Nicorandil prevents epinephrine-induced arrhythmias in halothane-anesthetized rats by nitric oxide-dependent mechanism

The effect of opening ATP-sensitive K(+) channels on the genesis of arrhythmias is still controversial. We investigated the effect of nicorandil, an ATP-sensitive K(+) channel opener, on the genesis of halothane-epinephrine arrhythmias in rats. We also clarified the involvement of nitric oxide in the effect of nicorandil. Furthermore, we studied the effect of levcromakalim, another ATP-sensitive K(+) channel opener, for comparison. Nicorandil and levcromakalim significantly increased the arrhythmogenic thresholds of epinephrine in a dose-dependent manner. On the other hand, nitroprusside, a potent vasodilator (5.0 micro g/kg per min), did not exert antiarrhythmic action significantly. Both glibenclamide (non-specific ATP-sensitive K(+) channel blocker) and 5-hydroxydecanoate (mitochondrial ATP-sensitive K(+) channel blocker) inhibited the antiarrhythmic action of nicorandil. Although pretreatment with N-omega-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, did not modulate the genesis of halothane-epinephrine arrhythmias in the absence of nicorandil, it completely abolished the antiarrhythmic action of nicorandil, but not the effect of levcromakalim. We concluded that nicorandil dose-dependently inhibited halothane-epinephrine arrhythmias through mitochondrial ATP-sensitive K(+) channels and nitric oxide is required for the antiarrhythmic effect of nicorandil.

The effects of dexmedetomidine on the ventilatory response to hypercapnia in rabbits

OBJECTIVE

Dexmedetomidine is a highly selective alpha(2)-adrenergic agonist that can reduce anesthetic requirements. This study, to assess its effect on respiration, examined the effects of various doses of dexmedetomidine (1, 10, 30 and 50 microg/kg) on the respiratory response to carbon dioxide (CO(2)) breathing in rabbits.

DESIGN

Randomized prospective study.

SETTING

Animal laboratory at a university school of medicine.

INTERVENTION

From 28 animals, four groups of seven were randomly assigned to receive different doses of dexmedetomidine (groups D1, D10, D30 and D50). Under inhalation of sevoflurane, each animal was tracheostomized and intubated with a 4 mm internal diameter (i.d.) endotracheal tube.

MEASUREMENTS AND RESULTS

After end-tidal sevoflurane concentration had decreased below 0.03% and during quiet breathing (QB); respiratory rate (RR), tidal volume (V(T)) and inspiratory time (T(I)) were measured, from which minute ventilation (MV) and mean inspiratory flow (V(T)/T(I)) were calculated. After these measurements had been completed, each animal breathed the balloon gas (5% CO(2) and 95% O(2)) until the end-tidal CO(2) (ETCO(2)) reached 10%. The respiratory measurements were repeated during the latter period. After the collection of these data, dexmedetomidine was infused intravenously and the same measurements were repeated 15 and 45 min after dexmedetomidine infusion. The slope of the ventilatory response to hypercapnia in D50 was significantly higher compared with D30 animals. In the range 1-30 microg/kg, during both QB and at 10% ETCO(2), MV was decreased in a dose-dependent manner. Dexmedetomidine depressed both V(T) and RR during QB and at 10% ETCO(2).

CONCLUSION

Dexmedetomidine depressed resting ventilation and the respiratory response to CO(2), but it did not induce profound hypoxemia or hypercapnia in rabbits.

[Venoarterial bypass in children with congenital heart disease--a retrospective study]

To investigate prognostic factors for patients supported by venoarterial (VA) bypass, we analyzed retrospectively 31 patients with congenital heart diseases supported by VA bypass between 1997 and 2000. Median age was 3.6 months and median body weight was 4.0 kg. Causes of VA bypass were difficult weaning from cardiopulmonary bypass in 8 patients, postoperative cardiac dysfunction in 5 and cardiopulmonary resuscitation in 18. Six (19.4%) of 31 patients were weaned successfully from VA bypass, and 2 (6.5%) survived to hospital discharge. In patients who were weaned from VA bypass successfully, VA bypass was instituted more quickly (41.6 +/- 5.0 vs 62.5 +/- 35.9 min), and good tissue perfusion was established in association with lower lactate levels at 12 hr (7.0 +/- 5.9 vs. 16.4 +/- 15.4 mmol.l-1) and larger urine output during first 24 h (81 +/- 68 vs. 22 +/- 43 ml.kg-1.day-1), compared to those who failed to be weaned. Major complications were intracranial hemorrhage in the newborn (50%), and hypoxic brain damage in patients with palliative operation (35%). It is necessary to establish guidelines of entry, weaning, and withholding of this support.

Evaluation of diagonal earlobe crease as a marker of coronary artery disease: the use of this sign in pre-operative assessment

In this study, we examined the usefulness of the earlobe crease sign as a marker of coronary artery disease in the pre-operative assessment of patients. We were interested in evaluating this sign for use in emergency patients. We investigated 530 patients, aged > 40 years, undergoing elective surgery. If the electrocardiogram was abnormal or the patient reported symptoms suggesting coronary artery disease, further cardiac examinations were performed. Patients who demonstrated evidence of coronary artery disease in the additional investigations or had a clear history of coronary artery disease were classified as the abnormal coronary group. Other patients with no history and/or normal investigations were classified as the normal coronary group. The assessment of earlobe crease sign was performed prior to anaesthesia, and the sensitivity, specificity and positive predictive value of this sign were calculated. We found that the sensitivity and specificity was high regardless of age, except for specificity in patients > 70 years old. The data suggest that the earlobe crease sign may be a useful marker for the presence of coronary artery disease in patients undergoing emergency operations in which little or no history and investigations are available. However, more work is required to assess the use of this sign in other ethnic groups.

Diabetes attenuates the minimum anaesthetic concentration (MAC) and MAC-blocking adrenergic response reducing actions of clonidine in rats

BACKGROUND

It is well known that clonidine, an alpha2 agonist, reduces anaesthetic requirement and attenuates haemodynamic responses against noxious stimuli. However, the diabetic state is known to affect several functions of alpha2 adrenoceptors. We investigated the effects of streptozotocin (STZ)-induced diabetes mellitus (DM) on these beneficial actions of clonidine in halothane-anaesthetized rats.

METHODS

The rats were randomly assigned to one of three groups: diabetes (n=24, induced by 50 mg x kg(-1) IV STZ), diabetes treated with insulin (n=24), or control (n=24). We evaluated the effects of clonidine on minimum anaesthetic concentration (MAC) and minimum concentration of halothane needed to suppress cardiovascular responses evoked by a noxious stimulus (MAC-blocking adrenergic responses: MAC-BAR) in each group. MAC and MAC-BAR of halothane were determined by the tail clamp method. MAC-BAR was defined as the MAC which attenuated haemodynamic responses within 10% following the tail clamp.

RESULTS

The diabetic state decreased MAC of halothane by approximately 10%, while MAC-BAR of halothane had been little affected. In the diabetes group, MAC reducing action of clonidine (30 and 100 microg x kg(-1), IV) was completely abolished and MAC-BAR reducing action of clonidine was partially reduced (30 but not 100 microg x kg(-1), IV). Insulin treatment preserved these actions of clonidine.

CONCLUSION

It is suggested that the diabetic state attenuates the beneficial actions of clonidine and that insulin treatment of diabetes preserves these actions of clonidine.

Optical manipulation of microscopic objects by means of vertical-cavity surface-emitting laser array sources

We report on experimental verification of optical trapping using multiple beams generated by a vertical-cavity surface-emitting laser (VCSEL) array. Control of the spatial and temporal emission of a VCSEL array provides flexibility for manipulation of microscopic objects with compact hardware. Simultaneous capture of multiple objects and translation of an object without mechanical movement are demonstrated by an experimental system equipped with 8 x 8 VCSEL array sources. Features and applicability of the method are also discussed.

Syndrome of inappropriate secretion of ADH (SIADH) following cisplatin administration in a pulmonary adenocarcinoma patient with a malignant pleural effusion

We report a patient with pulmonary adenocarcinoma complicated by the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) following systemic chemotherapy with cisplatin (CDDP) and vindesine (VDS). A 66-year-old woman was diagnosed as having pulmonary adenocarcinoma with malignant pleural effusion following investigations for cough and dyspnea. After drainage of the effusion she received combination chemotherapy with CDDP and VDS. She developed SIADH 48 hours following chemotherapy. Interestingly, the use of carboplatin (CBDCA) and VDS in the subsequent treatment course was well tolerated indicating that the SIADH was most likely to have been induced by administration of CDDP.

Intraaneurysmal embolization of an unruptured basilar tip aneurysm associated with moyamoya disease

We describe a patient with moyamoya disease associated with an unruptured basilar tip aneurysm which was treated by endovascular embolization using Guglielmi detachable coils (GDCs). A 53-year-old man presented with left hemiparesis persisting for 3 mon ths before admission. Cerebral angiography revealed occlusion of the bilateral middle cerebral arteries and the left anterior cerebral artery, stenosis of the right anterior cerebral artery, and basal moyamoya vessels. In addition, a saccular small aneurysm was seen at the top of the basilar artery. The aneurysm was completely embolized by intraaneurysmal GDCs. Direct surgical clipping is often selected for the treatment of posterior fossa aneurysms in moyamoya disease. However, complete clipping is usually difficult due to the difficulties in operative technique associated with moyamoya disease. We suggest that the endovascular treatment using GDCs is comparatively safe and effective for the treatment of surgically difficult aneurysms in patients with moyamoya disease.

[Cavernous sinus dural arteriovenous shunt presenting with subarachnoid hemorrhage and acute subdural hematoma: a case report]

Cavernous sinus dural arteriovenous shunt (CdAVS) usually presents with exophthalmos, conjunctival chemosis, ophthalmoplegia, headache, bruit, or pulsatile tinnitus. Intracranial hemorrhage associated with CdAVS is rare. We describe a patient with CdAVS presenting with subarachnoid hemorrhage and acute subdural hematoma. A 65-year-old woman presented headache and temporary loss of consciousness and was transferred to our hospital. On admission, the patient was alert and complained of a left-sided temporal headache. There were no ocular symptoms. A CT scan revealed subarachnoid hemorrhage and left acute subdural hematoma. When we prepared for cerebral angiography, the patient presented loss of consciousness following sudden onset of severe headache. Urgent angiography revealed left CdAVS, which was fed by both the internal carotid artery and the external carotid artery and drained only into ipsilateral (left) vein of the sylvian fissure. Aneurysmal dilatation of the draining veins and leptomeningeal drainage were present. No cerebral aneurysms were detected. After the angiography, a CT scan showed enlarged subdural hematoma, so left fronto-temporo-parietal craniotomy was immediately performed. On opening the dura mater, arterial bleeding from Sylvian fissure appeared and was uncontrollable. Unfortunately, the patient died 3 days after the operation. We concluded that subarachnoid hemorrhage and subdural hematoma were due to the rupture of engorged cortical veins. Our case report suggests that CdAVS with angiographic findings such as aneurysmal dilatation of the draining veins and leptomeningeal drainage should be treated urgently because of the high risk of the life-threatening complications resulting from a surgically uncontrollable hemorrhage.

Hypervascular liver metastasis from hypovascular ductal cell carcinoma of the pancreas

In a case of hypervascular metastatic liver tumor, the vascularity of primary focus, pancreatic carcinoma was hypovascular. Based on the imaging findings, we thought before the operation that the two lesions were double cancers. Histological examination showed that the stromal volume of metastatic tumorous tissue was richer than that of the primary focus. It was suggested that the difference in the stromal volume was related to the difference of the vascularity. Some foctors originating in stromal cells might be involved in angiogenesis.

Telemedicine system for home automated peritoneal dialysis

We have developed a new telemedicine system to monitor elderly and handicapped patients that use an automated peritoneal dialysis (APD) system to perform continuous ambulatory peritoneal dialysis (CAPD) at home. The system has two parts: (1) a data collection and transport system, and (2) an interview system ("View Send" system). The former is assembled from the APD cycler, an automated blood-pressure recorder, and a scale. The latter is a combination of a digital camera, television, and set-top box (a kind of computer). The APD system contains recording and data transport junctions, a monitoring device, and a data tabulation function. All data collected by the APD system are sent directly in real time to the physician's office. Patients can easily use this telemedicine system to contact the medical staff at the Saitama Medical School CAPD center and to consult concerning their condition. Furthermore, the staff can directly change the CAPD schedule (dose and duration). Seven patients, including some who are older than 90 years or who are handicapped, have been using this telemedicine system for between 1 and 6 months (average: 3 months). From our recent experience, our tentative conclusions are that (1) elderly and handicapped patients benefit from this system by being able to maintain CAPD without major problems and accidents; (2) other problems are mainly due to simple mistakes such as accidentally pushing the on and off switches; (3) quality of life is improved for the patients.

Optoelectronic parallel-matching architecture: architecture description, performance estimation, and prototype demonstration

We propose an optoelectronic parallel-matching architecture (PMA) that provides powerful processing capabilities in global processing compared with conventional parallel-computing architectures. The PMA is composed of a global processor called a parallel-matching (PM) module and multiple processing elements (PE's). The PM module is implemented by a large-fan-out free-space optical interconnection and a PM smart-pixel array (PM-SPA). In the proposed architecture, by means of the PM module each PE can monitor the other PE's by use of several kinds of global data matching as well as interprocessor communication. Theoretical evaluation of the performance shows that the proposed PMA provides tremendous improvement in global processing. A prototype demonstrator of the PM module is constructed on the basis of state-of-the-art optoelectronic devices and a diffractive optical element. The prototype is assumed for use in a multiple-processor system composed of 4 x 4 PE's that are completely connected through bit-serial optical communication channels. The PM-SPA is emulated by a complex programmable device and a complementary metal-oxide semiconductor photodetector array. On the prototype demonstrator the fundamental operations of the PM module were verified at 15 MHz.

Arrhythmogenic effect of hypercapnia in ducks anesthetized with halothane

OBJECTIVE

To determine effects of hypercapnia on arrhythmias in ducks anesthetized with halothane.

ANIMALS

12 ducks, 6 to 8 months old, weighing 1.1 to 1.6 kg.

PROCEDURES

Each duck was anesthetized with a 1.5% mixture of halothane in oxygen, and anesthetic depth was stabilized during a 20-minute period. We added CO2 to the inspired oxygen to produce CO2 partial pressures of 40, 60, and 80 mm Hg in the inspired gas mixture.The CO2 partial pressure was increased in a stepwise manner. When arrhythmias were not evident during inhalation of the gas mixture at a specific CO2 partial pressure, the CO2 partial pressure was maintained for 10 minutes before a sample was collected for blood gas analysis. When arrhythmias were detected, a sample for blood gas analysis was collected after the CO2 partial pressure was maintained for at least 2 minutes, and CO2 inhalation then was terminated.

RESULTS

During the stabilization period, PaCO2 (mean +/- SD) was 33 +/- 5 mm Hg,and arrhythmias were not detected. In 6 ducks, arrhythmias such as unifocal and multifocal premature ventricular contractions developed during inhalation of CO2. Mean PaCO2 at which arrhythmias developed was 67 +/- 12 mm Hg. In 5 of 6 ducks with arrhythmias, the arrhythmias disappeared after CO2 inhalation was terminated.

CONCLUSION AND CLINICAL RELEVANCE

Analysis of data from this study indicated that hypercapnia can lead to arrhythmias in ducks during halothane-induced anesthesia. Thus, ventilatory support to maintain normocapnia is important for managing ducks anesthetized with halothane.

Congenital extrahepatic portocaval shunt associated with hepatic hyperplastic nodules in a patient with Dubin-Johnson syndrome

We report a rare case of congenital extrahepatic portocaval shunt diagnosed during evaluation of hyperplastic nodules in the liver. Diagnostic imagings showed hypoplasia of the intrahepatic portal venous system and splanchnic portal venous return to the inferior vena cava through aberrant vessels. Altered hepatic blood flow dynamics due to this shunt may have been implicated in the etiology of the hepatic hyperplastic nodules.

Body position does not influence the location of ventilator-induced lung injury

OBJECTIVE

To ascertain whether the locations of ventilator-induced lung injury (VILI) are influenced by body position.

DESIGN

Randomized prospective short-term study.

SETTING

Animal laboratory at a university school of medicine.

INTERVENTIONS

Twelve white rabbits were mechanically ventilated in IMV mode with an infant ventilator (V.I.P. Bird, Bird Products, Palm Springs, Calif., USA). Based on the results of a preliminary study to determine the ventilator settings at which the lungs of rabbits were injured within 5 h in the supine position, the ventilator was set at F(I)O2 0.21, at a rate of 30/min, T(I) 0.6 s, peak inspiratory pressure 30 cm H2O, inspiratory flow 10 l/min with no applied positive end-expiratory pressure (PEEP). Six of the animals were tested in the supine position and the other six in the prone position. Respiratory gases were measured and CT scanning was performed every 30 min. The animals were ventilated for 5 h or until pulmonary parenchymal opacification was detected. The lungs were divided into three areas from apex to base and three levels from ventral to dorsal, and the location of opacification was ascribed according to this scheme. After the experiment, the lungs were excised and examined histologically.

MEASUREMENTS AND RESULTS

Parenchymal opacification occurred mainly in the dorsal lung areas. The time from the beginning of ventilation to the appearance of lung damage was 60-120 min in the supine (S) group, and 60-270 min in the prone (P) group, and it was significantly longer in the prone group (P < 0.01). We observed diffuse lung damage, including hyaline membrane formation, intra-alveolar edema, and infiltration of inflammatory cells.

CONCLUSIONS

Body position affected the time course of the development of VILI, but it did not affect the location.

Artificial ventilation-induced diffuse alveolar damage in rabbits: preliminary study of early detection on expiratory high-resolution computed tomography

RATIONALE AND OBJECTIVES

To investigate whether expiratory high-resolution computed tomography (HRCT) is more useful than inspiratory HRCT for the detection of early-phase diffuse alveolar damage.

METHODS

Eleven anesthetized rabbits were scanned with both inspiratory and expiratory HRCT every 30 minutes during mechanical ventilation. Ten rabbits were killed after the detection of pulmonary abnormalities on both inspiratory and expiratory HRCT. The remaining rabbit was killed when the pulmonary abnormalities appeared only on expiratory HRCT.

RESULTS

In four cases (36%), the abnormal findings were detected earlier on expiratory HRCT than on inspiratory HRCT. In seven cases (64%), the abnormalities appeared simultaneously on inspiratory and expiratory HRCT. In all 11 cases, the histopathological changes of areas with abnormal CT findings corresponded to the exudative or proliferative phase of diffuse alveolar damage.

CONCLUSIONS

Expiratory HRCT has the potential to detect the abnormalities of diffuse alveolar damage earlier than inspiratory HRCT.

alpha-eudesmol, a P/Q-type Ca(2+) channel blocker, inhibits neurogenic vasodilation and extravasation following electrical stimulation of trigeminal ganglion

In this study, we investigated the effect of alpha-eudesmol, which potently inhibits the presynaptic omega-agatoxin IVA-sensitive (P/Q-type) Ca(2+) channel, on neurogenic inflammation following electrical stimulation of rat trigeminal ganglion. Treatment with alpha-eudesmol (0.1-1 mg/kg. i.v.) dose-dependently attenuated neurogenic vasodilation in facial skin monitored by a laser Doppler flowmetry. In addition, alpha-eudesmol (1 mg/kg. i.v.) significantly decreased dural plasma extravasation in analysis using Evans blue as a plasma marker. On the other hand, alpha-eudesmol (1 mg/kg, i.v.) did not affect mean arterial blood pressure in rats. The calcitonin gene-related peptide (CGRP) and substance P (SP) released from activated sensory nerves have recently been suggested to be associated with the neurogenic inflammation. In this study, we also showed that alpha-eudesmol (0.45-45 microM) concentration-dependently inhibits the depolarization-evoked CGRP and SP release from sensory nerve terminals in spinal cord slices. These results indicate that the anti-neurogenic inflammation action of alpha-eudesmol, which does not affect the cardiovascular system, may be due to its presynaptic inhibition of the neuropeptide release from perivascular trigeminal terminals. We also suggest that the omega-agatoxin IVA-sensitive Ca(2+) channel blocker, alpha-eudesmol, may become useful for the treatment of the neurogenic inflammation in the trigemino-vascular system such as migraine.

omega-agatoxin IVA-sensitive Ca(2+) channel blocker, alpha-eudesmol, protects against brain injury after focal ischemia in rats

omega-Agatoxin IVA-sensitive Ca(2+) channels have been thought to be involved in physiological excitatory amino acid glutamate release and these channels may also contribute to the development of ischemic brain injury. Recently, we demonstrated that alpha-eudesmol from Juniperus virginiana Linn. (Cupressaceae) inhibits potently the presynaptic omega-agatoxin IVA-sensitive Ca(2+) channels. In the present study, we investigated the effects of alpha-eudesmol on brain edema formation and infarct size determined after 24 h of reperfusion following 1 h of middle cerebral artery occlusion in rats. We first found that alpha-eudesmol concentration-dependently inhibited glutamate release from rat brain synaptosomes and that its inhibitory effect was Ca(2+)-dependent. In the middle cerebral artery occlusion study, intracerebroventricular (i.c.v.) treatment with alpha-eudesmol significantly attenuated the post-ischemic increase in brain water content. alpha-Eudesmol also significantly reduced the size of the infarct area determined by triphenyltetrazolium chloride staining after 24 h of reperfusion. Using a microdialysis technique, we further demonstrated that alpha-eudesmol inhibits the elevation of the extracellular concentration of glutamate during ischemia. From these results, we suggest that alpha-eudesmol displays an ability to inhibit exocytotic glutamate release and to attenuate post-ischemic brain injury.

Supraspinal, not spinal, alpha(2) adrenoceptors are involved in the anesthetic-sparing and hemodynamic-stabilizing effects of systemic clonidine in rats

Clonidine, an alpha(2) agonist, reduces the anesthetic requirement and attenuates harmful hemodynamic responses to noxious stimuli. We examined the responsible sites of action in the central nervous system for the minimum alveolar anesthetic concentration (MAC) and MAC blocking adrenergic response (MAC-BAR) reducing effects of systemically administered clonidine in halothane-anesthetized rats. The MAC for halothane was determined by the tail clamp method, and MAC-BAR was defined as the MAC which attenuated hemodynamic responses within 10% after the tail clamp. We examined the effect of IV clonidine in the presence of rauwolscine, an alpha(2) antagonist given through IV, intrathecal (IT), intracisternal (IC), or intracerebroventrical (ICV) routes. IV clonidine reduced MAC and MAC-BAR dose-dependently. IV and ICV rauwolscine antagonized the MAC-reducing effect of clonidine, whereas IC and IT rauwolscine did not. In comparison, IV, ICV, and IC rauwolscine antagonized the MAC-BAR-reducing effect of clonidine; IT rauwolscine had no effect. Our data demonstrate that the alpha(2) adrenoceptors in the regions above mesencephalon and both the regions above mesencephalon and the lower brainstem are responsible for the MAC and MAC-BAR-reducing effect of systemic clonidine in rats, respectively. However, the spinal alpha(2) adrenoceptors were not involved in these effects of clonidine.

IMPLICATIONS

In the regions above mesencephalon, alpha(2) adrenoceptors were the most responsible for the minimum alveolar concentration-reducing effect and both the lower brainstem and regions above mesencephalon were involved in the minimum alveolar concentration blocking adrenergic response-reducing effect of clonidine. The spinal alpha(2) adrenoceptors did not significantly contribute to these effects of clonidine.

Reduction of peritonitis with the rectus abdominis muscle flap in a CAPD patient

An adolescent maintained on continuous ambulatory peritoneal dialysis (CAPD) for 8 years had relapsing peritonitis involving peritoneal catheter tunnel infections. We attempted catheter removal and replacement simultaneously, with the catheter covered cylindrically by a rectus abdominis muscle flap to prevent recurrent tunnel infections. During 3 years of follow-up, there have been no episodes of peritonitis involving tunnel infection. Our modified insertion technique can eradicate tunnel infection, thus reducing peritonitis.