Jae Hyon Bahk

The laryngeal mask airway in infants and children

Purpose: To compare the effectiveness of various laryngeal mask airway (LMA) sizes and their performance during positive pressure ventilation (PPV) in paralyzed pediatric patients.Methods: Pediatric patients (n=158),<30 kg, ASA 1 or 2 were studied. After paralysis, an LMA of the recommended size was inserted and connected to a volume ventilator. Fibreoptic bronchoscopy (FOB) was performed and graded: 1, larynx only seen; 2, larynx and epiglottis posterior surface seen; 3, larynx, and epiglottis tip or anterior surface seen—visual obstruction of epiglottis to larynx: <50%; 4, epiglottis down-folded, and its anterior surface seen—visual obstruction of epiglottis to larynx: >50%; 5, epiglottis down-folded and larynx not seen directly. Inspiratory and expiratory tidal volumes (VT), and airway pressure were measured by a pneumo-tachometer, and the fraction of leakage (FL) was calculated. In 79 cases, LMA was used for airway maintenance throughout surgery.Results: Successful LMA placement was achieved in 98% of cases: three failures were due to gastric insufflation. For LMA # 1, 1.5, 2, and 2.5, FOB grades [median (range)] were 3(1–5), 3(1–5), 1(1–5) and 1(1–3) respectively. In smaller LMAs, the cuff more frequently enclosed the epiglottis (P<.001). FL of LMA #1 was higher than those of LMA # 1.5 and LMA # 2.5 (P<.05), and FL of LMA # 2 was higher than that of LMA # 2.5 (P<.05). In the 79 patients, the number of patients experiencing complications decreased as LMA size increased (P<.05).Conclusion: Use of the LMA in smaller children results in more airway obstruction, higher ventilatory pressures, larger inspiratory leak, and more complications than in older children.RésuméObjectif: Comparer l’efficacité de masques laryngés (ML) de tailles différentes et leur performance pendant la ventilation à pression positive (VPP) chez des enfants curarisés.Méthode: On a étudié 158 patients pédiatriques, de moins de 30 kg et d’état physique ASA I ou II. Après la curarisation, un ML de taille appropriée a été inséré et raccordé à un ventilateur volumique. La fibroscopie bronchique (FB) réalisée a été graduée: 1, vision du larynx seulement; 2. vision du larynx et de de la surface postérieure de l’épiglotte; 3, vision du larynx, de la pointe et de la surface antérieure de l’épiglotte—vision du larynx obstruée par l’épiglotte: <50%; 4, épiglotte repliée vers le bas et vision de sa surface antérieure—vision du larynx obstruée par l’épiglotte: >50%; 5, épiglotte repliée vers le bas et vision indirecte du larynx. On a mesuré les volumes courants inspiratoire et expiratoire (VT) et la pression des voies aériennes avec un pneumotachomètre et on a calculé le pourcentage de fuite (PF). Dans 79 cas, le ML a été utilisé pour maintenir la perméabilité des voies aériennes tout au long de l’intervention.Résultats: La mise en place réussie du ML a été réalisée dans 98% des cas: trois échecs étaient liés à une insufflation gastrique. Les grades [médiane (intervalle)] de FB ont été, pour les ML 1, 1,5, 2 et 2,5 de 3(1–5), 3(1–5), 1(1–5) et 1(1–3) respectivement. Dans le cas des ML plus petits, le ballonnet couvrait fréquemment l’épiglotte (P<0,001). Le PF du ML 1 a été plus élevé que ceux des ML 1,5 et 2,5 (P<0,05); le PF du ML 2 a été plus élevé que celui du ML 2,5 (P<0,05). Parmi les 79 patients, plus la taille du ML était grande, moins nombreux étaient ceux qui présentaient des complications (P<0,05).Conclusion: L’utilisation du ML chez les jeunes enfants entraine davantage d’obstruction des voies aériennes, des pressions ventilatoires plus élevées, une fuite inspiratoire plus grande et plus de complications que chez les enfants plus agés.

Transesophageal echocardiographic evaluation of ECG-guided central venous catheter placement.

PurposeTo facilitate electrocardiography (ECG)-guided central venous catheter placement by observing the shape and size of the P wave at specific locations of a central venous catheter (CVC)tip.MethodsWe evaluated 54 patients for whom central venous catheterization was planned as part of routine care for their elective surgery. The junction of the superior vena cava (SVC) and the right atrium (RA) was defined as the superior border of the crista terminalis by transesophageal echocardiography. The RA ECGs were recorded while withdrawing the CVC into the SVC or advancing it into the RA at 1 -cm intervals. Saline was used as an electrical conductor via the distal lumen of the CVC.ResultsThe tallest peaked and biphasic P waves [median (interquartile range)] were observed when the CVC tip was located at positions 0.0 cm (-1.0 to 0.0) and -4.0 cm (-5.0 to-3.0) below the SVC/RA junction, respectively. The P wave returned to a normal shape and size at 4.0 cm (3.0 to 4.0) above the SVC/RA junction. Overshoot P waves were observed at — 4.0 cm (-5.0 to -3.0) below the SVC/RA junction in 22 patients, when the CVC tip appeared to be contacting or in close proximity to the RA wall.ConclusionsDuring ECG-guided central venous catheterization, the tallest peaked P wave may be used to place the CVC tip at the SVC/RA junction, the normally-shaped P wave identifies the mid to upper SVC, and biphasic P waves identify RA localization.RésuméObjectifFaciliter la pose d’un cathéter veineux central (CVC) guidée par électrocardiographie (ECG), observant la forme et la taille de l’onde P à des sites spécifiques de la pointe du cathéter.MéthodeNous avons évalué 54 patients après insertion d’un cathéter veineux central, partie des soins courants de l’intervention chirurgicale réglée. La jonction de la veine cave supérieure (VCS) et de l’oreillette droite (OD), définie par échocardiographie transœsophagienne, correspondait au bord supérieur de la crête terminale. Les ECG de l’OD ont été enregistrées lors du retrait du CVC de la VCS ou quand il a été poussé dans l’OD à intervalles de 1 cm. Une solution salée a servi de conducteur électrique passant par la lumière distale du CVC.RésultatsLes ondes P maximales et biphasiques [médiane (écart interquartile)] ont été observées quand la pointe du CVC était respectivement à 0,0 cm (-1,0 à 0,0) et à -4,0 cm (-5,0 à -3,0) sous la jonction VCS/OD. L’onde P a repris une forme et une taille normales à 4,0 cm (3,0 à 4,0) au-dessus de la jonction SVC/OD. Le dépassement des ondes P a été observé à -4,0 cm (-5,0 à -3,0) sous la jonction VCS/OD chez 22 patients au moment où la pointe du CVC paraissait en contact avec la paroi de l’OD ou très près d’elle.ConclusionPendant le cathétérisme veineux central guidé par ECG, l’onde P maximale peut servir à placer la pointe d’un cathéter veineux central à la jonction VCS/OD, l’onde P de forme normale indique la VCS, de son milieu à sa partie supérieure, et l’onde P biphasique situe l’OD.

Comparison of Thoracic Epidural Pressure in the Sitting and Lateral Decubitus Positions

Background:The hanging drop technique identifies the epidural space using the negative pressure of this space. Although the hanging drop technique is popular at the thoracic level, there is still controversy on the negative epidural pressure at this level. The authors hypothesized that the epidural pressure is more consistently negative in the sitting position than in the lateral decubitus position at the thoracic level. Methods:This study compared the epidural pressures of 28 awake patients in the sitting (sitting group, n = 14) or lateral decubitus (lateral group, n = 14) position. The T5–T6 epidural pressure was measured using a closed pressure measurement system connected to a Tuohy needle. Results:All of the thoracic epidural pressures in the sitting group were negative (median, −5 mmHg; range, −18 to −1; mean, −7.2; SD, 6.3), in contrast to the lateral group (median, 5 mmHg; range, −4 to 13; mean, 5.1; SD, 4.4). The thoracic epidural pressure in the sitting group was significantly lower than in the lateral group (P < 0.001). Conclusions:The thoracic epidural pressure is more negative in the sitting position than in the lateral decubitus position. These results suggest that the patient should be sitting when the hanging drop technique is used to identify the epidural space.

The influence of neck flexion and extension on the distribution of contrast medium in the high thoracic epidural space.

BACKGROUND:For safe and effective thoracic epidural analgesia (TEA), it is important to control the level of TEA and to identify factors that influence its spread. In this study, we observed the distribution of contrast injected into the high thoracic epidural space during neck flexion and extension. METHODS:An epidural catheter was inserted into the epidural space until its tip was located at the T1–2 intervertebral level. Patients were randomly allocated to three groups (extension, flexion, and neutral groups), and were injected with 5 mL of contrast when the neck was extended, flexed, or in the neutral position. Extent of contrast spread was determined by counting the number of vertebral body units (VBUs) through lateral epidurography. RESULTS:Forty-two patients were equally allocated to the three groups. Radiographic spreads in the cephalad direction (median) was 1.0, 5.5, and 1.5 VBUs in the extension, flexion, and neutral groups, and spread was greater in the flexion than in the other two groups (P < 0.001). Median radiographic caudal spread was 10.0, 10.0, and 7.0 VBUs in the extension, flexion, and neutral groups, respectively, which was not significantly different among groups (P = 0.145). CONCLUSIONS:Cranial spread of contrast in the high thoracic epidural space is limited. However, neck flexion increases cranial spread. These results suggest that when TEA is high, the tip of the epidural catheter should be located at the upper part of the level to be blocked and that neck flexion may cause an unwanted cervical block.

Rupture of endotracheal tube cuff during robot-assisted endoscopic thyroidectomy -A case report-

We encountered a case of a rupture of an endotracheal tube cuff during robot-assisted thyroid surgery in a 35-year-old male patient. Two hours after commencing surgery, the bellows of the ventilator were not filled and a rupture of the endotracheal tube cuff was suspected. Once the robot-manipulator is engaged, the position of the operating table cannot be altered without removing it from the patient. Reintubation with direct laryngoscopy was performed with difficulty in the narrow space between the patients head and robot-manipulator without moving the robot away from the patient. The rupture of the endotracheal tube cuff was confirmed by observing air bubbles exiting from the balloon in water. The patient was discharged 3 days after surgery without complications. In robot-assisted thyroid surgery, a preoperative arrangement of the robot away from the patients head to obtain easy access to the patient is essential for safe anesthetic care.

Comparison of Needle Insertion and Guidewire Placement Techniques During Internal Jugular Vein Catheterization: The Thin-Wall Introducer Needle Technique Versus the Cannula-Over-Needle Technique.

Objectives:For needle insertion and guidewire placement during central venous catheterization, a thin-wall introducer needle technique and a cannula-over-needle technique have been used. This study compared these two techniques regarding the success rates and complications during internal jugular vein catheterization. Design:Prospective, randomized, controlled study. Setting:A university-affiliated hospital. Patients:Two hundred sixty-six patients scheduled for thoracic surgery, gynecologic surgery, or major abdominal surgery, who required central venous catheterization. Interventions:Patients were randomly assigned to either the thin-wall introducer needle group (n = 134) or the cannula-over-needle group (n = 132). Central venous catheterization was performed on the right internal jugular vein under assistance with real-time ultrasonography. Needle insertion and guidewire placement were performed using a thin-wall introducer needle technique in the thin-wall introducer needle group and a cannula-over-needle technique in the cannula-over-needle group. Measurements and Main Results:The guidewire placement on the first skin puncture was regarded as a successful guidewire insertion on the first attempt. The number of puncture attempts for internal jugular vein catheterization was recorded. Internal jugular vein was assessed by ultrasonography to identify complications. The rate of successful guidewire insertion on the first attempt was higher in the thin-wall introducer needle group compared with the cannula-over-needle group (87.3% vs 77.3%; p = 0.037). There were fewer puncture attempts in the thin-wall introducer needle group than in the cannula-over-needle group (1.1 ± 0.4 vs 1.3 ± 0.6; p = 0.026). There was no significant difference in complications of internal jugular vein catheterization between the two groups. Conclusions:The thin-wall introducer needle technique showed a superior success rate for first attempt of needle and guidewire insertion and required fewer puncture attempts during internal jugular vein catheterization.

Effect-Site Concentration of Remifentanil for Minimizing Cardiovascular Changes by Inhalation of Desflurane

Purpose This study aims to investigate the most appropriate effect-site concentration of remifentanil to minimize cardiovascular changes during inhalation of high concentration desflurane. Materials and Methods Sixty-nine American Society of Anesthesiologists physical status class I patients aged 20-65 years were randomly allocated into one of three groups. Anesthesia was induced with etomidate and rocuronium. Remifentanil was infused at effect-site concentrations of 2, 4 and 6 ng/mL in groups R2, R4 and R6, respectively. After target concentrations of remifentanil were reached, desflurane was inhaled to maintain the end-tidal concentration of 1.7 minimum alveolar concentrations for 5 minutes (over-pressure paradigm). The systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR) and end-tidal concentration of desflurane were measured for 5 minutes. Results The end-tidal concentration of desflurane increased similarly in all groups. The SBP, DBP, MAP and HR within group R4 were not significantly different as compared with baseline values. However, measured parameters within group R2 increased significantly 1-3 minutes after desflurane inhalation. The MAP within group R6 decreased significantly at 1, 2, 4, and 5 minutes (p<0.05). There were significant differences in SBP, DBP, MAP and HR among the three groups 1-3 minutes after inhalation (p<0.05). The incidence of side effects such as hyper- or hypo-tension, and tachy- or brady-cardia in group R4 was 4.8% compared with 21.8% in group R2 and 15.0% in group R6. Conclusion The most appropriate effect-site concentration of remifentanil for blunting hemodynamic responses by inhalation of high concentration desflurane is 4 ng/mL.

Effect of Lumbar Flexion on the Extent of Epidural Blockade

Background and Objectives: This study examined the effect of lumbar flexion on the extent of the epidural block during lumbar epidural anesthesia. Methods: The epidural catheter was introduced at the L3-4 interspace with the patient in the lateral decubitus position with the surgical side down. After administering a test drug (3 mL of 2% lidocaine and 15 &mgr;g of epinephrine), the patients were randomly allocated to 1 of 2 groups: Group F (n = 16, lumbar spine flexed) and Group N (n = 17, lumbar spine in the neutral position). In both groups, 2% lidocaine (16 mL) mixed with sodium bicarbonate (2 mL) was administered through the epidural catheter while the patient maintained the lateral decubitus position with the lumbar spine either flexed or in the neutral position. All the patients maintained their respective positions for 5 minutes and were subsequently turned to the supine position. The pinprick block level and the degree of motor blockade were assessed every 10 minutes for 60 minutes after administering the local anesthetics. A 2-dermatomal difference in uppermost block between groups was determined to be clinically significant. Results: The median difference between groups in the uppermost pinprick block level was only 1.5 dermatomes and it did not satisfy our criteria for clinical significance. There were no significant differences between the 2 groups in the lowermost pinprick block level and the degree of motor block. Conclusions: Lumbar flexion has no clinically relevant effect on sensory spread during epidural anesthesia.

Severe hypoxemia during carinal resection in the lateral position under one-lung ventilation of a non-dependent lung: a case report.

During one-lung ventilation (OLV) in the lateral position, the dependent, ventilated lung receives more blood flow than the non-dependent, non-ventilated lung owing to gravity, improving the match of ventilation and perfusion. Conversely, in the rare clinical situations when OLV is applied to the non-dependent lung, arterial oxygenation can get worse due to considerable shunt flow to the dependent non-ventilated lung. We report a case of severe hypoxemia during carinal resection under OLV of a non-dependent lung. In this case, OLV had to be applied to the non-dependent lung in the lateral position because the bronchus of the non-dependent lung was anastomosed with the trachea, whereas the bronchus of the dependent lung had already been resected for carinal resection. The subsequent hypoxemia resulting from the shunt flow to the dependent non-ventilated lung was treated successfully by ligating the pulmonary artery of the dependent lung.

Preoperative platelet response to collagen is associated with myocardial injury after off-pump coronary bypass graft in patients taking aspirin.

Background We hypothesized that, even in patients taking aspirin, the variance of preoperative platelet response to collagen might be associated with myocardial injury during coronary artery bypass graft (CABG) surgery. Therefore, we evaluated the relationship between preoperative whole-blood aggregometry (WBA) by collagen and the postoperative myocardial injuries. Methods For 44 patients who were scheduled for elective off-pump CABG and taking aspirin, WBA was measured by the impedance method in the presence of collagen (2 mg/ml or 5 mg/ml) as stimulatory agents. After CABG, myocardial injury was evaluated by analysis of the creatine kinase (CK), creatine kinase-MB (CK-MB), and lactate dehydrogenase (LD), and by electrocardiography. Results High response group (n = 13) on preoperative WBA with collagen (2 and 5 mg/ml) showed significantly higher postoperative cardiac enzyme levels (CK, CK-MB and LD) than those of low response group (n = 31). Conclusions In patients who take aspirin and undergoing off-pump CABG, the preoperative platelet response to collagen is correlated with postoperative myocardial injury.