Anesthesiology
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Randomized Controlled Trial Clinical Trial
Air: an effective indicator of intravenously located epidural catheters.
The authors conducted a two-part study to evaluate the efficacy of 1 ml of air as a "test dose" for detection of intravenously located epidural catheters. In part 1, a Doppler fetal heart rate monitoring probe was placed over the precordium of 33 laboring patients in whom functioning epidural catheters were in place. Each patient received, more than 90 s apart, in random order: 10 ml of agitated saline (containing less than 0.5 ml of air microbubbles) via a peripheral vein; 2 ml of air via the epidural catheter; and a sham injection (i.e., nothing injected). ⋯ In part 2, the authors listened for Doppler heart tone changes while injecting 1 ml of air via catheters that were accidentally inserted in the epidural veins of five other patients. Unequivocal Doppler changes compatible with intracardiac air always occurred within 3 s, and no signs or symptoms of air embolism developed. The results suggest that 1 ml of air may be a suitable indicator of iv epidural catheter location.
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Excitatory amino acids accumulating in the brain during ischemia may cause selective neuronal damage postischemia. This hypothesis was tested in a series of studies using MK-801, an N-methyl-D-aspartate (NMDA) receptor blocker, in a reproducible outcome model of prolonged cardiac arrest in dogs. After normothermic ventricular fibrillation cardiac arrest, the dogs were resuscitated with closed-chest femoral veno-arterial cardiopulmonary bypass. ⋯ MK-801 delayed return of pupillary reactivity, EEG activity, consciousness, and respiration, necessitating longer periods of controlled ventilation. Neurologic deficit scores, overall performance categories, and brain and heart morphologic damage scores at 96 h did not differ between placebo and MK-801 pretreatment or post-treatment groups. These negative outcome results after prolonged cardiac arrest do not negate the hyperexcitability hypothesis of selective vulnerability, but suggest the existance of additional mechanisms of secondary brain damage.
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Intrathecally administered clonidine has been reported to produce analgesia in cancer patients tolerant to intrathecal opiates. To assess the efficacy, safety, and appropriate dose of epidurally administered clonidine for the treatment of cancer pain, clonidine (range, 100-900 micrograms in 100-micrograms increments) was injected in nine patients with severe, intractable cancer pain. Clonidine produced analgesia, as measured by change in verbal pain scores, lasting more than 6 h. ⋯ Clonidine was absorbed in a dose-dependent manner into the systemic circulation, although absorption and elimination kinetics were highly variable. Following study seven patients received epidural clonidine/morphine infusions at home for periods of up to 5 months with sustained analgesia. These results suggest that epidurally administered clonidine may offer effective analgesia in patients with severe, intractable cancer pain.
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Clinical Trial Controlled Clinical Trial
Transdermal scopolamine decreases nausea and vomiting following cesarean section in patients receiving epidural morphine.
The authors evaluated the antiemetic properties of transdermal scopolamine (TDS) in healthy patients undergoing elective cesarean section and receiving epidural morphine for postoperative analgesia. Prior to administration of anesthesia, 203 patients had either TDS or a placebo study patch applied behind one ear. All patients were hydrated with lactated Ringer's solution iv and given 2.0% lidocaine with 1:200,000 epinephrine epidurally for surgical anesthesia. ⋯ Side effects were minimal and equal in both groups. The authors conclude that TDS results in a decreased incidence of nausea and vomiting in patients who have delivered by cesarean section and received epidural morphine. TDS appears safe for continuous antiemetic administration.
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Epidurally administered clonidine has been reported to produce postoperative analgesia. To assess the efficacy, safety, and appropriate dose of epidural clonidine for postoperative analgesia, clonidine (range, 100-900 micrograms in 100-micrograms increments) was injected in 22 patients following abdominal surgery or total knee arthroplasty (TKA). Clonidine produced analgesia, as measured by change in verbal pain scores and supplemental iv morphine usage. ⋯ Oxyhemoglobin saturation, serum glucose, and arterial blood gas tensions were not altered by clonidine, whereas there was a small (28%) dose-independent decrease in serum cortisol following clonidine injection. Clonidine was absorbed in a dose-dependent manner into the systemic circulation, with plasma concentrations 0.1-3.3 ng/ml 1 h following injection. These results suggest that hemodynamic depression and short-lasting analgesia may limit the usefulness of bolus epidural clonidine analgesia in the postoperative setting.