Indirect videolaryngoscopy using Macintosh blades in patients with non-anticipated difficult airways results in significantly lower forces exerted on teeth relative to classic direct laryngoscopy: a randomized crossover trial.

BACKGROUND: Videolaryngoscopy has proven advantageous over direct laryngoscopy for a variety of outcome variables, most importantly, making laryngoscopy more successful. We tested whether three videolaryngoscopes (VLS), McGrath® series 5 (Aircraft Medical Ltd, Edinburgh, UK), C-MAC® (Karl Storz, Tuttlingen, Germany) and GlideScope® Cobalt (Verathon Medical, Bothell, WA, USA) exert reduced forces on maxillary incisors and lower teeth, and compared them with a classic Macintosh MAC 3 laryngoscope blade during laryngoscopy. METHODS: In this randomized crossover trial, we included 141 patients (ASA I-III) with non-anticipated difficult airways. They were randomly allocated to undergo direct laryngoscopy and videolaryngoscopy performed with one of three VLS. Primary outcome was the magnitude of forces applied to the maxillary incisors during laryngoscopy. Secondary outcomes were the frequency with which forces were applied, and the magnitude of forces applied to the lower teeth. RESULTS: Forces applied to the maxillary incisors during direct classic laryngoscopy were on average higher than forces applied during videolaryngoscopy. Among the VLS the average force applied was significantly lower for the C-MAC® as compared to the McGrath® and the GlideScope® VLS. The frequency with which a force was applied to the maxillary incisors was significantly lower for the C-MAC®, compared to the other VLS and classic Macintosh laryngoscope. The number of cases in which force was applied to the lower teeth was smallest for the McGrath VLS. CONCLUSION: Forces exerted on maxillary incisors are lower using video-assisted Macintosh blade laryngoscopy compared to classic direct laryngoscopy. The number and magnitude of forces applied to maxillary incisors also differ substantially between different VLS.

Endotracheal intubation using videolaryngoscopy causes less cardiovascular response compared to classic direct laryngoscopy, in cardiac patients according a standard hospital protocol.

INTRODUCTION: Previous studies comparing Glidescope and classic direct laryngoscopy did not show an attenuation of CV responses to endotracheal intubation. In the present study, we hypothesize that indirect videolaryngoscopy can attenuate cardiovascular responses to endotracheal intubation. METHODS: In a randomized cross-over study, eighty adults (ASA PS II-III) were included. Both direct and indirect videolaryngoscopies were used in a random order, in the same patient. Cardiovascular responses to intubation were recorded as a relative change in rate pressure product (RPP = systolic blood pressure times heart rate) from baseline values. A linear mixed model was used to study the association between the outcome variable RPP and the type of laryngoscope used. RESULTS: The relative increase of the RPP at intubation was significantly smaller (i.e. 27%, P < 0.001) using videolaryngoscopy compared to the classic direct laryngoscopy. Cardiovascular responses were blunted by an additional 10.2% (P = 0.029), when the patient was on beta blockade. CONCLUSIONS: Our study shows less hemodynamic responses during endotracheal intubation using indirect videolaryngoscopy compared to classic direct laryngoscopy.

Forces applied to the maxillary incisors by video laryngoscopes and the Macintosh laryngoscope.

BACKGROUND: Modern video laryngoscopes (VLSs) provide a superior view of the glottis, facilitating easier intubations. This study evaluates the forces applied to the maxillary incisors when using various VLSs and a Macintosh blade. METHODS: Fifty consecutive surgery patients were randomly assigned to receive laryngoscopy from a pair of four blades investigated in the study - the VLS GlideScope(®) (Verathon Inc., Bothell, WA, USA), V-Mac™ Storz(®) (Karl Storz, Tuttlingen, Germany), and McGrath™ (Aircraft Medical, Edinburgh, United Kingdom); and the classic Macintosh blade also from Storz(®) (Karl Storz). An endotracheal tube (ETT) was brought into position anterior to the vocal cords, with actual intubation carried out only with the second of the laryngoscopes. Sensors measured the forces directly applied to the patient's maxillary incisors while inserting the ETT. Other common metrics of intubation difficulty (e.g. Mallampati grade, Cormack-Lehane grade, and time) were also recorded. RESULTS: Only one patient was not intubated within the standard study parameters and was converted to the hospital protocols for difficult intubations. The forces applied to the maxillary incisors were significantly greater with the Macintosh blade compared with all VLSs. There were no differences between the VLSs with regard to the forces. Patient characteristics, including Mallampati grade, were not predictive of the forces applied. CONCLUSIONS: All VLSs considered were safer for the patient than was the Macintosh blade in terms of the forces applied to the maxillary teeth, time, number of insertion attempts, and view achieved of the glottic arch. There is a small, but significant, difference in the time and number of insertion attempts required during laryngoscopy with the different VLSs. There was no difference in the forces applied. The geometry of the respective blades may be an important component in the ease of laryngoscopy.

Leucocyte and platelet adhesion in different layers of the small bowel during experimental total warm ischaemia and reperfusion.

BACKGROUND: Ischaemia and reperfusion (IR) of the small bowel is involved in many clinical conditions. A key component in IR-induced tissue damage is microvascular dysfunction. The aim was to investigate the role of leucocytes and platelets in capillary flow impediment and tissue damage. METHODS: Anaesthetized rats were subjected to 30 min warm ischaemia of the small bowel, followed by 1 h reperfusion. To elucidate the influence of leucocytes on platelet adhesion, leucocyte-vessel wall interactions induced by IR were prevented by anti-platelet activating factor (PAF) or anti-intercellular adhesion molecule (ICAM)-1. Intravital videomicroscopy was performed and tissue injury was evaluated histologically. RESULTS: In submucosal venules, IR induced an increase in the median number of interacting leucocytes from 3 to 10 and 20 leucocytes per 100-microm venule segment after 10 and 60 min reperfusion respectively. Anti-PAF or anti-ICAM-1 completely attenuated this increase, resulting in an eightfold improvement in submucosal capillary flow and reduced tissue injury. Shedding of villi no longer occurred. Platelet-vessel wall interactions occurred particularly in submucosal venules, but were not affected by anti-PAF or anti-ICAM-1. CONCLUSION: Small bowel IR initiated an inflammatory and thrombotic response in the submucosal layer only. Attenuation of leucocyte adhesion improved submucosal capillary perfusion, preventing shedding of mucosal villi.

Antibacterial activity of antileukoprotease.

Antileukoprotease (ALP), or secretory leukocyte proteinase inhibitor, is an endogenous inhibitor of serine proteinases that is present in various external secretions. ALP, one of the major inhibitors of serine proteinases present in the human lung, is a potent reversible inhibitor of elastase and, to a lesser extent, of cathepsin G. In equine neutrophils, an antimicrobial polypeptide that has some of the characteristics of ALP has been identified (M. A. Couto, S. S. L. Harwig, J. S. Cullor, J. P. Hughes, and R. I. Lehrer, Infect. Immun. 60:5042-5047, 1992). This report, together with the cationic nature of ALP, led us to investigate the antimicrobial activity of ALP. ALP was shown to display marked in vitro antibacterial activity against Escherichia coli and Staphylococcus aureus. On a molar basis, the activity of ALP was lower than that of two other cationic antimicrobial polypeptides, lysozyme and defensin. ALP comprises two homologous domains: its proteinase-inhibitory activities are known to be located in the second COOH-terminal domain, and the function of its first NH2-terminal domain is largely unknown. Incubation of intact ALP or its isolated first domain with E. coli or S. aureus resulted in killing of these bacteria, whereas its second domain displayed very little antibacterial activity. Together these data suggest a putative antimicrobial role for the first domain of ALP and indicate that its antimicrobial activity may equip ALP to contribute to host defense against infection.

Free cortisol in serum assayed by temperature-controlled ultrafiltration before fluorescence polarization immunoassay.

A method is described for a temperature-controlled ultrafiltration procedure to measure free cortisol in serum. A special thermometer with a sensor was developed, measuring the temperature directly in the ultrafiltration device. The sensor is screwed on the axis of the centrifuge rotor, and the centrifuge is placed in a temperature-controlled box so that the temperature of the sample is kept at 37 degrees C +/- 0.1 degrees C. The overall CV of the free cortisol assay ranges from 2.2% to 11.4%, of which the ultrafiltration contributes only 2.2-3.6%. Increasing amounts of cortisol-binding protein, as found in women using estrogen-containing oral contraceptives, have minor but significant effects on the free cortisol concentrations in serum. Serum free cortisol concentrations in a reference population (n = 114; central 95 percentiles) were 12-43 nmol/L (4-9.5% of total cortisol); in the group of the oral-contraceptive users (n = 27), the reference interval was 11-53 nmol/L (1.5-4.5%).