Anesthesia and analgesia
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Detection of the intravascular placement of epidural catheters is an important but difficult task. In this study, we evaluated maternal and fetal hemodynamic responses to intravenous (i.v.) and epidural injection of isoproterenol (ISO), a proposed chronotropic test dose, in gravid ewes. Near-term, chronically instrumented, gravid ewes with single fetuses were studied at least 48 h after surgery. ⋯ However, ISO seems to be rapidly absorbed from the epidural space. Identifying the source of maternal tachycardia after epidural injection of a large dose of ISO could be difficult. If the absence of histopathological change is confirmed, ISO represents an alternative to EPI as a chronotropic test dose.
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Anesthesia and analgesia · Aug 1997
The effects of sevoflurane on population spikes in CA1 and dentate gyrus of the rat hippocampus in vitro.
We studied the effects of sevoflurane on population spikes (PSs) in two synaptic pathways in rat hippocampal slices. Stimulating electrodes were placed on Schaffer collateral fibers or perforant path to activate inputs to CA1 pyramidal neurons or dentate gyrus (DG) neurons, respectively. Extracellular glass microelectrodes were used to record PSs. The paired-pulse stimulus was used to induce the paired-pulse facilitation (PPF). Sevoflurane (0.4-5.0 vol%) significantly decreased the amplitudes of PSs of CA1 and DG in a dose-dependent and reversible manner (25% effective dose values were 4.1 and 0.9 vol%, respectively). The stimulus-response relationships for PS amplitudes revealed that sevoflurane increased the threshold for PS generation in CA1 and DG. Sevoflurane (2.0 vol%) significantly enhanced PPF from 127% and 263% to 153% and 494% in CA1 and DG, respectively. The results imply that the effects of sevoflurane on PSs are greater in DG than in CA1 neurons, that sevoflurane enhances the PPF in both CA1 and DG, and that the actions of sevoflurane are not similar to those of other volatile or intravenous anesthetics previously reported in hippocampal preparations. ⋯ The volatile anesthetic sevoflurane alters neural excitability of individual pathways in the hippocampus in a manner different from other general anesthetics. The results are consistent with a site-specific mechanism of action for general anesthesia.
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Anesthesia and analgesia · Aug 1997
Randomized Controlled Trial Comparative Study Clinical TrialEpidural meperidine after cesarean section: the effect of diluent volume.
We investigated the effect of diluent volume on analgesia and systemic absorption from epidural meperidine after cesarean section in a randomized, double-blind study. At the first request for postoperative analgesia, 36 parturients were given epidural meperidine 25 mg diluted with saline to either 2 mL (12.5 mg/mL), 5 mL (5 mg/mL), or 10 mL (2.5 mg/mL). Visual analog pain scores measured in the first 30 min were greater in the 2-mL group compared with both the 5-mL group (P = 0.028) and the 10-mL group (P = 0.031). ⋯ No adverse side effects were recorded. Previous work has suggested that injection of epidural opioids in large volumes increases the potential risk of respiratory depression from cephalad spread of the drug. Therefore, we conclude that analgesia is optimum when epidural meperidine is administered diluted to 5 mL.
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Anesthesia and analgesia · Aug 1997
Randomized Controlled Trial Clinical TrialEffect of dexmedetomidine on lumbar cerebrospinal fluid pressure in humans.
Dexmedetomidine's potential for analgesia without respiratory depression and its opioid- and anesthetic-sparing properties make it an attractive choice as an anesthetic adjunct for patients undergoing neurosurgery. However, the effects of dexmedetomidine on intracranial pressure are not known. We therefore studied the effect of dexmedetomidine on lumbar cerebrospinal fluid (CSF) pressure in patients after transphenoidal pituitary tumor surgery. Sixteen transphenoidal pituitary tumor surgery patients were randomized to receive placebo (n = 9) or dexmedetomidine (n = 7) for 60 min in the postanesthesia care unit. The study drug was administered by a continuous computer-controlled infusion to achieve an estimated plasma dexmedetomidine concentration of 600 pg/mL, the highest plasma concentration that has been used for clinical purposes. Patient-controlled analgesia was used to administer morphine for postoperative discomfort. Lumbar CSF pressure (via lumbar intrathecal catheter), intraarterial blood pressure, and heart rate were monitored continuously. There was no change in lumbar CSF pressure in either group. The highest values obtained were 19 mm Hg in the dexmedetomidine group and 20 mm Hg in the placebo group. During infusion, mean arterial pressure decreased from 103 +/- 10 mm Hg to 86 +/- 6 mm Hg (P < 0.05), heart rate decreased from 77 +/- 12 bpm to 64 +/- 7 bpm (P < 0.05), and cerebral perfusion pressure decreased from 95 +/- 8 mm Hg to 78 +/- 6 mm Hg (P < 0.05) in the dexmedetomidine group, but not in the placebo group. We conclude that dexmedetomidine does not have an effect on lumbar CSF pressure in patients with normal intracranial pressure who have undergone transphenoidal pituitary hypophysectomy. ⋯ The effects of dexmedetomidine (an alpha2-agonist) or placebo on lumbar cerebrospinal fluid pressure, measured via an intrathecal catheter, were studied postoperatively in 16 patients. Dexmedetomidine had no effect on lumbar cerebrospinal fluid pressure. We will continue to investigate the potential utility of dexmedetomidine for neurosurgical anesthesia.
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Anesthesia and analgesia · Aug 1997
Randomized Controlled Trial Comparative Study Clinical TrialEffect of the intensity of transcutaneous acupoint electrical stimulation on the postoperative analgesic requirement.
Given the inherent side effects associated with both opioid and nonopioid analgesic drugs, a nonpharmacologic therapy that could decrease the need for analgesic medication would be valuable. We designed a sham-controlled study to assess the effect of the intensity of transcutaneous acupoint electrical stimulation (TAES) on postoperative patient-controlled analgesia (PCA) requirement for hydromorphone (HM), the incidence of opioid-related side effects, and the recovery profile after lower abdominal surgery. One hundred one healthy consenting women undergoing lower abdominal procedures with a standardized general anesthetic technique were randomly assigned to one of four postoperative analgesic treatment regimens: Group I (n = 26) PCA only; Group II (n = 25), PCA + sham-TAES (no electrical stimulation); Group III (n = 25), PCA + low-TAES (4-5 mA of electrical stimulation); Group IV (n = 25), PCA + high-TAES (9-12 mA of electrical stimulation). ⋯ High-TAES decreased the HM requirement by 65% and reduced the duration of PCA therapy, as well as the incidence of nausea, dizziness, and pruritus. Low-TAES produced a 34% decrease in the HM requirement compared with only 23% in the "sham" TAES group. We conclude that high-TAES produced a significant decrease in the PCA opioid requirement and opioid-related side effects after low intraabdominal surgery.