Three-dimensional assessment of image distortion induced by active cardiac implants in 3.0T CMR

CMR at 3.0T in the presence of active cardiac implants remains a challenge due to susceptibility artifacts. Beyond a signal void that cancels image information, magnetic field inhomogeneities may cause distorted appearances of anatomical structures. Understanding influencing factors and the extent of distortion are a first step towards optimizing the image quality of CMR with active implants at 3.0T. All measurements were obtained at a clinical 3.0T scanner. An in-house designed phantom with a 3D cartesian grid of water filled spheres was used to analyze the distortion caused by four representative active cardiac devices (cardiac loop recorder, pacemaker, 2 ICDs). For imaging a gradient echo (3D-TFE) sequence and a turbo spin echo (2D-TSE) sequence were used. The work defines metrics to quantify the different features of distortion such as changes in size, location and signal intensity. It introduces a specialized segmentation technique based on a reaction-diffusion-equation. The distortion features are dependent on the amount of magnetic material in the active implants and showed a significant increase when measured with the 3D TFE compared to the 2D TSE. This work presents a quantitative approach for the evaluation of image distortion at 3.0T caused by active cardiac implants and serves as foundation for both further optimization of sequences and devices but also for planning of imaging procedures.

Fraction Size, Total Dose and Respiratory Control Impact Local Control in Adrenal SBRT

PURPOSE/OBJECTIVE(S)

Stereotactic body radiotherapy (SBRT) is an effective treatment for oligometastatic disease in multiple sites, however, the optimal radiation dose for long term local control of adrenal metastases has not yet been determined. The aim of this study is to evaluate outcomes of adrenal SBRT and to evaluate factors that correlate with local control MATERIALS/METHODS: After IRB approval, a retrospective data review of patients treated with SBRT on adrenal metastases was conducted, at a medical center in Israel between 2015 and 2021. Biologic Equivalent Dose (BED) were calculated using an alpha beta ration of 10. Kaplan Meier and Cox regression were calculated to describe the hazard ratio for local control and survival using statistical software.

RESULTS

Fifty-eight cases of adrenal SBRT were identified. The average age was 67 years (ranging 42-92). Forty-three percent of primary tumor was non-small cell lung cancer. The lesions were equally distributed between the right and left adrenal gland. Six patients had bilateral radiation treatment. Fifty-eight percent of the cases were in the setting of oligometastatic disease (less than 5 lesions) with the rest having progression in the adrenal. PET-CT scans were available for follow up in 55% of patients and CT in the rest. The average GTV volume was 42 cm2 respiratory control through 4D and breath hold was performed in 86% of cases. The median follow up time, for local control, was 10 months with a range of 1-54 mos. Univariate analysis local control, during the last follow up, was seen in 74% of cases. Total dosage was equal to or above 72 Gy and dosage per fraction was equal to or above 8 Gy. The use of respiratory motion was found significant for local control. Only a fraction size equal to or above 8 Gy and a total dosage equal to and above 72 Gy were found significant for local failure (HR = 0.26, p = 0.024 and HR = 0.28, p = 0.019). With multivariable analysis the dosage per fraction ≥8 Gy continued to be significant after adjusting for total dose, histology, side, and motion management. Two patients had clinical signs of adrenal insufficiency and both received bilateral adrenal radiation. Bowel toxicity was low: 1 patient had >G3 toxicity.

CONCLUSION

In the largest single institution series reported to date, we found unilateral adrenal SBRT to be safe, however, bilateral treatment harbors a risk of adrenal insufficiency. Dose per fraction ≥8 Gy was the most powerful predictor of local control, and a total dose ≥72gy and motion management were also significant. In conclusion, we propose a treatment regimen with a fraction size of at least 8 Gy and a total dosage of at least 72 Gy for evaluation, in a prospective clinical trial.

Signal voids of active cardiac implants at 3.0 T CMR

Recent technical advancements allow cardiac MRI (CMR) examinations in the presence of so-called MRI conditional active cardiac implants at 3.0 T. However, the artifact burden caused by susceptibility effects remain an obstacle. All measurements were obtained at a clinical 3.0 T scanner using an in-house designed cubic phantom and optimized sequences for artifact evaluation (3D gradient echo sequence, multi-slice 2D turbo spin echo sequence). Reference sequences according to the American Society for Testing and Materials (ASTM) were additionally applied. Four representative active cardiac devices and a generic setup were analyzed regarding volume and shape of the signal void. For analysis, a threshold operation was applied to the grey value profile of each data set. The presented approach allows the evaluation of the signal void and shape even for larger implants such as ICDs. The void shape is influenced by the orientation of the B0-field and by the chosen sequence type. The distribution of ferromagnetic material within the implants also matters. The void volume depends both on the device itself, and on the sequence type. Disturbances in the B0 and B1 fields exceed the visual signal void. This work presents a reproducible and highly defined approach to characterize both signal void artifacts at 3.0 T and their influencing factors.

New quantitative automated model to simulate bacterial dissemination in human tissue during irrigation of contaminated wounds

This study presents a simple and cost-effective model using microparticles to simulate the bacterial distribution pattern in soft tissue after low- and high-pressure irrigation. Silica coated iron microparticles [comparable diameter (1 µm) and weight (0.8333 pg) to Staphylococcus aureus] were applied to the surface of twenty fresh human muscle tissue samples in two amputated lower legs. Particle dissemination into deep tissue layers as an undesired side effect was investigated in four measuring fields as positive control (PC) as well as after performing pulsatile high-pressure (HP, 8 measuring fields) and low-pressure flushing (LP, 8 measuring fields). Five biopsies were taken out of each measuring field to get a total number of 100 biopsies. After histological and digital image processing, the specimens were analysed, and all incomplete sections were excluded. A special detection algorithm was parameterised using the open source bioimage analysis software QuPath. The application of this detection algorithm enabled automated counting and detection of the particles with a sensitivity of 95 % compared to manual counts. Statistical analysis revealed significant differences (p < 0.05) in our three different sample groups: HP (M = 1608, S = 302), LP (M = 2176, SD = 609) and PC (M = 4011, SD = 686). While both HP and LP flushing techniques are able to reduce the number of bacteria, a higher effectiveness is shown for HP irrigation. Nevertheless, a challenge for the validity of the study is the use of dead tissue and therefore a possible negative influence of high-pressure irrigation on tissue healing and further dispersion of particles cannot be evaluated.

Intervention to reduce heat stress and improve efficiency among sugarcane workers in El Salvador: Phase 1

BACKGROUND

Chronic heat stress and dehydration from strenuous work in hot environments is considered an essential component of the epidemic of chronic kidney disease in Central America.

OBJECTIVE

(1) To assess feasibility of providing an intervention modelled on OSHA's Water.Rest.Shade programme (WRS) during sugarcane cutting and (2) to prevent heat stress and dehydration without decreasing productivity.

METHODS

Midway through the 6-month harvest, the intervention introduced WRS practices. A 60-person cutting group was provided water supplied in individual backpacks, mobile shaded rest areas and scheduled rest periods. Ergonomically improved machetes and efficiency strategies were also implemented. Health data (anthropometric, blood, urine, questionnaires) were collected preharvest, preintervention, mid-intervention and at the end of harvest. A subsample participated in focus group discussions. Daily wet bulb globe temperatures (WBGT) were recorded. The employer provided individual production records.

RESULTS

Over the harvest WBGT was >26°C from 9:00 onwards reaching average maximum of 29.3±1.7°C, around 13:00. Postintervention self-reported water consumption increased 25%. Symptoms associated with heat stress and with dehydration decreased. Individual daily production increased from 5.1 to a high of 7.3 tons/person/day postintervention. This increase was greater than in other cutting groups at the company. Focus groups reported a positive perception of components of the WRS, and the new machete and cutting programmes.

CONCLUSIONS

A WRS intervention is feasible in sugarcane fields, and appears to markedly reduce the impact of the heat stress conditions for the workforce. With proper attention to work practices, production can be maintained with less impact on worker health.

Reducing RF-related heating of cardiac pacemaker leads in MRI: implementation and experimental verification of practical design changes

There are serious concerns regarding safety when performing magnetic resonance imaging in patients with implanted conductive medical devices, such as cardiac pacemakers, and associated leads, as severe incidents have occurred in the past. In this study, several approaches for altering an implant's lead design were systematically developed and evaluated to enhance the safety of implanted medical devices in a magnetic resonance imaging environment. The individual impact of each design change on radiofrequency heating was then systematically investigated in functional lead prototypes at 1.5 T. Radiofrequency-induced heating could be successfully reduced by three basic changes in conventional pacemaker lead design: (1) increasing the lead tip area, (2) increasing the lead conductor resistance, and (3) increasing outer lead insulation conductivity. The findings show that radiofrequency energy pickup in magnetic resonance imaging can be reduced and, therefore, patient safety can be improved with dedicated construction changes according to a "safe by design" strategy. Incorporation of the described alterations into implantable medical devices such as pacemaker leads can be used to help achieve favorable risk-benefit-ratios when performing magnetic resonance imaging in the respective patient group.

Direct cooling of the catheter tip increases safety for CMR-guided electrophysiological procedures

BACKGROUND

One of the safety concerns when performing electrophysiological (EP) procedures under magnetic resonance (MR) guidance is the risk of passive tissue heating due to the EP catheter being exposed to the radiofrequency (RF) field of the RF transmitting body coil. Ablation procedures that use catheters with irrigated tips are well established therapeutic options for the treatment of cardiac arrhythmias and when used in a modified mode might offer an additional system for suppressing passive catheter heating.

METHODS

A two-step approach was chosen. Firstly, tests on passive catheter heating were performed in a 1.5 T Avanto system (Siemens Healthcare Sector, Erlangen, Germany) using a ASTM Phantom in order to determine a possible maximum temperature rise. Secondly, a phantom was designed for simulation of the interface between blood and the vascular wall. The MR-RF induced temperature rise was simulated by catheter tip heating via a standard ablation generator. Power levels from 1 to 6 W were selected. Ablation duration was 120 s with no tip irrigation during the first 60 s and irrigation at rates from 2 ml/min to 35 ml/min for the remaining 60 s (Biotronik Qiona Pump, Berlin, Germany). The temperature was measured with fluoroscopic sensors (Luxtron, Santa Barbara, CA, USA) at a distance of 0 mm, 2 mm, 4 mm, and 6 mm from the catheter tip.

RESULTS

A maximum temperature rise of 22.4°C at the catheter tip was documented in the MR scanner. This temperature rise is equivalent to the heating effect of an ablator's power output of 6 W at a contact force of the weight of 90 g (0.883 N). The catheter tip irrigation was able to limit the temperature rise to less than 2°C for the majority of examined power levels, and for all examined power levels the residual temperature rise was less than 8°C.

CONCLUSION

Up to a maximum of 22.4°C, the temperature rise at the tissue surface can be entirely suppressed by using the catheter's own irrigation system. The irrigated tip system can be used to increase MR safety of EP catheters by suppressing the effects of unwanted passive catheter heating due to RF exposure from the MR scanner.

Spinning a laser web: predicting spider distributions using LiDAR

LiDAR remote sensing has been used to examine relationships between vertebrate diversity and environmental characteristics, but its application to invertebrates has been limited. Our objectives were to determine whether LiDAR-derived variables could be used to accurately describe single-species distributions and community characteristics of spiders in remote forested and mountainous terrain. We collected over 5300 spiders across multiple transects in the Bavarian National Park (Germany) using pitfall traps. We examined spider community characteristics (species richness, the Shannon index, the Simpson index, community composition, mean body size, and abundance) and single-species distribution and abundance with LiDAR variables and ground-based measurements. We used the R2 and partial R2 provided by variance partitioning to evaluate the predictive power of LiDAR-derived variables compared to ground measurements for each of the community characteristics. The total adjusted R2 for species richness, the Shannon index, community species composition, and body size had a range of 25-57%. LiDAR variables and ground measurements both contributed >80% to the total predictive power. For species composition, the explained variance was approximately 32%, which was significantly greater than expected by chance. The predictive power of LiDAR-derived variables was comparable or superior to that of the ground-based variables for examinations of single-species distributions, and it explained up to 55% of the variance. The predictability of species distributions was higher for species that had strong associations with shade in open-forest habitats, and this niche position has been well documented across the European continent for spider species. The similar statistical performance between LiDAR and ground-based measures at our field sites indicated that deriving spider community and species distribution information using LiDAR data can provide not only high predictive power at relatively low cost, but may also allow unprecedented mapping of community- and species-level spider information at scales ranging from stands to landscapes. Therefore, LiDAR is a viable tool to assist species-specific conservation as well as broader biodiversity planning efforts not only for a growing list of vertebrates, but for invertebrates as well.

Social isolation improves working memory at reversal but not primary radial-arm maze learning in rats

Social isolation starting from the 21st day of birth affected neither a short-term nor a long-term memory in male rats at primary acquisition learning in an 8-arm radial maze. A number of the short-term and long-term memory errors were substantially decreased during primary learning but the difference between groups was not significant. Isolates were faster to start a search in an individual trial and took less time to finish offa trial. During the reversal learning, when baited and non-baited arms were reversed, the isolates outperformed of socially reared rats on working but not reference memory task. In overall they made twice less working memory errors than socially reared animals. During the reversal learning the isolates were also faster than non-isolates in initiation and completion of a trial. Maternal separation of rat's pups on the postnatal days 1-21 for 4 hr per day did not affect either working or reference memory on both primary and reversal learning. The data obtained are discussed on basis of influence of stress in early postnatal life on hypothalamo-pituitary axis and its effects on behavior of adult animals.

Intrathoracic Far-Field Electrocardiogram Allows Continuous Monitoring of Ischemia After Total Coronary Occlusion

INTRODUCTION

Recording of intrathoracic far-field electrocardiograms (FF-ECG) via can and electrodes of implantable cardioverter-defibrillators (ICD) is a promising method for continuous monitoring of myocardial ischemia. We assessed the hypothesis that experimentally induced ischemia provokes segment changes in the FF-ECG that can be detected by the ICD.

METHODS AND RESULTS

In seven pigs with an ICD implanted in the left pectoral region and electrodes placed in the right ventricle and the superior vena cava, we occluded all major coronary arteries in proximal and distal locations for 180 s each. Surface and FF-ECGs were compared for presence and time course of ischemic ST segment changes. Reliable detection of ischemia by ST segment analysis was possible in all (38/38) experiments. Maximum deviation from baseline was larger in FF-ECG (1.21 mV) than surface ECG leads (0.23 mV, P < 0.01) for all occlusion sites. Ischemia could be detected earlier (P < 0.05) in the FF-ECG, with a sensitivity of 100%, 93%, and 100% after occlusions in the left anterior descending, left circumflex, and right coronary arteries, respectively.

CONCLUSION

Intrathoracic FF-ECG allows reliable and reproducible detection of experimentally induced ischemia originating from all major coronary arteries and therefore could be an interesting tool for clinicians in monitoring high risk patients.

Expression of receptors for plasminogen activators on endothelial cell surface depends on their origin

Receptors for plasminogen activators present on endothelial cell (EC) surface regulate local plasmin activity. Plasmin generation by human ECs, derived from cerebral cortex, skin and lung, iliac artery, iliac vein, aorta and coronary artery, was studied. The respective ECs were treated with recombinant tissue plasminogen activator (rt-PA) or with recombinant urokinase-type plasminogen activator (ru-PA), washed, plasminogen added and the plasmin generated then assayed. The largest amounts of plasmin were generated by cerebral ECs, under baseline conditions or after exposure to rt-PA or ru-PA (P < 0.0001). Exposure to rt-PA also resulted in more plasmin generation than ru-PA in the cerebral ECs (P < 0.0001) but not in the other ECs. Heparin enhanced plasmin generation by both rt-PA and ru-PA. Specific antibody against annexin II, a t-PA receptor, blocked plasmin generation by rt-PA. Western blotting showed higher amounts of annexin II on the cell membrane in cerebral ECs. This suggests that expression of annexin II in ECs depends on their location, being greatest in cerebral ECs. In contrast, expression of u-PA receptor was the same for all ECs. This has implications for higher risk of intracranial bleeding during thrombolytic therapy, and for a role of t-PA in neurological development and function.

Thrombogenic role of cells undergoing apoptosis

Apoptosis is involved in many biological processes, especially during chemotherapy in cancer patients. Chemotherapy is also associated with an increased risk of thrombosis. The relationship between thrombogenicity and apoptosis was studied in various human tumour cell lines and non-tumour cell lines. Apoptosis was induced by the chemotherapeutic agent camptothecin and by Fas ligand, then quantified by staining with fluorescein isothiocyanate-conjugated annexin V and propidium iodide. A significant correlation between thrombin generation and degree of apoptosis was observed (P < 0.0005). Addition of anti-tissue factor antibody in excess or of tissue factor pathway inhibitor partially inhibited thrombin generation, suggesting that tissue factor activation was responsible for this process. A statistical correlation between tissue factor activity and degree of apoptosis was also found (P < 0.005). Both thrombin generation and tissue factor activity were blocked by the addition of annexin V, which binds and inhibits phosphatidylserine. This indicates that the exteriorization and exposure of phosphatidylserine on the cell surface membrane during apoptosis were essential for both thrombin generation and tissue factor activation.

Comorbid anxiety and affective disorder in alcohol-dependent patients seeking treatment: the first Multicentre Study in Germany

The goals of this study were to describe demographic variables, drinking history, and the 6-month prevalence of Axis I comorbidity among alcohol-dependent subjects in GERMANY: The variables: amount of alcohol consumption, age at onset of the first alcohol consumed, age at onset of daily alcohol consumption, age at onset of withdrawal symptoms and number of detoxifications were related to the different comorbid disorders and gender. In this study, 556 patients from 25 alcohol treatment centres were enrolled between 1 January 1999 and 30 April 1999. After a minimum of 10 days of sobriety patients who fulfilled ICD-10 and DSM-IV criteria of alcohol dependence were interviewed for data collection using the Mini-DIPS (German version of the Anxiety Disorders Interview Schedule) and a standardized psychosocial interview. The 6-month prevalence of comorbid Axis I disorders was 53.1%. Among the patients with comorbidity, affective and anxiety disorders were most frequent. Comorbid stress disorder was associated with an early start of drinking, an early beginning of withdrawal symptoms, highest number of detoxifications, and the highest amount of alcohol consumed. Female patients with anxiety disorder consumed more alcohol and started earlier than females without this comorbid disorder. The data do not answer the question of the pathogenesis of comorbid disorders and alcoholism, but indicate that stress disorders in alcoholic patients and anxiety disorders in female alcoholics influence the course and severity of alcoholism.

Extubation failure in a large pediatric ICU population

OBJECTIVE

To review a large population of children receiving mechanical ventilation to establish a baseline rate of extubation success and failure and to identify those characteristics that place a patient at greater risk of failing planned extubation.

DESIGN

Retrospective chart review.

SETTING

University-affiliated children's hospital with a 20-bed pediatric ICU.

PATIENTS

All 632 patients receiving mechanical ventilation during the 2-year period from July 1, 1996, to June 30, 1998.

METHOD

Patients receiving mechanical ventilation were identified via a computerized database. Charts were reviewed of all patients who were reintubated within 72 h of extubation.

MEASUREMENTS AND RESULTS

There were 548 planned extubation events, of which 521 were successful. Twenty-seven patients failed planned extubation at least once; only the first attempt at extubation was included in the analysis. The failure rate of planned extubations was 4.9%. Including only patients who had received mechanical ventilation for > 24 h before extubation, the failure rate was 6.0%. For patients intubated > 48 h, the failure rate was 7.9%. The patients who failed extubation were found to be significantly younger and to have received mechanical ventilation longer than those who succeeded, in both the analysis of all patients receiving mechanical ventilation and the subgroup of those receiving mechanical ventilation > 24 h. When only patients who had received mechanical ventilation for > 48 h were analyzed, the difference in age was no longer significant, but the duration of ventilation before extubation was still significantly longer for those who failed.

CONCLUSION

We determined the overall failure rate of planned extubations in a large population of pediatric patients to be 4.9%. Those patients who were younger and had received mechanical ventilation longer were more at risk for extubation failure.

Spatial memory, habituation, and reactions to spatial and nonspatial changes in rats with selective lesions of the hippocampus, the entorhinal cortex or the subiculum

Various spatial memory deficits have been described in rats with damage to the hippocampal formation (including the subiculum and the entorhinal cortex) and particularly in rats with selective lesions of the hippocampus proper. So far, the involvement of the entorhinal cortex in spatial memory is still controversial and the role of the subiculum is poorly documented. The aim of the present study was to compare the behavioural effects of selective lesions of the hippocampus, the entorhinal cortex or the subiculum in (a) a water-maze task using testing procedures sensitive to the disruption of reference or working memory and (b) in an object exploration task designed to evaluate habituation and subsequently reactions to changes of the spatial layout of objects (spatial change) or to the substitution of a familiar object by a new one (nonspatial change). Our results showed several similarities between the behavioural consequences of damage to each of the three structures. A few differences were also noted. Hippocampal rats were impaired in all spatial tasks, but they reacted like controls to a nonspatial change. The rats sustaining lesions of the entorhinal cortex or the subiculum were not impaired in the reference-memory procedure of the water-maze task and showed a deficit in reacting to a nonspatial change. Overall, our results confirm the central role of the hippocampus in spatial memory and also suggest a role for the entorhinal cortex and the subiculum in processing spatial informations. In addition, they indicate that the entorhinal cortex and the subiculum may have a hippocampal-independent role in memory.

[Osmolarity of solutions used in nebulization]

Inhaled medications are widely used in patients suffering from bronchial diseases. Beside their pharmacological properties, nebulised solutions have physico-chemical characteristics that can alter bronchial reactivity. Non-isotonic solutions can induce a bronchial hyperresponsiveness and/or a severe bronchonconstriction. Nevertheless, multiple drugs are used for nebulisation despite their unknown osmolarity. The aim of this study was to measure the tonicity of drug solutions commonly used for nebulisation in patients suffering from bronchial disease. Drug solutions were prepared either according to manufacturer recommendations or by diluting the stock in 5 ml of NaCl (0.9%) or H2CO3 (0.14%). Although bronchodilatator solutions (i.e. salbutamol, terbulatine, ipratropium bromide) were nearly isotonic, some drugs prepared for nebulisation had either a very high (e.g. mesna, netilmicine) or a very low (e.g. gomenol, sodium cromoglycate) tonicity. These values may be responsible for bronchoconstriction. Some hypertonic solutions, prepared with drugs such as acetylcytein or netilmycin, are not commercialised for nebulisation but are commonly used for aerosol therapy. In addition, solutions initially isotonic could become significantly hypertonic towards the end of nebulisation. Taken together, these results suggest that non-isotonic solutions should be used with caution specially in patients with bronchial hyperresponsiveness, even when aerosol therapy is prescribed for upper airways.

[Model based study of myocardial stimulation mechanisms]

The present study investigated the mechanisms of electrical stimulation of a myocardial fibre with the aim of developing improved minimally invasive stimulation methods. Using a dynamic myocyte model, the ionic currents crossing the voltage-dependent channels of the membrane are computed. To trigger an action potential, the membrane must first be depolarized to the threshold potential, when further depolarization continues spontaneously through the avalanche-like opening of the sodium channels. For the development of an action potential, not merely the amount of charge injected into the cell during the stimulus is of importance, but an above-threshold magnitude of the stimulation current is also required. The smallest energy required is achieved when the stimulus duration is chosen to be equal to the chronaxie. A second aspect of the study concerned the far-field stimulation of a muscle fibre, achieved by generating a potential gradient along the fibre. First, using a continuous fibre model, the fibre activating function is computed. In a more detailed study, the discrete segmental structure of the fibre determined by the gap junctions is taken into account, and the impact of these junctions on the activating function analysed. By optimizing the electrode configuration, an appropriate activating function results which guarantees successful stimulation when its maximum is above than threshold potential. The most important finding is that the myocardium can be stimulated by floating electrodes, thus opening up new possibilities for a less invasive electro-stimulation of the heart.

Serotyping and susceptibility to macrolides and other antimicrobial drugs of Streptococcus pyogenes isolated from patients with invasive diseases in southern Israel

Fifty-seven strains of Streptococcus pyogenes isolated from septic patients and 52 isolates from nonbacteremic patients in southern Israel were investigated for their susceptibility to new macrolides and other antimicrobial drugs. In addition, typing of the isolates by M protein and T antigen was performed. All organisms were susceptible to penicillin and chloramphenicol, 59% to tetracycline, and 7% to trimethoprim-sulfamethoxazole. All isolates but one (99%) were susceptible to clarithromycin, azithromycin, erythromycin, and clindamycin. The MIC90 of clarithromycin, erythromycin, and clindamycin was 0.064, 0.125, and 0.094 microgram/ml, respectively. Overall, 96% of the isolates could be typed by T antigen, but only 43% were M-protein typeable. No predominance of any particular M-protein type was observed. No significant differences between blood isolates and organisms derived from other sources were observed in the antibiotic susceptibility patterns or the distribution of serotypes. It is concluded that invasive Streptococcus pyogenes infections in southern Israel are caused by multiple unrelated strains. The organism remains susceptible to macrolides and clindamycin.

Respiratory and cardiac function in children after acute hypoxemic respiratory failure

OBJECTIVE

To examine the pulmonary and cardiac function of children who survived an episode of acute hypoxemic respiratory failure.

DESIGN

Descriptive cohort analysis.

SETTING

Pediatric clinical research center of a university hospital.

PATIENTS

Utilizing the criteria of PaO2 < 75 torr (< 10 kPa) with an FIO2 of > 0.5 while intubated, bilateral diffuse pulmonary infiltrates on chest radiograph, and exclusion of cardiogenic pulmonary edema, 147 patients were identified during the 6-yr period from July 1, 1986 to August 1, 1993. Fifty patients survived to discharge and 37 were alive at the time of follow-up. Fourteen patients were eventually entered into the study.

INTERVENTIONS

The study patients were given a test battery consisting of a questionnaire specific for cardiopulmonary status, a physical examination, a chest radiograph, electrocardiography, echocardiography with detailed examination of the pulmonary circulation, pulse oximetry, complete blood count, and serum chemistries and pulmonary function testing with bronchoprovocation in selected patients.

MEASUREMENTS AND MAIN RESULTS

The 14 follow-up patients were evaluated an average of 23 +/- 23 months (range 3 to 66) following intensive care unit discharge. No child reported a significant alteration in lifestyle or limitation of activities. Physical examinations were generally unremarkable. The room air oxyhemoglobin saturation was > or = 0.98 in all patients. Comparison of chest radiographs at the time of follow-up with those chest radiographs during the period of critical illness showed marked but not complete improvement in all. Electrocardiograms and echocardiograms showed new evidence of left ventricular hypertrophy in one child. The right ventricular preejection period to ejection time ratio was normal in all subjects. Eleven patients completed spirometry. Four patients were normal and the other patients had evidence of restrictive or obstructive disease either at baseline or after bronchoprovocation challenge. Ten children had lung volume measurements. Five children were normal, two showed increased volumes consistent with obstruction, and three showed decreased volumes indicative of restriction. Four of seven patients showed evidence of decreased diffusion capacity. Six of seven patients with evidence of abnormal pulmonary function had a positive response to bronchodilator administration.

CONCLUSIONS

Although pediatric survivors of acute hypoxemic respiratory failure perceive neither a limitation in lifestyle nor chronic pulmonary morbidity, careful examination of the cardiopulmonary system demonstrates a significant number with abnormal chest radiographs and abnormalities in pulmonary function. These children require careful follow-up and may benefit from use of a bronchodilator.