Anesthesia and analgesia
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Anesthesia and analgesia · Aug 2002
A second-generation blood substitute (perflubron emulsion) increases the blood solubility of modern volatile anesthetics in vitro.
Perfluorocarbon-based emulsions increase the blood solubility of isoflurane, enflurane, and halothane, with a maximal effect reported for the less soluble isoflurane. Current volatile anesthetics are less soluble and may be more affected by this phenomenon. Perflubron (Oxygent(TM)) is a perfluorocarbon-based emulsion in late-stage clinical testing in surgical patients for use as a temporary oxygen carrier. We tested the hypothesis that perflubron increases the solubility of isoflurane, sevoflurane, and desflurane, as reflected by their blood/gas partition coefficient (lambda(Bl:g)). Fresh whole-blood samples were drawn from eight volunteers and mixed with perflubron to obtain concentrations of 1.2%, 1.8%, and 3.6% by volume (equivalent to in vivo doses of 1.8 to 5.4 g/kg, which represent up to twice the intended clinical dose range). By using the double-extraction method, we demonstrated increased lambda(Bl:g) for isoflurane, sevoflurane, and desflurane. However, the solubility in blood does not really change, because volatile anesthetics are actually partitioning into perflubron. Increasing the amount of emulsion in the blood consequently increases the amount of gas carried, as reflected by the measured linear correlation between the lambda(Bl:g) values of all three volatile anesthetics and perflubron doses. Even though the increase ranges from 0.9 (desflurane) to 2.6 (sevoflurane) times the normal value, the apparent lack of clinical implications in current trials with perflubron may trigger further in vivo experiments. ⋯ Perflubron increases the in vitro solubility of volatile anesthetics when present in the blood at clinically relevant concentrations. Volatile anesthetics actually partition into the emulsion, but the solubility in the blood does not change. Further studies are needed to assess whether perflubron will affect the pharmacokinetics of volatile anesthetics in vivo.
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Anesthesia and analgesia · Aug 2002
Randomized Controlled Trial Clinical TrialTemperature control and recovery of bowel function after laparoscopic or laparotomic colorectal surgery in patients receiving combined epidural/general anesthesia and postoperative epidural analgesia.
We compared the effects of a laparoscopic (n = 23) versus laparotomic (n = 21) technique for major abdominal surgery on temperature control in 44 patients undergoing colorectal surgery during a combined epidural/general anesthesia. A thoracic epidural block up to T4 was induced with 6-10 mL of 0.75% ropivacaine; general anesthesia was induced with thiopental, fentanyl, and atracurium IV and maintained with isoflurane. Core temperature was measured with a bladder probe and recorded every 15 min after the induction. In both groups, core temperature decreased to 35.2 degrees C (range, 34 degrees C-36 degrees C) at the end of surgery. After surgery, normothermia returned after 75 min (60-120 min) in the Laparoscopy group and 60 min (45-180 min) in the Laparotomy group (P = 0.56). No differences in postanesthesia care unit discharge time were reported between the two groups. The degree of pain during coughing was smaller after laparoscopy than laparotomy from the 24th to the 72nd observation times (P < 0.01). Morphine consumption was 22 mg (2-65 mg) in the Laparotomy group and 5 mg (0-45 mg) in the Laparoscopy group (P = 0.02). The time to first flatus was shorter after laparoscopy (24 h [16-72 h]) than laparotomy (72 h [26-96 h]) (P = 0.0005), and the first intake of clear liquid occurred after 48 h (24-72 h) in the Laparoscopy group and after 96 h (90-96 h) in the Laparotomy group (P = 0.0005). Although laparoscopic surgery provides positive effects on the degree of postoperative pain and recovery of bowel function, the reduction in heat loss produced by minimizing bowel exposure with laparoscopic surgery does not compensate for the anesthesia-related effects on temperature control, and active patient warming must also be used with laparoscopic techniques. ⋯ This prospective, randomized, controlled study demonstrates that laparoscopic colorectal surgery results in less postoperative pain and earlier recovery of bowel function than conventional laparotomy but does not reduce the risk for perioperative hypothermia. Accordingly, active warming must be provided to patients also during laparoscopic procedures.
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Anesthesia and analgesia · Aug 2002
Comparative Study Clinical Trial Controlled Clinical TrialEarly postoperative respiratory acidosis after large intravascular volume infusion of lactated ringer's solution during major spine surgery.
In this study, we compared the effects of large intravascular volume infusion of 0.9% saline (NS) or lactated Ringer's (LR) solution on electrolytes and acid base balance during major spine surgery and evaluated the postoperative effects. Thirty patients aged 18-70 yr were included in the study. General anesthesia was induced with 5 mg/kg thiopental and 0.1 mg/kg vecuronium IV. Anesthesia was maintained with oxygen in 70% nitrous oxide and 1.5%-2% sevoflurane. In Group I, the NS solution, and in Group II, the LR solution were infused 20 mL. kg(-1). h(-1) during the operation and 2.5 mL. kg(-1). h(-1), postoperatively. Electrolytes (Na+, K+, Cl-) and arterial blood gases were measured preoperatively, every hour intraoperatively and at the 1st, 2nd, 4th, 6th, and 12th hours postoperatively. In the NS group, pHa, HCO3 and base excess decreased, and Cl- values increased significantly at the 2nd hour and Na+ values increased at the 4th hour intraoperatively (P < 0.001). The values returned to normal ranges at the 12th hour postoperatively. In the LR group, blood gas analysis and electrolyte values did not show any significant difference intraoperatively, but the increase in PaCO2 and the decrease in pHa and serum Na+ was significant at the 1st hour postoperatively. Although intraoperative 20 mL. kg(-1). h(-1) LR infusion does not cause hyperchloremic metabolic acidosis as does NS infusion, it leads to postoperative respiratory acidosis and mild hyponatremia. ⋯ The infusion of large-volume lactated Ringer's solution does not cause hyperchloremic metabolic acidosis as does 0.9% saline during major surgery, but leads to postoperative mild hyponatremia and respiratory acidosis.
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Anesthesia and analgesia · Aug 2002
The technical aspects of epidural steroid injections: a national survey.
Although epidural steroid injections (ESIs) are a common treatment for chronic pain conditions, it is not clear whether there is consensus on their technical aspects. The current literature suggests that variations in technical aspects may affect ESI outcomes. The goal of the survey was to help establish a standard frame of reference for the performance of ESIs. We analyzed survey results from 68 academic anesthesia programs and 28 private practices in the United States. The main finding in this survey is that there is no clear-cut consensus as to the ideal method to perform ESI. There is a wide variation among individual practices in almost every technical aspect of ESI. Private practices use significantly more fluoroscopy than academic centers. The large difference was found in the cervical region where 73% of private practices and only 39% of academic institutions polled perform the ESIs with fluoroscopic guidance (P = 0.005). A similar discrepancy was found in approaches to the epidural space after laminectomy where 61% of private practices, but only 15% of academic centers, use the transforaminal approach. The study results indicate that there is no consensus, and that there is a wide variation in current practices. ⋯ A national survey of practices performing epidural steroid injections was conducted. The purpose was to establish whether consensus exists on technical aspects of this procedure. The study results indicate that there is no consensus, and that there is a wide variation in current practices.