Anesthesia and analgesia
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Anesthesia and analgesia · May 1995
The effect of graded hemorrhage and intravascular volume replacement on systolic pressure variation in humans during mechanical and spontaneous ventilation.
In dogs and humans, the magnitude of the variation in systolic pressure (SPV) over the respiratory cycle during mechanical ventilation appears to be inversely related to intravascular volume. Also reported to correlate with changes in volume status is delta down, the difference between systolic pressure at end-expiration and the lowest value during the respiratory cycle. These variables were examined during graded hemorrhage in eight anesthetized, mechanically ventilated subjects, and seven awake, spontaneously breathing subjects. ⋯ After hetastarch, both SPV and delta down were smaller than at baseline and may explain why the infusion of NS caused nonsignificant reductions in SPV and delta down. A SPV of 5 mm Hg or less, or a delta down of 2 mm Hg or less appeared to indicate minimal intravascular volume depletion. During spontaneous ventilation, delta down could not be determined accurately in several subjects, and SPV did not change in the appropriate direction in all cases of hemorrhage and volume infusion.(ABSTRACT TRUNCATED AT 250 WORDS)
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Anesthesia and analgesia · May 1995
Effects of sevoflurane on the middle latency auditory evoked response and the electroencephalographic power spectrum.
We investigated the effects of sevoflurane on the middle latency auditory evoked response (MLR) and the power spectrum of the electroencephalogram (EEG) in 10 elective surgical patients. The MLR and the EEG power spectrum were recorded with a surface electrode placed at the central (Cz) scalp location. End-tidal sevoflurane concentrations of 0%, 0.25%, 0.5%, 0.75%, 1.0%, and 1.5% in 50% nitrous oxide and oxygen were studied. ⋯ The beta power, median power frequency (MPF), and 95% spectral edge frequency (SEF) decreased significantly according to the increases by 0.5% sevoflurane. Regarding the changes evoked by 0.25% sevoflurane, the Nb latency of the MLR responded significantly under 0.75% of sevoflurane. At these low concentrations of sevoflurane, the MLR seemed to be more sensitive to changes in anesthetic concentration than the various EEG variables.
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Anesthesia and analgesia · May 1995
Comparative StudyHydroxyethyl starch versus lactated Ringer's solution in the chronic maternal-fetal sheep preparation: a pharmacodynamic and pharmacokinetic study.
Administration of fluids intravenously prior to spinal and epidural analgesia in obstetrics is required to prevent maternal hypotension and fetal hypoxia. A colloid solution, such as hydroxyethyl starch (HES), might be preferable considering the capacity to stay intravascularly for a longer period. In this study the placental transfer of HES and the hemodynamic effects after infusion were investigated using a chronic maternal-fetal sheep preparation. ⋯ In contrast, infusion of RL did not significantly change these variables. Infusion of HES increases UBF, CO, and uterine and total oxygen-carrying capacity in the pregnant ewe. No significant transplacental transfer of HES was shown.
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Anesthesia and analgesia · May 1995
Ventilatory effects, blood gas changes, and oxygen consumption during laparoscopic hysterectomy.
We evaluated the ventilatory effects and blood gas changes of prolonged CO2-pneumoperitoneum in nor-moventilated patients and examined the respiratory and gas exchange consequences of head-down positioning (25-30 degrees) and CO2 insufflation into the peritoneal cavity in 20 patients without major cardiorespiratory disorders in various phases of laparoscopic hysterectomy. The patients received general anesthesia with isoflurane, fentanyl, and vecuronium, and minute ventilation (MV) was adjusted to maintain the PETCO2 at 33-36 mm Hg throughout the entire procedure, either by increasing the tidal volume (TV) and keeping the respiratory rate (RR) at 12/min (10 patients) or by changing the RR and maintaining the TV at 8 mL/kg (10 patients). Arterial and mixed venous blood samples were collected simultaneously for blood gas analysis and for measurements of oxygen consumption, and respiratory mechanics and gases were recorded by an anesthetic gas analyzer and side stream spirometry device. ⋯ The compliance decreased by 20% with the head-down position and by an additional 30% with the increased intraabdominal pressure. PaCO2 and mixed venous PCO2 increased with CO2 insufflation, and the arterial to end-tidal PCO2 (a-etPCO2) gradient increased by 1.5 mm Hg during laparoscopy. A mild metabolic acidosis developed.(ABSTRACT TRUNCATED AT 250 WORDS)