Anesthesia and analgesia
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Anesthesia and analgesia · Oct 1999
Comparative StudyMouse strain modestly influences minimum alveolar anesthetic concentration and convulsivity of inhaled compounds.
In this study, we measured the minimum alveolar anesthetic concentration (MAC) in several mouse strains, including strains used in the construction of genetically engineered mice. This is important because defined genetic modifications are used increasingly to test mechanisms of inhaled anesthetic action, and background variability in MAC can potentially influence the interpretation of these studies. We investigated the effect of strain on MAC for desflurane, isoflurane, halothane, ethanol, the experimental anesthetic 1-chloro-1,2,2-trifluorocyclobutane, and convulsive 50% effective dose (the dose required to produce convulsions in 50% of animals) of the nonimmobilizer 1,2-dichlorohexafluorocyclobutane. These drugs were studied in eight inbred strains, including both laboratory and wild mouse strains (129/J, 129/SvJ, 129/Ola Hsd, C57BL/6NHsd, C57BL/6J, DBA/2J, Spret/Ei, and Cast/Ei), one hybrid strain (B6129F2/J, derived from the C57BL/6J and 129/J strains), and one outbred strain (CD-1). To test our ability to detect effects in a genetically modified mouse, we compared these data with those for a mouse lacking the gamma (neuronal) isoform of the protein kinase C gene (PKCgamma). We also assessed whether amputating the tail tip of mice (a standard method of obtaining tissue for genetic analysis) increased MAC (e.g., by sensitization of the spinal cord). MAC and convulsant 50% effective dose values differed modestly among strains, with a range of 17% to 39% from the lowest to highest values for MAC using conventional anesthetics, and up to 48% using the experimental anesthetic 1-chloro-1,2,2-trifluorocyclobutane. Convulsivity to the nonimmobilizer varied by 47%. Amputating the tail tip did not affect MAC. PKCgamma knockout mice had significantly higher MAC values than control animals for isoflurane, but not for halothane or desflurane, which implies that protein phosphorylation by PKCgamma can alter sensitivity to isoflurane. ⋯ Anesthetic potency differs by modest amounts among inbred, outbred, wild, and laboratory mouse strains. Absence of the neural form of protein kinase C increases minimum alveolar anesthetic concentration for isoflurane, indicating that protein phosphorylation by the gamma-isoform of protein kinase C (PKCgamma) can influence the potency of this anesthetic.
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Anesthesia and analgesia · Oct 1999
Meta AnalysisA meta-analysis of the effectiveness of cell salvage to minimize perioperative allogeneic blood transfusion in cardiac and orthopedic surgery. International Study of Perioperative Transfusion (ISPOT) Investigators.
Concern about risks of allogeneic transfusion has led to an interest in methods for decreasing perioperative transfusion. To determine whether cell salvage reduces patient exposure to allogeneic blood, we performed meta-analyses of randomized trials, evaluating the effectiveness and safety of cell salvage in cardiac or orthopedic elective surgery. The primary outcome was the proportion of patients who received at least one perioperative allogeneic red cell transfusion. Twenty-seven studies were included in the meta-analyses. Cell salvage devices that do not wash salvaged blood were marginally effective in cardiac surgery patients when used postoperatively (relative risk [RR] = 0.85, 95% confidence interval [CI] = 0.79-0.92). Devices that wash or do not wash salvaged blood considerably decreased the proportion of orthopedic surgery patients who received allogeneic transfusion (RR = 0.39, 95% CI = 0.30-0.51 and RR = 0.35, 95% CI 0.26-0.46, respectively). No studies of cell savers that wash salvaged blood during cardiac surgery were included. Cell salvage did not appear to increase the frequency of adverse events. We conclude that cell salvage in orthopedic surgery decreases the risk of patients' exposure to allogeneic blood transfusion perioperatively. Postoperative cell salvage in cardiac surgery, with devices that do not wash the salvaged blood, is only marginally effective. ⋯ This meta-analysis of all published randomized trials provides the best current estimate of the effectiveness of cell salvage and is useful in guiding clinical practice. We conclude that cell salvage in orthopedic surgery decreases the proportion of patients requiring allogeneic blood transfusion perioperatively, but postoperative cell salvage is only marginally effective in cardiac surgery.
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Anesthesia and analgesia · Oct 1999
Randomized Controlled Trial Comparative Study Clinical TrialPatient-controlled analgesia with morphine plus lysine acetyl salicylate.
Using a patient-controlled analgesia (PCA) delivery system, we evaluated the clinical advantages and disadvantages of morphine PCA compared with morphine plus lysine acetyl salicylate (LAS), a soluble aspirin. After major orthopedic surgery, 50 adult patients were enrolled in a prospective, randomized, and double-blinded study. When a patient in the recovery room complained of pain, an initial dose of morphine or the morphine/LAS mixture was titrated to achieve analgesia of visual analog score < or = 3 in 30 min. An equivalent volume PCA dose of either morphine 1 mg/mL or morphine 0.5 mg + LAS 90 mg/mL was used with a lockout interval of 10 min. Pain score, patient satisfaction, vital signs, and adverse effects were observed for 48 h. Adequate analgesia (visual analog scale score < or = 3) was achieved with either drug. Morphine consumption in the morphine/LAS group was significantly less than in morphine group (13.9 vs 18.4 mg in 24 h and 24.3 vs 32.4 mg in 48 h). Significantly more sedation was evident with the morphine group (P < 0.05). We conclude that injectable LAS can be used as an effective and safe adjuvant to morphine for PCA. This combination reduces dose requirements of morphine and hence some of its adverse effects. ⋯ Injectable aspirin could be used as an effective and safe adjuvant to morphine for patient-controlled analgesia. This combination reduces the dose requirement of morphine and therefore some of the morphine-related untoward effects.
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Anesthesia and analgesia · Oct 1999
Randomized Controlled Trial Clinical TrialThe impact of saline flush of the epidural catheter on resolution of epidural anesthesia in volunteers: a dose-response study.
We evaluated the effect of 1, 20, and 40 mL of epidural saline flush on recovery from lidocaine epidural anesthesia. Eight volunteers were studied for three study periods, each separated by 72 h. The volume of saline was randomized, and a new catheter was inserted for each study period. A standardized dose of 20 mL of 2% plain lidocaine was injected for 10 min, followed by an epidural saline flush 30 min later. Sensory block was assessed by pinprick and transcutaneous electrical stimulation and motor block by a modified Bromage scale and isometric maximal force contraction. Times to void and ambulate independently before discharge were recorded. Peak plasma lidocaine concentrations and time to peak concentration were determined. Results from six volunteers showed that epidural saline, 40 mL, significantly altered anesthetic resolution, accelerating the time of complete sensory and motor block regression (P < 0.05). Median peak levels of sensory and motor block and times to void and ambulate were similar among treatment groups. Peak plasma lidocaine concentrations were similar in all treatment groups. Our data suggest that a 40-mL epidural saline injection 30 min after the induction facilitates regression of epidural lidocaine anesthesia, but a 20-mL bolus does not. Epidural saline injection does not affect vascular absorption of epidural lidocaine. ⋯ Epidural catheter flushing with 40 mL of saline, after establishment of epidural lidocaine anesthesia, can facilitate sensory and motor block recovery. However, this does not affect vascular absorption of epidural lidocaine.