Anesthesiology
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Randomized Controlled Trial Comparative Study Clinical Trial
Patient-controlled epidural analgesia during labor: a comparison of three solutions with a continuous infusion control.
This study examined the efficacy of patient-controlled epidural analgesia (PCEA) during labor and compared the suitability of three different PCEA solutions. After establishing effective epidural analgesia with 12 ml of 0.25% bupivacaine, 72 parturients in active labor were randomly assigned to one of four groups: physician-controlled continuous epidural infusion using 0.125% bupivacaine (CEI); PCEA using 0.125% bupivacaine (B); PCEA using 0.125% bupivacaine with fentanyl 1 micrograms/ml (BF); and PCEA using 0.125% bupivacaine with fentanyl 1 micrograms/ml and 1:400,000 epinephrine (BFE). The CEI infusion was begun at 12-16 ml/h and adjusted to maintain a T10 sensory level and adequate pain relief. ⋯ Average hourly infusion rates were 13.0 +/- 1.1 ml/h (B), 10.6 +/- 0.6 ml/h (BF), and 9.6 +/- 0.5 ml/h (BFE); group B differs from others (P less than 0.05). No instance of respiratory depression or complication secondary to PCEA was observed. Mild pruritus occurred only with fentanyl-containing solutions, whereas dense motor block developed more frequently with the epinephrine-containing solution.(ABSTRACT TRUNCATED AT 250 WORDS)
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Randomized Controlled Trial Comparative Study Clinical Trial
A randomized study of carbon dioxide management during hypothermic cardiopulmonary bypass.
Eighty-six patients undergoing coronary artery bypass graft (n = 63) or intracardiac (n = 23) surgery were randomly assigned with respect to the target value for PaCO2 during cardiopulmonary bypass. In 44 patients the target PaCO2 was 40 mmHg, measured at the standard electrode temperature of 37 degrees C, while in 42 patients the target PaCO2 was 40 mmHg, corrected to the patient's rectal temperature (lowest value reached: mean 30.1, SD 1.9 degrees C). Other salient features of bypass management include use of bubble oxygenators without arterial filtration, flows of 1.8-2.4 l.min-1.m-2, mean hematocrit of 23%, and mean arterial blood pressure of approximately 70 mmHg, achieved by infusion of phenylephrine or sodium nitroprusside. ⋯ At 7 months no significant difference was observed in neuropsychologic performance between the PaCO2 groups. Regarding cardiac outcome, there were no significant differences between groups in the appearance of new Q-waves on the electrocardiogram, the postoperative creatine kinase-MB fraction, the need for inotropic or intraaortic balloon pump support, or the length of postoperative ventilation or intensive care unit stay. These findings support the hypothesis that CO2 management during cardiopulmonary bypass at moderate hypothermia has no clinically significant effect on either neurobehavioral or cardiac outcome.
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Comparative Study
Inconsistent esophageal Doppler cardiac output during acute blood loss.
Application of the Doppler principle can provide relatively noninvasive and continuous measurement of cardiac output. However, it is based on certain assumptions that may introduce error. Esophageal Doppler cardiac output was compared with Fick cardiac output during acute blood loss (35-45% estimated blood volume) in eight anesthetized pigs. ⋯ A sign test for mean differences indicated that Doppler derived cardiac output was higher than Fick cardiac output, and the chance of this occurring if the true difference was zero was less than 1 in 1,000. A test for homogeneity of correlations was also rejected. Inaccuracies in individual assumptions in the computation of esophageal Doppler cardiac output, especially unaccounted changes in aortic diameter, are responsible for the inconsistent and unpredictable values of Doppler cardiac output obtained in this experimental model of hemorrhage.
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Caffeine and halothane contracture testing is widely used to detect malignant hyperthermia (MH) susceptibility. The accuracy and reliability of the 3% halothane test and the incremental caffeine test, as recommended by the North American MH Group, were assessed in 11 swine (five MHS, six control). Nine swine were tested twice, 4-6 weeks apart. ⋯ Nonviable muscle bundles could not be relied upon to provide accurate results. In this porcine model, MH susceptibility could be detected by performing the Caffeine Halothane Contracture Test (CHCT) according to the guidelines of the North American MH Group. However, only the 3% halothane test and the response to 2 mM caffeine produced adequate diagnostic results in this breed of swine.
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Comparative Study
The cerebral pressure-flow relationship during 1.0 MAC isoflurane anesthesia in the rabbit: the effect of different vasopressors.
The influence of different vasopressors on the cerebral pressure-flow relationship during 1.0 MAC isoflurane anesthesia has been studied. Mean arterial pressure (MAP) was increased by one of three vasopressors [angiotensin II (AT), norepinephrine (NE), or phenylephrine (PE)] in three groups of New Zealand white rabbits (n = 11, 10, and 9, respectively). Regional cerebral blood flow (CBF) was measured at five intervals by the injection of radioactive microspheres at a stable 2.05% (1.0 MAC) end-tidal isoflurane concentration (baseline) and following elevation of mean arterial pressure (MAP) by 20%, 40%, 60%, and 80% above baseline MAP with either AT, NE, or PE. ⋯ For all regions examined, the slope of the pressure-flow curve was significantly less steep when MAP was elevated with AT versus NE or PE (P less than 0.05 Tukey's studentized range test). There was no difference in slope between the NE and PE groups for any region. These results indicate that either NE and PE result in indirect cerebral vasodilation or that AT has intrinsic cerebral vasoconstrictive effects during 1.0 MAC isoflurane anesthesia in the rabbit.(ABSTRACT TRUNCATED AT 250 WORDS)