bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Dantrolene on Rat Diaphragm Muscle during Postnatal Maturation
Authors: Orliaguet Gilles , Langeron Olivier , Coirault Catherine , Fratea Sylvia , Coriat Pierre , Riou Bruno 
Published: November 2003

Background
Dantrolene is the only known effective treatment for malignant hyperthermia. However, its effects on diaphragm muscle during postnatal maturation remain unknown.

Methods
The effects of dantrolene (10(-8) to 10(-4) M) were investigated in vitro on diaphragm muscle strips in adult rats and in postnatal rats aged 3, 10, and 17 days, and compared with those of ryanodine (10(-8) to 10(-6) M). The authors studied contraction and relaxation under isotonic and isometric conditions (29 degrees C, Krebs-Henseleit solution, tetanic stimulation at 50 Hz). Data are mean +/- SD.

Results
During postnatal maturation, the authors observed a progressive increase in active force developed per cross-sectional area (from 34 +/- 25 to 69 +/- 32 mN/mm2; P < 0.05) and maximum shortening velocity (from 2.9 +/- 0.5 to 4.9 +/- 1.4 Lmax/s; P < 0.05). Dantrolene induced a negative inotropic effect in diaphragm muscles in isotonic and isometric conditions in all groups, but this effect was significantly less marked in the 3-day-old rats compared with older rats. Dantrolene did not induce significant lusitropic effects during postnatal maturation. Developmental changes in the pharmacologic response to dantrolene were more rapid than those of ryanodine.

Conclusion
Dantrolene induced less pronounced negative inotropic effects on the diaphragm in neonatal rats as compared with adult rats. Our study suggests that developmental changes in the pharmacologic response to dantrolene are more rapid than those of ryanodine.
Blockade of AMPA Receptors and Volatile Anesthetics
Authors: Joo Daisy T. , Gong Diane , Sonner James M. , Jia Zhengping , MacDonald John F. , Eger Edmond I. , Orser Beverley A. 
Published: November 2003

Background
The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype of glutamate receptor mediates fast excitatory neurotransmission in the central nervous system. Many general anesthetics inhibit AMPA receptors in vitro; however, it is not certain if this inhibition contributes to the behavioral properties of these drugs. AMPA receptors lacking the GluR2 subunit are resistant to blockade by barbiturates in vitro. Paradoxically, GluR2 null mutant (-/-) mice are more sensitive to barbiturate-induced loss of the righting reflex (LORR) compared with wild-type (+/+) littermates. To determine if interactions between anesthetics and AMPA receptors account for the increased sensitivity of (-/-) mice, the effects of volatile anesthetics that do not directly inhibit AMPA receptors were examined.

Methods
Isoflurane, halothane, desflurane, or sevoflurane were administered to (-/-) and (+/+) littermate controls. Anesthetic requirements for LORR, movement to tail clamp (minimum alveolar concentration [MAC]), and hind-paw withdrawal latency (HPWL) were determined. Electrophysiologic methods examined the inhibition of AMPA receptors by isoflurane and halothane.

Results
Anesthetic requirements for LORR and HPWL were decreased, whereas MAC values were unchanged in (-/-) mice. Isoflurane and halothane caused minimal inhibition of AMPA receptors at clinically relevant concentrations.

Conclusions
Direct blockade of AMPA receptors did not account for the increased sensitivity to volatile anesthetics in GluR2 null mutant mice for HPWL or LORR. Thus, the deficiency of GluR2-containing AMPA receptors increases the sensitivity of neuronal circuitry mediating these end points, but not MAC. GluR2-containing receptors do not contribute appreciably to MAC in this mouse model. These results illustrate the difficulties in attributing behavioral responses to drug-receptor interactions in genetically engineered animals.
Mechanisms of Isoflurane-mediated Hyperpolarization of Vascular Smooth Muscle in Chronically Hypertensive and Normotensive Conditions
Authors: Stekiel Thomas A. , Contney Stephen J. , Kokita Naohiro , Bosnjak Zeljko J. , Kampine John P. , Stekiel William J. 
Published: November 2003

Background
The purpose of this study was to compare the effects of isoflurane on membrane and intracellular mechanisms that regulate vascular smooth muscle (VSM) transmembrane potential (Em; which is related to VSM tone) in the spontaneously hypertensive rat (SHR) model of essential hypertension and its normotensive Wistar-Kyoto (WKY) control.

Methods
Vascular smooth muscle Em values were measured in situ in locally denervated, superfused, intact, small (200-300-microm OD) mesenteric arteries and veins in anesthetized 9-12-week-old SHR and WKY. Effects of 1.0 minimum alveolar concentration (0.60 mM) superfused isoflurane on VSM Em were measured before and during superfusion with specific inhibitors of VSM calcium-activated (KCa) and adenosine triphosphate-regulated (KATP) potassium channels, and with endogenous mediators of vasodilatation (nitric oxide, cyclic guanosine monophosphate, protein kinase G, cyclic adenosine monophosphate, and protein kinase A).

Results
Isoflurane significantly hyperpolarized small arteries (5 +/- 3.4 mV) and veins (6 +/- 4.7 mV) (pooled SHR and WKY, mean +/- SD). Inhibition of KCa and KATP channels, cyclic adenosine monophosphate, and protein kinase A, but not nitric oxide, cyclic guanosine monophosphate, and protein kinase G, abolished such hyperpolarization equally in SHR and WKY vessels.

Conclusions
Isoflurane-induced in situ VSM hyperpolarization in denervated, small mesenteric vessels involves a similar activation of KCa and KATP channels and cyclic adenosine monophosphate, but not nitric oxide or cyclic guanosine monophosphate, second messenger pathways in both SHR and WKY. A greater isoflurane-induced VSM hyperpolarization (observed previously in neurally intact SHR vessels) suggests enhanced inhibition of elevated sympathetic neural input as a major mechanism underlying such hyperpolarization (and coupled relaxation) in this neurogenic model of hypertension.
The Concentration of Isoflurane Required to Suppress Learning Depends on the Type of Learning
Authors: Dutton Robert C. , Maurer Anya J. , Sonner James M. , Fanselow Michael S. , Laster Michael J. , Eger Edmond I. 
Published: November 2003

Background
Recent reports suggest that one type of learning, fear conditioning to context, requires more neural processing than a related type, fear conditioning to tone. To determine whether these types of learning were differentially affected by anesthesia, the authors applied isoflurane during the training phases of fear conditioning paradigms for freezing to context and freezing to tone.

Methods
The authors trained seven groups of eight rats to fear tone by administering a tone (conditioned stimulus) while breathing various concentrations of isoflurane from 0.00 to 0.75 minimum alveolar concentration (MAC; one concentration per group) separated by 0.12-MAC steps. On the succeeding day, and in the absence of isoflurane, the authors presented the tone (without shock) in a different context (different cage shape and odor) and measured the time each rat froze (became immobile). Six other groups of eight rats were trained to fear context by applying the shock in the absence of a tone but in the presence of environmental cues such as cage shape, texture, and odor. Fear to context was determined the succeeding day by returning the rat to the training cage (without shock) and measuring duration of freezing. Control groups (16 per group) received 0.75 MAC isoflurane but no foot shocks. Group scores were compared using analysis of variance, and the ED50 values for quantal responses of individual rats were calculated using logistic regression.

Results
Conditioning to context occurred at 0.00 and 0.13 MAC (P < 0.05 compared with unshocked control) but not 0.25 MAC; the ED50 was 0.25 +/- 0.03 MAC (mean +/- SEM). In contrast, conditioning to tone occurred at 0.48 MAC (P < 0.05) but not 0.62 MAC; the ED50 was 0.47 +/- 0.02 MAC (P < 0.01 for the difference between ED50 values).

Conclusions
Suppression of fear conditioning to tone required approximately twice the isoflurane concentration that suppressed fear conditioning to context. Thus, the concentration of anesthetic required to suppress learning may depend on the neural substrates of learning. Our results suggest that isoflurane concentrations greater than 0.5 MAC may be needed to suppress both forms of fear conditioning.
BIS Monitoring to Prevent Awareness during General Anesthesia
Authors: O’Connor Michael F. , Daves Suanne M. , Tung Avery , Cook Richard I. , Thisted Ronald , Apfelbaum Jeffery 
Published: November 2003

Background
Unexpected awareness is a rare but well-described complication of general anesthesia that has received increased scientific and media attention in the past few years. Transformed electroencephalogram monitors, such as the Bispectral Index monitor, have been advocated as tools to prevent unexpected recall.

Methods
The authors conducted a power analysis to estimate how many patients would be needed in an appropriately powered study to demonstrate the Bispectral Index monitor reduces awareness, as well as a cost analysis to assess the cost of using the monitor for this purpose alone.

Results
If unexpected recall is rare (1 in 20,000), it will require a large study to demonstrate that the monitor reduces awareness (200,000-800,000 patients), and the cost of using it for this purpose alone would be high ($400,000 per case prevented). If awareness is common (1 in 100), then the number of patients needed in a study to demonstrate that the monitor works becomes tractable (1,000-4,000 patients), and the cost of using the monitor for this purpose alone becomes lower ($2,000 per case prevented). Because there are reported cases of awareness despite Bispectral Index monitoring, the authors are certain that the effectiveness of the monitor is less than 100%. As the performance of the monitor decreases from 100%, the size of the study needed to demonstrate that it works increases, as does the cost of using it to prevent awareness.

Conclusion
The contention that Bispectral Index monitoring reduces the risk of awareness is unproven, and the cost of using it for this indication is currently unknown.
Celiac Plexus Block
Authors: De Cicco Marcello , Matovic Mira , Bortolussi Roberto , Coran Franco , Fantin Dario , Fabiani Fabio , Caserta Maria , Santantonio Cristina , Fracasso Augusto 
Published: November 2003

Background
The success of the neurolytic celiac plexus block, despite different approaches and methods used, depends on adequate spread of the injectate in the celiac area. This retrospective study was conducted to evaluate the patterns of alcohol spread and pain relief in patients with cancer or therapy-related anatomic distortion of the celiac area.

Methods
From 177 cancer patients who underwent computed tomography (CT)-guided single-needle neurolytic celiac plexus block via an anterior approach, a radiologist, blind to the aim of the study, retrospectively selected 105 patients with abnormal anatomy of the celiac area as judged by CT images obtained before the block. To evaluate CT patterns of neurolytic (mixed with contrast) spread, the celiac area was divided on the frontal plane into four quadrants: upper right and left and lower right and left, as related to the celiac artery. Results were expressed as the number of quadrants into which contrast spread, ie., four, three, two, or one quadrants with contrast. The patterns of contrast spread according to the number of quadrants with anatomic distortion were analyzed. Patient assessment by visual analog scale was reviewed to evaluate the degree of pain relief. Pain relief 30 days after block was considered long-lasting. Pain relief at 30 days after block was analyzed according to the number of quadrants with contrast.

Results
Overall, four, three, two, and one quadrants with contrast were observed in 9 (8%), 21 (20%), 49 (47%), and 26 (25%) patients, respectively. An inverse correlation was observed between the number of quadrants with anatomic distortion and the number of quadrants with contrast (P < 0.001). Long-lasting pain relief was noticed in nine of nine patients (100%; 95% confidence interval, 66-100) with contrast in four-quadrants, and in 10 of 21 patients (48%; 95% confidence interval, 26-70) with contrast in 3 quadrants (P < 0.01). None of the 75 patients with contrast in two quadrants or one quadrant experienced long-lasting pain relief.

Conclusions
These findings suggest that, using the single-needle anterior approach, the neurolytic spread in the celiac area is highly hampered by the regional anatomic alterations. It also appears that only a complete (four quadrants) neurolytic spread in the celiac area can guarantee long-lasting analgesia, and that this picture may be obtained in a very limited fraction of patients with regional anatomic alterations.
Caudal Ropivacaine in Infants
Authors: Hansen Tom G. , Ilett Kenneth F. , Reid Chris , Im Lim Soo , Peter Hackett L. , Bergesio Riccardo 
Published: November 2003

Background
Ropivacaine is a new long-acting amino-amide local anesthetic. However, there are no data on its use in infants. In the current study, the authors investigated the pharmacokinetics of caudal ropivacaine in 30 infants younger than 12 months.

Methods
Two groups of infants (group 1 [n = 15], aged 0-3 months; group 2 [n = 15], aged 3-12 months) were given a caudal bolus dose of 0.2% ropivacaine (2 mg/kg) and a standardized general anesthetic technique. Serial blood samples taken for up to 12 h were analyzed for total and free ropivacaine using high-performance liquid chromatography. Population pharmacokinetic modeling was performed to yield estimates of clearance, volume of distribution, and absorption rate constant. An analysis of covariates on the kinetic parameters also was made.

Results
Median maximum free ropivacaine concentration was significantly higher in group 1 (99 micog/l) than in group 2 (38 microg/l) (P = 0.0002), as was the median free fraction of ropivacaine (10% vs. 5%; P = 0.01). Pharmacokinetic variables of the total population were best described by a one-compartment model with first-order absorption. Mean clearance was 0.31 l.h(-1).kg(-1) (coefficient of variation [CV], 51%), volume of distribution was 2.12 l/kg (CV, 34%), and absorption rate constant was 1.61 h(-1) (CV, 46%). Mean absorption and elimination half-lives were 0.43 and 5.1 h, respectively. Age and percentage of free ropivacaine were significant covariates for clearance. Posterior Bayesian estimates of clearance were significantly higher (38%) in older children.

Conclusion
Total and free plasma ropivacaine concentrations after caudal ropivacaine (0.2%, 2 mg/kg) in infants were within the range of concentrations previously reported in adults and older children. Age and percentage of free ropivacaine were significant covariates of clearance.
Comparison of Multiplane Transesophageal Echocardiography and Contrast-enhanced Helical CT in the Diagnosis of Blunt Traumatic Cardiovascular Injuries
Authors: Vignon Philippe , Boncoeur Marie-Paule , François Bruno , Rambaud Geoffray , Maubon Antoine , Gastinne Hervé 
Published: November 2003

Background
Multiplane transesophageal echocardiography (TEE) and helical computed tomography (CT) of the chest have been validated separately against aortography for the diagnosis of acute traumatic aortic injuries (ATAI). However, their respective diagnostic accuracy in identifying blunt traumatic cardiovascular lesions has not been compared.

Methods
During a 3-yr period, 110 consecutive patients with severe blunt chest trauma (age: 41 +/- 17 yr; injury severity score: 34 +/- 14) prospectively underwent TEE and chest CT as part of their initial evaluation. Results of both imaging methods were interpreted independently by experienced investigators and subsequently compared. All cases of subadventitial acute traumatic aortic injury were surgically confirmed.

Results
Seventeen patients had vascular injury and 11 had cardiac lesions. TEE and CT identified all subadventitial disruptions involving the aortic isthmus (n = 10) or the ascending aorta (n = 1) that necessitated surgical repair. In contrast, CT only depicted one disruption of the innominate artery. TEE detected injuries involving the intimal or medial layer, or both, of the aortic isthmus in four patients with apparently normal CT results who underwent successful conservative treatment. All cardiac injuries but two were identified only by TEE.

Conclusions
In patients with severe blunt chest trauma, TEE and CT have similar diagnostic accuracy for the identification of surgical acute traumatic aortic injuy. TEE also allows the diagnosis of associated cardiac injuries and is more sensitive than CT for the identification of intimal or medial lesions of the thoracic aorta.
Propofol Attenuates Diaphragmatic Dysfunction Induced by Septic Peritonitis in Hamsters
Authors: Mikawa Katsuya , Nishina Kahoru , Kodama Shun-ichi , Obara Hidefumi 
Published: November 2003

Background
Sepsis or peritonitis impairs diaphragmatic contractility and endurance capacity. Peroxynitrite, a powerful oxidant formed by superoxide and nitric oxide, has been implicated in the pathogenesis. Propofol scavenges this reactive molecule. The authors conducted the current study to evaluate whether propofol prevents diaphragmatic dysfunction induced by septic peritonitis.

Methods
Forty male Golden-Syrian hamsters (120-140 g) were randomly classified into five groups. Groups sham and sham-propofol 50 underwent sham laparotomy alone, whereas groups sepsis, sepsis-propofol 25, and sepsis-propofol 50 underwent cecal ligation with puncture. Groups sham and sepsis received infusion of intralipid, whereas groups sham-propofol 50, sepsis-propofol 25, and sepsis-propofol 50 received propofol at rates of 50, 25, and 50 mg.kg(-1).h(-1), respectively. Intralipid or propofol was subcutaneously infused from 3 h before surgery until 24 h after operation, when all hamsters were killed. Diaphragmatic contractility and fatigability were assessed in vitro using diaphragm muscle strips. Peroxynitrite formation in the diaphragm was assessed by nitrotyrosine immunostaining. Plasma nitrite-nitrate concentrations and diaphragmatic concentrations of malondialdehyde were determined. Using another set of animals, diaphragmatic inducible nitric oxide synthase activity was also measured.

Results
Twitch, tetanic tensions, and tensions during fatigue trials were reduced in group sepsis compared with group sham. In group SEPSIS, diaphragm malondialdehyde and inducible nitric oxide synthase activity, and plasma nitrite-nitrate concentrations increased, and positive immunostaining for nitrotyrosine residues was found. Propofol attenuated these changes.

Conclusions
Pretreatment with propofol attenuated diaphragmatic dysfunction induced by septic peritonitis in hamsters assessed by contractile profiles and endurance capacity. This beneficial effect of propofol may be caused, in part, by inhibition of lipid peroxidation in the diaphragm caused by the powerful oxidant.
A Comparison of Tracheal Tube Tip Designs on the Passage of an Endotracheal Tube during Oral Fiberoptic Intubation
Authors: Ruari Greer J. , Smith Sharon P. , Strang Tim 
Published: November 2003

Background
The design of an endotracheal tube has been shown to influence the passage of the tube through the glottis during fiberoptic intubation. Difficulty in passing the endotracheal tube can occur if the aryepiglottic folds obstruct the passage of the bevel. The relevant aspects of endotracheal tube design include the shape of the bevel, the material used by the manufacturer, and the ability of the tube to conform to the shape of the fiberscope. The aim of the current study was to compare the ease of passage through the glottis of two different tubes. One tube was a wire reinforced polyvinyl chloride tube with a standard bevel and the other was a newly designed tube with a bevel of different shape and made of silicone rubber. The new design is for use with the a commerical intubating laryngeal mask.

Methods
The authors studied a population of 30 patients who received a standard anesthetic. In all cases, oral fiberoptic intubation was attempted. Anesthetic was administered to each patient using both tubes, and before the study the order of the tubes was randomized. The difficulty in passing the tube was assessed by a blinded observer and graded using a three-point scale (grade 1: no difficulty passing the tube; grade 2: obstruction to passing the tube relieved by withdrawal and a 90 degrees anticlockwise rotation; grade 3: obstruction necessitating more than one manipulation or external laryngeal manipulation).

Results
In 27 patients, no difficulty was shown by use of the silicone-tipped tube. In only three patients was there difficulty that necessitated a 90 degrees anticlockwise twist. With the wire-reinforced tube, no difficulty was experienced on 14 occasions. Grade 1 difficulty was experienced eight times and difficulty necessitating more than one maneuver, head movement, or external laryngeal manipulation was seen on eight occasions. Statistical significance was achieved at P = 0.0002 (Wilcoxon signed rank test).

Conclusions
The authors conclude that the use of the silicone-tipped tube with the new bevel design may provide an advantage in the clinical situation of fiberoptic intubation.
Minimum Analgesic Dose of Epidural Sufentanil for First-stage Labor Analgesia
Authors: Capogna Giorgio , Parpaglioni Raffaella , Lyons Gordon , Columb Malachy , Celleno Danilo 
Published: November 2003

Background
The aim of this prospective, double-blind, sequential allocation study was to compare the effects of spontaneous and prostaglandin-induced labor on the minimum analgesic dose of epidural sufentanil in the first stage of labor.

Methods
Seventy healthy, nulliparous women, at more than 37 weeks' gestation with cervical dilatation from 2 to 4 cm, requesting epidural pain relief in labor were enrolled. The subjects were assigned to two different groups according to whether labor was spontaneous or induced with dinoprostone 0.5 mg. Parturients received 10 ml of the study solution through a lumbar epidural catheter. The initial dose was sufentanil 25 microg, and subsequent doses were determined by the response of the previous patient in the same group using up-down sequential allocation. The analgesic effectiveness was assessed using 100-mm visual analog pain scores. The up-down sequences were analyzed using the method of independent paired reversals and probit regression.

Results
The minimum analgesic dose of sufentanil in spontaneous labor was 22.2 microg (95% CI: 19.6, 22.8) and 27.3 microg (95% CI: 23.8, 30.9) in induced labor. The minimum analgesic dose of sufentanil in induced labor was significantly greater (P = 0.0014) than that in spontaneous labor (95% CI difference: 2.9, 9.3) by a factor of 1.3 (95% CI: 1.1, 1.5).

Conclusion
Prostaglandin induction of labor produces a significantly greater analgesic requirement than does spontaneous labor.