Estimation of the nares-to-epiglottis distance and the nares-to-vocal cords distance in young children.

BACKGROUND: Estimation of the nares-to-epiglottis and nares-to-vocal cords distances would facilitate the selection of properly sized nasopharyngeal airways and appropriate positioning of a fibreoptic bronchoscope in young children. The purposes of this study were to measure the nares-to-epiglottis and nares-to-vocal cords distances and to create an algorithm to predict these distances based on anatomical landmarks and paediatric characteristic data. METHODS: Two hundred and eleven children, aged 1-10 yr, undergoing elective surgery were investigated. After induction of general anaesthesia, the distances from the nares to the epiglottis/vocal cords were measured using a nasogastric tube. After intubation, the distances from the lateral border of the nose to the ipsilateral mandible angle (nares-to-mandible distance) and the tragus of the ear (nares-to-tragus distance) were measured using a tape measure. RESULTS: The nares-to-epiglottis and nares-to-vocal cords distances were significantly correlated with the age, weight, height, and external measurements (P<0.001). By stepwise multiple linear regression analysis, formulas were obtained for the nares-to-epiglottis distance (cm)=2.606+0.058×height (cm)+0.231×the nares-to-mandible distance (cm)-0.304 (gender) (r(2)=0.754) and for the nares-to-vocal cords distance (cm)=4.947+0.06×height (cm)+0.228×nares-to-mandible distance (cm)-0.283 (gender) (r(2)=0.803). CONCLUSIONS: The nares-to-epiglottis and nares-to-vocal cords distances can be predicted using the height and the nares-to-mandible distance in young children. CLINICAL TRIAL REGISTRATION NUMBER: Clinical Research Information Service KCT0000150.

Venous flow dynamics during spinal block in normotensive and hypertensive elderly patients: a duplex ultrasonographic study.

BACKGROUND: Spinal block induces hyperkinetic change in lower extremity blood flow. We compared the venous flow dynamic responses to spinal block in normotensive and hypertensive elderly patients. METHODS: Following spinal block using 10 mg 0.5% (w/v) bupivacaine, we measured changes in blood pressure, heart rate, and venous flow dynamics of the popliteal vein by duplex ultrasonography in 20 normotensive (NBP group) and 18 hypertensive (HIBP group) patients. RESULTS: Spinal block caused significant decreases in blood pressure in both groups; similar rates of hypotension were observed. At baseline, peak velocity, time-averaged maximum velocity, and time-averaged mean velocity were higher in the HIBP than in the NBP group. During spinal block, peak velocity increased in both groups, and the between-group differences were no longer significant. At baseline, volume flow in the two groups was similar and increased by 141.5% in the NBP and 131.7% in the HIBP group during spinal block. CONCLUSIONS: Blood pressure and flow dynamics in the popliteal vein showed similar changes during spinal anaesthesia in elderly patients taking antihypertensive medication and normotensive patients, despite differences in baseline values.

Optimum bolus dose of propofol for tracheal intubation during sevoflurane induction without neuromuscular blockade in children.

The purpose of this study was to determine the optimum bolus dose of propofol required to provide excellent conditions for tracheal intubation following inhalational induction of anaesthesia using 5% sevoflurane without neuromuscular blockade. Twenty-eight children, aged three to seven years, requiring anaesthesia for short duration surgery were recruited. Two minutes after beginning the inhalational induction with 5% sevoflurane and 60% nitrous oxide, a predetermined dose of propofol was injected over 10 seconds. Propofol dose was determined using the Dixon's up-and-down method, starting from 3 mg/kg (0.5 mg/kg as a step size). Laryngoscopy was performed 50 seconds after propofol injection. The optimum dose of propofol required for excellent intubating conditions was 1.39 +/- 0.37 mg/kg in 50% of children during inhalation induction using 5% sevoflurane and 60% nitrous oxide in the absence of neuromuscular blocking agents. From probit analysis, the 95% effective dose of propofol was 2.33 mg/kg (95% confidence interval 1.78 to 6.21 mg/kg).

Estimation of teeth-to-vallecula distance for prediction of optimal oropharyngeal airway length in young children.

BACKGROUND: Estimation of teeth-to-vallecula distance would facilitate the selection of properly sized oropharyngeal airways in young children. The aims of the present study were to measure the teeth-to-vallecula distance and to create an algorithm to predict this distance based on anatomical landmarks and patient characteristics in children. METHODS: Two hundred children, aged 1-9 yr, undergoing elective surgery were investigated. After induction of general anaesthesia, the distance from the teeth to the vallecula was measured using a laryngoscope with a straight blade. After intubation, the distances from the mouth angle to the mandible angle and the tragus of the ear were measured with a tape measure. RESULTS: The teeth-to-vallecula distance was significantly correlated with the age, weight, height, and external measurements (P<0.001). By stepwise multiple linear regression analysis, a formula was obtained for the teeth-to-vallecula distance (cm) = 3.998 + 0.017 × age (months)+the mouth-to-mandible distance × 0.286 with a high coefficient of determination (r²=0.764). CONCLUSIONS: The teeth-to-vallecula distance can be predicted using the age and the mouth-to-mandible distance in young children.

Ultrasonographic evaluation of the femoral vein in anaesthetised infants and young children.

We investigated the cross-sectional area of the femoral vein and its relationship to the femoral artery at two anatomical levels, in infants and children. Sixty-six subjects were allocated to one of two groups: infants (< 1 year, n = 31) or children (1-6 years, n = 35). After induction of general anaesthesia, the femoral vein was evaluated by ultrasound with the patients' legs at 30° and 60° of abduction and their hips externally rotated. In each position, measurements were taken at the level of the inguinal crease and 1 cm below the crease. Hip rotation with 60° leg abduction decreased femoral artery overlap at the level of the inguinal crease in both infants (p = 0.013) and children (p = 0.003). Thus, the optimal place for femoral vein cannulation in paediatric patients seems to be at the level of the inguinal crease with 60° leg abduction and external hip rotation.

Effects of skin traction on cross-sectional area of the internal jugular vein in infants and young children.

Internal jugular veins (IJV) are commonly used to obtain central venous access. However percutaneous cannulation of the IJVis difficult in infants and young children because of its diminutive size. The aim of this study was to evaluate the effect of skin traction on the cross-sectional area of the IJV in anaesthetised infants (younger than one year) and young children (one to six years) using ultrasound. Sixty-seven subjects undergoing general anaesthesia were studied. The cross-sectional area of the IJV was measured at the junction of the two heads of the sternocleidomastoid using ultrasound. Skin traction was performed by stretching the skin over the puncture point with pieces of surgical tape in both cephalad and caudad directions. The measurements were made after the induction of anaesthesia with patients in the supine position and with positive pressure ventilation. Skin traction increased the maximum cross-sectional area of the IJV by 39.9 +/- 29.6% in infants and by 33.8 +/- 21.9% in children (P < 0.01). This increase might facilitate easier and safer IJV cannulation in infants and children.

Effects of head rotation on the right internal jugular vein in infants and young children.

We investigated the effects of head rotation on the cross-sectional area of the right internal jugular vein and its relative position to the carotid artery. Eighty-eight subjects were divided into infants and children groups. The cross-sectional area of the right internal jugular vein and the degree of the carotid artery overlap were measured at 0 degrees (neutral), 40 degrees and 80 degrees of head rotation. The cross-sectional area of the right internal jugular vein was significantly larger at 40 degrees and 80 degrees head rotation compared with the neutral position in both infants and children (p < 0.001). As the head was rotated, the percentage overlap of the carotid artery increased significantly (p < 0.001). We suggest that 40 degrees head rotation appears to be optimal for right internal jugular vein cannulation in paediatric patients.

Effects of reverse Trendelenburg position and inguinal compression on femoral vein cross-sectional area in infants and young children.

This study evaluated the effects of the reverse Trendelenburg position and additional inguinal compression on the cross-sectional area of the femoral vein in paediatric patients. Seventy subjects were allocated to two groups: the infants group and the children group. Cross-sectional area of the femoral vein was measured just below the inguinal ligament using ultrasound. Three measurements were obtained for each patient: (i) supine, (ii) reverse Trendelenburg position and (iii) reverse Trendelenburg position with inguinal compression. In the infants group, femoral vein cross-sectional area increased by a mean (SD) of 21.1 (15.2) % in the reverse Trendelenburg position and by 60.7 (30.8) % in the reverse Trendelenburg position with inguinal compression; whereas in the children group, femoral vein cross-sectional area increased by 24.7 (15.8) % in the reverse Trendelenburg position and by 100.3 (50.7) % in the reverse Trendelenburg position with inguinal compression. Inguinal compression in the reverse Trendelenburg position offers a useful means of increasing femoral vein cross-sectional area in paediatric patients.