Identifying Atrial Fibrillation With Sinus Rhythm Electrocardiogram in Embolic Stroke of Undetermined Source: A Validation Study With Insertable Cardiac Monitors

BACKGROUND AND OBJECTIVES

Paroxysmal atrial fibrillation (AF) is a major potential cause of embolic stroke of undetermined source (ESUS). However, identifying AF remains challenging because it occurs sporadically. Deep learning could be used to identify hidden AF based on the sinus rhythm (SR) electrocardiogram (ECG). We combined known AF risk factors and developed a deep learning algorithm (DLA) for predicting AF to optimize diagnostic performance in ESUS patients.

METHODS

A DLA was developed to identify AF using SR 12-lead ECG with the database consisting of AF patients and non-AF patients. The accuracy of the DLA was validated in 221 ESUS patients who underwent insertable cardiac monitor (ICM) insertion to identify AF.

RESULTS

A total of 44,085 ECGs from 12,666 patient were used for developing the DLA. The internal validation of the DLA revealed 0.862 (95% confidence interval, 0.850-0.873) area under the curve (AUC) in the receiver operating curve analysis. In external validation data from 221 ESUS patients, the diagnostic accuracy of DLA and AUC were 0.811 and 0.827, respectively, and DLA outperformed conventional predictive models, including CHARGE-AF, C2HEST, and HATCH. The combined model, comprising atrial ectopic burden, left atrial diameter and the DLA, showed excellent performance in AF prediction with AUC of 0.906.

CONCLUSIONS

The DLA accurately identified paroxysmal AF using 12-lead SR ECG in patients with ESUS and outperformed the conventional models. The DLA model along with the traditional AF risk factors could be a useful tool to identify paroxysmal AF in ESUS patients.

Predicting intraoperative hypotension using deep learning with waveforms of arterial blood pressure, electroencephalogram, and electrocardiogram: Retrospective study

To develop deep learning models for predicting Interoperative hypotension (IOH) using waveforms from arterial blood pressure (ABP), electrocardiogram (ECG), and electroencephalogram (EEG), and to determine whether combination ABP with EEG or CG improves model performance. Data were retrieved from VitalDB, a public data repository of vital signs taken during surgeries in 10 operating rooms at Seoul National University Hospital from January 6, 2005, to March 1, 2014. Retrospective data from 14,140 adult patients undergoing non-cardiac surgery with general anaesthesia were used. The predictive performances of models trained with different combinations of waveforms were evaluated and compared at time points at 3, 5, 10, 15 minutes before the event. The performance was calculated by area under the receiver operating characteristic (AUROC), area under the precision-recall curve (AUPRC), sensitivity and specificity. The model performance was better in the model using both ABP and EEG waveforms than in all other models at all time points (3, 5, 10, and 15 minutes before an event) Using high-fidelity ABP and EEG waveforms, the model predicted IOH with a AUROC and AUPRC of 0.935 [0.932 to 0.938] and 0.882 [0.876 to 0.887] at 5 minutes before an IOH event. The output of both ABP and EEG was more calibrated than that using other combinations or ABP alone. The results demonstrate that a predictive deep neural network can be trained using ABP, ECG, and EEG waveforms, and the combination of ABP and EEG improves model performance and calibration.

Artificial intelligence assessment for early detection and prediction of renal impairment using electrocardiography

Purpose

Although renal failure is a major healthcare burden globally and the cornerstone for preventing its irreversible progression is an early diagnosis, an adequate and noninvasive tool to screen renal impairment (RI) reliably and economically does not exist. We developed an interpretable deep learning model (DLM) using electrocardiography (ECG) and validated its performance.

Methods

This retrospective cohort study included two hospitals. We included 115,361 patients who had at least one ECG taken with an estimated glomerular filtration rate measurement within 30 min of the index ECG. A DLM was developed using 96,549 ECGs of 55,222 patients. The internal validation included 22,949 ECGs of 22,949 patients. Furthermore, we conducted an external validation with 37,190 ECGs of 37,190 patients from another hospital. The endpoint was to detect a moderate to severe RI (estimated glomerular filtration rate < 45 ml/min/1.73m²).

Results

The area under the receiver operating characteristic curve (AUC) of a DLM using a 12-lead ECG for detecting RI during the internal and external validation was 0.858 (95% confidence interval 0.851–0.866) and 0.906 (0.900–0.912), respectively. In the initial evaluation of 25,536 individuals without RI patients whose DLM was defined as having a higher risk had a significantly higher chance of developing RI than those in the low-risk group (17.2% vs. 2.4%, p < 0.001). The sensitivity map indicated that the DLM focused on the QRS complex and T-wave for detecting RI.

Conclusion

The DLM demonstrated high performance for RI detection and prediction using 12-, 6-, single-lead ECGs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-022-03165-w.

An artificial intelligence electrocardiogram analysis for detecting cardiomyopathy in the peripartum period

BACKGROUND

Peripartum cardiomyopathy (PPCM) is a fatal maternal complication, with left ventricular systolic dysfunction (LVSD; Left ventricular ejection fraction 45% or less) occurring at the end of pregnancy or in the months following delivery. The scarcity of screening tools for PPCM leads to a delayed diagnosis and increases its mortality and morbidity. We aim to evaluate an electrocardiogram (ECG)-deep learning model (DLM) for detecting cardiomyopathy in the peripartum period.

METHODS

For the DLM development and internal performance test for detecting LVSD, we obtained a dataset of 122,733 ECG-echocardiography pairs from 58,530 male and female patients from two community hospitals. For the DLM external validation, this study included 271 ECG-echocardiography pairs (157 unique pregnant and postpartum period women) examined in the Ajou University Medical Center (AUMC) between January 2007 and May 2020. All included cases underwent an ECG within two weeks before or after the day of transthoracic echocardiography, which was performed within a month before delivery, or within five months after delivery. Based on the diagnostic criteria of PPCM, we analyzed the area under the receiver operating characteristic curve (AUROC), sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) to evaluate the model effectiveness.

RESULTS

The ECG-based DLM detected PPCM with an AUROC of 0.877. Moreover, its sensitivity, specificity, PPV, and NPV for the detection of PPCM were 0.877, 0.833, 0.809, 0.352, and 0.975, respectively.

CONCLUSIONS

An ECG-based DLM non-invasively and effectively detects cardiomyopathies occurring in the peripartum period and could be an ideal screening tool for PPCM.

Deep-learning model for screening sepsis using electrocardiography

Background

Sepsis is a life-threatening organ dysfunction and a major healthcare burden worldwide. Although sepsis is a medical emergency that requires immediate management, screening for the occurrence of sepsis is difficult. Herein, we propose a deep learning-based model (DLM) for screening sepsis using electrocardiography (ECG).

Methods

This retrospective cohort study included 46,017 patients who were admitted to two hospitals. A total of 1,548 and 639 patients had sepsis and septic shock, respectively. The DLM was developed using 73,727 ECGs from 18,142 patients, and internal validation was conducted using 7774 ECGs from 7,774 patients. Furthermore, we conducted an external validation with 20,101 ECGs from 20,101 patients from another hospital to verify the applicability of the DLM across centers.

Results

During the internal and external validations, the area under the receiver operating characteristic curve (AUC) of the DLM using 12-lead ECG was 0.901 (95% confidence interval, 0.882–0.920) and 0.863 (0.846–0.879), respectively, for screening sepsis and 0.906 (95% confidence interval (CI), 0.877–0.936) and 0.899 (95% CI, 0.872–0.925), respectively, for detecting septic shock. The AUC of the DLM for detecting sepsis using 6-lead and single-lead ECGs was 0.845–0.882. A sensitivity map revealed that the QRS complex and T waves were associated with sepsis. Subgroup analysis was conducted using ECGs from 4,609 patients who were admitted with an infectious disease, and the AUC of the DLM for predicting in-hospital mortality was 0.817 (0.793–0.840). There was a significant difference in the prediction score of DLM using ECG according to the presence of infection in the validation dataset (0.277 vs. 0.574, p < 0.001), including severe acute respiratory syndrome coronavirus 2 (0.260 vs. 0.725, p = 0.018).

Conclusions

The DLM delivered reasonable performance for sepsis screening using 12-, 6-, and single-lead ECGs. The results suggest that sepsis can be screened using not only conventional ECG devices but also diverse life-type ECG machines employing the DLM, thereby preventing irreversible disease progression and mortality.

Detection and classification of arrhythmia using an explainable deep learning model

BACKGROUND

Early detection and intervention is the cornerstone for appropriate treatment of arrhythmia and prevention of complications and mortality. Although diverse deep learning models have been developed to detect arrhythmia, they have been criticized due to their unexplainable nature. In this study, we developed an explainable deep learning model (XDM) to classify arrhythmia, and validated its performance using diverse external validation data.

METHODS

In this retrospective study, the Sejong dataset comprising 86,802 electrocardiograms (ECGs) was used to develop and internally variate the XDM. The XDM based on a neural network-backed ensemble tree was developed with six feature modules that are able to explain the reasons for its decisions. The model was externally validated using data from 36,961 ECGs from four non-restricted datasets.

RESULTS

During internal and external validation of the XDM, the average area under the receiver operating characteristic curves (AUCs) using a 12‑lead ECG for arrhythmia classification were 0.976 and 0.966, respectively. The XDM outperformed a previous simple multi-classification deep learning model that used the same method. During internal and external validation, the AUCs of explainability were 0.925-0.991.

CONCLUSION

Our XDM successfully classified arrhythmia using diverse formats of ECGs and could effectively describe the reason for the decisions. Therefore, an explainable deep learning methodology could improve accuracy compared to conventional deep learning methods, and that the transparency of XDM can be enhanced for its application in clinical practice.

Impact of image compression on deep learning-based mammogram classification

Image compression is used in several clinical organizations to help address the overhead associated with medical imaging. These methods reduce file size by using a compact representation of the original image. This study aimed to analyze the impact of image compression on the performance of deep learning-based models in classifying mammograms as "malignant"-cases that lead to a cancer diagnosis and treatment-or "normal" and "benign," non-malignant cases that do not require immediate medical intervention. In this retrospective study, 9111 unique mammograms-5672 normal, 1686 benign, and 1754 malignant cases were collected from the National Cancer Center in the Republic of Korea. Image compression was applied to mammograms with compression ratios (CRs) ranging from 15 to 11 K. Convolutional neural networks (CNNs) with three convolutional layers and three fully-connected layers were trained using these images to classify a mammogram as malignant or not malignant across a range of CRs using five-fold cross-validation. Models trained on images with maximum CRs of 5 K had an average area under the receiver operating characteristic curve (AUROC) of 0.87 and area under the precision-recall curve (AUPRC) of 0.75 across the five folds and compression ratios. For images compressed with CRs of 10 K and 11 K, model performance decreased (average 0.79 in AUROC and 0.49 in AUPRC). Upon generating saliency maps that visualize the areas each model views as significant for prediction, models trained on less compressed (CR <  = 5 K) images had maps encapsulating a radiologist's label, while models trained on images with higher amounts of compression had maps that missed the ground truth completely. In addition, base ResNet18 models pre-trained on ImageNet and trained using compressed mammograms did not show performance improvements over our CNN model, with AUROC and AUPRC values ranging from 0.77 to 0.87 and 0.52 to 0.71 respectively when trained and tested on images with maximum CRs of 5 K. This paper finds that while training models on images with increased the robustness of the models when tested on compressed data, moderate image compression did not substantially impact the classification performance of DL-based models.

Artificial intelligence for detecting electrolyte imbalance using electrocardiography

Introduction

The detection and monitoring of electrolyte imbalance is essential for appropriate management of many metabolic diseases; however, there is no tool that detects such imbalances reliably and noninvasively. In this study, we developed a deep learning model (DLM) using electrocardiography (ECG) for detecting electrolyte imbalance and validated its performance in a multicenter study.

Methods and Results

This retrospective cohort study included two hospitals: 92,140 patients who underwent a laboratory electrolyte examination and an ECG within 30 min were included in this study. A DLM was developed using 83,449 ECGs of 48,356 patients; the internal validation included 12,091 ECGs of 12,091 patients. We conducted an external validation with 31,693 ECGs of 31,693 patients from another hospital, and the result was electrolyte imbalance detection. During internal, the area under the receiving operating characteristic curve (AUC) of a DLM using a 12‐lead ECG for detecting hyperkalemia, hypokalemia, hypernatremia, hyponatremia, hypercalcemia, and hypocalcemia were 0.945, 0.866, 0.944, 0.885, 0.905, and 0.901, respectively. The values during external validation of the AUC of hyperkalemia, hypokalemia, hypernatremia, hyponatremia, hypercalcemia, and hypocalcemia were 0.873, 0.857, 0.839, 0.856, 0.831, and 0.813 respectively. The DLM helped to visualize the important ECG region for detecting each electrolyte imbalance, and it showed how the P wave, QRS complex, or T wave differs in importance in detecting each electrolyte imbalance.

Conclusion

The proposed DLM demonstrated high performance in detecting electrolyte imbalance. These results suggest that a DLM can be used for detecting and monitoring electrolyte imbalance using ECG on a daily basis.

Prediction of Prolonged Length of Hospital Stay After Cancer Surgery Using Machine Learning on Electronic Health Records: Retrospective Cross-sectional Study

BACKGROUND

Postoperative length of stay is a key indicator in the management of medical resources and an indirect predictor of the incidence of surgical complications and the degree of recovery of the patient after cancer surgery. Recently, machine learning has been used to predict complex medical outcomes, such as prolonged length of hospital stay, using extensive medical information.

OBJECTIVE

The objective of this study was to develop a prediction model for prolonged length of stay after cancer surgery using a machine learning approach.

METHODS

In our retrospective study, electronic health records (EHRs) from 42,751 patients who underwent primary surgery for 17 types of cancer between January 1, 2000, and December 31, 2017, were sourced from a single cancer center. The EHRs included numerous variables such as surgical factors, cancer factors, underlying diseases, functional laboratory assessments, general assessments, medications, and social factors. To predict prolonged length of stay after cancer surgery, we employed extreme gradient boosting classifier, multilayer perceptron, and logistic regression models. Prolonged postoperative length of stay for cancer was defined as bed-days of the group of patients who accounted for the top 50% of the distribution of bed-days by cancer type.

RESULTS

In the prediction of prolonged length of stay after cancer surgery, extreme gradient boosting classifier models demonstrated excellent performance for kidney and bladder cancer surgeries (area under the receiver operating characteristic curve [AUC] >0.85). A moderate performance (AUC 0.70-0.85) was observed for stomach, breast, colon, thyroid, prostate, cervix uteri, corpus uteri, and oral cancers. For stomach, breast, colon, thyroid, and lung cancers, with more than 4000 cases each, the extreme gradient boosting classifier model showed slightly better performance than the logistic regression model, although the logistic regression model also performed adequately. We identified risk variables for the prediction of prolonged postoperative length of stay for each type of cancer, and the importance of the variables differed depending on the cancer type. After we added operative time to the models trained on preoperative factors, the models generally outperformed the corresponding models using only preoperative variables.

CONCLUSIONS

A machine learning approach using EHRs may improve the prediction of prolonged length of hospital stay after primary cancer surgery. This algorithm may help to provide a more effective allocation of medical resources in cancer surgery.

Artificial intelligence to diagnose paroxysmal supraventricular tachycardia using electrocardiography during normal sinus rhythm

Aims

Paroxysmal supraventricular tachycardia (PSVT) is not detected owing to its paroxysmal nature, but it is associated with the risk of cardiovascular disease and worsens the patient quality of life. A deep learning model (DLM) was developed and validated to identify patients with PSVT during normal sinus rhythm in this multicentre retrospective study.

Methods and results

This study included 12 955 patients with normal sinus rhythm, confirmed by a cardiologist. A DLM was developed using 31 147 electrocardiograms (ECGs) of 9069 patients from one hospital. We conducted an accuracy test with 13 753 ECGs of 3886 patients from another hospital. The DLM was developed based on residual neural network. Digitally stored ECG were used as predictor variables and the outcome of the study was ability of the DLM to identify patients with PSVT using an ECG during sinus rhythm. We employed a sensitivity map method to identify an ECG region that had a significant effect on developing PSVT. During accuracy test, the area under the receiver operating characteristic curve of a DLM using a 12-lead ECG for identifying PSVT patients during sinus rhythm was 0.966 (0.948-0.984). The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of DLM were 0.970, 0.868, 0.972, 0.255, and 0.998, respectively. The DLM showed delta wave and QT interval were important to identify the PSVT.

Conclusion

The proposed DLM demonstrated a high performance in identifying PSVT during normal sinus rhythm. Thus, it can be used as a rapid, inexpensive, point-of-care means of identifying PSVT in patients.

Explainable artificial intelligence to detect atrial fibrillation using electrocardiogram

INTRODUCTION

Early detection and intervention of atrial fibrillation (AF) is a cornerstone for effective treatment and prevention of mortality. Diverse deep learning models (DLMs) have been developed, but they could not be applied in clinical practice owing to their lack of interpretability. We developed an explainable DLM to detect AF using ECG and validated its performance using diverse formats of ECG.

METHODS

We conducted a retrospective study. The Sejong ECG dataset comprising 128,399 ECGs was used to develop and internally validated the explainable DLM. DLM was developed with two feature modules, which could describe the reason for DLM decisions. DLM was external validated using data from 21,837, 10,605, and 8528 ECGs from PTB-XL, Chapman, and PhysioNet non-restricted datasets, respectively. The predictor variables were digitally stored ECGs, and the endpoints were AFs.

RESULTS

During internal and external validation of the DLM, the area under the receiver operating characteristic curves (AUCs) of the DLM using a 12‑lead ECG in detecting AF were 0.997-0.999. The AUCs of the DLM with VAE using a 6‑lead and single‑lead ECG were 0.990-0.999. The AUCs of explainability about features such as rhythm irregularity and absence of P-wave were 0.961-0.993 and 0.983-0.993, respectively.

CONCLUSIONS

Our DLM successfully detected AF using diverse ECGs and described the reason for this decision. The results indicated that an explainable artificial intelligence methodology could be adopted to the DLM using ECG and enhance the transparency of the DLM for its application in clinical practice.

The predictors for continuous renal replacement therapy in liver transplant recipients

BACKGROUND

Acute renal failure (ARF) after liver transplantation requiring continuous renal replacement therapy (CRRT) adversely affects patient survival. We suggested that postoperative renal failure can be predicted if a clinically simple nomogram can be developed, thus selecting potential risk factors for preventive strategy.

METHODS

We retrospectively reviewed the medical records of 153 liver transplant recipients from January 2008 to December 2011 at Severance Hospital, Yonsei University Health System, in Seoul, Korea. There were 42 patients treated with CRRT (20 and 22 patients received transplants from living and deceased donors, respectively) and 115 were not. Univariate and stepwise logistic multivariate analyses were performed. A clinical nomogram to predict postoperative CRRT application was constructed and validated internally.

RESULTS

Hepatic encephalopathy (HEP; odds ratio OR, 5.47), deceased donor liver donations (OR, 3.47), Model for End-Stage Liver Disease (MELD) score (OR, 1.09), intraoperative blood loss (L; OR, 1.16), and tumor (hepatocellular carcinoma) as the indication for liver transplantation (OR, 0.11) were identified as independent predictive factors for postoperative CRRT on multivariate analysis. A clinical prediction model constructed for calculating the probability of CRRT post-transplantation was 1.7000 × HEP + [-4.5427 + 1.2440 × (deceased donor) + 0.0830 × (MELD score) + 0.000149 × the amount of intraoperative bleeding (L) - 2.1785 × tumor]. The validation set discriminated well with an area under the curve (AUC) of 0.90 (95% confidence interval, 0.85-0.95). The predicted and the actual probabilities were calibrated with the clinical nomogram.

CONCLUSIONS

We developed a predictive model of postoperative CRRT in liver transplantation patients. Perioperative strategies to modify these factors are needed.

Effects of high positive end-expiratory pressure on haemodynamics and cerebral oxygenation during pneumoperitoneum in the Trendelenburg position

We investigated the effects of 10 cmH2O positive end-expiratory pressure on cerebral haemodynamics and cerebral oxygenation in patients undergoing laparoscopic lower abdominal surgery in the 30° Trendelenburg position during desflurane anaesthesia. Twenty-six patients were enrolled in this study. After anaesthesia induction, pneumoperitoneum was applied in Trendelenburg position. Twenty minutes later, positive end-expiratory pressure was applied. There was no change in regional cerebral oxygen saturation (p = 0.376). Cerebral perfusion pressure decreased significantly over time (p < 0.001) and positive end-expiratory pressure caused a further decrease in cerebral perfusion pressure (p = 0.036). The application of 10 cmH2O positive end-expiratory pressure during pneumoperitoneum in the Trendelenburg position preserved regional cerebral oxygen saturation, but cerebral perfusion pressure decreased significantly due to its secondary haemodynamic effects.

Optimal dose of propofol for intubation after sevoflurane inhalation without neuromuscular blocking agent in children

BACKGROUND

This study was designed to determine the optimal dose of propofol for excellent intubating conditions in children without neuromuscular blockade at various alveolar concentrations of sevoflurane.

METHODS

Sixty-three children, aged 0.5-5 years, were randomized to three groups of end-tidal sevoflurane concentration (ETsevo) 3%, 3.5%, and 4%. Inhalation anesthesia was started with sevoflurane 7% in 100% oxygen. When the patients became unconscious, inspired concentration was adjusted to obtain the target ETsevo for each group. When ETsevo reached the target concentration, a predetermined dose of propofol was given and tracheal intubation was performed. The proper dose of propofol was determined using the 'up-and-down' method.

RESULTS

The median dose (95% confidence intervals) of propofol for excellent tracheal intubating conditions in 50% of children were 1.25 mg/kg (0.84-1.75) at ETsevo of 3%, 0.76 mg/kg (0.35-1.21) at 3.5%, and 0.47 mg/kg (0.26-1.09) at 4%. The frequency of adverse effects was not different between groups during induction and recovery.

CONCLUSION

Propofol 1.5-2 mg/kg provides excellent intubating conditions at 3-4% ETsevo in children without using any neuromuscular blocking agent.

Ketorolac or fentanyl continuous infusion for post-operative analgesia in children undergoing ureteroneocystostomy

BACKGROUND

children undergoing ureteroneocystostomy suffer from post-operative pain due to the surgical incision and bladder spasm. A single-shot caudal block is a common technique for paediatric analgesia, but a disadvantage is the limitation of a short duration in spite of the additives co-administered. A few clinical trials have shown that ketorolac provides an effective post-operative analgesia and reduces the bladder spasms after ureteral implantation in children. We compared the efficacy of a continuous infusion of ketorolac and fentanyl in post-operative analgesia and bladder spasm in children who underwent ureteroneocystostomy.

METHODS

fifty-two children were allocated to the ketorolac group (Group K, n=26) and fentanyl group (Group F, n=26). After general anaesthesia, a caudal block was performed with 1.5 ml/kg of 0.15% ropivacaine. At the beginning of surgery, an infusion was started after the bolus injection of ketorolac 0.5 mg/kg or fentanyl 1 microg/kg. An infusion device was programmed to deliver ketorolac 83.3 microg/kg/h or fentanyl 0.17 microg/kg/h for 48 h.

RESULTS

two of Group F and three of Group K were excluded from the study. Post-operative pain scores were similar between the two groups. One of Group K (4%) and seven of Group F (30.4%) experienced bladder spasms. The rescue analgesic requirements were significantly less in Group K.

CONCLUSIONS

a Continuous infusion of ketorolac provided effective analgesia after operation in children who underwent ureteroneocystostomy as well as a low dosage of fentanyl. Ketorolac was more effective in reducing the frequency of bladder spasms and rescue analgesic requirements.

The relative position of ilioinguinal and iliohypogastric nerves in different age groups of pediatric patients

BACKGROUND

Ilioinguinal nerve (IIN) and iliohypogastric nerve (IHN) blocks provide good perioperative pain relief for children undergoing inguinal procedures such as inguinal hernia repair, orchiopexy, and hydrocelectomy. The aim of this ultrasound imaging study is to compare the relative anatomical positions of IIN and IHN in different age groups of pediatrics.

METHODS

Two-hundred children (aged 1-82 months, ASA I or II) undergoing day-case surgery were consecutively included in this study. Following the induction of general anesthesia, an ultrasonographic exam was performed using a high-frequency linear probe that was placed on an imaginary line connecting the anterior superior iliac spine (ASIS) to the umbilicus.

RESULTS

There were significant differences in ASIS-IIN (distance from ASIS to IIN), ASIS-IHN (distance from the ASIS to the IHN), and IIN-IHN (distance between IIN and IHN) between the age groups: <12 months (n=84), 12-36 months (n=80), and >37 months (n=36). However, IIN-Peritoneum (distances from IIN to peritoneum), skin-IIN, and skin-IHN (depth of IIN and IHN relative to skin) were similar in three groups. ASIS-IIN and ASIS-IHN showed significantly positive correlations with age.

CONCLUSIONS

Age should be considered when placing a needle in landmark techniques for pediatric II/IH nerve blocks. However, needle depth should be confirmed by the fascial click due to the lack of predictable physiologic factors.

A new glycosaminoglycan from the giant African snail Achatina fulica

A new glycosaminoglycan has been isolated from the giant African snail Achatina fulica. This polysaccharide had a molecular weight of 29,000, calculated based on the viscometry, and a uniform repeating disaccharide structure of -->4)-2-acetyl,2-deoxy-alpha-D-glucopyranose (1-->4)-2-sulfo-alpha-L-idopyranosyluronic acid (1-->. This polysaccharide represents a new, previously undescribed glycosaminoglycan. It is related to the heparin and heparan sulfate families of glycosaminoglycans but is distinctly different from all known members of these classes of glycosaminoglycans. The structure of this polysaccharide, with adjacent N-acetylglucosamine and 2-sulfo-iduronic acid residues, also poses interesting questions about how it is made in light of our current understanding of the biosynthesis of heparin and heparan sulfate. This glycosaminoglycan represents 3-5% of the dry weight of this snail's soft body tissues, suggesting important biological roles for the survival of this organism, and may offer new means to control this pest. Snail glycosaminoglycan tightly binds divalent cations, such as copper(II), suggesting a primary role in metal uptake in the snail. Finally, this new polysaccharide might be applied, like the Escherichia coli K5 capsular polysaccharide, to the study of glycosaminoglycan biosynthesis and to the semisynthesis of new glycosaminoglycan analogs having important biological activities.