Anesthesia and analgesia
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Anesthesia and analgesia · Sep 2003
The effect of lidocaine on the globule size distribution of propofol emulsions.
In this study, we sought to determine the globule size distribution of a propofol/lidocaine mixture as a function of lidocaine concentration and time elapsed after mixing in a standard formulation of propofol emulsion (Diprivan) and in a new formulation containing L-lysine to improve stability. The globule size was measured with a laser diffraction technique. The median diameter of the globule size in 20 mL of Diprivan immediately after the addition of 0, 10, 20, 30, 40, and 50 mg of lidocaine was similar to that of chylomicrons, ranging from 0.28 +/- 0.01 micro m to 0.30 +/- 0.02 micro m, over the whole range of lidocaine concentration. ⋯ The maximum globule diameter in the propofol emulsion to which L-lysine was added as a stabilizer did not exceed 3.0 micro m even when the largest amount of lidocaine was added. This study demonstrated that when 30 mg of lidocaine was added to 20 mL of Diprivan and the solution was left for a period of time, the globule size increased. Its increase was minimized by the addition of L-lysine to the propofol emulsion.
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Anesthesia and analgesia · Sep 2003
Epidural clonidine suppresses the baroreceptor-sympathetic response depending on isoflurane concentrations in cats.
Epidural administration of clonidine induces hypotension and bradycardia secondary to decreased sympathetic nerve activity. In this study, we sought to elucidate the change in baroreflex response caused by epidural clonidine. Thirty-six cats were allocated to six groups (n = 6 each) and were given either thoracic epidural clonidine 4 micro g/kg or lidocaine 2 mg/kg during 0.5, 1.0, or 1.5 minimum alveolar anesthetic concentration (MAC) isoflurane anesthesia. ⋯ Epidural clonidine and lidocaine decreased HR, MAP, and CSNA by similar extents. deltaCSNA/deltaMAP and deltaHR/deltaMAP for depressor response were suppressed with epidural lidocaine and clonidine in all groups but the clonidine 0.5 MAC isoflurane group (0.197 +/- 0.053 to 0.063 +/- 0.014 and 0.717 +/- 0.156 to 0.177 +/- 0.038, respectively, by epidural lidocaine [P < 0.05] but 0.221 +/- 0.028 to 0.164 +/- 0.041 and 0.721 +/- 0.177 to 0.945 +/- 0.239, respectively, by epidural clonidine during 0.5 MAC isoflurane). Those for pressor response were suppressed in all groups. We conclude that thoracic epidural clonidine suppresses baroreflex gain during isoflurane anesthesia >1.0 MAC but may offer certain advantages compared with epidural lidocaine during 0.5 MAC isoflurane by virtue of preserving baroreflex sensitivity when inadvertent hypotension occurs.
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Anesthesia and analgesia · Sep 2003
Comparative StudyPulmonary uptake of ropivacaine and levobupivacaine in rabbits.
Local anesthetic toxicity produced by an inadvertent IV injection is attenuated by the pulmonary uptake of local anesthetics. We compared the pulmonary uptake of ropivacaine and levobupivacaine after a bolus injection in rabbits. Sixteen anesthetized rabbits were randomly assigned to either a ropivacaine group or a levobupivacaine group. ⋯ The first-pass uptake of levobupivacaine (31.4% +/- 8.3%; mean +/- SD) was larger than that of ropivacaine (22.9% +/- 5.6%), and the maximum arterial concentration of ropivacaine (21.2 +/- 2.8 micro g/mL) was larger than that of levobupivacaine (18.6 +/- 1.9 micro g/mL). We conclude that the pulmonary uptake of levobupivacaine is larger than that of ropivacaine after a bolus injection. Therefore, the advantages of ropivacaine over levobupivacaine in terms of less cardiovascular toxicity may be offset by the smaller pulmonary uptake after an inadvertent IV injection.
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Anesthesia and analgesia · Sep 2003
Midazolam-induced muscle dysfunction and its recovery in fatigued diaphragm in dogs.
Midazolam, widely used for sedation and anesthesia, decreases contractility in nonfatigued diaphragm; however, its effects on contractility in fatigued diaphragm that are implicated as a cause of respiratory failure have not been established. We therefore studied the effects of midazolam on diaphragm muscle function and recovery in fatigued diaphragm. Dogs were divided into three groups of eight each. ⋯ At 60 min after the cessation of midazolam administration, in Group II, Pdi and Edi recovered from midazolam-induced values (P < 0.05) and returned to fatigued values. In Group III, Pdi and Edi did not change from midazolam-induced values. We conclude that midazolam causes, in a dose-related manner, diaphragm muscle dysfunction in fatigued canine diaphragm and that at a sedative dose, but not at an anesthetic dose, midazolam does not delay its recovery.
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Anesthesia and analgesia · Sep 2003
The effects of surgical case duration and type of surgery on hourly clinical productivity of anesthesiologists.
Surgical duration (hours per case; h/case) and type of surgery (ASA base units per case; base/case) determine the hourly clinical productivity (total ASA units per hour of anesthesia care; tASA/h) for anesthesiology groups. In previous studies, h/case negatively influenced tASA/h, but base/case did not differ significantly. However, when cases are grouped by surgical service, the mean base/case varies. ⋯ The services with the shortest h/case had the highest tASA/h. The accurate prediction of both clinical and billing productivity requires inclusion of both base/case and surgical duration data. Anesthesiology groups should consider surgical duration when making strategic decisions.