Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2003
Clinical TrialThe effect of graded hypothermia (36 degrees C-32 degrees C) on hemostasis in anesthetized patients without surgical trauma.
The isolated effects of hypothermia on hemostasis have not been investigated in healthy humans. We cooled 16 anesthetized patients scheduled for elective intracranial surgery to 32 degrees C body core temperature and assessed prothrombin time (PT), activated partial thromboplastin time, thrombelastogram (TEG), closure time, and platelet count at 36 degrees C, 34 degrees C, and 32 degrees C body core temperature after the induction of anesthesia but before surgical intervention. Activated partial thromboplastin time, hematocrit, and closure time did not change, whereas PT and platelet count decreased during cooling. Platelet count decreased without a decrease in hematocrit; hence, a dilution by administered fluids seemed unlikely. The small decrease of platelet count is probably clinically irrelevant in patients with normal platelet count and function. The small decrease in PT indicates an alteration of the extrinsic pathway of coagulation. TEG measurements showed a delay of clot formation in temperature-adjusted measurements but showed no change if the test temperature was 37 degrees C. This indicates that hypothermia reduces plasmatic coagulation and platelet reactivity. However, the clot strength is not altered by hypothermia. All coagulation variables remained within the normal ranges. Our results may indicate that moderate short-term (4-h) hypothermia has only minor adverse effects in healthy humans. We can make no statement about the effects of hypothermia of longer duration. ⋯ This study investigated the isolated effects of hypothermia in healthy anesthetized humans. We found only minor effects of body temperature reduction to 32 degrees C on assessed coagulation variables, indicating only minor effects in otherwise healthy humans.
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Anesthesia and analgesia · Jun 2003
Case ReportsRight ventricular exclusion surgery for arrhythmogenic right ventricular dysplasia with cardiomyopathy.
The authors describe the management of a patient with arrhythmogenic right ventricular dysplasia treated with right ventricular exclusion surgery.
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Anesthesia and analgesia · Jun 2003
The effect of hypothermia on myogenic motor-evoked potentials to electrical stimulation with a single pulse and a train of pulses under propofol/ketamine/fentanyl anesthesia in rabbits.
In the present study, we investigated the effect of hypothermia on myogenic motor-evoked potentials (MEPs) in rabbits. The influence of stimulation paradigms to induce MEPs was evaluated. Twelve rabbits anesthetized with ketamine, fentanyl, and propofol were used for the study. Myogenic MEPs in response to electrical stimulation of the motor cortex with a single pulse and a train of three and five pulses were recorded from the soleus muscle. After the control recording of MEPs at 38 degrees C of esophageal temperature, the rabbits were cooled by surface cooling. Esophageal temperature was maintained at 35 degrees C, 32 degrees C, 30 degrees C, and 28 degrees C, and MEPs were recorded at each point. MEP amplitude to single- pulse stimulation was significantly reduced with a re-duction of core temperature to 28 degrees C compared with the control value at 38 degrees C (0.8 +/- 0.4 mV versus 2.3 +/- 0.3 mV; P < 0.05), whereas MEP amplitude to train-pulse stimulation did not change significantly during the cooling. MEP latency was increased linearly with a reduction of core temperature regardless of stimulation paradigms. In conclusion, these results indicate that a reduction of core temperature to 28 degrees C did not influence MEP amplitudes as long as a train of pulses, but not a single pulse, was used for stimulation in rabbits under propofol/ketamine/fentanyl anesthesia. ⋯ Intraoperative monitoring of myogenic motor-evoked potentials (MEPs) may be required under hypothermic conditions because of its neuroprotective efficacy. However, data on the influence of hypothermia on myogenic MEPs are limited. The results indicate that multipulse stimulation may be better than single-pulse stimulation when monitoring MEPs during hypothermia.
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Anesthesia and analgesia · Jun 2003
Comparative StudyCutaneous analgesia after transdermal application of amitriptyline versus lidocaine in rats.
Amitriptyline, a tricyclic antidepressant, has potent local anesthetic properties. However, there is no report of cutaneous analgesic effects after transdermal application. We report here that transdermally applied amitriptyline is more potent than lidocaine in providing cutaneous analgesia in rats. Solutions of amitriptyline base in 50, 100, and 500 mM concentrations were applied as a patch to rats, and their effects were compared with those of lidocaine base at the same concentrations and of the vehicle alone (45% water, 45% isopropyl alcohol, and 10% glycerin). Rats in each test group developed a concentration-dependent cutaneous analgesic block in the areas to which the drugs were applied; however, amitriptyline produced a longer block than lidocaine at the same concentration. The development of amitriptyline as a longer-lasting topical analgesic may improve our ability to treat chronic pain, such as neuropathic pain and neuralgia, and to prevent pain in procedures such as venipuncture. ⋯ The tricyclic antidepressant amitriptyline, often used perorally for the management of chronic pain, is shown here to be more potent than lidocaine in providing cutaneous analgesia when applied transdermally with an occlusive dressing in rats.
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Anesthesia and analgesia · Jun 2003
Comparative StudyThe effects of enflurane, isoflurane, and intravenous anesthetics on rat diaphragmatic function and fatigability.
We examined the effect of isoflurane, enflurane, midazolam, ketamine, propofol, and thiopental on diaphragmatic functions under unfatigued and fatigued conditions in 228 rat isolated muscle strips. Diaphragmatic twitch characteristics and tetanic contractions were measured before and after muscle fatigue, which was induced by repetitive tetanic contraction with or without exposure to one of the anesthetics at clinically relevant plasma concentrations, and at 10 and 100 times this concentration, or at 1, 2, and 3 minimum alveolar anesthetic concentration (MAC). Isoflurane, midazolam, ketamine, propofol, and thiopental did not induce a direct inotropic or lusitropic effect under unfatigued and fatigued conditions. Enflurane did not change contraction or relaxation in fresh isolated diaphragm, but enflurane at 2-3 MAC enhanced diaphragmatic fatigability itself and fatigue-induced impairment of twitch characteristics and tetanic tensions. These effects were greater at 3 MAC than at 2 MAC. Our findings suggest that the reduction of diaphragm function previously reported in in vivo experiments using propofol, midazolam, and isoflurane is not related to a direct effect on intrinsic diaphragmatic contractility. Our results also indicate that large concentrations of enflurane may impair the diaphragmatic function at sites other than excitation-contraction coupling. ⋯ Enflurane did not change contraction or relaxation in fresh isolated rat diaphragm, but enhanced diaphragmatic fatigability itself and fatigue-induced impairment of twitch characteristics and tetanic tensions. Isoflurane, midazolam, ketamine, propofol, and thiopental had no direct effects on diaphragmatic functions under unfatigued and fatigued conditions. Isoflurane and these i.v. anesthetics may be advantageous over enflurane to anesthetize and/or sedate patients who are predisposed to diaphragmatic fatigue.