Stewart Siu-Wa Chan

The normal ranges of cardiovascular parameters in children measured using the Ultrasonic Cardiac Output Monitor.

Objective:The Ultrasonic Cardiac Output Monitor is a noninvasive method of hemodynamic assessment and monitoring in critically ill patients. There are no published reference ranges for normal values in children for this device. This study aimed to establish normal ranges for cardiovascular indices measured using Ultrasonic Cardiac Output Monitor in children aged 0–12 yrs old and to assess interobserver reliability. Design:This was a population-based cross-sectional observational study. Setting:Schools and kindergartens in Hong Kong. Subjects:Chinese children aged up to 12 yrs old. Interventions:Two operators performed Ultrasonic Cardiac Output Monitor scans on each child together with standard oscillometric measurement of blood pressure and heart rate. Software intrinsic to the Ultrasonic Cardiac Output Monitor device produces values for stroke volume, cardiac output, and systemic vascular resistance. For each parameter, normal ranges were defined as lying between the 2.5th and 97.5th percentiles. Interobserver reliability was assessed with Bland-Altman plots, coefficients of variation, and intraclass correlation. Measurements and Main Results:A total of 1,197 Chinese children (55% boys) were scanned. Normal ranges of values for cardiac output, stroke volume, and systemic vascular resistance indices are presented. Interobserver reliability for Ultrasonic Cardiac Output Monitor was superior to that for standard blood pressure and heart rate measurement. Conclusions:This large study presents normal values for cardiovascular indices in children using the Ultrasonic Cardiac Output Monitor with good interobserver reliability.

Predictors of positive stool culture in adult patients with acute infectious diarrhea

Stool cultures for bacterial pathogens are often requested for investigation of patients with infectious diarrhea, but the literature reports low yield for this diagnostic test. The identification of clinical predictors of positive stool culture will help the physician in determining the necessity for stool requests. A retrospective study was performed in the setting of an Emergency Department (ED) in Hong Kong, to compare presenting features of adult patients with positive stool culture against those with negative culture. We compared 130 consecutive cases with positive stool culture, over a 12-month period, against 119 control cases obtained from a random sampling of 524 consecutive negative cases over the same period. In multivariate analysis, the independent variables found to be associated with positive stool culture were: the month of presentation (summer season), fever, duration of abdominal pain, and requirement of IV fluid therapy. Neither bloody diarrhea nor persistent diarrhea was associated with positive stool culture.

The normal ranges of cardiovascular parameters measured using the ultrasonic cardiac output monitor

The ultrasonic cardiac output monitor (USCOM) is a noninvasive transcutaneous continuous wave Doppler method for assessing hemodynamics. There are no published reference ranges for normal values in adults (aged 18–60 years) for this device. This study aimed to (1) measure cardiovascular indices using USCOM in healthy adults aged 18–60 years; (2) combine these data with those for healthy children (aged 0–12), adolescents (aged 12–18), and the elderly (aged over 60) from our previously published studies in order to present normal ranges for all ages, and (3) establish normal ranges of USCOM‐derived variables according to both weight and age. This was a population‐based cross‐sectional observational study of healthy Chinese subjects aged 0.5–89 years in Hong Kong. USCOM scans were performed on all subjects, to produce measurements including stroke volume, cardiac output, and systemic vascular resistance. Data from previously published studies (children, adolescents, and the elderly) were included. Normal ranges were defined as lying between the 2.5th and 97.5th percentiles. A total of 2218 subjects were studied (mean age = 16.4, range = 0.5–89; 52% male). From previous studies, 1197 children (aged 0–12, 55% male), 590 adolescents (aged 12–18, 49% male), and 77 elderly (aged 60–89, 55% male) were included. New data were collected from 354 adults aged 18–60 (47% male). Normal ranges are presented according to age and weight. We present comprehensive normal ranges for hemodynamic parameters obtained with USCOM in healthy subjects of all ages from infancy to the elderly.

Noninvasive transcutaneous Doppler ultrasound-derived hemodynamic reference ranges in Chinese adolescents.

Objectives: The ultrasonic cardiac output monitor is a noninvasive, quantitative method for measuring and monitoring cardiovascular hemodynamic parameters in patients. The aims of this study were first to establish reference ranges for cardiovascular indices measured by the ultrasonic cardiac output monitor in Chinese children aged 12–18 yr, second to assess the interobserver reliability of the method, and third to compare these ranges with a Caucasian group from Australia. Design, Setting, and Subjects: This was a population-based cross-sectional cohort study of Chinese adolescents 12–18 years old, performed in secondary schools in Hong Kong. Interventions: Ultrasonic cardiac output monitor scans were performed on each subject to measure stroke volume, cardiac output, and systemic vascular resistance together with standard oscillometric measurement of blood pressure and heart rate. Ultrasonic cardiac output monitor parameters were also standardized by deriving body surface area referenced indices. Normal ranges were defined as lying within two standard deviations on either side of the mean. To assess interobserver variability, a second, blinded operator repeated 17% of scans. Measurements and Main Results: A total of 590 Chinese adolescents (49% boys) were scanned. Normal ranges for cardiac output, cardiac index, stroke volume, stroke volume index, stroke volume resistance, and systemic vascular resistance index are presented. Males had a significantly higher mean stroke volume, cardiac output, and systemic vascular resistance index compared with females (p < 0.05), but no significant differences were found for the indexed values. When compared with a group of 31 Australian Caucasian adolescents (71% boys), Chinese adolescents have a significantly lower cardiac output and stroke volume (p <0.05), but these differences disappeared when adjusted for body surface area (i.e., stroke volume index, cardiac index, and systemic vascular resistance index). Interobserver variability of ultrasonic cardiac output monitor–derived stroke volume showed a coefficient of variation of 10.2%, a correlation coefficient of 0.90 (95% confidence interval 0.85–0.93), while Bland-Altman analysis showed a mean bias of 1.5% (95% limits of agreement were –19.9% to 23.0%). Conclusions: This study presents normal values for cardiovascular indices in Chinese adolescents using the ultrasonic cardiac output monitor. When referenced to body surface area, the differences between Caucasians and Chinese were insignificant.

Noninvasive Doppler ultrasound cardiac output monitor for the differential diagnosis of shock

An 88-year-old lady was transported from the nursing home to the ED after being found to have sustained hypotension (blood pressure [BP], 82/45 mm Hg). On arrival, her BP was 100/54 mm Hg, her pulse rate was 97 beats/min, and she was afebrile and was not in respiratory distress. She was unable to communicate well, although her relatives indicated that her mental state was similar to her usual status and she had no apparent complaint. Nevertheless, it was difficult to ascertain whether her oral intake of late had been satisfactory. Her usual medications included nifedipine (slow release), of which she had been given a dose of 20 mg at the nursing home several hours before the finding of hypotension. Her abdomen was soft, nontender, and not distended. Her electrocardiogram showed sinus rhythm with a rate of 92 per minute and no acute ischemic change. The differential diagnoses at this juncture would include dehydration with hypovolemia and vasodilatation from her calcium-channel blocker. Cardiogenic shock would also need to be excluded.

Preventive treatment for re-expansion pulmonary oedema

: Re-expansion pulmonary oedema is a rare but life-threatening condition that may complicate the treatment of pneumothorax. Current opinions vary regarding how this condition can be prevented. The concepts behind these various theories are discussed with an emphasis on applying available evidence and expert guidelines to practice.

Influence of different positions on hemodynamics derived from noninvasive transcutaneous Doppler ultrasound

A proper alignment of the ultrasound beam to the aortic or pulmonary outflow tracts is essential to acquire accurate signals. This study aimed to investigate the influence of different positions on the acquisition of Doppler signals using a noninvasive transcutaneous Doppler ultrasound. This was a prospective observational crossover study. Two operators performed hemodynamics measurements on each subject in supine, sitting, semirecumbent, passive leg raising (PLR) 20°, and PLR 60° positions using both aortic and pulmonary approaches. All Doppler flow profile images were assessed using the Fremantle and Prince of Wales Hospital criteria. Time required to obtain Doppler signals was recorded. A total of 60 subjects (50% males) aged 18–60 years old were investigated. In both sitting and semirecumbent positions, aortic stroke volume indexes (SVIs) and cardiac indexes (CIs) were significantly lower than those in the other three positions while the pulmonary CIs were comparable to that in the supine position. In the sitting position, the aortic signal qualities were lower and the time to obtain the pulmonary Doppler signals was prolonged. Instead, the signal quality and the time to obtain the Doppler signals in the semirecumbent position were similar to those in the other three positions using the pulmonary approach. PLR did not cause a significant increase in SVI regardless of the degree of leg elevation. These data show that it is feasible to perform the noninvasive transcutaneous Doppler ultrasound using the pulmonary approach in the semirecumbent position for patients unable to maintain the supine position. The aortic approach in the sitting and semirecumbent positions is not suitable as it is not sufficiently reliable.

First-Line Treatment for Hypertension

Expert recommendations have until nowfocused on comparative analyses of cardiovascularoutcomes, efficacy in reducing blood pressure (BP),adverse effects, and cost. Essential hypertension can beclassified into distinct subtypes depending on the pri-mary hemodynamic derangement, which can either beincreased cardiac output (CO), as is more commonlyseen in the younger age group with sympathetic ner-vous system overactivity; or elevated systemic vascularresistance (SVR), as is seen in older patients.

Chest radiograph screening for severe acute respiratory syndrome in the ED

Abstract The purpose of the study was to evaluate the use of chest radiography for the screening of severe acute respiratory syndrome (SARS). We retrospectively analyzed all patients who attended an Emergency Department SARS screening clinic during the outbreak in Hong Kong, from March 10 to June 5, 2003. Patients with clinical and epidemiologic suspicion of SARS were evaluated by serial chest radiography. All radiographs were reported by consensus from 2 radiologists, blinded to the clinical records. The prevalence of SARS was 13.3% among 1328 patients included. The initial radiograph had sensitivity 50.3%, specificity 95.0%, positive likelihood ratio 10.06, negative likelihood ratio 0.52, positive predictive value 61.5%, and negative predictive value 92.3% for diagnosing SARS. Serial chest radiography had sensitivity 94.4%, specificity 93.9%, positive likelihood ratio 15.48, negative likelihood ratio 0.06, positive predictive value 71.4%, and negative predictive value 99.0%. The initial chest radiograph has poor sensitivity, and serial radiographs are required to rule out SARS.

Gestalt for shock and mortality in the emergency department: A prospective study

Objective The diagnosis of shock in patients presenting to the emergency department (ED) is often challenging. We aimed to compare the accuracy of experienced emergency physician gestalt against Lis pragmatic shock (LiPS) tool for predicting the likelihood of shock in the emergency department, using 30‐day mortality as an objective standard. Method In a prospective observational study conducted in an urban, academic ED in Hong Kong, adult patients aged 18 years or older admitted to the resuscitation room or high dependency unit were recruited. Eligible patients had a standard ED workup for shock. The emergency physician treating the patient was asked whether he or she considered shock to be probable, and this was compared with LiPS. The proxy ‘gold’ or reference standard was 30‐day mortality. The area under the receiver operating curve (AUROC) was used to predict prognosis. The primary outcome measure was 30‐day mortality. Results A total of 220 patients fulfilled the inclusion criteria and were included in the analysis. The AUROC for LiPS (0.722; sensitivity = 0.733, specificity = 0.711, P < 0.0001) was greater than emergency physician gestalt (0.620, sensitivity = 0.467, specificity = 0.774, P = 0.0137) for diagnosing shock using 30‐day mortality as a proxy (difference P = 0.0229). LiPS shock patients were 6.750 times (95%CI = 2.834–16.076, P < 0.0001) more likely to die within 30‐days compared with non‐shock patients. Patients diagnosed by emergency physicians were 2.991 times (95%CI = 1.353–6.615, P = 0.007) more likely to die compared with the same reference. Conclusions LiPS has a higher diagnostic accuracy than emergency physician gestalt for shock when compared against an outcome of 30‐day mortality.