Anesthesia and analgesia
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Anesthesia and analgesia · Dec 1997
Randomized Controlled Trial Comparative Study Clinical TrialSevoflurane or halothane anesthesia: can we tell the difference?
This study was performed to evaluate the ability of anesthesiologists to differentiate between sevoflurane, a newer, more expensive anesthetic, and halothane. A total of 113 assessments were made by 36 anesthesiologists on 58 children, aged 6 mo to 6 yr, scheduled for bilateral myringotomy and tube placement. All patients received midazolam (0.5 mg/kg per os) approximately 30 min before the induction of anesthesia. Sevoflurane or halothane was randomly selected for anesthetic induction and maintenance. The anesthesiologists, who were unaware of the anesthetic being used, were asked to identify the anesthetic based on clinical signs and to assess the quality of induction, speed of induction, and speed of emergence using a visual analog scale (VAS; minimum score = 0, maximum score = 100). The anesthesiologists correctly identified the anesthetic only 56.6% of the time. This was not significantly different from the 50% that would result from random guessing (P = 0.08). Further, there were no significant differences in VAS scores between the two groups. This study suggests that in premedicated pediatric patients undergoing brief surgical procedures, anesthesiologists cannot correctly differentiate between sevoflurane and halothane. The lack of significant differences in VAS scores suggests that the speed of induction, the speed of emergence, and the quality of induction are similar under these clinical conditions. Any purported benefits of sevoflurane seem to be of minor consequence under the circumstances studied. ⋯ When the anesthetic halothane or sevoflurane is administered in a blind, randomized fashion, anesthesiologists could not reliably identify which drug was being used to anesthetize children for a brief surgical procedure. These results suggest that the differences between the two drugs in clinical practice are small and may not justify the additional cost of sevoflurane.
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Anesthesia and analgesia · Dec 1997
Randomized Controlled Trial Comparative Study Clinical TrialEpidural analgesia and intravenous patient-controlled analgesia result in similar rates of postoperative myocardial ischemia after aortic surgery.
To assess the role of postoperative analgesia on myocardial ischemia after aortic surgery, we compared intravenous patient-controlled analgesia (PCA) with thoracic epidural analgesia (TEA). One hundred twenty-four patients were prospectively randomized to the PCA or TEA group. In the TEA group, a T6-7 or T7-8 epidural catheter was inserted before the induction of general anesthesia. Within 1 h of the end of surgery, analgesia and 24-h two-channel Holter monitoring were begun. Myocardial ischemia was defined as ST segment depression > or = 1 mm, 0.06 s after the J point, and lasting for more than 1 min. In the PCA group, a bolus of morphine, 0.05 mg/kg, was given, followed by 0.02 mg/kg of morphine on demand every 10 min. Bupivacaine 0.125% and fentanyl 10 microg/mL was used in the TEA group. Analgesics were titrated to maintain a visual analog scale score < or = 3. The overall incidence of myocardial ischemia was 18.4%-18.2% for TEA and 18.6% for PCA (P = not significant). There were no differences between the groups in the total duration of ischemia per patient (22.2 +/- 119.8 min for TEA and 20.5 +/- 99 min for PCA) and the number of episodes per patient (0.69 +/- 2.1 for TEA and 1.2 +/- 4.9 for PCA). Twenty-three patients had an adverse cardiac outcome, although there were no differences between the groups. The postoperative pain control was superior with TEA. In these patients undergoing elective aortic surgery, the use of postoperative TEA did not result in a lower incidence of early myocardial ischemia compared with intravenous PCA with morphine, despite better analgesia with TEA. ⋯ Postoperative myocardial ischemia is associated with adverse cardiac outcome. Using Holter monitoring after aortic surgery, this study shows that the use of thoracic epidural analgesia with bupivacaine and fentanyl did not result in a lower incidence of myocardial ischemia compared with intravenous patient-controlled analgesia with morphine.
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Anesthesia and analgesia · Dec 1997
Randomized Controlled Trial Clinical TrialThe choice of anesthetic maintenance technique influences the antiinflammatory cytokine response to abdominal surgery.
Outcome in some diseases is determined by the relationship between pro- and antiinflammatory cytokines. Surgery may also provoke a cytokine response, which has both pro- and antiinflammatory components. The aim of this study was to ascertain whether anesthetic technique can modify the balance of cytokines associated with abdominal surgery. Twenty patients scheduled to undergo elective abdominal hysterectomy were randomly allocated to receive maintenance of anesthesia with isoflurane (IH group) or propofol (IV group). Venous blood samples for measurement of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), interleukin-10 (IL-10), and interleukin-1 receptor antagonist (IL-1ra) were taken before the induction of anesthesia and at set intervals until 24 h postoperatively. TNF-alpha levels remained low throughout the study; however, all patients showed a significant postoperative increase in IL-6, IL-10, and IL-1ra (P < 0.05). Levels of the proinflammatory cytokine IL-6 were similar in both groups, whereas the antiinflammatory cytokine IL-10 was higher in the IV group at 4 h postoperatively (P < 0.02). The difference between groups in terms of IL-1ra production just failed to reach significance (P < 0.06). We conclude that the cytokine response to abdominal surgery has both pro- and antiinflammatory components and that the choice of anesthetic may modify the balance of these cytokines. ⋯ This study demonstrates that in addition to the widely reported proinflammatory cytokine response, elective abdominal surgery provokes an antiinflammatory response, which may be enhanced by total intravenous anesthesia. The ability of anesthetics to modify the cytokine response to surgery may have therapeutic potential.
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Anesthesia and analgesia · Dec 1997
Pharmacokinetics and efficacy of long-term epidural ropivacaine infusion for postoperative analgesia.
The aim of this study was to evaluate the pharmacokinetics and efficacy of the new local anesthetic ropivacaine when used for epidural infusion for up to 72 h after major orthopedic surgery. Immediately after surgery, an epidural infusion of ropivacaine 2 mg/mL was begun at a rate of 6 mL/h in 11 patients. The infusion rate was then adjusted according to patient analgesic needs or side effects. Blood samples were taken during and after the infusion to determine total and unbound ropivacaine and alpha1-acid glycoprotein (AAG) concentrations. Patients were assessed regularly for sensory and motor block and pain using a visual analog scale (VAS) score (0-100 mm). Ten patients received 63-72 h of infusion. Total plasma concentrations of ropivacaine and binding protein (AAG) increased during the infusion such that free concentrations plateaued or began to fall over time. VAS values during mobilization were less than 40 mm in 93% of patients. The majority of patients had no measurable motor block once the surgical block had regressed. When epidural ropivacaine was titrated to achieve a stable sensory block, there was a low incidence of motor block, and free plasma ropivacaine levels were well below the toxic range. ⋯ The pharmacokinetics of continuous epidural infusions of ropivacaine are described in patients for up to 72 h postoperatively. Clinical efficacy and side effects are also reported. An understanding of the plasma concentrations obtained and modes of elimination during prolonged epidural infusion is important for safe, routine clinical use in postoperative analgesia.
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Anesthesia and analgesia · Dec 1997
Carbon dioxide spirogram (but not capnogram) detects leaking inspiratory valve in a circle circuit.
Expiratory valve incompetence in the circle circuit is diagnosed by using capnography (PCO2 versus time) when significant CO2 is present throughout inspiration. However, inspiratory valve incompetence will allow CO2-containing expirate to reverse flow into the inspiratory limb. CO2 rebreathing occurs early during the next inspiration, generating a short extension of the alveolar plateau and decreased inspiratory downslope of the capnogram, which may be indistinguishable from normal. We hypothesized that CO2 spirography (PCO2 versus volume) would correctly measure inspired CO2 volume (VCO2) during inspiratory valve leak. Accordingly, a metabolic chamber (alcohol combustion) was connected to a lung simulator, which was mechanically ventilated through a standard anesthesia circle circuit. By multiplying and integrating airway flow and PCO2, overall, expired, and inspired VCO2 (VCO2,br = VCO2,E - VCO2,I) were measured. When the inspiratory valve was compromised (by placing a wire between the valve seat and diaphragm), VCO2,I increased from 2.7 +/- 1.7 to 5.7 +/- 0.2 mL (P < 0.05), as measured by using CO2 spirography. In contrast, the capnogram demonstrated only an imperceptible lengthening of the alveolar plateau and did not measure VCO2,I. To maintain effective alveolar ventilation and CO2 elimination, increased VCO2,I requires a larger tidal volume, which could result in pulmonary barotrauma, decreased cardiac output, and increased intracranial pressure. ⋯ Circle circuit inspiratory valve leak will allow CO2-containing expirate to reverse flow into the inspiratory limb, with subsequent rebreathing during the next inspiration. This CO2 rebreathing causes imperceptible lengthening of the alveolar plateau of the capnogram and is detected only by using the CO2 spirogram (PCO2 versus volume).