Anesthesia and analgesia
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Anesthesia and analgesia · Dec 1998
The role of the N-methyl-D-aspartic acid receptor in the relaxant effect of ketamine on tracheal smooth muscle.
Ketamine and magnesium (Mg2+), well known bronchodilators, have been used to treat patients with status asthmaticus. Both can block the N-methyl-D-aspartic acid (NMDA) receptor. NMDA receptors exist in the airway, and their activation seems to be linked to the release actions of sensory neuropeptides resulting in increased airway tone. We sought to determine whether ketamine relaxes the guinea pig trachea contracted by histamine by blocking the NMDA receptor. Female guinea pigs (250-400 g) were killed with an overdose of pentobarbital. The trachea was removed and cut spirally into strips 3 mm wide and 15 mm long. The strips were mounted in a 10-mL organ bath filled with Tyrode's solution bubbled through with 95% O2/5% CO2 at 37 degrees C. Strip contractions were measured isometrically with a force displacement transducer. We then studied the effect of NMDA receptor antagonists on histamine-induced tracheal contraction. In this protocol, we examined the effect of ketamine, Mg2+, zinc (Zn2+), or MK-801 (a noncompetitive NMDA receptor blocker) on strips contracted by 10(-5) M histamine. After full contraction was attained, ketamine (0.5-1.5 mM), MgSO4 (2-8 mM), ZnCl2(0.2-0.8 mM), or MK-801 (1.5-6 x 10(-5) M) was added, and the strip tension was measured again. We also studied the effect of NMDA on the relaxation by ketamine. After full contraction by 10(-5) M histamine, 0.5-1.5 mM KET was added alone or in combination with 0.1 mM NMDA, and the strip tension was measured again. Finally, we measured the effect of MK-801 on the relaxant effect of ketamine. After full contraction by 10(-5) M histamine, 0.5-2 mM ketamine was added alone or in combination with 0.75 or 1.5 x 10(-5) M MK-801, and the strip tension was measured again. All NMDA receptor antagonists tested reversed the tracheal contraction induced by histamine in a dose-dependent manner. However, neither the agonist NMDA nor the noncompetitive receptor blocker MK-801 affected tracheal relaxation induced by ketamine. We conclude that ketamine relaxes the tracheal smooth muscle contracted by histamine through a mechanism independent of NMDA receptors. The decreased bronchomotor tone induced by ketamine is probably due to interference with a Ca2+-requiring step necessary to maintain the contraction caused by histamine. ⋯ Stimulation of the N-methyl-D-aspartic acid (NMDA) receptor in the airway results in airway constriction. The bronchodilator ketamine blocks the NMDA receptor. However, ketamine relaxes the guinea pig trachea contracted by histamine through a mechanism independent of the NMDA receptor.
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Anesthesia and analgesia · Dec 1998
Comment Letter Comparative StudyTracheal intubation for awake versus paralyzed infants with pyloric stenosis.
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Anesthesia and analgesia · Dec 1998
Randomized Controlled Trial Comparative Study Clinical TrialPostoperative analgesia with intramuscular morphine at fixed rate versus epidural morphine or sufentanil and bupivacaine in patients undergoing major abdominal surgery.
We assessed the efficacy and side effects of postoperative analgesia with three different pain regimens in 90 patients undergoing major abdominal surgery. The patients were randomly assigned to one of three groups: epidural morphine (EM) or sufentanil (ES), both combined with bupivacaine, or IM morphine (IM) at fixed intervals. Before incision, patients in the epidural groups received sufentanil or morphine in bupivacaine via a thoracic catheter, followed by a continuous infusion 1 h later. General anesthesia consisted of N2O/O2 and isoflurane for all groups. Patients in all groups received IV sufentanil as part of their anesthetic management. Patients in the IM group received IV sufentanil 1 microg/kg before incision, and patients in all groups received sufentanil 10 microg for inadequate analgesia. Postoperatively, the epidural or IM treatment was continued for > or =5 days. Postoperative analgesia at rest and during coughing and movement was significantly better in the epidural groups than in the IM group during the 5 consecutive days. There were no significant differences between the epidural groups. The incidence of most side effects was similar in all groups. We conclude that epidural analgesia provided better pain relief than IM analgesia, even if the latter was optimized by fixed-dose administration at fixed intervals and included adjustments on demand. Epidural sufentanil and morphine, both combined with bupivacaine, seemed to be equally effective with similar side effects. ⋯ Postoperative analgesia with epidural sufentanil or morphine and bupivacaine after major abdominal surgery seemed to be better than the conventional method of IM morphine treatment, despite optimal administration, i.e., fixed doses at fixed intervals with regular adjustments. Analgesic efficacy and side effects of epidural sufentanil and morphine were similar.