Anesthesiology
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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.