Serotonin, estrus, and social context influence c-Fos immunoreactivity in the inferior colliculus.

A fundamental task of sensory systems is to extract relevant social information from a range of environmental stimuli in the face of changing behavioral contexts and reproductive states. Neuromodulatory pathways that interact with such contextual variables are 1 mechanism for achieving this. In the mouse inferior colliculus (IC), a midbrain auditory region, the neuromodulator serotonin increases in females interacting with courting males, but events downstream of serotonin release have not been investigated. Here, we manipulated serotonin levels in female mice with the serotonin releaser fenfluramine or the serotonin depleter para-chlorophenylalaninemethyl ester (pCPA). Females were then exposed to an empty cage, a male partner, or a playback of courtship vocalizations, and the numbers of neurons in the IC with positive immunoreactivity for the immediate early gene product c-Fos were measured. The effects of drug treatments depended on social context and estrous state. Fenfluramine had greater effects in the nonsocial than in the partner social treatments. Females in proestrus or estrus and given fenfluramine had higher densities of c-Fos immunoreactive neurons, while females in diestrus had fewer immunoreactive neurons. The drug pCPA had the expected opposite effect of fenfluramine, causing a decreased response in pro/estrus females and an increased response in diestrus females. These findings show that the effects of serotonin on c-Fos activity in the IC of females is dependent on both external context and reproductive state, and suggest that these effects occur downstream of serotonin release. (PsycINFO Database Record

Airway management using a supraglottic airway device without endotracheal intubation for positive ventilation of anaesthetized rats.

Endotracheal intubation is often necessary for positive pressure ventilation of rats during open thoracic surgery. Since endotracheal intubation in rats is technically difficult and is associated with numerous complications, many techniques using various devices have been described in the scientific literature. In this study, we compared the effectiveness of airway management of a home-made supraglottic airway device (SAD), which is cheap to fabricate and easy to place with that of an endotracheal intubation tube in enflurane-anaesthetized rats. Twenty male Sprague-Dawley rats (200-300 g) were randomly assigned to two equal groups for positive pressure mechanical ventilation using either the SAD or an endotracheal intubation tube. The carotid artery of each rat was cannulated for continuous blood pressure measurements and obtaining blood samples for determination of oxygen tension, carbon dioxide tension, and blood acidity before, during and after SAD placement or endotracheal intubation. Proper placement of the SAD was confirmed by observing chest wall movements that coincided with the operation of the mechanical ventilator. No complications and adverse events were encountered in the rats in which the SAD was placed, during SAD placement and immediate removal, during their mechanical ventilation through the SAD, and one week after SAD removal. From the results of blood gas analyses, we conclude that anaesthetized rats can be successfully ventilated using an SAD for open thoracic surgery.

Enflurane requirement for blocking adrenergic responses to incision in infants and children.

BACKGROUND: Enflurane is one of the most commonly used inhaled anesthetics in China, but its requirement to block adrenergic responses after skin incision in pediatric patients is still unknown. This study was to determine the minimum alveolar anesthetic concentration (MAC) of potent inhaled anesthetics required to blunt the adrenergic response to skin incision of enflurane (MACBAR) in infants and children. METHODS: Twenty-eight patients, 10 infants (6-12 months) and 18 young children (1-6 years), were studied. The 18 children were randomly assigned into two groups, with or without fentanyl. Anesthesia was induced with 3 mg/kg propofol and 0.15 mg/kg vecuronium, and maintained with enflurane in 100% oxygen. Fentanyl (3 microg/kg) was given intravenously 5 minutes before incision for the patients of fentanyl group. The "up and down" method (with 0.3 MAC as a step size and 1 MAC as the start dose) was applied to determine MACBAR. The response was considered positive if the mean arterial pressure (MAP) or heart rate (HR) increased > or =15% after incision. The MACBAR was calculated as the mean of four independent cross-over responses in each group. RESULTS: MACBAR of enflurane in children of 1-6 years old was 3.2% (95% CI, 2.8%-3.6%) and was reduced to 2.2% (95% CI, 1.8%-2.5%) by 3 microg/kg fentanyl. In infants of 6-12 months old, the MACBAR of enflurane was 3.4% (95% CI, 3.0%-3.8%). CONCLUSIONS: MACBAR of enflurane in infants older than 6 months is similar to that in young children. The MACBAR of enflurane decreases with co-administration of fentanyl in the pediatric population.

Fresh gas flow is not the only determinant of volatile agent consumption: a multi-centre study of low-flow anaesthesia.

METHODS: Seven academic centres studied 302 patients, using desflurane, enflurane, halothane, or isoflurane using circle-systems and Dräger Julian anaesthetic machines, with fresh gas flows (V(F)) of 3, 1, and 0.5 litre min(-1). Volatile agent partial pressures in the breathing system were recorded and agent consumptions measured by weighing. RESULTS: At these flows, desflurane consumption depended on V(F). In contrast, halothane consumption was not influenced by V(F). Isoflurane and enflurane showed differences in consumption between flows of 0.5 and 3 litre min(-1). Stepwise linear regression suggested that besides V(F), other factors influenced consumption of the more soluble agents (sex, age, weight, height, altitude, and temperature). The partial pressure ratios were independent of V(F) for desflurane (end-tidal to fresh gas=0.8), but the ratios of the more soluble agents varied with V(F) (end-tidal to fresh gas=0.3-0.7). CONCLUSIONS: At V(F) that involves significant re-breathing, consumption of soluble agents depends only partially on V(F). These results can be explained using Mapleson's hydraulic analogue model.

The minimum alveolar concentration of enflurane for laryngeal mask airway extubation in deeply anesthetized children.

UNLABELLED: The end-tidal anesthetic gas concentration required to prevent the anesthetized patient from coughing or moving during or immediately after the laryngeal mask airway (LMA) extubation is not known. We sought to determine the minimum alveolar concentration of enflurane required for the removal of the LMA in children. We studied 21 nonpremedicated children between 4 and 11 yr of age, ASA physical status I, undergoing procedures below the umbilicus. General anesthesia was induced with a mask by using sevoflurane, nitrous oxide, and oxygen, and the LMA was inserted. Anesthesia was maintained with enflurane, nitrous oxide, and oxygen. At the end of surgery, a predetermined end-tidal enflurane concentration was achieved, and the LMA was removed. Each concentration at which the LMA extubation was attempted was predetermined by the up-and-down method (with 0.1% as a step size). When LMA removal was accomplished without coughing, clenching teeth, or gross purposeful muscular movements during or within 1 min after removal, it was considered a successful LMA removal. Removal was considered to be unsuccessful in patients who developed breath holding or laryngospasm during or immediately after LMA removal. The minimum alveolar concentration of enflurane at which 50% of children had a successful LMA removal was found to be 1.02% (95% CL, 0.95%-1.11%), and the 95% effective dose for successful extubation was 1.14% (95% CL, 1.07%-1.66%). In conclusion, the LMA removal may be accomplished without coughing or moving at 1.02% end-tidal enflurane concentration in 50% of anesthetized children aged 4-11 yr. IMPLICATIONS: There may be fewer problems associated with the laryngeal mask airway extubation when patients are deeply anesthetized. The purpose of this study was to determine the minimum concentration of enflurane for successful removal of the laryngeal mask in children.

Efeitos do sevoflurano isoladamente ou associado ao fentanil nas respostas hemodinâmicas, endócrinas e eletroencefalográficas à intubaçäo traqueal / Effects of sevoflurane or sevoflurane plus fentanyl in hemodynamic, endocrine and electroencephalographic responses to tracheal intubation

Justificativa e objetivo - a laringoscopia e intubaçäo traqueal frequentemente causam importantes modificaçöes hemodinâmicas, endócrinas, metabólicas e corticais cerebrais. Este trabalho tem como objetivo avaliar o sevoflurano isoladamente ou associado a várias doses de fenantil no bloqueio das respostas deletérias à intubaçäo traqueal. Método - participaram do estudo 32 voluntários com idades entre 20 e 40 anos, estado físico ASA I, e distribuidos em quatro grupos de oito, submetidos a intubaçäo traqueal (IOT). Em todos os grupos a anestesia foi induzida com sevoflurano, associado ou näo ao fentanil, de acordo com o seguinte esquema: (G1 = sevoflurano e 2,5 µg.kg elevado a menos um de fentanil; G2 = sevoflurano e 5 µg.kg elevado a menos um de fentanil; G3 = sevoflurano e 7,5 µg.kg elevado a menos um de fentanil e G4 = sevoflurano e soluçäo fisiológica). Foram avaliados o comportamento dos seguintes parâmetros: PAS, PAD, FC, BIS, SEF95 por cento, rSO2, concentraçäo expirada do sevoflurano (CE) e catecolaminas plasmáticas em três momentos: M1 = imediatamente antes da induçäo; M2 = imediatamente antes da intubaçäo traqueal e M3 = um minuto após a intubaçäo traqueal. Resultados - No G1, houve variaçäo hemodinâmica significativa entre M1 e M3. Entretanto, näo foram clinicamente importantes, apesar de 25 por cento dos voluntários reagirem à insuflaçäo do balonete. BIS, SEF 95 por cento e catecolaminas näo variaram significativamente nos momentos M2 e M3. Nos grupos 2 e 3, apesar dos parâmetros hemodinâmicos mostrarem-se significantes entre M1 e M3, clinicamente näo foram importantes. Todos os outros parâmetros analisados näo variaram significativamente, näo havendo, nestes grupos, respostas motoras às manobras de IOT. No G4, observamos modificaçöes significativas na FC, tanto clínica como estatisticamente. O BIS variou significativamente entre os momentos M2 e M3, assim como as concentraçöes de noradrenalina plasmática. Neste grupo, todos os pacientes apresentaram resposta motora esquelética à IOT

The influence of anesthetic concentrations of enflurane and ethanol on caffeine metabolism in mice.

Enflurane is a fluorinated volatile anesthetic, mostly eliminated unchanged in exhaled air. About 10% of inhaled enflurane undergoes oxidative metabolism in liver via mixed function oxidase. We examined the influence of ethanol and subchronical exposition (6 hours a day, during five consecutive days) to subanesthetic and anesthetic concentrations of enflurane on liver function in BALB/c mice. Specially designed chamber for inhalatory application of anesthetics was constructed for this study. Animals were divided in six groups of twenty. The ethanol treated group was injected with ethanol intraperitoneally (1 g/kg). Two enflurane treated groups were intraperitoneally injected with 0.9% solution of sodium chloride (10 ml/kg) and one of them exposed to subanesthetic (0.5 Vol%) and the other one to anesthetic (2.75 Vol%) concentrations of enflurane. Following two groups received ethanol (1 g/kg) and each of them inhaled enflurane at previously mentioned doses. The control group was intraperitoneally injected with 0.9 % solution of sodium chloride (10 ml/kg) and did not receive any anesthetic. On the day following the last day of exposure half of the animals from each group were sacrificed for determination of glucose levels, erythrocyte glutathion levels, haematocrit, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), liver protein and glutathion levels, and total cytochrome P-450 (CYP P-450). The other half of animals from each group were injected intraperitoneally with caffeine (20 mg/kg). Caffeine and its metabolites in 8 hour urine were analyzed by high performance liquid chromatography (HPLC) method. Excretion of caffeine and its metabolites was different among the groups. We followed two caffeine metabolic ratios - 1,3-dimethyl uric acid and 3,7-xanthine (1,3-U/3,7-X) and 3,7-dimethyl xanthine + 7-xanthine and 1-xanthine + 1,7-dimethyl uric acid (3,7-X + 7-X/1-X + 1,7-U). The difference in caffeine metabolites ratios suggests that enflurane changes oxidative metabolism in liver via certain subtypes of mixed function oxidase, probably via CYP-4502E1. This effect is more expressed when ethanol and enflurane are applied together. Ethanol is well known inductor of CYP-4502E1 and the registrated enzyme induction could be explained by both influences - of ethanol and enflurane.

Recovery of LV contractility in man is enhanced by preischemic administration of enflurane.

BACKGROUND: Volatile anesthetics enhance postischemic functional recovery in animal models; this effect has not been investigated in man. METHODS: Twenty-two patients undergoing coronary surgery were randomized to enflurane administration (0.5% to 2%) for 5 minutes to reduce systolic blood pressure by 20% to 25% immediately before cardioplegic arrest. Left ventricular contractility was assessed by pressure-area relations using echocardiographic automated border detection during inflow occlusion before and after cardiopulmonary bypass. Linear regression analysis in 16 patients with paired data sets assessed changes in contractility. RESULTS: The relation was highly linear (r = 0.95+/-0.02). A change of slope versus the change in x intercept was detected in controls (mean difference, 16.1 mm Hg/cm2, 95% confidence limits, 5.9 to 26.3; 2.2 cm2, 95% confidence limits, -1.1 to 5.5; p = 0.007), which was different from those of treated patients (mean difference, 0.7 mm Hg/cm2, 95% confidence limits, -2.2 to 3.7; -0.06 cm2, 95% confidence limits, -1.6 to 1.5; p > 0.2). Analysis of covariance in the overall group confirmed a significant effect of treatment (p = 0.002). CONCLUSIONS: Enflurane enhances postischemic functional recovery, possibly through pharmacologic preconditioning of myocardium.

Comparaçäo da recuperaçäo de anestesia venosa com propofol e anestesia inalatória com sevoflurano para laparoscopia ginecológica / Comparison of intravenous propofol anesthesia and inhalational sevoflurane anesthesia recovery times in gynecologic laparoscopy

Justificativa e objetivos: tanto anestesia venosa contínua com propofol como inalatória com sevoflurano propiciam acordar rápido com poucos efeitos colaterais. O objetivo deste estudo foi comparar os tempos de despertar da anestesia e o tempo de recuperaçäo pós-anestésica em pacientes submetidos a estes dois agentes. Método: 43 pacientes entre 18 e 50 anos, ASA I ou II, submetidas à laparoscopia ginecológica foram divididas em 2 grupos: G1 - propofol em fusäo contínua de 115µg.kg(elevado a menos um).min(elevado a menos um) e G2 sevoflurano. Todas as pacientes receberam midazolam na MPA, sufentanil 0,5 g.kg(elevado a menos um), propofol 2mg.kg(elevado a menos um), atracúrio 0,5mg.kg(elevado a menos um), N2O em 50 por cento de O2 em sistema sem reinalaçäo. Avaliaram-se profundidade da anestesia, tempo de despertar (índice Bispectral -BIS), intervalo entre término da anestesia e abertura dos olhos, resposta a ordens e orientaçäo no tempo e espaço. Resultados: os tempo foram: G1 -abertura dos olhos 8,2ñ2,9 nin, resposta a ordens 8.6ñ3,1 minutos, orientaçäo 9,8ñ3,4, recuperaçäo pós-anestésica 31.6ñ3,8; G2 -abertura dos olhos 4,5ñ3, resposta a ordens 4,9ñ3,4, orientaçäo 6,2ñ3,4, tempo de recuperaçäo pós-anestésica 66ñ8. Exceto o tempo de recuperaçäo pós-anestésica, os valores foram maiores no grupo I. Conclusöes: tanto propofol quanto sevoflurano demonstraram ser excelentes com relaçäo ao tempo de despertar e de permanência na SRPA. Com sevoflurano o despertar foi mais precoce, porém a permanência na SRPA foi mais demorada que o propofol

Anesthesia for cesarean section in two patients with brain tumours.

PURPOSE: To describe two patients with brain tumours where general anesthesia was used for cesarean sections under emergency and urgent conditions. CLINICAL FEATURES (CASE #1): The first patient presented at 38 wk gestation with an acute intracranial tumour herniation, requiring emergency craniotomy and simultaneous cesarean section. General anesthesia was induced with thiopental and vecuronium, maintained with enflurane 1% in O2 100%. Maternal P(ET)CO2 was maintained at 25 mmHg. After delivering a healthy infant, she was given syntocinon, mannitol and dexamethasone i.v. anesthesia was maintained with fentanyl, nitrous oxide 50% in O2 and isoflurane 1% during frontal-lobe tumour resection. CLINICAL FEATURES (CASE #2): The second patient presented at 37 wk gestation for urgent cesarean section because of placental insufficiency. She had had a brain tumour resection four years earlier. An increase in intracranial pressure necessitated craniotomy for decompression at 20 wk gestation. She was further treated with dexamethasone, carbamazepine and radiation for control of cerebral oedema at 34 wk. Cesarean section was performed under general anesthesia; rapid-sequence-induction with thiopental and succinylcholine, followed by isoflurane 1% in O2 100%. Syntocinon, fentanyl and atracurium i.v. were administered after delivery of a healthy infant. Although neurosurgeons stood by, their intervention was unnecessary. CONCLUSION: General anesthesia remains safe and dependable for operative delivery in parturients with intracranial tumour. Tracheal intubation allows maternal hyperventilation thereby controlling raised intracranial pressure. Hemodynamic stability is readily achieved to maintain cerebral perfusion. However, a multidisciplinary-team approach is critical for successful patient management.