Anesthesia and analgesia
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Anesthesia and analgesia · Jun 1986
Randomized Controlled Trial Clinical TrialRoles of fentanyl and nitroglycerin in prevention of myocardial ischemia associated with laryngoscopy and tracheal intubation in patients undergoing operations of short duration.
The purpose of this study was to evaluate intravenous nitroglycerin given during induction of anesthesia as a means for prevention of myocardial ischemia and hemodynamic changes associated with induction, laryngoscopy, and intubation, in patients with stable angina scheduled for vascular operations of moderate duration. Forty-six patients were randomly assigned to receive either fentanyl, 3 micrograms/kg (group 1, n = 6), fentanyl, 8 micrograms/kg (group 2, n = 20), or fentanyl 3 micrograms/kg plus a continuous intravenous nitroglycerin infusion, 0.9 microgram X kg-1 X min-1 (group 3, n = 20), in addition to thiopental-pancuronium anesthetic induction, prior to laryngoscopy and intubation. The criteria for recognizing myocardial ischemia were the following: horizontal or downsloping ST segment depression equal to or greater than 1 mV, and/or ventricular arrhythmia, on CM5 recording. ⋯ Despite greater stability in MBP and heart rate in group 2, myocardial ischemia still occurred in four patients (not significantly different from group 1). Nitroglycerin added to low-dose fentanyl (group 3) produced significant reduction in myocardial ischemia (1/20) when compared with group 1 (P less than 0.01), and significantly greater stability in PCWP during laryngoscopy and intubation in comparison to groups 1 and 2. In patients with stable angina undergoing operations of short duration, the use of nitroglycerin infusion and low-dose fentanyl significantly decreases the incidence of myocardial ischemia associated with induction of anesthesia and tracheal intubation.
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Anesthesia and analgesia · Jun 1986
Partial preservation of cerebral vascular responsiveness to hypocapnia during isoflurane-induced hypotension in dogs.
This study was undertaken to determine whether the cerebral vascular response to hypocapnia is preserved during isoflurane-induced hypotension. In six dogs (group 1) cerebral vascular resistance and cerebral blood flow were determined at normocapnia (PaCO2 40 mm Hg) and at hypocapnia (PaCO2 20 mm Hg) while mean arterial pressure was normal, and then again during isoflurane-induced hypotension to a mean arterial pressure of 50 mm Hg. Hypocapnia increased cerebral vascular resistance and decreased cerebral blood flow during both normotension and isoflurane-induced hypotension. ⋯ In contrast, in group 2 during sodium nitroprusside-induced hypotension, hypocapnia caused no significant change of cerebral vascular resistance or cerebral blood flow. It is concluded that cerebral vessels respond to changes in PaCO2 differently during isoflurane-induced hypotension than during hypotension with other commonly used hypotensive treatments. Hypocapnia decreases cerebral blood flow during isoflurane-induced hypotension and, therefore, may also decrease cerebral blood volume, brain bulk, and intracranial pressure.
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Anesthesia and analgesia · Jun 1986
Endotracheal tube leak pressure and tracheal lumen size in swine.
Endotracheal tube "leak" is often estimated in children to judge the fit of uncuffed endotracheal tubes within the trachea. Twenty-five swine were intubated with uncuffed tracheal tubes to determine whether a more sensitive measurement of leaks could be devised and whether leak pressure estimates fit between tracheal tube and trachea. ⋯ Regression analysis revealed a linear relationship between tracheal lumen size and tracheal tube size for both low leak pressure (y = -0.4 + 0.79x, r = 0.88, P less than 0.05) and high leak pressure (y = -2.9 + 0.71x, r = 0.92, P less than 0.05) groups. We conclude that leak testing with a stethoscope and aneroid manometer is sensitive and accurate, and that tracheal tube leak pressure accurately portrays fit between tube and trachea.
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Anesthesia and analgesia · Jun 1986
Augmentation of venous return by adrenergic agonists during spinal anesthesia.
To test the effectiveness of adrenergic agonists in correcting the vascular sequelae of spinal anesthesia, we used venous reservoir volume (RV) and mean arterial pressure (MAP) as indices of the changes in venous capacitance and arterial resistance produced by adrenergic agonists in dogs anesthetized with pentobarbital and undergoing cardiopulmonary bypass (CPB). A CPB-based technique was chosen both to prevent drug and reflex effects on the heart from influencing the results and to provide a convenient means by which to monitor venous capacitance. Total spinal anesthesia significantly decreased both RV and MAP relative to steady-state CPB values. ⋯ Phenylephrine increased MAP but not RV. Ephedrine increased both MAP and RV. We conclude that a mixed adrenergic agonist such as ephedrine more ideally corrects the noncardiac circulatory sequelae of spinal anesthesia than does either a pure alpha- or beta-adrenergic agonist.