Anesthesia and analgesia
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Anesthesia and analgesia · Aug 2005
Randomized Controlled Trial Clinical TrialThe effect of different isoflurane-fentanyl dose combinations on early recovery from anesthesia and postoperative adverse effects.
We evaluated the effect of different combinations of fentanyl-isoflurane on early recovery from anesthesia in 80 adult patients undergoing laparoscopic cholecystectomy. Anesthesia was induced with fentanyl 2 microg/kg and thiopental 5 mg/kg. Nitrous oxide was not used and patients were randomly assigned to one of four groups: Group 1 (n = 20) received 0.6% end-tidal isoflurane plus fentanyl, Group 2 (n = 20) received 1.2% end-tidal isoflurane plus fentanyl, Group 3 (n = 20) received 1.8% end-tidal isoflurane plus fentanyl, and Group 4 (n = 20) received only isoflurane. In Groups 1, 2 and 3 isoflurane concentration was kept constant and fentanyl was given as necessary to maintain the mean arterial blood pressure within +/- 10% of the minimum mean arterial blood pressure measured in the ward. In Group 4, isoflurane concentration was adjusted to maintain mean arterial blood pressure as above. At the end of skin closure isoflurane was discontinued and the time to spontaneous breathing (TSB), time to extubation (TE) and time to eye opening (TEO) were recorded. In the postanesthesia care unit, the degree of sedation, respiratory rate, Spo(2), emesis, pain, and morphine consumption were evaluated every 15 min for 1 h, and thereafter every 30 min until discharge. Fentanyl requirements were 8.3 +/- 4.5 microg/kg (mean +/- sd) in Group 1, 3.8 +/- 1.3 microg/kg in Group 2, and 3.0 +/- 0.7 microg/kg in Group 3 (P < 0.001), whereas in Group 4 the mean end-tidal concentration of isoflurane was 2.0% +/- 0.4%. Although the mean TSB was <5.5 min in all groups, TE increased from 7.3 +/- 5.1 min in Group 1 to 20.6 +/- 10.7 min in Group 4 (P < 0.001), and TEO increased from 7.4 +/- 5.1 min in Group 1 to 25.8 +/- 9.4 min in Group 4 (P < 0.001). There were no differences among the groups in any of the variables measured in the postanesthesia care unit. This study shows that the combination of a small concentration of isoflurane and a relatively larger dose of fentanyl results in a faster recovery from anesthesia than the inverse combination of doses. ⋯ A fast recovery from anesthesia increases patient safety. This study shows that the combination of a small concentration of isoflurane and a relatively larger dose of fentanyl results in a faster recovery from anesthesia than the inverse combination of doses.
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Anesthesia and analgesia · Aug 2005
ReviewIntraoperative fluid restriction improves outcome after major elective gastrointestinal surgery.
Fluid therapy is one of the most controversial topics in perioperative management. There is continuing debate with regard to the quantity and the type of fluid resuscitation during elective major surgery. However, there are increasing reports of perioperative excessive intravascular volume leading to increased postoperative morbidity and mortality. ⋯ Furthermore, predetermined algorithms that suggest replacement of third space losses and losses through diuresis are unnecessary. Significant reduction in crystalloid volume can be achieved without encountering intraoperative hemodynamic instability or reduced (i.e., < 0.5 mL x kg(-1) x h(-1)) urinary output just by avoiding replacement of third space losses and preloading. Finally, there is a need for well-controlled studies in a well-defined patient population using clear criteria or end-points for perioperative fluid therapy.
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Anesthesia and analgesia · Aug 2005
Clinical TrialMonitoring activated clotting time for combined heparin and aprotinin application: an in vitro evaluation of a new aprotinin-insensitive test using SONOCLOT.
The kaolin-based activated clotting time (ACT) is commonly used for monitoring heparin-induced anticoagulation alone and combined with aprotinin during cardiopulmonary bypass. However, aprotinin prolongs ACT measurements. Recently, a new so-called 'aprotinin-insensitive' ACT test (SaiACT) has been developed for the SONOCLOT analyzer. In this study we evaluated and compared this new test for the SONOCLOT analyzer in vitro with an established kaolin-based ACT from HEMOCHRON (HkACT). Twenty-five patients undergoing elective valve surgery donated 80 mL of blood after induction of anesthesia. The blood was withdrawn in citrated tubes and processed to analyze effects of heparin (0, 1, 2, and 3 U x mL(-1)), aprotinin (0, 200 kIU x mL(-1)), and 25% hemodilution with calcium-free lactated Ringer's solution on ACT measurements. A total of 400 blood samples were analyzed and ACT was measured in a wide, clinically relevant range in duplicate with SaiACT and HkACT. Addition of aprotinin to heparinized blood samples induced no significant changes of SaiACT measurements. By contrast, HkACT readings increased significantly: aprotinin prolonged HkACT in heparinized blood samples by 20% +/- 37% (2 U x mL(-1)) and 24% +/- 18% (3 U x mL(-1)), respectively, and in vitro hemodilution increased this effect. ⋯ Current standard techniques to measure heparin-induced anticoagulation during cardiopulmonary bypass are affected by aprotinin, a drug widely used in this setting. The aim of this study was to investigate in vitro a new, so-called 'aprotinin-insensitive' test from SONOCLOT to measure heparin-induced anticoagulation more reliably in combination with aprotinin.
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Anesthesia and analgesia · Aug 2005
Preoperative "fentanyl challenge" as a tool to estimate postoperative opioid dosing in chronic opioid-consuming patients.
When opioids are used for postoperative pain control, it is useful to define the dose-response relationship for analgesia and respiratory depression. We studied 20 chronically opioid-consuming patients having elective multilevel spine fusion. Preoperatively, each patient received a fentanyl infusion of 2 microg x kg(-1) x min(-1) until the respiratory rate was <5 breaths/min. Pharmacokinetic simulations were used to estimate the effect site concentration at the time of respiratory depression and to predict the patient-controlled analgesia settings that would provide an effect-site fentanyl concentration that was 30% of the concentration associated with respiratory depression. Postoperatively, patient-controlled analgesia settings were adjusted to achieve 2-3 demand doses per hour. At steady-state patient-controlled analgesia settings, arterial blood gases and plasma fentanyl levels were measured. Sixteen patients required no adjustment or one patient-controlled analgesia adjustment. The median arterial Pco(2) level was 41 mm Hg and the interquartile range was 39-46 mm Hg. Plasma fentanyl levels demonstrated a significant correlation to the estimated effect-site concentration associated with respiratory depression determined during the preoperative fentanyl challenge. A preoperative fentanyl challenge used with pharmacokinetic simulations may be a useful tool to individualize the administration of analgesics to chronically opioid-consuming patients. ⋯ In chronically opioid-consuming patients, doses causing respiratory depression and analgesia may differ from those in opioid-naive individuals. A preoperative infusion of fentanyl, used in conjunction with pharmacokinetic simulation, may be a valuable tool for identifying clinical end-points, such as respiratory depression and analgesia, and individualizing postoperative treatment of pain in patients who chronically consume opioids.
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Anesthesia and analgesia · Aug 2005
Beta3-containing gamma-aminobutyric acidA receptors are not major targets for the amnesic and immobilizing actions of isoflurane.
Mice bearing an N265M point mutation in the gamma-aminobutyric acid (GABA)(A) receptor beta3 subunit resist various anesthetic effects of propofol and etomidate. They also require a 16% larger concentration of enflurane and a 21% larger concentration of halothane to abolish the withdrawal reflex than do wild-type mice. Using a Pavlovian test, we measured whether this mutation increased the concentration of isoflurane required to impair learning and memory relative to wild-type mice. We found that the concentration was not significantly increased. We also measured MAC (the minimum alveolar concentration required to eliminate movement in response to noxious stimulation in 50% of subjects). Isoflurane MAC for mutant mice (1.93% +/- 0.0.03%; mean +/- se; n = 14) was 17.0% larger than MAC for wild-type mice (1.65 +/- 0.04; n = 14; P < 0.001). Similarly, the cyclopropane MAC for mutant mice (27.6% +/- 0.55%; n = 16) was 13.6% larger than MAC for wild-type mice (24.3 +/- 0.46; n = 8; P < 0.01). The increase in MAC for cyclopropane was unexpected, because published reports find only minimal actions at alpha1beta2gamma2 GABA(A) receptors whereas isoflurane provides a large enhancement. Consistent with previous work on alpha1beta2gamma2 GABA(A) receptors, we found in Xenopus oocytes that 5 MAC cyclopropane enhanced the effect of GABA on alpha1beta2gamma2 GABA(A) receptors by only 76%, and by a nearly identical enhancement in alpha1beta3gamma2, and alpha6beta3gamma2 receptors. In contrast, a much smaller concentration of isoflurane (1 MAC) produced a 160% to 310% enhancement in these receptors. If, relative to isoflurane, cyclopropane minimally increases GABA-induced chloride currents at any GABA(A) receptor subtype, the present data for MAC are consistent with the notion that GABA(A) receptors do not mediate the immobility produced by inhaled anesthetics. ⋯ The results of the present study indicate that beta3-containing gamma-aminobutyric acidA receptors do not mediate the amnesia produced by isoflurane and do not mediate, or only partially mediate, the immobility produced by inhaled anesthetics.