Anesthesia and analgesia
-
Anesthesia and analgesia · Feb 1996
Randomized Controlled Trial Comparative Study Clinical TrialContinuous hypopharyngeal pH measurements in spontaneously breathing anesthetized outpatients: laryngeal mask airway versus tracheal intubation.
We measured the hypopharyngeal pH to compare the incidence of regurgitation associated with the laryngeal mask airway (LMA) and the tracheal tube (TT) in spontaneously breathing, anesthetized patients. Sixty outpatients scheduled for elective peripheral surgery with a standardized general anesthetic technique were randomly allocated to receive either a LMA (n = 28) or a TT (n = 32) for airway management. A 4-mm pH electrode was placed in the hypopharynx, and pH values were continuously collected and stored in a portable pH data logger system until the end of the operation. ⋯ The hypopharyngeal pH values in both groups were similar, ranging between 5.5 and 7.5, with median values of 5.7 and 6.2 in the LMA and TT groups, respectively. The pH in any given patient did not vary more than 1.0 unit from the initial value recorded at the start of the operation. We conclude that continuous monitoring of the hypopharyngeal pH in spontaneously breathing, anesthetized outpatients failed to detect evidence of pharyngeal regurgitation.
-
Anesthesia and analgesia · Feb 1996
Bupivacaine plasma concentrations during continuous epidural anesthesia in infants and children.
Venous bupivacaine plasma concentrations were measured in six neonates and infants aged 4 days to 3.9 mo (mean, 2.1 mo) and 10 infants and children aged 9 mo to 6 yr (mean, 3.1 yr) after administration of an initial bolus of 0.5 mL/kg bupivacaine 0.25%, followed by a continuous infusion of local anesthetic (0.25 mL.kg-1.h-1) over a period of 4 h (first hour: bupivacaine 0.25%, then reduced to 0.125%). Plasma concentrations of local anesthetic measured at 180 min and 300 min after beginning of bupivacaine administration were significantly higher in younger infants when compared to older infants and children (180 min: 0.67 +/- 0.24 micrograms/mL [0.25-0.97] vs 0.27 +/- 0.11 micrograms/mL [0.19-0.55], P < 0.01; 300 min: 0.86 +/- 0.36 micrograms/mL [0.35-1.25] vs 0.34 +/- 0.12 micrograms/mL [0.18-0.57], P < 0.01). The results of our study show that despite applying the same dosage of epidural bupivacaine significantly higher plasma concentrations were seen after short periods of continuous infusion in infants up to 4 mo than in children older than 9 mo.
-
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.
-
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.