Hypersensitivity Reaction to Perioperative Drug Mistaken for Local Anesthetic Systemic Toxicity in a Patient under Brachial Plexus Block / 고신대학교의과대학학술지

Perioperative anaphylaxis, although rare, is a severe, life-threatening unexpected systemic hypersensitivity reaction. Simultaneous administration of various drugs during anesthesia, the difficulty of communicate with patients in sedation and anesthesia, and coverage of the patient with surgical drapes are considered to be factors that impede early recognition of anaphylactic reactions. It is very important to perform an intradermal skin test because antibiotics are the most common cause of perioperative anaphylaxis. We report a case of negative-intradermal skin test antibiotic anaphylaxis mistaken for local aesthetic systemic toxicity without increase of serum tryptase for confirmative diagnostic biomaker during surgery under brachial plexus block. It is not possible to exclude the danger of anaphylaxis completely, even if it is negative-intradermal skin test and normal tryptase level. Therefore, anesthesiologists should be closely monitored and treated early for antibiotics related hypersensitive reaction, like other medicines during anesthesia.

Influence of the Phase of Menstrual Cycle on Postoperative Nausea and Vomiting after Breast Cancer Surgery / 이화의대지

OBJECTIVES: The phase of the menstrual cycle was demonstrated to have an influence on the incidence of postoperative nausea and vomiting (PONV) after gynecologic laparoscopic surgery, but little was known for breast surgery, which was shown to have relatively higher incidence of PONV, >60%. We performed this study to investigate the influence of the phase of menstrual cycle on PONV after breast cancer surgery. METHODS: A total of 103 patients, who were scheduled for breast cancer surgery under general anesthesia, were recruited, and patients with irregular menstrual cycles, history of previous history of PONV were excluded. Groups were divided in two ways as follows: 1) gynecologic classification: premenstrual and menstrual (days 25 to 6), follicular (days 8 to 12), ovulation (days 13 to 15), and luteal phase (days 20 to 24); 2) menstrual classification: menstrual (days 1 to 8) and non-menstrual (days 9 to 28). PONV were recorded using Rhodes index of nausea, vomiting and retching at postoperative 6 and 24 hours. RESULTS: The overall incidence of PONV during postoperative 24 hours was 35.4%. At the menstrual classification, the incidence of PONV at postoperative 24 hours was higher in the menstrual group than that in the non-menstrual group (16.7% vs. 4.2%, P=0.057). The severity of PONV, measured with Rhodes index of nausea, vomiting and retching was significantly different between menstrual and non-menstrual groups (P=0.034). CONCLUSION: The duration and severity of the PONV after breast cancer surgery were demonstrated to be prolonged and aggravated during menstruation, respectively. Therefore, consideration of menstrual cycle for scheduling breast cancer surgery could effectively prevent the PONV and reduce medical cost.

Changes in Serum Concentrations of Insulin-like Growth Factor Binding Protein-3 after General Anesthesia Using Propofol or Isoflurane / 이화의대지

OBJECTIVES: The insulin-like growth factor binding proteins (IGFBP) regulate the bioavailability and bioactivity of insulin-like growth factor. We aimed to evaluate whether the IGFBP-3 level undergo major changes during perioperative periods according to the different kind of anesthetic agents. METHODS: Eighteen adults scheduled for elective total abdominal hysterectomy were enrolled. The patients were randomly assigned to have either propofol or isoflurane for maintenance of general anesthesia. A venous sample was taken for analysis of IGFBP-3 at the following time points: before induction, at the time of peritoneal closure, 1 hour after extubation at recovery room, and 2 and 5 postoperative days. The samples were analyzed by enzyme linked immunosolvent assay. RESULTS: Demographic data were similar between groups. In the both groups, the IGFBP-3 concentration decreased after anesthesia induction, reaching a nadir at the time of peritoneal closure without a significant difference between groups. In analysis between groups, the IGFBP-3 concentration in the isoflurane group on the postoperative 5th day was recovered to preoperative value and significantly higher than that in the propofol group (P < 0.05). CONCLUSION: This is the first study to show that the anesthetics used for general anesthesia affect the IGFBP-3 level during perioperative periods. The decrease of IGFBP-3 level following anesthesia induction in the isoflurane group was recovered to preoperative value, whereas that observed in the propofol group was not recovered on the postoperative 5th day. Further study is needed to establish the definitive effect of general anesthetics on IGFBP-3 and provide a comprehensive interpretation.

Retrospective Analysis of Difficult Intubation / 이화의대지

OBJECTIVES: We analyzed retrospectively incidence, management, and predictors of difficult intubation, which have been known through practical cases. METHODS: A total of 217 cases of difficult intubation (DI) between 2010 and 2014 were investigated. Risk factors such as age, body mass index, Mallampati score, thyromental distance, degree of mouth opening and range of neck motion, Cormack-Lehane grade, intubation and airway management techniques were investigated. The cases of each department were analyzed and the airway management techniques according to simplified risk scores (SRS) were also investigated. RESULTS: The average incidence of DI was 0.49%. Patients undergoing surgery in the departments of oro-maxillo-facial surgery (1.35%), ophthalmologic surgery (0.96%), urologic surgery (0.80%), and head and neck surgery of ear-nose-throat (0.62%) showed the higher incidence of DI. Difficult mask ventilation (10 of 217, 4.6%) was occurred with DI. Higher SRS were related to high rates of video laryngoscope use and fiberoptic guided intubation. There was a decrease in the use of McCoy blades after 2013, an increase in the use of video laryngoscope, and a consistent rate of fiberoptic intubation. CONCLUSION: It is not easy to check all the predictors of DI in a preanesthetic evaluation and the predictors are not accurate. The role of clinical preparation and practical management is important, and the most important thing is to establish a planned induction strategy. Multiple factors system, such as simplified risk factors should be used to evaluate patients to prepare for appropriate airway management techniques in case of DI.

Dyspnea due to Residual Neuromuscular Blockade in Elderly Patient with Unrecognized Pre-existing Unilateral Vocal Cord Paralysis / 이화의대지

Muscle relaxation using neuromuscular blocking agent is an essential process for endotracheal intubation and surgery, and requires adequate recovery of muscle function after surgery. Residual neuromuscular blockade is defined as an insufficient neuromuscular recovery that can be prevented by confirming train-of-four ratio >0.9 using objective neuromuscular monitoring. Sugammadex, a novel selective relaxant-binding agent, produces rapid and effective reversal of rocuronium-induced neuromuscular blockade. We report a case of the residual neuromuscular blockade accompanying dyspnea and stridor after general anesthesia in an unrecognized pre-existing symptomless unilateral vocal cord paralysis patient, who had experienced the disappearance of dyspnea and stridor after administration of sugammadex.

Ultrasound measurement of the vertebral level of Tuffier's line in elderly women / 대한마취과학회지

BACKGROUND: It would be imprecise to generalize the vertebral level determined by palpation to patients of all ages. The purpose of this study was to compare the vertebral level passed by Tuffier's line in elderly women with that passed in adult women using ultrasound in the left lateral decubitus flexed position. METHODS: We enrolled 50 female patients over the age of 65 (elderly group) and 50 female patients between ages 20 and 50 (control group) who had been scheduled to undergo spinal anesthesia. Using ultrasound, we marked the L2–5 lumbar spinous processes and intervertebral spaces. The most cephalad part was labeled 1 and the most caudal part was labeled 11. We then identified which line of these vertebral levels Tuffier's line crossed. RESULTS: The median value of the numbers signifying the vertebral level of Tuffier's line was 3 (the L2–3 intervertebral space) in the elderly group, while it was 8 (the lower part of the L4 vertebra) in the control group. The vertebral level of Tuffier's line had statistically significant correlations with age, body mass index, and weight in the elderly group (P < 0.001). CONCLUSIONS: The vertebral level of Tuffier's line determined with ultrasound measurement in the left lateral decubitus flexed position was more cephalad in the elderly women than in those of the control group. Therefore, we should consider that the needle could be inserted at a higher level than expected, and use care in determining the level of needle insertion during spinal anesthesia in elderly women.

Comparison of Ultrasound-Guided Axillary Brachial Plexus Block Techniques: Perineural Injection versus Single or Double Perivascular Infiltration

PURPOSE: We compared three methods of ultrasound-guided axillary brachial plexus block, which were single, and double perivascular (PV) infiltration techniques, and a perineural (PN) injection technique. MATERIALS AND METHODS: 78 patients of American Society of Anesthesiologists physical status I-II undergoing surgery of the forearm, wrist, or hand were randomly allocated to three groups. 2% lidocaine with epinephrine 5 microg/mL was used. The PN group (n=26) received injections at the median, ulnar, and radial nerve with 8 mL for each nerve. The PV1 group (n=26) received a single injection of 24 mL at 12-o'clock position of the axillary artery. The PV2 group (n=26) received two injections of 12 mL each at 12-o'clock and 6-o'clock position. For all groups, musculocutaneous nerve was blocked separately. RESULTS: The PN group (391.2+/-171.6 sec) had the longest anesthetic procedure duration than PV1 (192.8+/-59.0 sec) and PV2 (211.4+/-58.6 sec). There were no differences in onset time. The average induction time was longer in PN group (673.4+/-149.6 sec) than PV1 (557.6+/-194.9 sec) and PV2 (561.5+/-129.8 sec). There were no differences in the success rate (89.7% vs. 86.2% vs. 89.7%). CONCLUSION: The PV injection technique consisting of a single injection in 12-o'clock position above the axillary artery in addition to a musculocutaneous nerve block is equally effective and less time consuming than the PN technique. Therefore, the PV technique is an alternative method that may be used in busy clinics or for difficult cases.

The Effect of Stellate Ganglion Block on Intractable Lymphedema after Breast Cancer Surgery

Lymphedema of the upper limb after breast cancer surgery is a disease that carries a life-long risk and is difficult to cure once it occurs despite the various treatments which have been developed. Two patients were referred from general surgery department for intractable lymphedema. They were treated with stellate ganglion blocks (SGBs), and the circumferences of the mid-point of their each upper and lower arms were measured on every visit to the pain clinic. A decrease of the circumference in each patient was observed starting after the second injection. A series of blocks were established to maintain a prolonged effect. Both patients were satisfied with less swelling and pain. This case demonstrates the benefits of an SGB for intractable upper limb lymphedema.

The degree of labor pain at the time of epidural analgesia in nulliparous women influences the obstetric outcome / 대한마취과학회지

BACKGROUND: The increased pain at the latent phase can be associated with dysfunctional labor as well as increases in cesarean delivery frequency. We aimed to research the effect of the degree of pain at the time of epidural analgesia on the entire labor process including the mode of delivery. METHODS: We performed epidural analgesia to 102 nulliparous women on patients' request. We divided the group into three based on NRS (numeric rating scale) at the moment of epidural analgesia; mild pain, NRS 1-4; moderate pain, NRS 5-7; severe pain, NRS 8-10. The primary outcome was the mode of delivery (normal labor or cesarean delivery). RESULTS: There were significant differences in the mode of delivery among groups. Patients with severe labor pain had a significantly higher cesarean delivery compared to patients with moderate labor pain (P = 0.006). The duration of the first and second stage of labor, fetal heart rate, use of oxytocin and premature rupture of membranes had no differences in the three groups. CONCLUSIONS: Our research showed that the degree of pain at the time of epidural analgesia request might influence the rate of cesarean delivery. Further research would be necessary for clarifying the mechanism that the augmentation of pain affects the mode of delivery.

Vertebral level of Tuffier's line measured by ultrasonography in parturients in the lateral decubitus position / 대한마취과학회지

BACKGROUND: It is known that Tuffier's line intersects the spine at the L4 spinous process or at the L4-L5 intervertebral space. Full term parturient women undergo various physical changes. Therefore, determining the vertebral level with Tuffier's line based on palpation inevitably is not very accurate. The aim of this study was to use ultrasound to verify the difference between vertebral levels for the palpated Tuffier's line in parturient and non-parturient women in the lateral decubitus position. METHODS: We consecutively enrolled 40 parturient women at 37-41 weeks of gestation and 40 non-parturient women scheduled for regional anesthesia. In the left lateral position, the location of the vertebra was identified using ultrasonography. We marked every intervertebral space from L5 to L2 vertebra, divided each spinous process into two equal parts, and numbered the spaces sequentially from 1 to 9. We drew a Tuffier's line by palpating, recorded the vertebral level that this line intersected. RESULTS: The mean value of an arbitrary number of vertebral level of Tuffier's line was 6.4 +/- 0.9 in the non-pregnant group and this represents L4-lower vertebral level. In the pregnant group, the mean value was 3.0 +/- 1.0 which represents L3-lower vertebral level. There was a significant difference between the two groups (P < 0.05). CONCLUSIONS: We compared using an available ultrasound technique the vertebral levels intersected by the palpated Tuffier's line between parturient and non-parturient women and found that the vertebral levels were more cephalad in the parturient women compared to the non-parturient women.

Double-injection perivascular ultrasound-guided axillary brachial plexus block according to needle positioning: 12 versus 6 o'clock position of the axillary artery / 대한마취과학회지

BACKGROUND: We conducted prospective, randomized, observer-blinded trial to compare two double-injection perivascular (PV) ultrasound-guided techniques of axillary brachial plexus block (BPB). METHODS: American Society of Anesthesiologists physical status I-II, 50 patients undergoing surgery of the forearm, wrist or hand were randomly allocated to two groups. For PV12 group, injection was carried out at the 12 o'clock position using 24 ml of 2% lidocaine. Patients of PV6 group got their injection of 24 ml of 2% lidocaine at direction of 6 o'clock of axillary artery. For all 2 groups, the musculocutaneous nerve was identified and 5 ml of 2% lidocaine was deposited around the nerve. The performance time and the onset time were recorded. The induction time (sum of performance and onset time), the success rate of the block, the need rate of rescue block, and incidence of adverse events was compared. RESULTS: The success rate was same (84%) in two groups. The performance time, onset time, and induction time showed no differences between two groups. There were no differences in vessel puncture, paresthesia, and numbness. CONCLUSIONS: Double-injection perivascular ultrasound-guided axillary BPB can be performed at 12 o'clock or 6 o'clock position of axillary artery, and performer may choose needle targeting position by considering surgery site. Thus perivascular double-injection technique may be an alternative method for axillary BPB and useful in case of difficult block.

Anesthetic Management for Lung Adenocarcinoma Experienced Acute Neurocardiogenic Syncope and Cardiac Arrest / 이화의대지

Vasovagal syncope is one of the most common causes of transient syncope during anesthesia for elective surgery in patients with a history of syncope and requires special attention and management of anesthetics. The causes and pathophysiological mechanism of this condition are poorly understood, but it has a benign clinical course and recovers spontaneously. However, in some cases, this condition may cause cardiovascular collapse resulting in major ischemic organ injury and be life threatening. Herein we report a case and review literature, regarding completing anesthesia safely during an elective surgery of a 59-year-old female patient with history of loss of consciousness due to suspected vasovagal syncope followed by cardiovascular collapse and cardiac arrest, which required cardiopulmonary resuscitation and insertion of a temporary pacemaker and intra-aortic balloon pump immediately after a fine-needle aspiration biopsy of a lung nodule located in the right middle lobe.

Hypertensive crisis during percutaneous radiofrequency ablation of a metastatic adrenal tumor under general anesthesia: A case report

Radiofrequency ablation (RFA) has been used as an alternative method of surgical treatment to treat neoplasms of variable body organs. In considerable proportion of RFA cases, anesthesiologists are asked to conduct general anesthesia. RFA has been known to be a safe and effective treatment, however injury to adjacent normal tissue during RFA develops serious complications. In particular, unintended injury to normal adrenal tissue of adrenal tumors can cause severe complications such as hypertensive crisis due to excessive secretion of catecholamine. However, serious complications of primary or metastatic adrenal tumors have been rarely reported due to RFA. We report a case of hypertensive crisis with associated tachycardia and ventricular arrhythmia during RFA of hepatocellular carcinoma metastatic to the adrenal gland.

Is small tidal volume with low positive end expiratory pressure during one-lung ventilation an effective ventilation method for endoscopic thoracic surgery? / 대한마취과학회지

BACKGROUND: The present study will focus on the rationale for the use of small tidal volume with 6 cmH2O positive end expiratory pressure (PEEP) with the changes of arterial oxygen tension, plateau airway pressure, and static lung compliance during one lung ventilation for endoscopic thoracic surgery. METHODS: Forty-three patients were intubated with a double-lumen endobronchial tube. After positioning the patients in the lateral decubitus, one-lung ventilation was started with 100% oxygen, tidal volume 10 ml/kg without PEEP; arterial oxygen tension, plateau airway pressure, and static compliance were checked as baseline values (T0). Fifteen minutes later, same parameters were measured (T15). The tidal volume had changed to 6 ml/kg with 6 cmH2O PEEP. Fifteen minutes later, the same parameters were measured (T30). RESULTS: Oxygen tension had decreased at T15 (282.1 +/- 83.4 mmHg) compared to T0 (477.2 +/- 82.4 mmHg) (P < 0.0001), but was maintained at T30 (270.4 +/- 81.9 mmHg). There was no difference in peak inspiratory pressure at T15 or T30 compared to T0, plateau airway pressure was increased at T15 and T30 (P < 0.05) and static lung compliance was decreased at T15 and T30 (P < 0.0001). CONCLUSIONS: In carrying out one-lung ventilation for thoracic surgery using an endoscope, the addition of a PEEP of 6 cmH2O in the dependent lung, while reducing the tidal volume of 6 ml/kg, both oxygen tension and lung compliance are maintained without increasing the plateau airway pressure. Protective lung ventilation is useful for one lung ventilation.

Topographic pattern of the brachial plexus at the axillary fossa through real-time ultrasonography in Koreans / 대한마취과학회지

BACKGROUND: The ability to explore the anatomy has improved our appreciation of the brachial anatomy and the quality of regional anesthesia. Using real-time ultrasonography, we investigated the cross-sectional anatomy of the brachial plexus and of vessels at the axillary fossa in Koreans. METHODS: One hundred and thirty-one patients scheduled to undergo surgery in the region below the elbow were enrolled after giving their informed written consent. Using the 5-12 MHz linear probe of an ultrasound system, we examined cross-sectional images of the brachial plexus in the supine position with the arm abducted by 90degrees, the shoulder externally rotated, and the forearm flexed by 90degrees at the axillary fossa. The results of the nerve positions were expressed on a 12-section pie chart and the numbers of arteries and veins were reported. RESULTS: Applying gentle pressure to prevent vein collapse, the positions of the nerves changed easily and showed a clockwise order around the axillary artery (AA). The most frequent positions were observed in the 10-11 section (79.2%) for the median, 1-2 section (79.3%) for the ulnar, 3-5 section (78.4%) for the radial, and 8-9 section (86.9%) for the musculocutaneous nerve. We also noted anatomical variations consisting of double arteries (9.2%) and multiple axillary veins (87%). CONCLUSIONS: Using real-time ultrasonography, we found that the anatomical pattern of the major nerves in Koreans was about 80% of the frequent position of individual nerves, 90.8% of the single AA, and 87% of multiple veins around the AA.

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.

Analysis of predictive factors for difficult ProSeal laryngeal mask airway insertion and suboptimal positioning

BACKGROUND: There has been controversy about predicting difficult LMA insertion and suboptimal position. Our aim was to evaluate bedside predictors for difficult LMA ProSeal(TM) (PLMA) insertion and suboptimal position. METHODS: As the potential predictive factors for difficult PLMA insertion and suboptimal position, we considered male gender, increased body mass index (BMI), seven individual items suggesting difficult airway [modified Mallampati classification > or = III, inter-incisor distance or = moderate, upper lip bite test (ULBT) > or = II] and > or = 3 of total airway score which is the sum of scores assessed by a score of 0, 1, 2 in seven individual items. The PLMA position was assessed by fiberoptic bronchoscopy to determine whether these predictors predict suboptimal position of PLMA (fiberoptic score or = 3 indicates suboptimal position of PLMA.

Direction of catheter insertion and the incidence of paresthesia during continuous epidural anesthesia in the elderly patients / 대한마취과학회지

BACKGROUND: Continuous epidural anesthesia is useful for endoscopic urologic surgery, as mostly performed in the elderly patients. In such a case, it is necessary to obtain successful sacral anesthesia, and the insertion of epidural catheter in the caudad direction may be needed. However, continuous epidural catherization has been related to paresthesias. This study aimed to evaluate the effects of the direction of the catheter insertion on the incidence of paresthesias in the elderly patients. METHODS: Two hundred elderly patients scheduled for endoscopic urologic surgery were enrolled. The epidural catheter was inserted at L2-3, L3-4, and L4-5 using the Tuohy needle. In Group I (n = 100), the Tuohy needle with the bevel directed the cephalad during the catheter insertion. In Group II (n = 100), it directed the caudad. During the catheter insertion, an anesthesiologist evaluated the presence of paresthesias and the ease or difficulty during the catheter insertion. RESULTS: In Group I (n = 97), 15.5% of the patients had paresthesias versus 18.4% in Group II (n = 98), and there was no significant difference between the two groups. In paresthesia depending on the insertion site and the ease or difficulty during the catheter insertion, there were no significant differences between the two groups. CONCLUSIONS: Our results concluded that the direction of epidural catheter insertion did not significantly influence the incidence of paresthesias in the elderly patients.

Clinical comparisons of 0.5% and 0.375% levobupivacaine for ultrasound-guided axillary brachial plexus block with nerve stimulation / 대한마취과학회지

BACKGROUND: In an axillary brachial plexus block (ABPB), where relatively large doses of local anesthetics are administered, levobupivacaine is preferred due to a greater margin of safety. However, the efficacy of levobupivacaine in ABPB has not been studied much. We performed a prospective, double-blinded study to compare the clinical effect of 0.375% levobupivacaine with 0.5% levobupivacaine for ultrasound (US)-guided ABPB with nerve stimulation. METHODS: Forty patients undergoing elective upper limb surgery were randomized into two groups: Group I (0.375% levobupivacaine) and Group II (0.5% levobupivacaine). All four main terminal nerves of the brachial plexus were blocked separately with 7 ml of levobupivacaine using US guidance with nerve stimulation according to study group. A blinded observer recorded the onset time for sensory and motor block, elapsed time to be ready for surgery, recovery time for sensory and motor block, quality of anesthesia, patient satisfaction and complications. RESULTS: There were no significant differences in the time to find nerve locations, time to perform block and number of skin punctures between groups. Insufficient block was reported in one patient of Group I, but no failed block was reported in either group. There were no differences in the onset time for sensory and motor block, elapsed time to be ready for surgery, patient satisfaction and complications. CONCLUSIONS: 0.375% levobupivacaine produced adequate anesthesia for ABPB using US guidance with nerve stimulation, without any clinically significant differences compared to 0.5% levobupivacaine.

Preoxygenation in pediatric patients

BACKGROUND: Preoxygenation with tidal volume breathing for 3 min is a standard technique using 100% oxygen for prevention of hypoxia during the induction of general anesthesia. The measurement of end tidal oxygen concentration is useful in preoxygenation monitoring. The aim of the study was to determine the effects of preoxygenation in pediatric patients during 3 min with tidal volume breathing. METHODS: Sixty patients who were scheduled for general surgery were divided into 0-6 yr old children (Group I, n = 20), 7-15 yr old children (Group II, n = 20) and adults (Group III, n = 20). Patients with an inflatable mask connected to an anesthesia machine breathed 100% oxygen spontaneously for 3 min with tidal volume in all three groups. End tidal oxygen concentration, end tidal carbon dioxide concentration and respiratory rate were measured simultaneously for 3 min. RESULTS: Group I and II showed significantly higher end tidal oxygen concentrations than Group III from 10 sec to 160 sec with 3 min tidal volume breathing (P < 0.05). The mean time required for end tidal oxygen concentration of 90% was 85.5 +/- 18.5 sec for Group I, 101.5 +/- 21.5 sec for Group II and 148.0 +/- 24.0 sec for Group III. Therefore, Group I and II showed a significantly shorter time than Group III (P < 0.05). CONCLUSIONS: Pediatric patients showed a significantly shorter time to obtain the required preoxygenation.