Anesthesia and analgesia
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Anesthesia and analgesia · Aug 2005
Clinical TrialA pilot study of continuous transtracheal mixed venous oxygen saturation monitoring.
In this study, we investigated the feasibility and the accuracy of transtracheal mixed venous oxygen saturation (Svo(2)) monitoring. Ten patients undergoing thoracic surgery were included in this study. A single-use pediatric pulse oximetry sensor was attached to the double-lumen tube between the tracheal and bronchial cuff. After anesthesia was induced, the double-lumen tube was inserted into the trachea and adjusted to the proper position. During surgery, the pulmonary arterial blood was sampled every 3 min for 15 min to measure the Svo(2). The measurements made by the transtracheal pulmonary pulse oximeter (Sto(2)) were recorded at the same time that blood was sampled from the pulmonary artery for Svo(2) measurements. The levels of measurement agreement between the Sto(2) and the Svo(2) were analyzed using the Bland and Altman method. The mean +/- sd (range) oxygen saturation values during the data collecting period were 82.0% +/- 4.9% (72%-91%) for the Sto(2) and 82.2% +/- 5.5% (71%-91%) for the Svo(2), respectively. The linear correlation coefficient of the regression analysis between the Sto(2) and the Svo(2) was 0.934 (P < 0.05). A 95% confidence interval for absolute difference between the Sto(2) and the Svo(2) was 1.58%-2.09%. The mean +/- 2 sd difference between the Sto(2) and the Svo(2) was 0.12% +/- 3.97% on the Bland and Altman graph. We conclude that it is feasible to monitor the pulmonary artery oxygen saturation continuously by a transtracheal pulse oximetry technique and that it can be done so accurately. ⋯ Mixed venous oxygen saturation (Svo2) is a measure of the balance between oxygen supply and consumption throughout the whole body. Svo2 can be measured invasively by inserting a pulmonary artery catheter with the associated disadvantages of cost and potential for patient injury. In this study, we investigated the feasibility of noninvasive Svo2 measurement using a transtracheal pulse oximetry technique.
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Anesthesia and analgesia · Aug 2005
The long term myotoxic effects of bupivacaine and ropivacaine after continuous peripheral nerve blocks.
Compared with bupivacaine, acute myotoxicity of ropivacaine is less severe. Thus, in this study we compared the long term myotoxic effects of both drugs in a clinically relevant setting. Femoral nerve catheters were inserted in anesthetized pigs, and either 20 mL of bupivacaine (5 mg/mL) or ropivacaine (7.5 mg/mL) was injected. Subsequently, bupivacaine (2.5 mg/mL) and ropivacaine (3.75 mg/mL) were continuously infused (8 mL/h) over 6 h. Control animals were treated with corresponding volumes of normal saline. After 7 and 28 days, respectively, muscle samples were dissected at the former injection sites, and histological patterns of muscle damage were blindly scored (0 = no damage to 3 = marked lesions/myonecrosis) and compared. No morphological tissue changes were detected in control animals. In the observed period, both local anesthetics induced morphologically identical patterns of calcific myonecrosis, formation of scar tissue, and a marked rate of fiber regeneration. However, bupivacaine's effects were constantly more pronounced than those of ropivacaine. These data show that both drugs induce irreversible skeletal muscle damage in a clinically relevant model, and confirm the exceeding rate of myotoxicity of bupivacaine. However, the clinical impact of these long term myotoxic effects still has to be assessed. ⋯ In a period of 4 wk after peripheral nerve block, both long-acting local anesthetics, bupivacaine and ropivacaine, produced calcific myonecrosis suggestive of irreversible skeletal muscle damage. In comparison with ropivacaine, however, the extent of bupivacaine-induced muscle lesions was significantly larger.
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Anesthesia and analgesia · Aug 2005
The gamma-subunit governs the susceptibility of recombinant gamma-aminobutyric acid type A receptors to block by the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (F6, 2N).
To identify anesthetic effects that produce the different components of the complex anesthetic state, the so-called nonanesthetics/nonimmobilizer classes of compounds have been introduced. Because ionotropic gamma-aminobutyric acid type A (GABA(A)) receptors play an important role in the mediation of the central nervous system (CNS) effects of general anesthetics, and their susceptibility to modulation by various drugs depends on subunit composition, we have compared the effect of the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (F6) on GABA(A) receptors expressed in human embryonic kidney 293 cells transfected with alpha1beta2 versus alpha1beta2gamma2s subunits. Using rapid perfusion and whole-cell recording techniques, we found that, like isoflurane, F6 blocked GABA-induced currents through alpha1beta2 receptors but, unlike isoflurane, the presence of the gamma2s subunit conferred complete resistance to block by F6. Also, in contrast to isoflurane, F6 had no effect on deactivation kinetics of GABA-induced currents in either type of receptor. We conclude that modulation of alphabetagamma receptors plays little or no role in the actions of F6, but the block of alphabeta receptors may contribute to its effects on the CNS. ⋯ Gamma-aminobutyric acidA receptors are the target of numerous drugs affecting the central nervous system. The subunit composition of the GABAA receptors governs their interaction with many drugs. We investigated whether the gamma-subunit influences the interaction with the nonimmobilizer F6.
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Anesthesia and analgesia · Aug 2005
Randomized Controlled Trial Comparative Study Clinical TrialA comparison of Espocan and Tuohy needles for the combined spinal-epidural technique for labor analgesia.
When using the needle-through-needle combined spinal-epidural (CSE) technique for labor analgesia, failure to obtain cerebrospinal fluid (CSF), paresthesias, and intrathecal or intravascular migration of the catheter are of concern. Epidural needles with spinal needle apertures, such as the back-hole Espocan (ES) needles, are available and may reduce these risks. We describe the efficacy and adverse events associated with a modified epidural needle (ES) versus a conventional Tuohy needle for CSE. One-hundred parturients requesting labor analgesia (CSE) were randomized into 2 groups: 50-ES 18-gauge modified epidural needle with 27-gauge Pencan atraumatic spinal needle, 50-conventional 18-gauge Tuohy needle with 27-gauge Gertie Marx atraumatic spinal needle. Information on intrathecal or intravascular catheter placement, paresthesia on introduction of spinal needle, failure to obtain CSF through the spinal needle after placement of epidural needle, unintentional dural puncture, and epidural catheter function was obtained. No intrathecal catheter placement occurred in either group. Rates of intravascular catheter placement and unintentional dural puncture were similar between the groups. Significant differences were noted regarding spinal needle-induced paresthesia (14% ES versus 42% Tuohy needles, P = 0.009) and failure to obtain CSF on first attempt (8% ES versus 28% Tuohy needles, P < 0.02). Use of ES needles for CSE significantly reduces paresthesia associated with the insertion of the spinal needle and is associated with more frequent successful spinal needle placement on the first attempt. ⋯ The use of modified epidural needles with a back hole for combined spinal-epidural technique significantly reduces paresthesia associated with the insertion of the spinal needle and is associated with more frequent successful spinal needle placement on the first attempt.
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Anesthesia and analgesia · Aug 2005
Randomized Controlled Trial Comparative Study Clinical TrialThe short-lasting analgesia and long-term antihyperalgesic effect of intrathecal clonidine in patients undergoing colonic surgery.
In this study, we investigated the antihyperalgesic effect of clonidine after surgery. Sixty patients undergoing right colic resection were studied. Patients were randomized to receive prior to general anesthesia a 2-mL intrathecal (IT) injection of 300 microg of clonidine or saline, or 10 mg of bupivacaine. General anesthesia was achieved using a target concentration propofol infusion and monitored using bispectral index. Postoperative analgesia was provided by morphine IV given through a patient-controlled analgesia device. Postoperative analgesia was assessed by morphine requirements and visual analog scale pain scores at rest, cough, and movement during the first 72 h. Mechanical hyperalgesia was measured by von Frey filaments. Patients were questioned regarding residual pain at 2 wk,1, 6, and 12 mo. The patient-controlled analgesia morphine requirements were significantly smaller in the IT clonidine group (31.5 +/- 12 versus 91 +/- 25.5 and 43 +/- 15 mg, respectively, in groups clonidine, saline, and bupivacaine: P < 0.05 at 72 postoperative hours). The area of hyperalgesia at 72 h was 3 +/- 5 cm(2) in the clonidine group versus 90 +/- 30 and 35 +/- 20 cm(2) in the saline and bupivacaine groups (P < 0.05). At 6 mo, fewer patients in the clonidine group experienced residual pain than in the saline group (0 of 20 versus 6 of 20, P < 0.05). We conclude that both intraoperative spinal clonidine and bupivacaine improve immediate postoperative analgesia. IT clonidine was, however, more potent than IT bupivacaine to reduce postoperative secondary hyperalgesia. ⋯ Spinal clonidine contributes to the reduction of secondary hyperalgesia in patients recovering from abdominal surgery.