of thromboxane synthesis would ameriolate postischemic neuronal death. Three groups of six Mongolian gerbils were subjected to different treatments: untreated control, untreated ischemia, and treated ischemia. Immediately after forebrain ischemia, OKY-046 (10 mg/kg) was injected intraperitoneally into the treated group. After 7 days of survival, the histopathology of the brain was examined. Pyramidal cell density in the CA1 sector in the treated group was 147 +/- 70 nuclei/mm (mean +/- SD), which was significantly (p < 0.05) higher than than in the untreated group (33 +/- 10 (nuclei/mm). The findings were 231 +/- 7 nuclei/mm for the control group. No significant difference was seen in the profile of temporal muscle temperature before and after ischemia between the groups. Ultrastructurally, the vessels in the CAI sector showed lumen patency in the treated group, whereas occluded vessels with an extended perivascular space were observed in the untreated group. Thromboxane synthetase inhibitor thus partly ameliorates the selective vulnerability of the hippocampus after forebrain ischemia, suggesting that thromboxane A2 is involved in the development of delayed neuronal death, independently of any thermal effect.

Animals↗
PubMed1996

Intracranial aneurysms: diagnostic accuracy of MR angiography with evaluation of maximum intensity projection and source images.

PURPOSE: To determine whether evaluation of source images from magnetic resonance (MR) angiography in addition to maximum-intensity projection (MIP) images improves the detection of aneurysms. MATERIALS AND METHODS: Conventional and MR angiography were performed in 193 patients with various intracranial vascular lesions or normal findings. Images were evaluated in a blinded manner. Two readings were performed 6 weeks apart by evaluating MIP images with and without source images. Results were evaluated with receiver operating characteristic analysis. RESULTS: Sensitivity for the detection of aneurysms increased slightly when source images were included. The detection rate of internal carotid artery aneurysms was most improved with the addition of source images. No statistically significant differences in performance were found between the readings with MIP images alone and with source images. CONCLUSION: Sensitivity may improve with combined reading of nonselective MIP and source images.

Case-Control Studies↗