bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of Ventricular Arrhythmias Induced by Myocardial Contusion
Authors: Robert Emmanuelle , de La Coussaye Jean E. , Aya Antoine G. M. , Bertinchant Jean-Pierre , Polge Anne , Fabbro-Pèray Pascale , Pignodel Christine , Eledjam Jean-Jacques
Published: August 2004

Background

The aims of the Langendorff-perfused rabbit heart study were to evaluate the arrhythmogenic consequences of myocardial contusion and to determine the mechanism of arrhythmia.

Methods

Six hearts were in the control group, and 24 hearts (intact heart protocol) were submitted to one of four different contusion kinetic energies (75, 100, 150, or 200 millijoules [mJ]; n = 6). Occurrence of arrhythmia, of an electrically silent area (i.e., area with no electrical activity), and of line of fixed conduction block were reported before and for 1 h after contusion. In 16 hearts (frozen hearts) submitted to cryoprocedure and contusion impact of 100 or 200 mJ, ventricular conduction velocities, anisotropic ratio, wavelengths, ventricular effective refractory period, and its dispersion were measured before and for 1 h after contusion. Using high-resolution mapping, arrhythmias were recorded and analyzed.

Results

The intact heart study showed that the number and seriousness of contusion-induced arrhythmias increased with increasing contusion kinetic energy, as did the number of electrically silent areas (five of six ventricular fibrillations and five of six electrically silent areas at 200 mJ). In the frozen heart study, immediately after contusion ventricular effective refractory periods were shortened and dispersed, and wavelengths were also shortened. The arrhythmia analysis showed that all ventricular tachycardias but one were based on reentry developed around an electrically silent area or a line of fixed conduction block.

Conclusions

Myocardial contusion has direct arrhythmogenic effects, and the seriousness of arrhythmia increases with the level of contusion kinetic energy. The mechanism of arrhythmia was mainly based on reentrant circuit around a fixed obstacle.
Airway Management during Spaceflight
Authors: Keller Christian , Brimacombe Joseph , Giampalmo Marzia , Kleinsasser Axel , Loeckinger Alex , Giampalmo Giuseppe , Pühringer Fritz
Published: August 2004

Background

The authors compared airway management in normogravity and simulated microgravity with and without restraints for laryngoscope-guided tracheal intubation, the cuffed oropharyngeal airway, the standard laryngeal mask airway, and the intubating laryngeal mask airway.

Methods

Four trained anesthesiologist-divers participated in the study. Simulated microgravity during spaceflight was obtained using a submerged, full-scale model of the International Space Station Life Support Module and neutrally buoyant equipment and personnel. Customized, full-torso manikins were used for performing airway management. Each anesthesiologist-diver attempted airway management on 10 occasions with each device in three experimental conditions: (1) with the manikin at the poolside (poolside); (2) with the submerged manikin floating free (free-floating); and (3) with the submerged manikin fixed to the floor using a restraint (restrained). Airway management failure was defined as failed insertion after three attempts or inadequate device placement after insertion.

Results

For the laryngoscope-guided tracheal intubation, airway management failure occurred more frequently in the free-floating (85%) condition than the restrained (8%) and poolside (0%) conditions (both, P < 0.001). Airway management failure was similar among conditions for the cuffed oropharyngeal airway (poolside, 10%; free-floating, 15%; restrained, 15%), laryngeal mask airway (poolside, 0%; free-floating, 3%; restrained, 0%), and intubating laryngeal mask airway (poolside, 5%; free-floating, 5%; restrained, 10%). Airway management failure for the laryngoscope-guided tracheal intubation was usually caused by failed insertion (> 90%), and for the cuffed oropharyngeal airway, laryngeal mask airway, and intubating laryngeal mask airway, it was always a result of inadequate placement.

Conclusion

The emphasis placed on the use of restraints for conventional tracheal intubation in microgravity is appropriate. Extratracheal airway devices may be useful when restraints cannot be applied or intubation is difficult.
Succinylcholine Metabolite Succinic Acid Alters Steady State Activation in Muscle Sodium Channels
Authors: Haeseler Gertrud , Petzold Jacqueline , Hecker Hartmut , Würz Axel , Dengler Reinhard , Piepenbrock Siegfried , D M. , Leuwer Martin
Published: August 2004

Background

Animal experiments revealed that succinylcholine produced masseter muscle rigidity and activated myotonic discharges despite neuromuscular blockade with a nondepolarizing blocker. These results suggest that either succinylcholine or its metabolites might interfere directly with voltage-operated ion channels of the sarcolemma. The aim of this study was to examine effects of one product of succinylcholine hydrolysis, succinic acid, on voltage-gated muscle sodium (Na+) channels.

Methods

Alpha subunits of human muscle sodium channels were heterologously expressed in HEK293 cells. Activation of Na+ currents was examined applying standard whole-cell voltage-clamp protocols in the absence (control and washout) and presence of succinic acid in different concentrations (0.05-10 mm).

Results

Succinic acid shifted the midpoints of steady state activation plots in the direction of more negative test potentials, indicating that channels open during smaller depolarizations in the presence of the drug. The maximum amount of the negative shift in 10 mm succinic acid was -6.3 +/- 1.7 mV; the EC50 for this effect was 0.39 mm. In addition, succinic acid (10 mm) significantly enhanced maximum currents after depolarizations with respect to a series of control experiments.

Conclusion

Succinic acid facilitates voltage-dependent activation in muscle sodium channels in vitro. This might lead to muscle hyperexcitability in vivo.
Intravenous Anesthetics Differentially Modulate Ligand-gated Ion Channels
Authors: Flood Pamela , Krasowski Matthew D.
Published: August 2004

Background

Heteromeric neuronal nicotinic acetylcholine receptors (nAChRs) are potently inhibited by volatile anesthetics, but it is not known whether they are affected by intravenous anesthetics. Ketamine potentiates gamma-aminobutyric acid type A (GABAA) receptors at high concentrations, but it is unknown whether there is potentiation at clinically relevant concentrations. Information about the effects of intravenous anesthetics with different behavioral profiles on specific ligand-gated ion channels may lead to hypotheses as to which ion channel effect produces a specific anesthetic behavior.

Methods

A heteromeric nAChR composed of alpha4 and beta4 subunits was expressed heterologously in Xenopus laevis oocytes. Using the two-electrode voltage clamp technique, peak ACh-gated current was measured before and during application of ketamine, etomidate, or thiopental. The response to GABA of alpha1beta2gamma2s GABAA receptors expressed in human embryonic kidney cells and Xenopus oocytes was compared with and without coapplication of ketamine from 1 microm to 10 mm.

Results

Ketamine caused potent, concentration-dependent inhibition of the alpha4beta4 nAChR current with an IC50 of 0.24 microm. The inhibition by ketamine was use-dependent; the antagonist was more effective when the channel had been opened by agonist. Ketamine did not modulate the alpha1beta2gamma2s GABAA receptor response in the clinically relevant concentration range. Thiopental caused 27% inhibition of ACh response at its clinical EC50. Etomidate did not modulate the alpha4beta4 nAChR response in the clinically relevant concentration range, although there was inhibition at very high concentrations.

Conclusions

The alpha4beta4 nAChR, which is predominantly found in the central nervous system (CNS), is differentially affected by clinically relevant concentrations of intravenous anesthetics. Ketamine, commonly known to be an inhibitor at the N-methyl-D-aspartate receptor, is also a potent inhibitor at a central nAChR. It has little effect on a common CNS GABAA receptor in a clinically relevant concentration range. Interaction between ketamine and specific subtypes of nAChRs in the CNS may result in anesthetic behaviors such as inattention to surgical stimulus and in analgesia. Thiopental causes minor inhibition at the alpha4beta4 nAChR. Modulation of the alpha4beta4 nAChR by etomidate is unlikely to be important in anesthesia practice based on the insensitivity of this receptor to clinically used concentrations.
Lung Function under High Thoracic Segmental Epidural Anesthesia with Ropivacaine or Bupivacaine in Patients with Severe Obstructive Pulmonary Disease Undergoing Breast Surgery
Authors: Groeben Harald , Schäfer Beatrix , Pavlakovic Goran , Silvanus Marie-Theres , Peters Juergen
Published: August 2004

Background

Because general anesthesia with tracheal intubation can elicit life-threatening bronchospasm in patients with bronchial hyperreactivity, epidural anesthesia is often preferred. However, segmental high thoracic epidural anesthesia (sTEA) causes pulmonary sympathetic and respiratory motor blockade. Whether it can be safely used for chest wall surgery as a primary anesthetic technique in patients with chronic obstructive pulmonary disease or asthma is unclear. Furthermore, ropivacaine supposedly evokes less motor blockade than bupivacaine and might minimize side effects. To test the feasibility of the technique and the hypotheses that (1) sTEA with ropivacaine or bupivacaine does not change lung function and (2) there is no difference between sTEA with ropivacaine or bupivacaine, the authors studied 20 patients with severe chronic obstructive pulmonary disease (forced expiratory volume in 1 s [FEV1] = 52.1 +/- 17.3% of predicted [mean +/- SD]) or asthma who were undergoing breast surgery.

Methods

In a double-blind, randomized fashion, sTEA was performed with 6.6 +/- 0.5 ml of either ropivacaine, 0.75% (n = 10), or bupivacaine, 0.75% (n = 10). FEV1, vital capacity, FEV1 over vital capacity, spread of analgesia (pin prick), hand and foot skin temperatures, mean arterial pressure, heart rate, and local anesthetic plasma concentrations were measured with patients in the sitting and supine positions before and during sTEA.

Results

Segmental high thoracic epidural anesthesia (segmental spread C4-T8 [bupivacaine] and C5-T9 [ropivacaine]) significantly decreased FEV1 from 1.22 +/- 0.54 l (supine) to 1.09 +/- 0.56 l (ropivacaine) and from 1.23 +/- 0.49 l to 1.12 +/- 0.46 l (bupivacaine). In contrast, FEV1 over vital capacity increased from 64.6 +/- 13.5 to 68.2 +/- 14.5% (ropivacaine) and from 62.8 +/- 12.4 to 66.5 +/- 13.6% (bupivacaine). There was no difference between ropivacaine and bupivacaine. Skin temperatures increased significantly, whereas arterial pressure and heart rate significantly decreased indicating widespread sympathetic blockade. All 20 patients tolerated surgery well.

Conclusions

Despite sympathetic blockade, sTEA does not increase airway obstruction and evokes only a small decrease in FEV1 as a sign of mild respiratory motor blockade with no difference between ropivacaine and bupivacaine. Therefore, sTEA can be used in patients with severe chronic obstructive pulmonary disease and asthma undergoing chest wall surgery as an alternative technique to general anesthesia.
Implicit Memory for Words Played during Isoflurane- or Propofol-based Anesthesia
Authors: Münte Sinikka , Schmidt Maren , Meyer Maren , Nager Wido , Lüllwitz Ekkehard , Münte Thomas F. , Piepenbrock Siegfried
Published: August 2004

Background

Unconscious processing of words during general anesthesia has been suggested after surgery with several tests of implicit memory. Patients can neither recall those words nor do they have explicit memories of other intraoperative events. It is unclear to what degree information is processed during general anesthesia and which tests are best suited to detect implicit memory. In the current study, a lexical decision paradigm not previously used to demonstrate implicit memory during anesthesia was used.

Methods

Sixty patients undergoing lumbar disc surgery were assigned to receive isoflurane infusion- or propofol infusion-based anesthesia combined with alfentanil infusions and a nitrous oxide-oxygen mixture. A control group of 10 medical students listened to tapes without receiving anesthesia. Two tapes, each containing a list of 30 low-frequency German nouns repeated for 15 min, were prepared, with half of the patients listening to tape A and the other half listening to tape B during the operation. Exposure time was 15 min from the time of skin incision onward. In the test phase, approximately 7 h later, words from lists A and B plus 60 nonwords were presented in random order by a computer program. Subjects were asked to indicate, by pressing one of two response buttons, whether the spoken word was or was not a legal German word (lexical decision).

Results

A recognition test revealed chance recognition for words presented during anesthesia. Lexical decision responses, however, were slightly faster to primed (previously presented) words than to unprimed (not previously presented) words when the entire group of patients was tested, suggesting a small implicit memory effect, which barely failed to reach the significance level. When the two medication groups were tested separately, no significant implicit memory effect could be ascertained statistically. The effects of previous exposure were much more pronounced in the control group.

Conclusions

Balanced anesthesia techniques with isoflurane or propofol lead to only a minimal, statistically borderline implicit memory effect in the lexical decision paradigm.
The Diverse Actions of Volatile and Gaseous Anesthetics on Human-cloned 5-Hydroxytryptamine3Receptors Expressed in Xenopus Oocytes
Authors: Suzuki Takahiro , Koyama Hideki , Sugimoto Masahiro , Uchida Ichiro , Mashimo Takashi
Published: August 2004

Background

General anesthetics can modulate the 5-hydroxytryptamine type 3 (5-HT3) receptor, which may be involved in processes mediating nausea and vomiting, and peripheral nociception. The effects of the new volatile anesthetic sevoflurane and the gaseous anesthetics nitrous oxide (N2O) and xenon (Xe) on the 5-HT3 receptor have not been well-characterized.

Methods

Homomeric human-cloned 5-HT3A receptors were expressed in Xenopus oocytes. The effects of halothane, isoflurane, sevoflurane, N2O, and Xe on 5-HT-induced currents were studied using a two-electrode, voltage clamping technique.

Results

Halothane (1%) and isoflurane (1%) potentiated 1 mum 5-HT-induced currents to 182 +/- 12 and 117 +/- 2%, respectively. In contrast, sevoflurane (1%), N2O (70%), and Xe (70%) inhibited 5-HT-induced currents to 76 +/- 1, 77 +/- 4, and 34 +/- 4%, respectively. The inhibitory effects were noncompetitive for sevoflurane and competitive for N2O and Xe. None of these inhibitory effects showed voltage dependency.

Conclusion

Inhalational general anesthetics produce diverse effects on the 5-HT3 receptor. Both halothane and isoflurane enhanced 5-HT3 receptor function in a concentration-dependent manner, which is consistent with previous studies. Sevoflurane inhibited the 5-HT3 receptor noncompetitively, whereas N2O and Xe inhibited the 5-HT3 receptor competitively, suggesting the inhibitory mechanism of sevoflurane might be different from those of N2O and Xe.
Sigh Improves Gas Exchange and Lung Volume in Patients with Acute Respiratory Distress Syndrome Undergoing Pressure Support Ventilation
Authors: Patroniti Nicoló , Foti Giuseppe , Cortinovis Barbara , Maggioni Elena , Bigatello Luca M. , Cereda Maurizio , Pesenti Antonio
Published: August 2004

Background

The aim of our study was to assess the effect of periodic hyperinflations (sighs) during pressure support ventilation (PSV) on lung volume, gas exchange, and respiratory pattern in patients with early acute respiratory distress syndrome (ARDS).

Methods

Thirteen patients undergoing PSV were enrolled. The study comprised 3 steps: baseline 1, sigh, and baseline 2, of 1 h each. During baseline 1 and baseline 2, patients underwent PSV. Sighs were administered once per minute by adding to baseline PSV a 3- to 5-s continuous positive airway pressure (CPAP) period, set at a level 20% higher than the peak airway pressure of the PSV breaths or at least 35 cm H2O. Mean airway pressure was kept constant by reducing the positive end-expiratory pressure (PEEP) during the sigh period as required. At the end of each study period, arterial blood gas tensions, air flow and pressures traces, end-expiratory lung volume (EELV), compliance of respiratory system (Crs), and ventilatory parameters were recorded.

Results

Pao2 improved (P < 0.001) from baseline 1 (91.4 +/- 27.4 mmHg) to sigh (133 +/- 42.5 mmHg), without changes of Paco2. EELV increased (P < 0.01) from baseline 1 (1,242 +/- 507 ml) to sigh (1,377 +/- 484 ml). Crs improved (P < 0.01) from baseline 1 (40.2 +/- 12.5 ml/cm H2O) to sigh (45.1 +/- 15.3 ml/cm H2O). Tidal volume of pressure-supported breaths and the airway occlusion pressure (P0.1) decreased (P < 0.01) during the sigh period. There were no significant differences between baselines 1 and 2 for all parameters.

Conclusions

The addition of 1 sigh per minute during PSV in patients with early ARDS improved gas exchange and lung volume and decreased the respiratory drive.
Effects of Dexamethasone on Intravascular and Extravascular Fluid Balance in Patients Undergoing Coronary Bypass Surgery with Cardiopulmonary Bypass
Authors: von Spiegel Tilman , Giannaris Savvas , Wietasch Götz J. K. , Schroeder Stefan , Buhre Wolfgang , Schorn Bernd , Hoeft Andreas
Published: August 2004

Background

Cardiac surgery with cardiopulmonary bypass is often associated with postoperative hemodynamic instability. In this regard beneficial effects of corticosteroids are known. The purpose of this study was to investigate whether these effects are due mainly to a modification of the intravascular and extravascular volume status or whether a more direct improvement of cardiovascular performance by corticosteroids is the underlying mechanism.

Methods

Twenty patients undergoing elective coronary bypass grafting were included in this randomized double-blind study. Patients of the treatment group received 1 mg/kg-1 dexamethasone after induction of anesthesia. In addition to the use of standard monitors and detailed fluid balance assessments, the transpulmonary double-indicator technique was used to measure extravascular lung water, total blood volume, and intrathoracic blood volume. Measurements were done after induction of anesthesia and 1 h, 6 h, and 20 h after the end of surgery.

Results

After cardiopulmonary bypass, no relevant increase in extravascular lung water was observed, despite highly positive fluid balances in all patients. A significantly smaller increase in extravascular fluid content was observed in the dexamethasone group. Total blood volume and intrathoracic blood volume did not differ in the two groups. Patients pretreated with dexamethasone had a decreased requirement for vasoactive substances and, in contrast with the control group, no increase in pulmonary artery pressure.

Conclusions

Extravascular fluid but not extravascular lung water is increased in patients after surgery with cardiopulmonary bypass. Pretreatment of adult patients with 1 mg/kg-1 dexamethasone before coronary bypass grafting decreases extravascular fluid gain and seems to improve postoperative cardiovascular performance. This effect is not caused by a better intravascular volume status.
Standard versus Fiberoptic Pulmonary Artery Catheterization for Cardiac Surgery in the Department of Veterans Affairs
Authors: London Martin J. , Moritz Thomas E. , Henderson William G. , Sethi Gulshan K. , O'Brien Maureen M. , Grunwald Gary K. , Beckman Catherine B. , Shroyer A. Laurie , Grover Frederick L.
Published: August 2004

Background

Controversy exists regarding the utility of continuous monitoring of mixed venous oxygen saturation (STvo2) during cardiac surgery. During a multicenter, prospective, observational study in the Department of Veterans Affairs (Cooperative Study #5), frequency of use of standard pulmonary artery catheterization (PAC) and STvo2-PAC was recorded. Here the authors relate these data to clinical outcomes.

Methods

Logistic and Cox regression models evaluating the association of PAC type with mortality, one or more postoperative complications, cardiac complications, time to extubation, and intensive care unit length of stay were constructed. The number of thermodilution cardiac outputs and arterial blood gas analyses performed in the first 24 h postoperatively were compared.

Results

Data from 3,265 patients undergoing myocardial revascularization (81.7%) or valve replacement-repair (18.3%) were considered. STvo2-PAC was used in 49% and PAC in 51% of patients. In the 14 hospitals, STvo2-PAC was used in all patients in four, in some patients in four, and never in six. No association of STvo2-PAC use with outcome were observed aside from unexplained hospital level effects. A small but statistically significant reduction in the number of arterial blood gas analyses (8 +/- 3 vs. 10 +/- 4, P < 0.0001, STvo2-PAC vs. PAC, respectively) and thermodilution cardiac outputs (14 +/- 8 vs. 15 +/- 9, P < 0.0001, STvo2-PAC vs. PAC, respectively) was observed with use of STvo2-PAC.

Conclusions

Despite higher cost, STvo2-PAC was commonly used in this cohort. Our analysis failed to detect associations with improved outcomes aside from a small reduction in resource utilization. The precise role of STvo2-PAC remains uncertain.
Comparison of Acustimulation and Ondansetron for the Treatment of Established Postoperative Nausea and Vomiting
Authors: Coloma Margarita , White Paul F. , Ogunnaike Babatunde O. , Markowitz Scott D. , Brown Philip M. , Lee Alex Q. , Berrisford Sally B. , Wakefield Cynthia A. , Issioui Tijani , Jones Stephanie B. , Jones Daniel B.
Published: August 2004

Background

This study was designed to evaluate transcutaneous electrical acupoint stimulation (acustimulation) using the ReliefBand compared with ondansetron for the treatment of established postoperative nausea and vomiting (PONV) after outpatient laparoscopic surgery.

Methods

After the authors obtained institutional review board approval and written informed consent, 268 outpatients were enrolled in this randomized, double-blind, placebo- and sham-controlled study. All patients received antiemetic prophylaxis with metoclopramide, 10 mg intravenously, or droperidol, 0.625 mg intravenously, after induction of anesthesia. A total of 90 patients developed PONV in the recovery units and were randomized to one of three treatment groups: (1) the ondansetron group received 4 mg intravenous ondansetron and a sham ReliefBand; (2) the acustimulation group received 2 ml intravenous saline and a ReliefBand; and (3) the combination group received 4 mg intravenous ondansetron and a ReliefBand. A rescue antiemetic (10 mg intravenous metoclopramide) was administered only if the PONV symptoms persisted for 15 min or longer after initiating the treatment. A blinded observer recorded the recovery times, emetic symptoms, rescue antiemetics, maximum nausea scores, complete response to study treatment, and time to achieve discharge criteria. Postdischarge side effects, as well as patient satisfaction and quality of recovery scores, were assessed at 24 and 72 h after surgery.

Results

The combination group had a significantly higher complete response rate than the acustimulation group (73% vs.40%, P <0.01). In addition, fewer patients (8 vs. 18) in the combination (vs. acustimulation) group experienced subsequent emetic events (P < 0.03). However, there were no significant differences between the three groups with respect to patient satisfaction and quality of recovery scores.

Conclusions

Acustimulation with the ReliefBand can be used as an alternative to ondansetron for the treatment of established PONV. However, the use of ondansetron (4 mg intravenously) in combination with the ReliefBand device improved the complete response rate to the acustimulation therapy.
Effect of Local Anesthetic on Neuronal Cytoplasmic Calcium and Plasma Membrane Lysis (Necrosis) in a Cell Culture Model
Authors: Johnson Michael E. , Saenz J. Armando , DaSilva Assir Daniel , Uhl Cindy B. , Gores Gregory J.
Published: August 2004

Background

To investigate the mechanism by which rare cases of spinal local anesthetic (LA) neurotoxicity occur, we have tested the hypotheses that LAs elevate cytoplasmic calcium (Ca2+(cyt)), that this is associated with a neurotoxic effect, and that lidocaine and bupivacaine differ in their neurotoxicity.

Methods

Neurons of the ND7 cell culture line, derived from dorsal root ganglion, were loaded with fura-2 and analyzed by digitized video fluorescence microscopy during 60 min LA exposure, allowing determination of Ca2+(cyt) and time of necrotic cell death (plasma membrane lysis) at the single neuron level.

Results

Lidocaine 0.1% and bupivacaine 0.025% caused minimal changes in Ca. Lidocaine 0.5-5% and bupivacaine 0.125-0.625% caused an early, small (less than threefold), concentration-dependent increase in Ca2+(cyt) that was transient and returned to near baseline within 10 min. Lidocaine 2.5% and 5% then caused a sustained, greater than ten-fold increase in Ca2+(cyt) and death in some neurons during the 60 min exposure period. Pretreatment with thapsigargin eliminated the initial transient increase in Ca2+(cyt), consistent with endoplasmic reticulum (ER) as its source, and increased neuronal death with 5% lidocaine, suggesting that lidocaine neurotoxicity can be increased by failure of ER to take up elevated Ca2+(cyt). The later sustained increase in Ca2+(cyt) seen with 2.5 and 5% lidocaine was prevented in Ca2+ -free medium, and restored when Ca2+ was added back to the buffer in the presence of lidocaine, suggesting that higher concentrations of lidocaine increase influx of Ca2+ through the plasma membrane.

Conclusions

In this model, lidocaine greater than 2.5% elevates Ca2+(cyt) to toxic levels. Bupivacaine and lower concentrations of lidocaine transiently alter Ca2+(cyt) homeostasis for several minutes, but without an immediate neurotoxic effect within 60 min.
Myocardial Effects of Halothane and Isoflurane in Senescent Rats
Authors: Rozenberg Sandrine , Besse Sophie , Vivien Benoît , Coriat Pierre , Riou Bruno
Published: August 2004

Background

Aging is associated with marked alterations in myocardial contraction and relaxation, whereas halogenated anesthetics depress myocardial contractility. However, their effects on aging myocardium are unknown.

Methods

Mechanical variables of left ventricular papillary muscles from adult and senescent rats (29 degrees C; pH 7.40; Ca2+ 1.0 or 0.5 mM; stimulation frequency, 12 pulses/min) were studied. The expression of genes coding for the alpha and beta-myosin heavy chain (MHC) and Ca2+ -ATPase of the sarcoplasmic reticulum (SR) were studied. The effects of halothane and isoflurane were studied. The inotropic effects were compared under low and high loads, using the maximum unloaded shortening velocity (Vmax) and maximum isometric active force (AF). The lusitropic effects were compared in isotonic and isometric conditions.

Results

Senescent rats had a decrease in contraction and relaxation velocities, associated with a reexpression of beta-MHC mRNAs and a decrease in SR Ca2+ -ATPase mRNAs. Halothane induced a lower negative inotropic effect in senescent rats (1.5 vol%, AF: 53 +/- 14% vs. 39 +/- 12% of baseline values; P < 0.01) whereas isoflurane induced a similar negative inotropic effect (1.5 vol%, AF: 81 +/- 7% vs. 87 +/- 7% of baseline values; NS). Halothane induced a negative lusitropic effect in isotonic conditions in adult, but not in senescent, rats.

Conclusions

The inotropic and lusitropic effects of halothane were less important in senescent than in adult rats, whereas the effects of isoflurane were similar. These differences are probably related to differences in SR function and in the effects of halogenated anesthetics on the SR.
General Anesthetics Do Not Affect Release of the Neuropeptide Cholecystokinin from Isolated Rat Cortical Nerve Terminals
Authors: Pashkov Victor N. , Westphalen Robert I. , Hemmings Hugh C.
Published: August 2004

Background

General anesthetics inhibit evoked release of classic neurotransmitters. However, their actions on neuropeptide release in the central nervous system have not been well characterized.

Methods

The effects of representative intravenous and volatile anesthetics were studied on the release of sulfated cholecystokinin 8 (CCK8s), a representative excitatory neuropeptide, from isolated rat cerebrocortical nerve terminals (synaptosomes). Basal, elevated KCl depolarization-evoked and veratridine-evoked release of CCK8s from synaptosomes purified from rat cerebral cortex was evaluated at 35 degrees C in the absence or presence of extracellular Ca2+. CCK8s released into the incubation medium was determined by enzyme-linked immunoassay after filtration.

Results

Elevation of extracellular KCl concentration (to 15-30 mM) or veratridine (10-20 microm) stimulated Ca2+ -dependent CCK8s release. Basal, elevated KCl- or veratridine-evoked CCK8s release was not affected significantly by propofol (12.5-50 microm), pentobarbital (50 and 100 microm), thiopental (20 microm), etomidate (20 microm), ketamine (20 microm), isoflurane (0.6-0.8 mM), or halothane (0.6-0.8 mMm).

Conclusions

Clinically relevant concentrations of several classes of general anesthetics did not affect basal, KCl-evoked, or veratridine-evoked CCK8s release from isolated rat cortical nerve terminals. This is in contrast to the demonstrable effects of certain general anesthetics on the release of amino acid and catecholamine transmitters. These transmitter-specific presynaptic effects of general anesthetics suggest that anesthetic-sensitive presynaptic targets are not common to all transmitter classes.
Mechanisms of Postoperative Pain: Clinical Indications for a Contribution of Central Neuronal Sensitization
Authors: Dirks Jesper , Møiniche Steen , Hilsted Karen-Lisa , Dahl Jørgen B.
Published: August 2004

Background

The relative importance of different nociceptive mechanisms for the intensity, duration, and character of postoperative pain is not well established. It has been suggested that sensitization of dorsal horn neurones may contribute to pain in the postoperative period. We hypothesized that wound hyperalgesia in postoperative patients and experimentally heat-induced secondary hyperalgesia share a common mechanism, sensitization of central neurones, and consequently, that the short-acting opioid remifentanil would have comparable effects on hyperalgesia in both conditions.

Methods

In a randomized, controlled, double-blind trial, we assessed mechanical hyperalgesia in skin bordering the surgical wound, and an area of experimentally heat-induced secondary hyperalgesia on the thigh, in 12 patients who underwent abdominal hysterectomy within 5 days prior to the investigation. Observations were made before and during a drug challenge with remifentanil, which has been demonstrated to reduce the area of heat-induced secondary hyperalgesia in volunteers.

Results

The area of skin with surgically-induced mechanical hyperalgesia, the area of heat-induced secondary hyperalgesia, and pain during cough, were significantly reduced during remifentanil infusion compared with placebo (P = 0.008, P = 0.006, and P = 0.002, respectively). The relative reduction (% of baseline) of the area of skin with surgically-induced hyperalgesia and heat-induced secondary hyperalgesia during infusion of remifentanil was significantly associated (R2 = 0.72, P = 0.001).

Conclusions

Although remifentanil is not a highly targeted "antihyperalgesic," these results support the hypothesis that both wound hyperalgesia in postoperative patients and experimentally heat-induced secondary hyperalgesia may share common mechanisms, and that central neuronal sensitization may contribute to some aspects of postoperative pain. Antihyperalgesic drugs should be further developed and evaluated in clinical trials of postoperative pain.
Alcohol Withdrawal Increases Neuropeptide Y Immunoreactivity in Rat Brain
Authors: Bison Silvia , Crews Fulton
Published: August 2004

Background: Neuropeptide Y (NPY) is widely expressed in the brain and is known to affect consummatory behaviors including drinking alcohol as well as to play a role in seizures. We investigated the effects of a 4 day binge ethanol treatment model that is known to induce physical dependence and withdrawal seizures to determine the effects of ethanol dependence and withdrawal on NPY expression.

Methods: Male Sprague Dawley® rats were treated with ethanol or control nutritionally complete diets by intragastric treatment three times per day for 2 or 4 days with an average daily dose of approximately 8 g/kg ethanol per day. Ethanol‐fed rats treated for 4 days and then withdrawn for 24, 72, and 168 hr also were studied. Brains were perfused and sectioned for immunohistochemistry for NPY, phospho‐cyclic adenosine monophosphate responsive element binding (pCREB), and other proteins.

Results: NPY immunoreactivity (NPY‐IR) was found in several brain regions, with the hippocampus and cerebral cortex showing the most pronounced changes. NPY‐IR was reduced by ethanol treatment in hippocampus and cortex, although at 72 hr of withdrawal there was a dramatic increase in NPY‐IR in the hilus of the dentate gyrus and in CA3 and CA2 fields of hippocampus. Ethanol withdrawal seizures occurred around 12 to 24 hr of withdrawal, preceding the changes in NPY‐IR at 72 hr. pCREB immunoreactivity (pCREB‐IR) tended to decrease during ethanol treatment but showed a dramatic increase in dentate gyrus at 72 hr of withdrawal. Parvalbumin immunoreactivity indicated that some of the pCREB‐IR and NPY‐IR were within inhibitory interneuron basket cells of the hippocampal hilus. NPY‐IR returned to control levels by 168 hr of withdrawal.

Conclusions: These studies suggest that hippocampal NPY is reduced during the development of ethanol dependence. Ethanol withdrawal seizures precede a dramatic increase in hippocampal NPY‐IR. Previous studies have suggested that NPY in the hippocampus reduces seizure activity and that NPY is induced by seizure activity. Thus, the increase in NPY‐IR at 72 hr of withdrawal after binge ethanol treatment may be protective against prolonged withdrawal seizure activity.
Work, work ethic, work excess
Authors: Porter Gayle
Published: August 2004

Organizational change initiatives are successful only through the efforts of the people, so it is important to look beyond surface reactions and understand the deeper implications of employees' visible work habits. By integrating work from several disciplines, this paper poses a series of questions aimed at creating better awareness of differences in how and why people work. Historic tracking of beliefs about work in the USA is provided as an example of how a positive foundation of strong work ethic can become the dysfunctional extreme of workaholism.
Workaholism among Norwegian managers
Authors: Burke Ronald J. , Richardsen Astrid M. , Mortinussen Monica
Published: August 2004

This study examines the relationship of three workaholism components proposed by Spence and Robbins and several work and psychological well‐being outcomes using hierarchical regression analysis. Data were collected from 171 construction company owners and senior managers in Norway using questionnaires. Work enjoyment was found to be positively related with work outcomes. Work enjoyment was also generally positively related with psychological well‐being while feeling driven to work was generally negatively related with psychological well‐being.
Schools in logistics research?
Authors: Gammelgaard Britta
Published: August 2004

In the logistics literature, it is stated that research results are produced almost entirely within a positivistic paradigm. As a consequence, there is only one school in logistics research, and it is based on the positivistic approach. It also means that the research questions are derived from the same methodological approach, which tends to produce similar questions and answers. In this paper, Arbnor and Bjerke's methodological framework is presented as a basic platform for analysing logistics research. By using the framework, it becomes evident that logistics research can be divided into two schools based on the underlying methodological approach. The schools are the analytical school, building on positivism, and the systems school, building on systems theory. Arbnor and Bjerke's framework also provides a basis for expanding the logistics discipline with yet another school, the actors school, based on sociological meta‐theories. Hence, the framework provides logistics research with a solid basis for analyzing existing research and a direction for future research.
Determining the importance of the supplier selection process in manufacturing: a case study
Authors: González Marvin E. , Quesada Gioconda , Mora Monge Carlo A.
Published: August 2004

This article investigates the importance of the supplier management process in the quality of the final product. A methodology is developed to analyze the variables involved in the supplier management process and it is illustrated with a case study of the chair manufacturing industry. Research results indicate that the supplier selection process appears to be the most significant variable as it helps in achieving high quality products and customer satisfaction. This paper shows the different analytical steps that arise naturally in the systematic categorization of variables for supplier management. Nine variables related to the supplier selection process were analyzed. Each of these variables was then evaluated through an experimental design using statistical information based on three factors, namely, quality, cost and productivity.
A study on supply chain management practices
Authors: Chin Kwai‐Sang , Rao Tummala V.M. , Leung Jendy P.F. , Tang Xiaoqing
Published: August 2004

This paper presents the results of a study that examines the success factors in developing and implementing supply chain management strategies for Hong Kong manufacturers. A survey was conducted recently in Hong Kong manufacturing industries to examine the importance and the extent to which the Hong Kong manufacturers practiced the strategies based on these identified success factors. The results will help further in providing greater understanding of the success factors that lead to successful implementation of SCM strategies to reduce supply chain wide costs and to improve customer service levels.
Numerical simulations of natural convection around a line‐source
Authors: Xin Shihe , Duluc Marie‐Christine , Lusseyran François , Le Quéré Patrick
Published: August 2004

External natural convection is rarely studied by numerical simulation in the literature due to the fact that flow of interest takes place in an unbounded domain and that if a limited computational domain is used the corresponding outer boundary conditions are unknown. In this study, we propose outer boundary conditions for a limited computational domain and make the corresponding numerical implementation in the scope of a projection method combining spectral methods and domain decomposition techniques. Numerical simulations are performed for both steady natural convection about an isothermal cylinder and transient natural convection around a line‐source. An experiment is also realized in water using particle image velocimetry and thermocouples to make a comparison during transients of external natural convection around a platinum wire heated by Joule effect. Good agreement, observed between numerical simulations and experiments, validated the outer boundary conditions proposed and their numerical implementation. It is also shown that, if one tolerates prediction error, numerical results obtained remain at least reasonable in a region near the line‐source during the entire transients. We thus paved the way for numerical simulation of external natural convection although further studies remain to be done for higher heating power (higher Rayleigh number).
Optimization of aerodynamic and acoustic performances of supersonic civil transports
Authors: Mohammadi Bijan
Published: August 2004

This paper presents a shape optimization problem under acoustic, aerodynamic and geometric constraints. The acoustic specification concerns the generated sonic boom. The aim is to see the validity of incomplete sensitivities when a nonlinear CFD model is coupled with a nonlinear wave transport model to define pressure rise on the ground.
Customer and company voices in e‐commerce: a qualitative analysis
Authors: McLean Rachel , Blackie Nigel M.
Published: August 2004

Consumer knowledge is a very important asset for an organisation. Two types of consumer knowledge have been identified, “knowledge about customers” including customer segments, individual customer preferences, potential customers, and “knowledge possessed by customers” including knowledge about product ranges, companies, and the marketplace. e‐Commerce offers an ideal medium for the creation and exchange of both types of knowledge. This paper presents the results of an initial phase in a research cycle that looks at e‐Commerce through the lens of knowledge management. It examines e‐Commerce provision made by organisations for customers across seven facets ranging from transactional to relational facilities. The results of a self‐evaluation of companies' e‐commerce propositions are contrasted with customer expectations to determine divergence and alignment. Implications are discussed and conclusions proposed.
Channel benefits portfolio management in the eBusiness era
Authors: Louvieris Panos , Oppewal Harmen
Published: August 2004

The role of channels and their management in the eBusiness era is becoming increasingly important to customer relationship management. Traditional use of the application portfolio approach has been concerned with providing an appropriate basis for making investment decisions about IT applications for the firm. This paper argues that there is a gap between the established IS portfolio application theory and the requirements to support management investment decisions about eBusiness applications; Therefore, the paper proposes a channel benefits portfolio (CBP) approach to inform managers' channel investment decisions concerning business‐to‐customer channel interface. The suggested approach provides a conceptual framework and means to facilitate the alignment of the firm's portfolio with their customers' portfolio. The paper reports exploratory findings regarding customer channel preference and customer channel choice behaviour in the information search and purchasing stages during the customer decision‐making process on the basis of the CBP.
Constructivist learning theory and human capital theory: shifting political and educational frameworks for teachers’ ICT professional development
Authors: Coupal Linda V.
Published: August 2004

This case study discusses the influence of politics on educational technology policies and practices by tracing the effects of a change of governing political parties with differing ideologies and advisory constituencies. It begins by describing a democratic socialist government initiative based on social capital theory and emphasising connections among individuals. The information and communications technology (ICT) initiative is a peer mentorship model of teacher professional development using constructivist learning theory that emphasises activity‐based situated learning processes. The article then describes a shift in the political context with the election of a political party with a market orientation guided by principles of fiscal responsibility and free enterprise. The subsequent reformulation of educational policy draws from human capital theory and emphasises accountability and the measurement of students’ achievement of technological skills against standard learning outcomes. The significance of the political dimension on the development of educational policies for ICT is discussed, with the conclusion that the exclusion of particular constituent groups can result in narrowly defined educational needs.
The Stories We Keep: Autobiographical Memory in American and Chinese Middle‐Aged Adults
Authors: Wang Qi , Conway Martin A.
Published: August 2004

Abstract
One hundred and eight European American and Chinese adults, aged between 38 and 60, participated in this questionnaire study. They each recalled 20 memories from any period of their lives. Memory content was analyzed as a function of culture (U.S. and China), life period (childhood, youth, early midlife, and peak midlife), and gender (female and male). Across the four life periods, Americans provided more memories of individual experiences and unique, one‐time events and focused on their own roles and emotions. In contrast, Chinese were more inclined to recall memories of social and historical events and placed a great emphasis on social interactions and significant others in their memory narratives. Chinese also more frequently drew upon past events to convey moral messages than did Americans. In addition, memory content evidenced age‐related increases in both autonomous and social orientations. Findings are discussed in light of the self‐definitional and directive functions of Autobiographical memory in the context of culture.
Projections of demand and capacity for colonoscopy related to increasing rates of colorectal cancer screening in the United States
Authors: Vijan S. , Inadomi J. , Hayward R. A. , Hofer T. P. , Fendrick A. M.
Published: August 2004

Background : There is debate about the optimal colorectal cancer screening test, partly because of concerns about colonoscopy demand.

Aim : To quantify the demand for colonoscopy with different screening tests, and to estimate the ability of the United States health care system to meet demand.

Methods : We used a previously published Markov model and the United States census data to estimate colonoscopy demand. We then used an endoscopic database to compare current rates of screening‐related colonoscopy with those projected by the model, and to estimate the number of endoscopists needed to meet colonoscopy demand.

Results : Annual demand for colonoscopy ranges from 2.21 to 7.96 million. Based on current practice patterns, demand exceeds current supply regardless of screening strategy. We estimate that an increase of at least 1360 gastroenterologists would be necessary to meet demand for colonoscopic screening undergone once at age 65, while colonoscopy every 10 years could require 32 700 more gastroenterologists. A system using dedicated endoscopists could meet demand with fewer endoscopists.

Conclusions : Colorectal cancer screening leads to demand for colonoscopy that outstrips supply. Systems to train dedicated screening endoscopists may be necessary in order to provide population‐wide screening. The costs and feasibility of establishing this infrastructure should be studied further.