Comparison of the Mallampati Classification in Sitting and Supine Position to Predict Difficult Tracheal Intubation: A Prospective Observational Cohort Study.

BACKGROUND: The Mallampati classification (MLPT) is normally evaluated in the sitting position. However, many patients cannot be evaluated in the sitting position for medical reasons. Thus, we compared the MLPT in sitting and supine positions in predicting difficult tracheal intubation (DTI). We hypothesized that the diagnostic accuracy of the MLPT performed in sitting and supine positions would differ. METHODS: We performed a single-center prospective observational study in adult patients who received general anesthesia and orotracheal intubation for noncardiac surgery. During the preanesthesia consultation, the MLPT in the sitting position was recorded. The day of surgery, the MLPT in the supine position and the difficulty of intubation (DTI) were recorded by an independent observer. The diagnostic performance of the MLPT for the prediction of DTI was evaluated in the sitting and supine positions through the area under the receiver operating characteristic (ROC) curve. The performance of the Naguib score in predicting DTI was calculated with the MLPT in sitting and supine positions. RESULTS: Among the 3036 patients, 157 (5.1%) had DTI. The area under the ROC curve for the MLPT in supine position (0.82 [0.78-0.84]) was greater than that for the MLPT in the sitting position (0.70 [0.66-0.75]; P < .001). The relationship between the sitting and supine MLPTs was moderate (Spearman rank correlation coefficient: 0.50; P < .001). The area under ROC curve for predicting DTI by the Naguib score calculated with the supine MLPT (0.78 [95% confidence interval, 0.74-0.82]) was greater than that for the Naguib score calculated with MLPT in the sitting position (0.69 [95% confidence interval, 0.63-0.74)]; P < .001). CONCLUSIONS: The MLPT performed in the supine position is possibly superior to that performed in the sitting position for predicting difficult intubation in adults.

Near-Infrared Spectroscopy Hemoglobin Index Measurement During Fluid Challenge: A Prospective Study in Cardiac Surgery Patients.

OBJECTIVE: Little is known about changes in near-infrared spectroscopy-derived tissue hemoglobin index (HbI). The authors tested the hypothesis that absolute values and changes in brain hemoglobin index (HbIb) and skeletal muscle hemoglobin index (HbIm) could differ from the reference arterial hemoglobin (Hb) during fluid challenge. DESIGN: A prospective, monocenter observational study. SETTING: A 16-bed cardiac surgical intensive care unit in a teaching university hospital. PARTICIPANTS: Fifty consecutive adult patients. INTERVENTIONS: Investigation before and after a fluid challenge. MEASUREMENTS AND MAIN RESULTS: Simultaneous comparative Hb, HbIb and HbIm data points were collected from a blood-gas analyzer and the EQUANOX device (Nonin Medical Inc., Plymouth, MN). Correlations were determined by linear regression. No significant relationship was found between absolute values of Hb and HbIb before (R(2)= 0.04, p = 0.627) and after (R(2) = 0.00006, p = 0.956) fluid challenge. No significant relationship was found between absolute values of Hb and HbIm before (R(2)= 0.030, p = 0.226) and after (R(2) = 0.05, p = 0.117) the fluid challenge. No significant relationship was found between changes in Hb and HbIb (R(2)= 0.26, p = 0.263) and between changes in Hb and HbIm (R(2) = 0.001, p = 0.801) after the fluid challenge. Bland-Altman analysis showed a poor concordance between changes in Hb and HbIb, and changes in Hb and HbIm, with large limits of agreement. CONCLUSIONS: HbIb and HbIm cannot be used to provide continuous noninvasive estimation of Hb, and trends in HbIb and HbIm cannot be considered as noninvasive surrogates for the trend in Hb after cardiac surgery.

Noninvasive assessment of peripheral microcirculation by near-infrared spectroscopy: a comparative study in healthy smoking and nonsmoking volunteers.

Smokers are exposed to early endothelial dysfunction. This microcirculatory damage can be demonstrated by near-infrared spectroscopy (NIRS). The aim of this study was to compare microvascular reactivity by NIRS during a dynamic vascular occlusion test in healthy smokers and nonsmokers volunteers. Twenty healthy volunteers (10 men, 10 women), aged from 22 to 38 years old, were included after approval of the local Ethics Committee and divided into two groups: smokers (n = 10) and nonsmokers (n = 10). Tissue oxygen saturation (StO2) was measured at the level of each individual's calves during an ischemia and reperfusion test. In addition, during the ischemia phase, the slope of decline in StO2 was determined. Therefore, for each group, we were able to deduce the speed of desaturation (ΔStO2/ischemia time). The same was applied for resaturation rates during the reperfusion phase (ΔStO2/reperfusion time). StO2 values were comparable at all experimental steps between smokers and nonsmokers. During the vascular occlusion test, rates of desaturation were the same between smokers and nonsmokers [respectively 3.7%·min(-1) (range 2.5-12.6) and 3.7%·min(-1) (range 1.8-15.1); p = 0.50]. It was the same for the rate of resaturation [smokers 30.4%·min(-1) (range 14.2-51.6) and nonsmokers 30.5%·min(-1) (range 18.6-44.5); p = 0.82]. NIRS study of microvascular reactivity during a dynamic vascular occlusion test did not reveal any difference between smokers and nonsmokers. Therefore, NIRS could not be sensitive enough to highlight endothelial dysfunction in healthy subjects exposed to tobacco smoke.

Dynamic evaluation of near-infrared peripheral oximetry in healthy volunteers: a comparison between INVOS and EQUANOX.

PURPOSE: The present study aimed to compare peripheral regional tissue oxygen saturation (rSO2) values and desaturation/resaturation rates given by INVOS and EQUANOX devices. MATERIALS AND METHODS: Twenty healthy volunteers were investigated during 4 experimental steps: baseline, hyperoxia, ischemia, and reperfusion. For each volunteer, 2 sensors INVOS and 2 sensors EQUANOX were placed on both left and right calves. Blood pressure, heart rate, and peripheral pulse oximetry were monitored. RESULTS: Peripheral rSO2 ranged from 40% to 95% (INVOS) and from 47% to 100% (EQUANOX): 81±12 vs 82±9 (P=.469). A significant relationship was found at baseline between absolute values of INVOS and EQUANOX (n=40; R2=0.159; P=.011). Bias was -0.4%, and limits of agreement were ±15.1%. The percent maximum differences vs baseline values during dynamic maneuvers were 33%±19% (95% confidence interval, 24-42) and 21%±14% (95% confidence interval, 15-28) for INVOS and EQUANOX, respectively. No significant relationship was observed between percent maximum differences in INVOS and EQUANOX (n=20; R2=0.128; P=.122). Rates of desaturation/resaturation during occlusive vascular tests were 3.65% per minute vs 2.36% per minute (P=.027) and 30.42% per minute vs 16.28% per minute (P=.004) for INVOS and EQUANOX, respectively. CONCLUSIONS: INVOS and EQUANOX are not comparable in measuring both absolute values and dynamic changes of peripheral rSO2 and near-infrared spectroscopy-derived parameters during occlusion vascular tests.