Anesthesia and analgesia
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Anesthesia and analgesia · Feb 1996
The effects of N-methyl-D-aspartate agonists and antagonists on isolated bovine cerebral arteries.
This pharmacologic study examines the direct cerebrovascular effects of N-methyl-D-aspartate (NMDA) receptor agonists and antagonists to determine whether large cerebral arteries have NMDA receptors. Bovine middle cerebral arteries were cut into rings to measure isometric tension development in vitro. Two competitive agonists, L-glutamate and NMDA, each had negligible effects on ring tension in the absence of exogenous vasoconstrictors. ⋯ Three noncompetitive antagonists (S(+)-ketamine, dizocilpine, and dextrorphan) and their steroeisomers (R(-)-ketamine, (-)MK-801, and levorphanol) each produced dose-dependent relaxation of K(+)- or U-46,619-constricted arteries; relaxation was not selective for the (+) or (-) stereoisomers. These results suggest that large cerebral arteries lack NMDA receptors mediating constriction or relaxation. All noncompetitive antagonists dilated cerebral arteries, but by mechanisms that were not stereospecific.
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Anesthesia and analgesia · Feb 1996
Comparative StudyRelationship between end-tidal and arterial carbon dioxide with laryngeal mask airways and endotracheal tubes in children.
The laryngeal mask airway (LMA) is a useful tool for securing the airway in adults and children and may be substituted for an endotracheal tube (ETT) in selected patients undergoing general anesthesia. The correlation between end-tidal and arterial carbon dioxide during controlled ventilation via LMA has not been reported in a within-patient design in pediatric patients. After induction of general anesthesia, 22 children had a LMA placed and mechanical ventilation initiated. ⋯ Analysis of differences between PaCO2 and PETCO2 revealed a bias +/- precision of 4.0 +/- 3.42 and 4.2 +/- 3.66 with ventilation via ETT and LMA, respectively. The root mean square error was 0.85 for the ETT and 0.89 for the LMA. Our results indicate that in infants and children weighing more than 10 kg who are mechanically ventilated via the LMA PETCO2 is as accurate an indicator of PaCO2 as when ventilated via ETT.
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Anesthesia and analgesia · Feb 1996
Responses to nondepolarizing neuromuscular blockers and succinylcholine in von Recklinghausen neurofibromatosis.
Patients with type 1 neurofibromatosis (NF-1) have been reported to have prolonged responses to nondepolarizing (ND) neuromuscular blockers (NMBs). Responses to succinylcholine (SCh) have been described as increased, decreased, or normal. The purpose of this study was to assess responses to NMBs in NF-1 patients in order to determine the clinical significance of abnormal responses. ⋯ Standard milligram per kilogram doses of NMBs were used in all cases, and in none was there evidence of abnormal response. The risk of abnormal response to NMBs in individuals with NF-1 appears to be minimal. We recommend no alteration in dosing of either SCh or ND NMBs in patients with NF-1.
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Anesthesia and analgesia · Feb 1996
Displacement of the endotracheal tube caused by change of head position in pediatric anesthesia: evaluation by fiberoptic bronchoscopy.
Displacement of the endotracheal tube (ETT) caused by flexion and extension of the neck and the placement of a tongue depressor was investigated in 10 small children between the ages of 16 and 19 mo by means of a fiberoptic bronchoscope. The ETT tip moved a mean distance of 0.9 cm toward the carina with flexion and 1.7 cm toward the vocal cords with extension of the neck. After the placement of a tongue depressor, the ETT tip, which had once moved toward the vocal cords with neck extension, was displaced a mean distance of 1.2 cm toward the carina. Our results demonstrate that endobronchial intubation and accidental extubation could occur after significant changes of the head position and careless placement of a tongue depressor in small children.