Anesthesiology
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Intraspinal clonidine injection produces analgesia free of respiratory depression, but also decreases blood pressure and causes sedation. Spinal neostigmine injection alone increases blood pressure in animals and enhances clonidine-induced analgesia. ⋯ These data are consistent with neostigmine's counteraction of clonidine-induced hypotension by a spinal muscarinic mechanism and support investigation of spinal alpha 2-adrenergic-cholinergic combinations for pain therapy.
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Randomized Controlled Trial Comparative Study Clinical Trial
Epidural sufentanil and bupivacaine for labor analgesia and Doppler velocimetry of the umbilical and uterine arteries.
The pain of parturition is associated with major physiologic alterations mediated by neurohumoral factors and increased activation of the sympathetic nervous system. Epidural local anesthetics abolish or alleviate many of the pain-mediated responses by reducing maternal catecholamine levels, inducing sympathectomy and consequent vasodilatation. The hormone response to surgical stress is not attenuated after epidural opioids as efficiently as after local anesthetics. Opioid receptors may modulate sympathetic outflow at a spinal level. This study was performed to compare the effects of epidural sufentanil and bupivacaine on the uterine and placental circulation. ⋯ Epidural sufentanil and bupivacaine provide effective analgesia with acceptable side effects during the first stage of labor in healthy parturients. Neither drug had any detrimental effects on blood flow indexes reflecting peripheral vascular resistance in the umbilical and uterine arteries in healthy parturients.
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Randomized Controlled Trial Clinical Trial
Increases in hemodynamic variables and catecholamine levels after rapid increase in isoflurane concentration.
Ventilation of the lungs with isoflurane in nitrous oxide and oxygen has been shown to increase the plasma concentration of norepinephrine. Whether this increase is related to the tachycardia and increased arterial blood pressures, seen following a sudden increase in the concentration of isoflurane, was tested in humans. ⋯ A sudden increase in isoflurane concentration is associated with a transient but clinically significant increase in heart rate, arterial pressures, and norepinephrine concentration.
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alpha 2-Adrenergic agonists such as clonidine produce behavioral analgesia and cardiovascular depression in animals, but clonidine's site of action in clinical analgesia and cerebrospinal fluid (CSF) pharmacokinetics have not been defined. ⋯ These data support previous studies in animals and provide the scientific rationale for this novel analgesic therapy. In comparison to the potent opioid alfentanil, epidural clonidine produces a similar degree of analgesia but less respiratory depression.
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The severity of spontaneous myocardial hypercarbic acidosis during cardiac arrest previously has been predictive of the likelihood of restoring spontaneous circulation. The present study investigated whether hypercarbia itself impairs cardiac resuscitation. Since coronary perfusion pressure is the overriding determinant of cardiac resuscitability, we used a porcine model of cardiac arrest in which coronary perfusion pressure was controlled. ⋯ Hypercarbia, in this experimental setting, was therefore a quantitative determinant of both myocardial resuscitability and the restoration of spontaneous circulation.