Complications following the use of the Combitube, tracheal tube and laryngeal mask airway.

In a prospective, randomised trial, 75 patients scheduled for routine surgery were randomly allocated to one of three groups to evaluate trauma and postoperative complications after insertion of the Combitube, tracheal tube or laryngeal mask airway. Insertion of the Combitube was associated with a higher incidence of sore throat (48% vs. 16% vs. 12% [p < 0.01]) and dysphagia (68% vs. 12% vs. 8% [p < 0.01]) compared with tracheal intubation or insertion of the laryngeal mask airway, respectively. Hoarseness was significantly less common in both the Combitube and the laryngeal mask groups (both 12%) than in the tracheal tube group (44%; p < 0.01). Haematoma occurred in 36% of the Combitube group compared with 4% in both the laryngeal mask and the tracheal tube groups (p < 0.01). The higher incidence of complications should be considered when using the Combitube.

The kinetic cycle of cardiac troponin C: calcium binding and dissociation at site II trigger slow conformational rearrangements.

The goal of this study is to characterize the kinetic mechanism of Ca2+ activation and inactivation of cardiac troponin C (cTnC), the Ca2+ signaling protein which triggers heart muscle contraction. Previous studies have shown that IAANS covalently coupled to Cys84 of wild-type cTnC is sensitive to conformational change caused by Ca2+ binding to the regulatory site II; the present study also utilizes the C35S mutant, in which Cys84 is the lone cysteine, to ensure the specificity of IAANS labeling. Site II Ca2+ affinities for cTnC-wt, cTnC-C35S, cTnC-wt-IAANS2, and cTnC-C35S-IAANS were similar (KD = 2-5 microM at 25 degrees C; KD = 2-8 microM at 4 degrees C), indicating that neither the IAANS label nor the C35S mutation strongly perturbs site II Ca2+ affinity. To directly determine the rate of Ca2+ dissociation from site II, the Ca2+-loaded protein was rapidly mixed with a spectroscopically sensitive chelator in a stopped flow spectrometer. The resulting site II Ca2+ off-rates were k(off) = 700-800 s(-1) (4 degrees C) for both cTnC-wt and cTnC-C35S, yielding calculated macroscopic site II Ca2+ on-rates of k(on) = k(off)/KD = 2-4 x 10(8) M(-1) s(-1) (4 degrees C). As observed for Ca2+ affinities, neither the C35S mutation nor IAANS labeling significantly altered the Ca2+ on- and off-rates. Using IAANS fluorescence as a monitor of the protein conformational state, the intramolecular conformational changes (delta) induced by Ca2+ binding and release at site II were found to be significantly slower than the Ca2+ on- and off-rates. The conformational rate constants measured for cTnC-wt-IAANS2 and cTnC-C35S-IAANS were k(delta on) = 120-210 s(-1) and k(delta off) = 90-260 s(-1) (4 degrees C) . Both conformational events were slowed in cTnC-wt-IAANS2 relative to cTnC-C35S-IAANS, presumably due to the bulky IAANS probe coupled to Cys35. Together, the results provide a nearly complete kinetic description of the Ca2+ activation cycle of isolated cTnC, revealing rapid Ca2+ binding and release at site II accompanied by slow conformational steps that are likely to be retained by the full troponin complex during heart muscle contraction and relaxation.