Anesthesia and analgesia
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Anesthesia and analgesia · Oct 1995
The effects of increased abdominal pressure on lung and chest wall mechanics during laparoscopic surgery.
We tested the hypothesis that increases in pressure in the abdomen (Pab) exerted by CO2 insufflation during laparoscopy would increase elastance (E) and resistance (R) of both the lungs and chest wall. We measured airway flow and airway and esophageal pressures of 12 anesthetized/paralyzed tracheally intubated patients during mechanical ventilation at 10-30/min and tidal volume of 250-800 mL. From these measurements, we used discrete Fourier transformation to calculate E and R of the lungs and chest wall. ⋯ Both Es and Rs also increased while head-up at Pab = 15 mm Hg (P < 0.05), but increases in lung E and R were less than while head-down (P < 0.05). The increase in lung E and R at Pab = 15 mm Hg in either posture were positively correlated to body weight or body mass index, whereas the increases in chest wall E and R were negatively correlated to the same factors (P < 0.05). Lung and chest wall mechanical impedances increase with increasing Pab; the increases depend on body configuration and are greater while head-down.(ABSTRACT TRUNCATED AT 250 WORDS)
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Anesthesia and analgesia · Oct 1995
Comparative StudyComparison of isoflurane and desflurane anesthetic depth using burst suppression of the electroencephalogram in neurosurgical patients.
We compared the anesthetic effects of desflurane and isoflurane using percent burst suppression of the electroencephalogram (EEG) as an end-point in 10 neurosurgical patients. The EEG was recorded from frontal leads and processed variables were analyzed as a function of increasing isoflurane and desflurane concentration with age and baseline delta EEG power (0.5-3.75 Hz) as independent variables. Isoflurane and desflurane (0.5, 1.0, 1.5, 2.0 minimum alveolar anesthetic concentration [MAC]) were incrementally administered until the EEG was quiesecent at least 40% of the time. ⋯ Patients with baseline delta EEG power > 80% of total power produced no change in EEG frequency with increasing anesthesia but revealed a greater sensitivity to the development of burst suppression. These results show that isoflurane and desflurane produce similar EEG suppression in neurosurgical patients. If the EEG is initially slow, further slowing cannot be used to assess anesthetic depth.
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Anesthesia and analgesia · Oct 1995
The effect of midazolam on left ventricular pump performance and contractility in anesthetized patients with coronary artery disease: effect of preoperative ejection fraction.
Forty patients undergoing coronary artery bypass grafting were studied, of whom 24 had depressed global left ventricular (LV) function at preoperative catheterization, to evaluate the effects of midazolam on LV pump performance and contractility. Transesophageal echocardiography and simultaneous hemodynamic measurements were used to assess LV preload, afterload, and systolic performance during inhalation of 100% O2 and after 0.1 mg/kg of midazolam. Systolic function indices were expressed as a percent of the predicted value for observed end-systolic stress to estimate LV contractility. ⋯ As a result, systolic function decreased in relation to observed end-systolic stress, providing evidence of reduced LV contractility. Thus, midazolam administration (0.1 mg/kg) caused no change in cardiac pump performance but decreased LV contractility in the entire population. Myocardial contractility was lower at baseline and after the administration of midazolam in the depressed ejection fraction group, but the decrease in contractility was not exaggerated in the depressed ejection fraction group.(ABSTRACT TRUNCATED AT 250 WORDS)
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Anesthesia and analgesia · Oct 1995
The arterial to end-tidal carbon dioxide difference in neurosurgical patients during craniotomy.
PETCO2 is often used as an estimate of PaCO2, with the understanding that PaCO2 usually exceeds PETCO2. During intraoperative craniotomies, because hyperventilation is used to therapeutically lower intracranial pressure, the difference between PaCO2 and PETCO2 (P(a-ET)CO2) has therapeutic implications. The P(a-ET)CO2 was hypothesized to be stable during craniotomies with relatively short-term monitoring and controlled cardiorespiratory variables. ⋯ On comparison of subsequent measurements, 18.4% of changes in PaCO2 and PETCO2 (although sometimes small) were in opposite directions. P(a-ET)CO2 did not change with time. The PETCO2 does not provide a stable reflection of PaCO2 in many patients undergoing craniotomies.