Anesthesia and analgesia
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Anesthesia and analgesia · Nov 1998
Clinical TrialRespiratory effects of desflurane anesthesia on spontaneous ventilation in infants and children.
Volatile anesthetics depress spontaneous ventilation in a dose-dependent manner with variations in effects among different drugs. The goal of this prospective study was to assess respiratory changes during spontaneous ventilation using desflurane/O2/N2O anesthesia in two groups of children. Both groups were undergoing minor surgery and consisted of children < 2 yr old (Group I) and children > 2 yr old (Group II). They were examined at 0.5, 1, and 1.5 minimum alveolar anesthetic concentration desflurane anesthesia. Induction of anesthesia was performed via a face mask and a mixture of O2/N2O (40:60) with halothane. At lease 20 min after stopping halothane, the respiratory variables were recorded on desflurane anesthesia. Tidal volume and minute ventilation decreased significantly (P <0.05) as desflurane increased from 0.5 to 1.5 MAC in both groups. At 1.5 MAC, the respiratory rate was greater in Group II than in Group I (P <0.05). In both groups, the increase in end-tidal CO2 was significant at 1.5 MAC versus 1 and 0.5 MAC (P <0.05). Apnea, i.e., no respiratory movement for 20 s, occurred at 1.5 MAC in one patient in each group. The respiratory duty cycle did not change in any of the groups. Both indices of paradoxical respiration--amplitude index and delay index--did not change. ⋯ Desflurane induces respiratory depression at concentrations higher than 1 minimum alveolar anesthetic concentration mainly due to a decrease in tidal volume. Therefore, desflurane at high concentrations should be used cautiously in infants and children with spontaneous ventilation.
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Anesthesia and analgesia · Oct 1998
Randomized Controlled Trial Clinical TrialNeuromuscular effects of rocuronium during sevoflurane, isoflurane, and intravenous anesthesia.
The potency and time course of action of rocuronium were studied in patients anesthetized with 66% nitrous oxide in oxygen and 1.5 minimum alveolar anesthetic concentration of sevoflurane or isoflurane, or a propofol infusion. Potency was estimated by using the single-bolus technique. Neuromuscular block was measured by stimulation of the ulnar nerve and by recording the force of contraction of the adductor pollicis muscle. The mean (95% confidence limits) of the 50% and 95% effective doses were estimated tobe 142 (129-157) and 265 (233-301) microg/ kg, 165 (146-187) and 324 (265-396) microg/kg, and 183 (163-207) and 398 (316-502) microg/kg during sevoflurane, isoflurane, and propofol anesthesia, respectively (P < 0.05 for sevoflurane versus propofol). The mean +/- SD times to onset of maximal block after rocuronium 0.6 mg/kg were 0.96 +/- 0.16, 0.90 +/- 0.16, and 1.02 +/- 0.15 min during sevoflurane, isoflurane, and propofol anesthesia, respectively. The respective times to recovery of the first response in the train-of-four (TOF) stimulation (T1) to 25% and 90% were 45 +/- 13.1 and 83 +/- 29.3 min, 35 +/- 6.1 and 56 +/- 15.9 min, and 35 +/- 9.2 and 55 +/- 19.4 min. The times to recovery of the TOF ratio to 0.8 were 103 +/- 30.7, 69 +/- 20.4, and 62 +/- 21.1 min, and the 25%-75% recovery indices were 26 +/- 11.7, 12 +/- 5.0, and 14 +/- 6.9 min, respectively. There were no differences among groups in the times for onset of action or to recovery of T1 to 25%. However, the times for recovery of T1 to 90%, TOF ratio to 0.8, and recovery index in the sevoflurane group were all significantly longer compared with the other two groups (P < 0.05, < 0.01, and < 0.01, respectively). We conclude that the effects of rocuronium, especially duration of action, are significantly enhanced during sevoflurane compared with isoflurane and propofol anesthesia. ⋯ In routine clinical use, the effects of rocuronium are enhanced by sevoflurane, in comparison with isoflurane and propofol anesthesia, and the recovery is slower. Particular attention should be paid to monitoring of neuromuscular block during sevoflurane anesthesia.
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Anesthesia and analgesia · Oct 1998
The analgesic potency of dexmedetomidine is enhanced after nerve injury: a possible role for peripheral alpha2-adrenoceptors.
This study investigated the analgesic potency and site of action of systemic dexmedetomidine, a selective alpha2-adrenoceptor (alpha2AR) agonist, in normal and neuropathic rats. Ligation of the L5-6 spinal nerves produced a chronic mechanical and thermal neuropathic hyperalgesia in rats. von Frey fibers and a thermoelectric Peltier device were used to measure mechanical and heat withdrawal thresholds over the hindpaw. Systemic dexmedetomidine dose-dependently increased the mechanical and thermal thresholds in the control animals (50% effective dose [ED50] 144 and 180 microg/kg intraperitoneally [i.p.], respectively). Neuropathic animals responded to much smaller doses of dexmedetomidine with mechanical and thermal ED50 values of 52 and 29 microg/kg i.p., respectively. There was no difference between the control and neuropathic animals with respect to dexmedetomidine-evoked sedation, as determined by decreased grid crossings in an open-field activity chamber (ED50 12 and 9 microg/kg i.p., respectively). Atipamezole, a selective alpha2AR antagonist, blocked the analgesic and sedative actions of dexmedetomidine inboth the neuropathic and control animals. However, L-659,066, a peripherally restricted alpha2AR antagonist, could only block the analgesic actions of dexmedetomidine in the neuropathic rats, with no effect in control animals. In conclusion, nerve injury enhanced the analgesic but not the sedative potency of systemic dexmedetomidine and may have shifted the site of alpha2 analgesic action to outside the blood-brain barrier. ⋯ We tested the analgesic efficacy of the alpha2 agonist dexmedetomidine in normal and nerve-injured rats. The analgesic potency of dexmedetomidine was enhanced after nerve injury with a site of action outside the central nervous system. Peripherally restricted alpha2 agonists may be useful in the management of neuropathic pain.
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Anesthesia and analgesia · Oct 1998
Randomized Controlled Trial Comparative Study Clinical TrialDesflurane and isoflurane produce similar alterations in systemic and pulmonary hemodynamics and arterial oxygenation in patients undergoing one-lung ventilation during thoracotomy.
We tested the hypothesis that desflurane (DES) and isoflurane (ISO) produce similar effects on systemic and pulmonary hemodynamics and arterial oxygenation before, during, and after one-lung ventilation (OLV) in patients undergoing thoracotomy. After obtaining informed consent, anesthesia was induced with sodium thiopental or thiamylal, fentanyl, and vecuronium in 61 ASA physical status II-IV patients. Patients were randomly assigned to receive either DES (n = 30) or ISO (n = 31) in 100% O2 in separate groups. Hemodynamic data (radial and pulmonary artery [PA] catheters) were recorded, and blood gas values were obtained before and after induction; at selected intervals before, during, and after OLV; and before emergence. DES significantly (P < 0.05) increased heart rate (HR) and decreased mean arterial pressure (MAP) and cardiac output (CO). PA pressures and pulmonary vascular resistance (PVR) increased; systemic vascular resistance (SVR) was unchanged. Increases in HR and CO and decreases in MAP and SVR occurred during OLV and DES. Reductions in PaO2 (411 +/- 88 to 271 +/- 131 mm Hg 5 min after beginning OLV; mean +/- SD) and content (CaO2) and increases in shunt fraction (Qs/Qt; 0.25 +/- 0.12 to 0.40 +/- 0.19 at 5 min after beginning OLV) were also observed. ISO increased HR and PA pressures but did not alter MAP, CO, and PVR, in contrast to the findings with DES. Reductions in MAP and SVR and increases in CO and PA pressures were observed during OLV in the presence of ISO. Similar to the findings during DES, decreases in PaO2 and CaO2 and increases in Qs/Qt occurred during OLV and ISO. We conclude that DES and ISO produce very similar alterations in systemic and pulmonary hemodynamics and arterial oxygenation in patients undergoing OLV during thoracotomy. ⋯ Desflurane and isoflurane produce similar cardiovascular and pulmonary effects before, during, and after one-lung ventilation in patients undergoing lung surgery.
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Anesthesia and analgesia · Oct 1998
Randomized Controlled Trial Comparative Study Clinical TrialComparison of patient-controlled epidural analgesia with and without background infusion after gastrectomy.
To assess the analgesic efficacy and side effects of concurrent infusion in patient-controlled epidural analgesia (PCEA) after upper abdominal surgery, 40 patients undergoing elective gastrectomy under general anesthesia were allocated to two groups in this randomized, double-blind study: one received a 2.5-mL incremental bolus in a solution of 0.2% bupivacaine and 10 microg/mL fentanyl, and the other received the same bolus dose plus a 2.5-mL/h infusion of the same solution. The number of demands was smaller (P < 0.001) in the PCEA plus infusion group than in the PCEA alone group during the 48-h postoperative period. The average hourly fentanyl and bupivacaine doses were larger (P < 0.0001) in the PCEA plus infusion group than in the PCEA alone group. Visual analog scale pain scores on coughing in the PCEA plus infusion group were lower than in the PCEA alone group (P < 0.05). There was a greater incidence of pruritus in the PCEA plus infusion group (P < 0.05), but no serious side effects were observed in either group. In conclusion, a background infusion in PCEA with a mixture of fentanyl and bupivacaine decreases the incidence of postoperative pain and reduces the degree of pain associated with coughing without serious side effects after gastrectomy. ⋯ A background infusion in patient-controlled epidural analgesia with a mixture of fentanyl and bupivacaine decreased the incidence of postoperative pain and reduced the degree of the pain associated with coughing without serious side effects in this randomized, double-blind study after gastrectomy.