Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2003
Neurologic complications of 405 consecutive continuous axillary catheters.
Continuous axillary brachial plexus block may theoretically increase the risk of neurologic complications because of catheter-induced mechanical trauma or local anesthetic toxicity. In this study, we retrospectively reviewed the frequency of complications using current techniques and applications. There were 405 continuous axillary catheters in 368 patients. A preexisting neurologic condition was present in 41 (10.1%) patients, including 30 patients with a preoperative ulnar neuropathy. In 305 (75.3%) cases, the axillary catheter was placed to facilitate rehabilitation after major elbow surgery. Catheters were typically placed postoperatively, after documentation of the patient's normal neurologic examination. The local anesthetic infusion contained bupivacaine in 355 (88.7%) patients and mepivacaine in 45 (11.1%) patients. The mean infusion rate was 10 +/- 2 mL/h. Catheters remained indwelling for 55 +/- 32 h. In 31 patients, the axillary catheter was replaced because of technical problems or inadequate analgesia. There were 9 complications in 8 patients for an overall frequency of 2.2%. Complications included one each of the following: localized infection (treated with catheter removal and antibiotics), axillary hematoma, and retained catheter fragment requiring surgical excision. In addition, two patients reported signs and symptoms of systemic (preseizure) local anesthetic toxicity. Four (1.0%) patients reported new neurologic deficits postoperatively. In two patients, the neural dysfunction was non-anesthesia related. All four had continuous catheters placed after major elbow surgery. We conclude that the risk of neurologic complications associated with continuous axillary blockade is similar to that of single-dose techniques. ⋯ We evaluated the risk of neurologic complications in 368 patients undergoing 405 consecutive continuous axillary blocks. New neurologic deficits were reported in four patients. This series suggests that the risk of neurologic complications associated with continuous axillary block is similar to that of single-dose techniques.
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Anesthesia and analgesia · Jan 2003
Minimum alveolar anesthetic concentration of isoflurane with different xenon concentrations in Swine.
For patients requiring a fraction of inspired oxygen more than 0.3, the use of xenon (Xe) as the sole anesthetic is limited because of its large minimum alveolar anesthetic concentration (MAC) of 71%. This warrants investigating the combination of Xe with other inhaled anesthetics. We therefore investigated the influence of Xe on the MAC of isoflurane. The study was performed in 10 swine (weight, 28-35 kg) ventilated with Xe 0%, 15%, 30%, 40%, 50%, and 65% in oxygen. For each Xe concentration, various concentrations of isoflurane were administered in a step-wise design. For each combination, a supramaximal pain stimulus (claw-clamp) was applied, and the appearance of a withdrawal reaction was recorded. The isoflurane MAC was defined as the end-tidal concentration required to produce a 50% response rate. At each Xe concentration, the responses to the pain stimulus were categorized, and a logistic regression model was fitted to the results to determine isoflurane MAC. Isoflurane MAC was decreased by inhalation of Xe in a nonlinear manner from 1.92% (95% confidence interval, 1.70%-2.15%) with 0% Xe to 1.17% (95% confidence interval, 0.75%-1.59%) with 65% Xe. Although this indicates partial antagonism of the two anesthetics, a combination of Xe with isoflurane may prove valuable for patients requiring a fraction of inspired oxygen more than 0.3. ⋯ We investigated the influence of the anesthetic gas xenon on the minimum alveolar anesthetic concentration (MAC) for isoflurane (another anesthetic gas). The study was performed in 10 swine ventilated with fixed xenon and various concentrations of isoflurane. The isoflurane MAC is decreased by inhalation of xenon in a nonlinear relationship.
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Anesthesia and analgesia · Jan 2003
Case ReportsHemodynamic response to caudal epidural clonidine in a pediatric cardiac patient.
Postoperative management of sedation and analgesia in pediatric cardiac patients presents many challenges. This case report describes a child who experienced dramatic clinical improvement with the postoperative use of caudal morphine and clonidine after conventional therapy had failed.
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Anesthesia and analgesia · Jan 2003
Preconditioning with isoflurane produces dose-dependent neuroprotection via activation of adenosine triphosphate-regulated potassium channels after focal cerebral ischemia in rats.
In this study, we determined whether repeated brief isoflurane (Iso) anesthesia induces ischemic tolerance to focal cerebral ischemia in a dose-response manner and whether the effect is dependent on adenosine triphosphate-regulated potassium channels. In Experiment 1, 40 rats were randomly assigned to 4 groups: control animals received 100% oxygen 1 h/d for 5 days, whereas the isoflurane (Iso)1, Iso2, and Iso3 groups received 0.75%, 1.5%, or 2.25% Iso in oxygen 1 h/d for 5 days. In Experiment 2, 36 rats were randomly assigned to 4 groups: controls received 100% oxygen 1 h/d for 5 days; animals in the Iso and I+G (Iso+glibenclamide) groups received 2% Iso in oxygen 1 h/d for 5 days, and the I+G group received glibenclamide (GLB) (5 mg/kg intraperitoneally) before each Iso pretreatment. Animals in the GLB group received GLB (5 mg/kg intraperitoneally) once a day for 5 days. Twenty-four hours after the last pretreatment, the right middle cerebral artery was occluded for 120 min. Neurologic deficit scores (NDS) and brain infarct volumes were evaluated at 24 h. The NDS and infarct volumes of Iso2 and Iso3 were less than those of the controls (P < 0.05). The infarct volume in Iso3 was smaller than in Iso2 (P < 0.05). The NDS and infarct volume in the Iso group were less than in the control and I+G groups (P < 0.05). There was no statistical difference among the control, I+G, and GLB groups. The study demonstrated that repeated Iso anesthesia induces ischemic tolerance in rats in a dose-response manner. GLB, an adenosine triphosphate-regulated potassium channel blocker, abolished the tolerance induced by Iso. ⋯ Brief isoflurane anesthesia induces ischemic tolerance in the brain. The effect was found to be dose dependent in a rat focal cerebral ischemia model. Ischemic tolerance induced by isoflurane preconditioning is dependent on activation of adenosine triphosphate-regulated potassium channels.
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Anesthesia and analgesia · Jan 2003
Comparative StudyA comparison of lactated ringer's solution to hydroxyethyl starch 6% in a model of severe hemorrhagic shock and continuous bleeding in dogs.
In this randomized, controlled study in dogs, we examined the short-term effects of blood pressure targeted fluid resuscitation with colloids or crystalloids solutions on systemic oxygen delivery, and lactate blood concentration. Fluid resuscitation using hydroxyethyl starch (HES) 6% to a mean arterial blood pressure (MAP) of 60 mm Hg was compared with lactated Ringer's solution (LR) to a MAP of 60 or 80 mm Hg (LR60 and LR80, respectively). The model was one of withdrawal of blood to a MAP of 40 mm Hg through an arterial catheter that was then connected to a system allowing bleeding to occur throughout the study whenever MAP exceeded 40 mm Hg. Target MAP was maintained for 60 min with a continuous infusion of the designated fluid replacement. All 15 dogs (5 in each group) survived until the last measurement. Blood loss in the LR80 group (2980 +/- 503 mL) (all values mean +/- SD) was larger than in the LR60 and HES60 groups (1800 +/- 389 mL, and 1820 +/- 219 mL, respectively) (P < 0.001). Whereas 840 +/- 219 mL of HES60 was needed to maintain target MAP, 1880 +/- 425 mL of LR was needed in the LR60 group, and 4590 +/- 930 mL in the LR80 group (P < 0.001). Lactate blood concentrations were smaller and delivered O(2) higher in the HES60 group (35 +/- 17 mg/dL and 239 +/- 61 mL/min, respectively) in comparison to the LR60 group (89 +/- 18 mg/dL and 140 +/- 48 mL/min, respectively) and the LR80 group (75 +/- 23 mg/dL and 153 +/- 17 mL/min, respectively) (P = 0.02 and P = 0.026). In conclusion, fluid resuscitation during uncontrolled bleeding, to a target MAP of 60 mm Hg, using HES60 resulted in larger oxygen delivery and smaller systemic lactate A resuscitation to a target MAP of 60 or 80 mm Hg using LR. ⋯ Fluid resuscitation to a target mean arterial blood pressure of 60 mm Hg during uncontrolled bleeding resulted in larger oxygen delivery and smaller systemic lactate concentrations when hydroxyethyl starch 6% was used, in comparison to lactated Ringer's solution resuscitation to a target mean arterial blood pressure of 60 or 80 mm Hg.