Forces applied by the laryngoscope blade onto the base of the tongue and their relation with postoperative sore throat

The forces applied by the laryngoscope blade onto the base of the tongue have been measured indirectly by some investigators. The relation between these forces and postoperative sore throat has not been studied previously. The aim of this study was to directly measure the forces applied by the tip of the laryngoscope blade onto the base of the tongue and its relation to incidence and severity of sore throat. One hundred patients, 18-65 years old, all candidates for abdominal or lower limb operations under general anesthesia were selected. Maximum and mean force, laryngoscopic time and force-time product were measured using a modified macintosh laryngoscope blade during laryngoscopy. The occurrence and severity of postoperative sore throat were determined after operation using visual analogue scale. Data were analyzed statistically using t-test and Spearman's correlation coefficient. The laryngoscopic time was 10.57 +/- 1.66 seconds, the maximum force was 61.56 +/- 8.07 N, the mean force and force - time product were 38.29 +/- 6.74 N and 404.72 +/- 71.24 N.S. respectively. There was a positive correlation between sore throat intensity, its maximum intensity maximum and mean forces. This study showed that these forces were higher than those of previous reports. Instant forces applied by the laryngoscope blade may be a more important factor than duration of applied forces regarding the severity of postoperative sore throat

Effect of digital block on pulse oximeter signal detection during general anesthesia

Pulse oximetry is dependent upon the presence of a pulsating vascular bed. Low pulsatile blood flow in the digits is caused by various factors. Regardless of the cause, if there is sufficient arterial pulse pressure, blocking the sympathetic nerve should cause a local increase in capillary flow and pulse volume. This study was performed to evaluate the effect of digital nerve block on pulse oximetric signal detection [SpO2, Lag time and amplitude of plethismographic wave] during general anesthesia. After induction of general anesthesia in 105 patients, SpO2, Lag time and amplitude of plethismographic wave in index fingers of two hands were determined by pulse oximeter. Then 2 ml of 2% lidocaine was injected to index fingers of one hand and these parameters were determined at 10, 20, 30, 40 and 60 minutes after digital nerve block, in blocked and unblocked fingers. The data were compared between two groups. Mean lag time of plethismographic wave in 10, 20, 30, 40 and 60 minutes after digital block was shorter in blocked fingers than unblocked fingers [p<0.05]. Mean amplitude of plethismographic wave in these times after digital block was greater in blocked fingers than unblocked fingers [p<0.05]. No statistical difference in SpO2 was determined between blocked and unblocked fingers. In conclusion, the digital block is an effective and safe technique for better pulse oximetric signal detection during general anesthesia. Short lag time and high amplitude of plethismographic wave probably can facilitate the accuracy of SpO2 calculation and therefore rapid detection of hypoxemia