Anesthesia and analgesia
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Anesthesia and analgesia · Jul 1993
Electroencephalographic burst suppression by propofol infusion in humans: hemodynamic consequences.
The hemodynamic effects of a propofol infusion adjusted to achieve and maintain a burst-suppression pattern [episodes of depressed background activity (electrical silence) more than 4 s alternating with a high-voltage slow activity], were studied in 10 patients without cardiorespiratory disease undergoing elective neurosurgical interventions. Propofol infusion was started after a bolus dose of 1 mg/kg at a rate of 20 mg.kg-1 x h-1, reduced after 30 min to 15 mg.kg-1 x h-1, and terminated after 60 min (1926 +/- 346 mg cumulative propofol dose, maximal serum concentration 9.2 +/- 2.9 micrograms/dL; mean +/- SD). Hemodynamic data and arterial blood samples were collected during a sedated, resting control period, and then every 15 min during drug infusion. ⋯ No adverse consequences were caused by the propofol or crystalloid infusion. The results demonstrate that doses of propofol sufficient to silence the electroencephalogram are associated with venodilating and myocardial depressant properties. However, propofol can be administered with minimal hemodynamic risk in healthy patients when cardiac filling pressures are maintained by intravenous fluid administration.
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Anesthesia and analgesia · Jul 1993
Laboratory evaluation of the Baxter Patient-Controlled Analgesia Infusor System: a disposable patient-controlled analgesia device.
The purpose of this study was to determine the accuracy of bolus-demand volumes obtained from the Baxter Patient-Controlled Analgesia Infusor System, a disposable patient-controlled analgesia device. An automated system was used to make demands in a pattern designed to simulate those made by a patient in the first 24 postoperative hours. Following this, a pattern of varying short interdemand intervals was used to evaluate performance of the device when demands were made near the nominal lockout interval of 6 min. ⋯ Evaluation near the nominal lockout interval revealed a departure of delivered volume from nominal (worst = 73.9% at an interdemand interval of 6 min). As the reservoir became exhausted, delivery increased to a maximum value, ranging from 118% to 137% of nominal, before falling to zero. In general, the devices performed consistently and the departures from nominal delivery were not considered to be of clinical significance.
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To investigate how epidural anesthesia changes intrathoracic gas volume, high epidural anesthesia was administered to five pentobarbital-anesthetized dogs lying supine, and the total intrathoracic volume at end-expiration was measured with a high-speed three-dimensional x-ray scanner. The amount of gas in the lungs at end-expiration [the functional residual capacity (FRC)] was measured with a nitrogen washout technique, and the intrathoracic tissue volume, including the intrathoracic blood volume, was calculated as the difference between intrathoracic volume at end-expiration and FRC. ⋯ We conclude that increases in FRC caused by epidural anesthesia in anesthetized dogs lying supine may be minimized by a concurrent increase in intrathoracic blood volume. These results suggest that measurements of thoracic gas volume alone may be insufficient to describe chest wall responses to epidural anesthesia.