Anesthesia and analgesia
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Anesthesia and analgesia · Apr 2003
Randomized Controlled Trial Comparative Study Clinical TrialHydroxyethyl starch (HES) 130/0.4 provides larger and faster increases in tissue oxygen tension in comparison with prehemodilution values than HES 70/0.5 or HES 200/0.5 in volunteers undergoing acute normovolemic hemodilution.
Stable hemodynamics and improved rheology are important effects of hemodilution with hydroxyethyl starch (HES) infusions. One clinical indicator of improved rheology is increased tissue oxygen tension (tpO(2)). In this prospective, randomized, double-blinded, crossover study, we examined the effects of acute normovolemic hemodilution with HES 130/0.4 on hemodynamics and skeletal muscle tpO(2) in comparison with conventional HES solutions. Twelve healthy volunteers were randomly enrolled in each group. At an interval of >8 days, volunteers donated 18% of their calculated blood volume within 30 min and randomly received 6% HES 130/0.4, 6% HES 70/0.5, or 6% HES 200/0.5 (crossover design) in a 1:1.2 ratio to their blood loss. Hemodynamic variables, tpO(2) in the quadriceps muscle, hematocrit, plasmatic HES concentrations, plasma viscosity, colloid osmotic pressures, and platelet aggregation were measured until 6 h after the infusion of HES. No differences were found among groups with respect to changes of hemodynamics, hematocrit, or platelet aggregation. With HES 200, colloid osmotic pressures and plasma viscosities were larger than after HES 70 (P < 0.05). HES 130 in comparison with HES 70 and 200 caused the fastest (30 min versus 90 min and 150 min after hemodilution; P < 0.05) and largest increase of tpO(2) in comparison to baseline (+93% versus +33% and 40%; P < 0.05). In healthy volunteers undergoing acute normovolemic hemodilution, the newly designed HES 130/0.4 showed a more pronounced and earlier increase of skeletal muscle tpO(2) in comparison with prehemodilution values than HES 70/0.5 or 200/0.5. ⋯ The effects of three different hydroxyethyl starch (HES) solutions on hemodynamics, rheology, and skeletal muscle tissue tension after acute normovolemic hemodilution were examined in awake volunteers. With HES 130/0.4, increases of tissue oxygen tension in comparison to baseline were larger and more rapid than with HES 70/0.5 or HES 200/0.5.
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Anesthesia and analgesia · Apr 2003
Randomized Controlled Trial Comparative Study Clinical TrialIntrathecal clonidine added to a bupivacaine-morphine spinal anesthetic improves postoperative analgesia for total knee arthroplasty.
Postoperative pain after total knee arthroplasty (TKA) is severe and can complicate early physical therapy. We tested the hypothesis that intrathecal clonidine would improve postoperative analgesia for TKA using a hyperbaric bupivacaine spinal anesthetic. In a double-blinded, placebo-controlled protocol, 81 ASA physical status I-III patients undergoing either a single or bilateral TKA were randomized into 4 groups with the following 2-mL solutions added to 15 mg of hyperbaric bupivacaine: 1) sterile saline, 2) morphine (250 microg), 3) morphine (250 microg) with clonidine (25 microg), and 4) morphine (250 microg) with clonidine (75 microg). At 1, 2, 4, 6, 12, and 24 h postoperatively, we measured visual analog scales (VAS), cumulative IV morphine consumption, hemodynamics, nausea, ancillary drugs, and side effects. Our primary comparison was between the clonidine with morphine groups versus the morphine group. We found that the combined administration of intrathecal clonidine and morphine decreased 24 h IV morphine consumption by 13 mg (P = 0.028) when compared with intrathecal morphine alone. This corresponded to a decrease in the VAS score of 1.3 cm at 24 h postoperatively (P = 0.047). Adverse side effects were similar among all groups with the exception of more relative hypotension in the clonidine groups through postoperative hour 6. We conclude that the coadministration of intrathecal clonidine and morphine decreases the 24-h IV morphine consumption and improves the 24-h VAS score when compared with intrathecal morphine alone. ⋯ In this prospective, randomized, double-blinded, and placebo-controlled trial, we identify an effective postoperative analgesic approach in total knee replacement surgery. Intrathecal morphine (250 microg) combined with clonidine (25 or 75 microg) provided superior analgesia compared with intrathecal morphine alone.
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Anesthesia and analgesia · Apr 2003
Randomized Controlled Trial Comparative Study Clinical TrialThe anesthetic conserving device compared with conventional circle system used under different flow conditions for inhaled anesthesia.
The Anesthetic Conserving Device (ACD) is a high-flow anesthesia system closed to volatile anesthetics only. We compared the ACD with a circle system under different fresh gas flow (FGF) conditions. Eighty-one patients undergoing major surgery were randomly allocated to receive sevoflurane from a circle circuit combined either with the ACD placed at the Y-piece (n = 41) or with a vaporizer (n = 40). The FGF was set to 8 L/min in the ACD system, where the circle circuit served as a nonrebreather. In the conventional circle system without ACD, the vaporizer was supplied with 1-, 1.5-, 3-, and 6-L/min FGFs. We compared the ACD with the circle system under the four FGFs in terms of sevoflurane dosing, sevoflurane consumption, humidification efficiency, and environmental pollution. The ACD and the low-flow circle system (1.5- and 1-L/min FGFs) resulted in the smallest sevoflurane consumption. The increase in inspired sevoflurane concentration was faster with the circle system than with the ACD only with FGFs > or =3 L/min. The removal of ACD from the circuit allowed the fastest washout of sevoflurane. Respiratory gas humidification was always adequate. Sevoflurane ambient concentration with the ACD was 1-70 ppb. The ACD is a valid and simple alternative to low-flow systems. ⋯ The Anesthetic Conserving Device (ACD) is a new device for anesthetic vapor delivery. We demonstrated that the ACD reduces anesthetic consumption and environmental pollution similarly to a low-flow circle system, offering advantages such as simplicity, no toxicity from compounds produced in the absorber, and potential cost savings.
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Anesthesia and analgesia · Apr 2003
Sevoflurane exposure generates superoxide but leads to decreased superoxide during ischemia and reperfusion in isolated hearts.
Reactive oxygen species (ROS) are largely responsible for cardiac injury consequent to ischemia and reperfusion, but, paradoxically, there is evidence suggesting that anesthetics induce preconditioning (APC) by generating ROS. We hypothesized that sevoflurane generates the ROS superoxide (O(2)(.-)), that APC attenuates O(2)(.-) formation during ischemia, and that this attenuation is reversed by bracketing APC with the O(2)(.-) scavenger manganese (III) tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP) or the putative mitochondrial adenosine triphosphate-sensitive potassium (mK(ATP)) channel blocker 5-hydroxydecanoate (5-HD). O(2)(.-) was measured continuously in guinea pig hearts by using dihydroethidium. Sevoflurane was administered alone (APC), with MnTBAP, or with 5-HD before 30 min of ischemia and 120 min of reperfusion. Control hearts underwent no pretreatment. Sevoflurane directly increased O(2)(.-); this was blocked by MnTBAP but not by 5-HD. O(2)(.-) increased during ischemia and during reperfusion. These increases in O(2)(.-) were attenuated in the APC group, but this was prevented by MnTBAP or 5-HD. We conclude that sevoflurane directly induces O(2)(.-) formation but that O(2)(.-) formation is decreased during subsequent ischemia and reperfusion. The former effect appears independent of mK(ATP) channels, but not the latter. Our study indicates that APC is initiated by ROS that in turn cause mK(ATP) channel opening. Although there appears to be a paradoxical role for ROS in triggering and mediating APC, a possible mechanism is offered. ⋯ Reactive oxygen species (ROS) are implicated in triggering anesthetic preconditioning (APC). The ROS superoxide (O(2)(.-)) was measured continuously in guinea pig isolated hearts. Sevoflurane directly increased O(2)(.-) but led to attenuated O(2)(.-) formation during ischemia. This demonstrates triggering of APC by ROS and clarifies the mechanism of cardioprotection during ischemia.
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Anesthesia and analgesia · Apr 2003
Clinical TrialThe effect of epidural neostigmine combined with ropivacaine and sufentanil on neuraxial analgesia during labor.
Spinal neostigmine produces analgesia without respiratory depression or hypotension but provokes major gastrointestinal side effects. Epidural injection of this drug, however, appears to induce analgesia devoid of such side effects. In this study, we evaluated the effect of a bolus of epidural neostigmine on the duration and magnitude of analgesia in early labor and assessed its eventual sparing effect on subsequent local anesthetic requirements. Epidural neostigmine methylsulfate (maximal dose 4 microg/kg) was added to 10 mL of ropivacaine 0.1%, with and without sufentanil 10 microg, to initiate analgesia. Twenty minutes after injection, pain score, sensory level, and motor block were assessed. Time until request for supplemental epidural medication was also recorded. Patient-controlled epidural analgesia with ropivacaine 0.1% was used for epidural supplementation. Maternal and fetal side effects were closely recorded. Neostigmine (4 microg/kg), when added to ropivacaine 10 mg, provided equivalent analgesia to ropivacaine 20 mg but was less effective than sufentanil 10 microg for the initiation of labor epidural analgesia. Further, neostigmine did not modify the subsequent patient-controlled epidural analgesia local anesthetic requirements during labor. No hemodynamic instability, additional motor block, or bothersome side effects were recorded. ⋯ The combination of epidural neostigmine (4 microg/kg) with the local anesthetic ropivacaine, with or without sufentanil, does not significantly enhance neuraxial analgesia during labor. Such a dose, however, has no bothersome side effects.