Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2004
Clinical TrialA novel infraclavicular brachial plexus block: the lateral and sagittal technique, developed by magnetic resonance imaging studies.
A new infraclavicular brachial plexus block method has the patient supine with an adducted arm. The target is any of the three cords behind the pectoralis minor muscle. The point of needle insertion is the intersection between the clavicle and the coracoid process. The needle is advanced 0 degrees -30 degrees posterior, always strictly in the sagittal plane next to the coracoid process while abutting the antero-inferior edge of the clavicle. We tested the new method using magnetic resonance imaging (MRI) in 20 adult volunteers, without inserting a needle. Combining 2 simulated needle directions by 15 degrees posterior and 0 degrees in the images of the volunteers, at least one cord in 19 of 20 volunteers was contacted. This occurred within a needle depth of 6.5 cm. In the sagittal plane of the method the shortest depth to the pleura among all volunteers was 7.5 cm. The MRI study indicates that the new infraclavicular technique may be efficient in reaching a cord of the brachial plexus, often not demanding more than two needle directions. The risk of pneumothorax should be minimal because the needle is inserted no deeper than 6.5 cm. However, this needs to be confirmed by a clinical study. ⋯ A new infraclavicular brachial plexus block method was investigated using magnetic resonance imaging without inserting needles in the volunteers. The study suggests two needle directions for performance of the block and that the risk of lung injury should be minimal. Expectations need to be confirmed by a clinical study.
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Anesthesia and analgesia · Jan 2004
Amiodarone decreases heat, cold, and mechanical hyperalgesia in a rat model of neuropathic pain.
Lidocaine is effective in controlling ventricular dysrhythmia and neuropathic pain. Amiodarone, like lidocaine, has sodium channel blocking properties. In the present study we explore whether amiodarone has a similar effect as lidocaine on the heat, cold, and mechanical hyperalgesia seen in the rat model of neuropathic pain. Ten male Sprague-Dawley rats were anesthetized. Four loose ligatures were placed on the sciatic nerve of the right hindpaw. A sham operation was performed on the contralateral hindpaw (control). Heat hyperalgesia was determined by comparing each paw withdrawal latency to heat stimulation (radiant heat source, 50 degrees C). Cold hyperalgesia was assessed with acetone application. Mechanical hyperalgesia was determined by comparing the mechanical threshold in the ligated and control hind paws using calibrated von Frey filaments. Amiodarone was intraperitoneally administered at doses of 1, 5, 10, 20, 50, and 100 mg/kg after the development of hyperalgesia. The animals were tested for hyperalgesia before and 1, 3, and 24 h after the administration of a single dose of amiodarone. Intrathecal catheters were implanted in 5 new rats, and amiodarone 5 mg/kg was injected. Testing for heat, mechanical, and cold hyperalgesia was performed similarly in the intrathecal amiodarone administration group. Amiodarone produces statistically significant decreases of heat, cold, and mechanical hyperalgesia after intraperitoneal administration. Results are statistically significant at 10 mg/kg (heat hyperalgesia), 20 mg/kg (mechanical hyperalgesia), and 100 mg/kg (cold hyperalgesia) intraperitoneally. Hyperalgesia returns 24 h after a dose. The intrathecal administration of amiodarone produces a nonstatistically significant reduction of hyperalgesia. Amiodarone seems to have a similar effect as lidocaine on the hyperalgesia seen in the rat model of neuropathic pain. As the half-life of amiodarone is significantly longer that that of lidocaine (mean, 53 days versus 90 min) in humans, it may have the potential to provide a longer lasting (and perhaps more effective) effect than lidocaine on neuropathic pain states. ⋯ Amiodarone was found to produce a statistically significant decrease in heat, cold, and mechanical hyperalgesia in a rat model of neuropathic pain after intraperitoneal injection. Considering its long half-life in humans, amiodarone has the potential to provide long lasting pain relief in neuropathic pain states.
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Anesthesia and analgesia · Jan 2004
Ventilation-perfusion distribution related to different inspiratory flow patterns in experimental lung injury.
In acute lung injury (ALI), controlled mechanical ventilation with decelerating inspiratory flow (.V(dec)) has been suggested to improve oxygenation when compared with constant flow (.V(con)) by improving the distribution of ventilation and perfusion (.V(A)/.Q). We performed the present study to test this hypothesis in an animal model of ALI. Furthermore, the effects of combined decelerating and constant flow (Vdot;(deco)) were evaluated. Thus, 18 pigs with experimental ALI were randomized to receive mechanical ventilation with either .V(con), .V(dec) or a fixed combination of both flow wave forms (.V(deco)) at the same tidal volume and positive end-expiratory pressure level for 6 h. Hemodynamics, gas exchange, and .V(A)/.Q distribution were determined. The results revealed an improvement of oxygenation resulting from a decrease of pulmonary shunt within each group (P < 0.05). However, blood flow to lung areas with a normal .V(A)/.Q distribution increased only during ventilation with .V(con) (P < 0.05). Accordingly, PaO(2) was higher with .V(con) than with .V(dec) and .V(deco) (P < 0.05). We conclude that contrary to the hypothesis, .V(con)provides a more favorable .V(A)/.Q distribution, and hence better oxygenation, when compared with .V(dec) and .V(deco) in this model of ALI. ⋯ In acute lung injury, mechanical ventilation with decelerating flow has been suggested to improve ventilation-perfusion distribution when compared with constant flow. We tested this hypothesis in an animal model. Contrary to the hypothesis, we found a more favorable ventilation-perfusion distribution during constant flow when compared with decelerating flow.
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Anesthesia and analgesia · Jan 2004
Reduction in [D-Ala2, NMePhe4, Gly-ol5]enkephalin-induced peripheral antinociception in diabetic rats: the role of the L-arginine/nitric oxide/cyclic guanosine monophosphate pathway.
To test our hypothesis that the abnormally small efficacy of mu-opioid agonists in diabetic rats may be due to functional changes in the L-arginine/nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway, we evaluated the effects of N-iminoethyl-L-ornithine, methylene blue, and 3-morpholino-sydnonimine on [D-Ala(2), NMePhe(4), Gly-ol(5)]enkephalin (DAMGO)-induced antinociception in both streptozotocin (STZ)-diabetic and nondiabetic rats. Animals were rendered diabetic by an injection of STZ (60 mg/kg intraperitoneally). Antinociception was evaluated by the formalin test. The mu-opioid receptor agonist DAMGO (1 microg per paw) suppressed the agitation response in the second phase. The antinociceptive effect of DAMGO in STZ-diabetic rats was significantly less than in nondiabetic rats. N-Iminoethyl-L-ornithine (100 microg per paw), an NO synthase inhibitor, or methylene blue (500 microg per paw), a guanylyl cyclase inhibitor, significantly decreased DAMGO-induced antinociception in both diabetic and nondiabetic rats. Furthermore, 3-morpholino-sydnonimine (200 microg per paw), an NO donor, enhanced the antinociceptive effect of DAMGO in nondiabetic rats but did not change in diabetic rats. These results suggest that the peripheral antinociceptive effect of DAMGO may result from activation of the L-arginine/NO/cGMP pathway and dysfunction of this pathway; also, events that are followed by cGMP activation may have contributed to the demonstrated poor antinociceptive response of diabetic rats to mu-opioid agonists. ⋯ This is the first study on the role of the nitric oxide (NO)/cyclic guanosine monophosphate pathway on [D-Ala(2), NMePhe(4), Gly-ol(5)]enkephalin (DAMGO)-induced peripheral antinociception and the effect of diabetes on this pathway. The study suggests a possible role of DAMGO as a peripherally-acting analgesic drug.
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Anesthesia and analgesia · Jan 2004
Comment Letter Comparative StudyDueling fiberoptic bronchoscope techniques.