La entropía espectral en la monitorización de la profundidad de la anestesia / Spectral entropy in monitoring anesthetic depth

La posibilidad de monitorizar la respuesta cerebral a los hipnóticos en cada una de las fases de la anestesia general, en la que interactúan además estímulos nociceptivos y hemodinámicos, es un tema objeto de intensa investigación desde hace muchos años. Los monitores de profundidad de la anestesia de los que disponemos en la actualidad utilizan el procesamiento del registro electroencefalográfico mediante diferentes algoritmos, algunos no conocidos en su totalidad, para, de una forma simplificada, obtener un parámetro numérico que se aproxima al estado de la actividad cerebral en cada momento. En esta revisión descriptiva se evalúa la capacidad de la entropía espectral de reflejar adecuadamente el comportamiento eléctrico cerebral en respuesta a los hipnóticos y al efecto de los estímulos nociceptivos de diferente intensidad que tienen lugar durante una intervención quirúrgica (AU)

Monitoring the brain response to hypnotics in general anesthesia, with the nociceptive and hemodynamic stimulus interaction, has been a subject of intense investigation for many years. Nowadays, monitors of depth of anesthesia are based in processed electroencephalogram by different algorithms, some of them unknown, to obtain a simplified numeric parameter approximate to brain activity state in each moment. In this review we evaluate if spectral entropy suitably reflects the brain electric behavior in response to hypnotics and the different intensity nociceptive stimulus effect during a surgical procedure (AU)

Anesthetic constituents of Zanthoxylum bungeanum Maxim.: A pharmacokinetic study.

A sensitive and selective ultra high performance liquid chromatography with tandem mass spectrometry method was established and validated for the simultaneous determination of hydroxy-α-sanshool, hydroxy-ß-sanshool, and hydroxy-γ-sanshool in rat plasma after the subcutaneous and intravenous administration of an extract of the pericarp of Zanthoxylum bungeanum Maxim. Piperine was used as the internal standard. The analytes were extracted from rat plasma by liquid-liquid extraction with ethyl acetate and separated on a Thermo Hypersil GOLD C18 column (2.1 mm × 50 mm, 1.9 µm) with a gradient elution system at a flow rate of 0.4 mL/min. The mobile phase consisted of acetonitrile/0.05% formic acid in water and the total analysis time was 4 min. Positive electrospray ionization was performed using multiple reaction monitoring mode for the analytes. The calibration curves of the three analytes were linear over the tested concentration range. The intra- and interday precision was no more than 13.6%. Extraction recovery, matrix effect, and stability were satisfactory in rat plasma. The developed and validated method was suitable for the quantification of hydroxy-α-sanshool, hydroxy-ß-sanshool, and hydroxy-γ-sanshool and successfully applied to a pharmacokinetic study of these analytes after subcutaneous and intravenous administration to rats.

[Anaesthesia and breast-feeding: should breast-feeding be discouraged?]. / Leser fragen - Experten antworten - Stillen nach Narkosen: Ist eine Stillpause obligat?

Until a few years ago an interruption of breast-feeding for 12 or even 24 hours was recommended for breast-feeding mothers after anaesthesia, this is no longer valid. If it is the mother's wish, if she is sufficiently awake and physically able, there is no reason not to start breast-feeding a mature and healthy baby immediately after recovery from a general or regional anaesthesia. Even breast-feeding after a Caesarean delivery with administration of the common anaesthetics in the usual (single) doses is no longer considered to be a problem since the amount of the substance taken up from colostrum is vanishingly small in comparison to the amount that is transferred by transplacental routes. Neither the pharmacological properties of the drugs used in association with anaesthesia nor clinical experience justify an interruption of breast-feeding.

[Risks and dangers in pediatric regional anesthesia]. / Fehler und Gefahren in der Regionalanästhesie bei Kindern.

In recent years peripheral and central regional anesthesia have become increasingly more important in pediatric anesthesia. Unlike adult patients, children typically receive regional anesthesia while under general anesthesia, an approach generally accepted among pediatric anesthesiologists. A well-founded knowledge of the specific anatomical, physiological and pharmacokinetic characteristics of pediatric patients is indispensable for safely practicing pediatric regional anesthesia. If attention is paid to these characteristics, complications are rare. The use of ultrasound when administering regional anesthesia can help reduce the risk of complications even further. Peripheral and central regional anesthesia are safe procedures which pediatric patients should not be deprived of. The present article discusses frequent as well as rare complications of pediatric regional anesthesia.

Incorporation of acute dynamic ventilation changes into a standardized physiologically based pharmacokinetic model.

A seven-compartment physiologically based pharmacokinetic (PBPK) model incorporating a dynamic ventilation response has been developed to predict normalized internal dose from inhalation exposure to a large range of volatile gases. The model uses a common set of physiologic parameters, including standardized ventilation rates and cardiac outputs for rat and human. This standardized model is validated against experimentally measured blood and tissue concentrations for 21 gases. For each of these gases, body-mass-normalized critical internal dose (blood concentration) is established, as calculated using exposure concentration and time duration specified by the lowest observed adverse effect level (LOAEL) or the acute exposure guideline level (AEGL). The dynamic ventilation changes are obtained by combining the standardized PBPK model with the Toxic Gas Assessment Software 2.0 (TGAS-2), a validated acute ventilation response model. The combined TGAS-2P model provides a coupled, transient ventilation and pharmacokinetic response that predicts body mass normalized internal dose that is correlated with deleterious outcomes. The importance of ventilation in pharmacokinetics is illustrated in a simulation of the introduction of Halon 1301 into an environment of fire gases.

[Drug interactions and the anesthesiologist]. / Medikamenteninteraktionen für den Anästheisten.

Modern anesthesiology employs the combined administration of several drugs belonging to different pharmacological classes. Additionally, anesthesiologists are facing the challenge of polypharmacy regimens utilized by patients considered for surgical treatment When drugs are combined, the pharmacological effect may considerably differ from the individually expected properties. This may be beneficial or potentially lead to adverse drug reactions harming the patient. The incidence of drug interaction increases exponentially with the number of drugs administered. Depending on the mechanism involved, drug interactions can be classified as pharmaceutical, pharmacodynamic, or pharmacokinetic. Although there are enormous possibilities for adverse drug reactions nd the complexity is hard to identify, prediction of drug interaction is possible. Besides recognizing the general risk factors, fundamental knowledge of basic and clinical pharmacology is important to prevent serious or fatal drug interactions before they occur.

Drug interactions with neuromuscular blockers.

Drugs administered to patients undergoing anaesthesia may complicate the use of the neuromuscular blockers that are given to provide good surgical conditions. The various sites of interaction include actions on motor nerve conduction and spinal reflexes, acetylcholine (ACh) synthesis, mobilisation and release, sensitivity of the motor end plate to ACh and the ease of propagation of the motor action potential. In addition, many drugs affect the pharmacokinetics of neuromuscular blockers, especially as most drugs depend to a greater or lesser extent upon renal excretion. The clinically significant interaction between nondepolarisers and depolarisers may be due to blockade of the pre-synaptic nicotinic receptors by the depolarisers, leading to decreased ACh mobilisation and release. Synergism between nondepolarisers probably results from post-synaptic receptor mechanisms. Volatile anaesthetic agents affect the sensitivity of the motor end-plate (post-synaptic receptor blockade) in addition to having effects on pre-synaptic nicotinic function. The effects of nondepolarisers are likely to be potentiated and their action prolonged by large doses of local anaesthetics due to depression of nerve conduction, depression of ACh formation, mobilisation and release, decreases in post-synaptic receptor channel opening times and reductions in muscular contraction. Most antibacterials have effects on pre-synaptic mechanisms. Procainamide and quinidine principally block nicotinic receptor channels. Magnesium has a marked inhibitory effect on ACh release. Calcium antagonists could theoretically interfere with neurotransmitter release and muscle contractility. Phenytoin and lithium decrease ACh release, whilst corticosteroids and furosemide (frusemide) tend to increase the release of the transmitter. Ecothiopate, tacrine, organophosphates, propanidid, metoclopramide and bambuterol depress cholinesterase activity and prolong the duration of the neuromuscular block. The probability of clinically significant interactions increases in patients receiving several drugs with possible effects on neuromuscular transmission and muscle contraction.

Polyhalogenated and perfluorinated compounds that disobey the Meyer-Overton hypothesis.

Fourteen polyhalogenated, completely halogenated (perhalogenated), or perfluorinated compounds were examined for their anesthetic effects in rats. Anesthetic potency or minimum alveolar anesthetic concentration (MAC) was quantified using response/nonresponse to electrical stimulation of the tail as the end-point. For compounds that produced excitable behavior, and/or did not produce anesthesia when given alone, we determined MAC by additivity studies with desflurane. Nine of 14 compounds had measurable MAC values with products of MAC x oil/gas partition coefficient ranging from 3.7 to 24.8 atm. Because these products exceed that for conventional inhaled anesthetics (1.8 atm), they demonstrate a deviation from the Meyer-Overton hypothesis. Five compounds (CF3CCIFCF3, CF3CCIFCCIFCF3, perfluorocyclobutane, 1,2-dichloroperfluorocyclobutane, and 1,2-dimethylperfluorocyclobutane) had no anesthetic effect when given alone, had excitatory effects when given alone, and tended to increase the MAC for desflurane. These five compounds had no anesthetic properties in spite of their abilities to dissolve in lipids and tissues, to penetrate into the central nervous system, and to be administered at high enough partial pressures so that they should have an anesthetic effect as predicted by the Meyer-Overton hypothesis. Such compounds will be useful in identifying and differentiating anesthetic sites and mechanisms of action. Any physiologic or biophysical/biochemical change produced by conventional anesthetics and deemed important for the anesthetic state should not be produced by nonanesthetics.

Contralateral spread of local anesthetic with stellate ganglion block.

BACKGROUND AND OBJECTIVES. Stellate ganglion block is a technically simple procedure but is liable to many complications because of the adjacent structures. We report a contralateral and bilateral Horner's syndrome with stellate ganglion block in the same patient on different occasions. We also report a bilateral recurrent laryngeal nerve block with this procedure.

Influence of volume on the spread of local anesthetic-methylene blue solution after injection for intercostal block.

The purpose of this study was to evaluate the influence of the volume of methylene blue-local anesthetic on the spread of the injectate along the costal pleura. Twenty patients undergoing elective thoracotomy were studied. Twelve patients received intercostal nerve injection with 10 mL of 0.5% bupivacaine with methylene blue (10-mL group), and eight patients received 5 mL of 0.5% bupivacaine with methylene blue (5-mL group). The area of spread of the methylene blue was measured after the pleural cavity was incised. The 10-mL group had a mean area of spread of 51.1 cm2 as opposed to 17.6 cm2 for the 5-mL group (P less than 0.05). In the 10-mL group, eight patients had bupivacaine-methylene blue spread to two intercostal spaces, three patients to three intercostal spaces, and one patient to four intercostal spaces. In the 5-mL group, seven patients had bupivacaine methylene blue spread confined to one intercostal space and one patient to two intercostal spaces. We conclude that a potential anatomic space exists between the costal pleura and the internal intercostal muscle and that the spread of local anesthetic after intercostal nerve block injection is volume dependent.