An electroencephalography-based sleep index and supervised machine learning as a suitable tool for automated sleep classification in children

STUDY OBJECTIVES

Although sleep is frequently disrupted in the pediatric intensive care unit, it is currently not possible to perform real-time sleep monitoring at the bedside. In this study, spectral band powers of electroencephalography data are used to derive a simple index for sleep classification.

METHODS

Retrospective study at Erasmus MC Sophia Children's Hospital, using hospital-based polysomnography recordings obtained in non-critically ill children between 2017 and 2021. Six age categories were defined: 6-12 months, 1-3 years, 3-5 years, 5-9 years, 9-13 years, and 13-18 years. Candidate index measures were derived by calculating spectral band powers in different frequent frequency bands of smoothed electroencephalography. With the best performing index, sleep classification models were developed for two, three, and four states via decision tree and five-fold nested cross-validation. Model performance was assessed across age categories and electroencephalography channels.

RESULTS

In total 90 patients with polysomnography were included, with a mean (standard deviation) recording length of 10.3 (1.1) hours. The best performance was obtained with the gamma to delta spectral power ratio of the F4-A1 and F3-A1 channels with smoothing. Balanced accuracy was 0.88, 0.74, and 0.57 for two-, three-, and four-state classification. Across age categories, balanced accuracy ranged between 0.83 and 0.92 and 0.72 and 0.77 for two- and three-state classification, respectively.

CONCLUSIONS

We propose an interpretable and generalizable sleep index derived from single-channel electroencephalography for automated sleep monitoring at the bedside in non-critically ill children ages 6 months to 18 years, with good performance for two- and three-state classification.

CITATION

van Twist E, Hiemstra FW, Cramer ABG, et al. An electroencephalography-based sleep index and supervised machine learning as a suitable tool for automated sleep classification in children. J Clin Sleep Med. 2024;20(3):389-397.

Microcirculatory Monitoring in Children with Congenital Heart Disease Before and After Cardiac Surgery

In this prospective observational study, we investigated whether congenital heart disease (CHD) affects the microcirculation and whether the microcirculation is altered following cardiac surgery with cardiopulmonary bypass (CPB). Thirty-eight children with CHD undergoing cardiac surgery with CPB and 35 children undergoing elective, non-cardiac surgery were included. Repeated non-invasive sublingual microcirculatory measurements were performed with handheld vital microscopy. Before surgery, children with CHD showed similar perfused vessel densities and red blood cell velocities (RBCv) but less perfused vessels (p < 0.001), lower perfusion quality (p < 0.001), and higher small vessel densities (p = 0.039) than children without CHD. After cardiac surgery, perfused vessel densities and perfusion quality of small vessels declined (p = 0.025 and p = 0.032), while RBCv increased (p = 0.032). We demonstrated that CHD was associated with decreased microcirculatory perfusion and increased capillary recruitment. The microcirculation was further impaired after cardiac surgery. Decreased microcirculatory perfusion could be a warning sign for altered tissue oxygenation and requires further exploration.

Adverse Events in Pediatric Critical Care Nonsurvivors With a Low Predicted Mortality Risk: A Multicenter Case Control Study

OBJECTIVES

Some patients with a low predicted mortality risk in the PICU die. The contribution of adverse events to mortality in this group is unknown. The aim of this study was to estimate the occurrence of adverse events in low-risk nonsurvivors (LN), compared with low-risk survivors (LS) and high-risk PICU survivors and nonsurvivors, and the contribution of adverse events to mortality.

DESIGN

Case control study. Admissions were selected from the national Dutch PICU registry, containing 53,789 PICU admissions between 2006 and 2017, in seven PICUs. PICU admissions were stratified into four groups, based on mortality risk (low/high) and outcome (death/survival). Random samples were selected from the four groups. Cases were "LN." Control groups were as follows: "LS," "high-risk nonsurvivors" (HN), and "high-risk survivors" (HS). Adverse events were identified using the validated trigger tool method.

SETTING

Patient chart review study.

PATIENTS

Children admitted to the PICU with either a low predicted mortality risk (< 1%) or high predicted mortality risk (≥ 30%).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

In total, 419 patients were included (102 LN, 107 LS, 104 HN, and 106 HS). LN had more complex chronic conditions (93.1%) than LS (72.9%; p < 0.01), HN (49.0%; p < 0.001), and HS (48.1%; p < 0.001). The occurrence of adverse events in LN (76.5%) was higher than in LS (13.1%) and HN (47.1%) ( p < 0.001). The most frequent adverse events in LN were hospital-acquired infections and drug/fluid-related adverse events. LN suffered from more severe adverse events compared with LS and HS ( p < 0.001). In 30.4% of LN, an adverse event contributed to death. In 8.8%, this adverse event was considered preventable.

CONCLUSIONS

Significant and preventable adverse events were found in low-risk PICU nonsurvivors. 76.5% of LN had one or more adverse events. In 30.4% of LN, an adverse event contributed to mortality.

Coagulation complications after conversion from roller to centrifugal pump in neonatal and pediatric extracorporeal membrane oxygenation

BACKGROUND/PURPOSE

Coagulation complications are frequent, unwanted occurrences in extracorporeal membrane oxygenation (ECMO) treatment, possibly influenced by the pump in the ECMO-circuit. We hypothesized that fewer complications would occur with a smaller, heparin-coated ECMO system with a centrifugal pump (CP) than with one with a roller pump (RP) and that after conversion, complication rates would decrease over time.

METHODS

This single-center, retrospective chart study included all first neonatal and pediatric ECMO runs between 2009 and 2015. Differences between groups were assessed with Mann-Whitney U tests and Kruskal-Wallis tests. Determinants of complication rates were evaluated through Poisson regression models. The CP group was divided into three consecutive groups to assess whether complication rates decreased over time.

RESULTS

The RP group comprised 90 ECMO runs and the CP group 82. Hemorrhagic complication rates were significantly higher with the CP than with the RP, without serious therapeutic consequences, while thrombotic complications rates were unaffected. Intracranial hemorrhage rates and coagulation-related mortality rates were similar. Gained experience with the CP did not improve complication rates or survival over time.

CONCLUSIONS

Although the CP seems safe, it does not seem beneficial over the RP. Further research is warranted on how pump type affects coagulation, taking into account the severity and implications of coagulation complications.

LEVEL OF EVIDENCE

Level III.

The Sublingual Microcirculation Throughout Neonatal and Pediatric Extracorporeal Membrane Oxygenation Treatment: Is It Altered by Systemic Extracorporeal Support?

Background: Extracorporeal membrane oxygenation (ECMO) treatment alleviates systemic cardiorespiratory failure. However, it is unclear whether ECMO also improves microcirculatory function, as the microcirculation can be disturbed despite normal systemic hemodynamics. We therefore aimed to study the sublingual microcirculation (SMC) throughout neonatal and pediatric ECMO treatment. We hypothesized that the SMC improves after starting ECMO, that the SMC differs between venovenous (VV) and venoarterial (VA) ECMO, and that insufficient recovery of microcirculatory disturbances during ECMO predicts mortality. Methods: This single-center prospective longitudinal observational study included 34 consecutive children (April 2016-September 2018). The SMC was assessed daily with a handheld vital microscope (integrated with incident dark field illumination) before, during, and after ECMO. Validated parameters of vessel density, perfusion, and flow quality were assessed for all vessels (diameter <100 μm) and small vessels (<20 μm). Linear mixed models and logistic regression models were built to assess changes over time and identify significant covariates. Using ROC curves, the predictive values of microcirculatory parameters were assessed for mortality on ECMO and overall mortality. Results: The study population comprised 34 patients (median age 0.27 years, 16 neonates, 16 females). Twelve patients were treated with VV and 22 with VA ECMO. Twelve patients died during ECMO (stopped due to futility) and 3 died after ECMO but before discharge. Microcirculatory parameters did not change significantly before, during or after ECMO. Except between microcirculatory flow index (MFI) and mean arterial pressure (MAP), no significant associations were found between microcirculatory parameters and global systemic hemodynamics. The probability of an undisturbed MFI (>2.6) increased with higher MAP (OR: 1.050, 95%CI: 1.008-1.094). Microcirculatory parameters did not significantly differ between VV and VA ECMO or between survivors and non-survivors. None of the microcirculatory parameters could predict mortality on ECMO or overall mortality. Conclusion: In this heterogeneous study population, we were not able to demonstrate an effect of ECMO on the sublingual microcirculation. Microcirculatory parameters did not change throughout ECMO treatment and did not differ between VV and VA ECMO or between survivors and non-survivors. Future research should focus on determining which neonatal and pediatric ECMO patients would benefit from microcirculatory monitoring and how.

Assessing the Microcirculation With Handheld Vital Microscopy in Critically Ill Neonates and Children: Evolution of the Technique and Its Potential for Critical Care

Assuring adequate tissue oxygenation in the critically ill, but still developing child is challenging. Conventional hemodynamic monitoring techniques fall short in assessing tissue oxygenation as these are directed at the macrocirculation and indirect surrogates of tissue oxygenation. The introduction of handheld vital microscopy (HVM) has allowed for the direct visualization of the microcirculation and with this has offered insight into tissue oxygenation on a microcirculatory level. Since its introduction, technical improvements have been made to HVM, to both hardware and software, and guidelines have been developed through expert consensus on image assessment and analysis. Using HVM, the microcirculation of the skin, the buccal mucosa, and the sublingual mucosa of healthy and (critically) ill neonates and children have been visualized and investigated. Yet, integration of HVM in hemodynamic monitoring has been limited due to technical shortcomings. Only superficial microcirculatory beds can be visualized, inter-observer and intra-observer variabilities are not accounted for and image analysis happens offline and is semi-automated and time-consuming. More importantly, patients need to be cooperative or fully sedated to prevent pressure and movement artifacts, which is often not the case in children. Despite these shortcomings, observational research with HVM in neonates and children has revealed the following: (1) age-related developmental changes in the microcirculation, (2) loss of hemodynamic coherence, i.e., microcirculatory disturbances in the presence of a normal macrocirculation and, (3) microcirculatory disturbances which were independently associated with increased mortality risk. Although these observations underline the importance of microcirculatory monitoring, several steps have to be taken before integration in the decision process during critical care can happen. These steps include technological innovations to ease the use of HVM in the pediatric age group, measuring additional functional parameters of microvascular blood flow and integrated automated analysis software. As a next step, reference values for microcirculatory parameters need to be established, while also accounting for developmental changes. Finally, studies on microcirculatory guided therapies are necessary to assess whether the integration of microcirculatory monitoring will actually improve patient outcome. Nevertheless, HVM remains a promising, non-invasive tool to help physicians assure tissue oxygenation in the critically ill child.

Corrigendum: Assessing the Microcirculation With Handheld Vital Microscopy in Critically lll Neonates and Children: Evolution of the Technique and Its Potential for Critical Care

[This corrects the article DOI: 10.3389/fped.2019.00273.].

The vulnerable microcirculation in the critically ill pediatric patient

In neonates, cardiovascular system development does not stop after the transition from intra-uterine to extra-uterine life and is not limited to the macrocirculation. The microcirculation (MC), which is essential for oxygen, nutrient, and drug delivery to tissues and cells, also develops. Developmental changes in the microcirculatory structure continue to occur during the initial weeks of life in healthy neonates. The physiologic hallmarks of neonates and developing children make them particularly vulnerable during critical illness; however, the cardiovascular monitoring possibilities are limited compared with critically ill adult patients. Therefore, the development of non-invasive methods for monitoring the MC is necessary in pediatric critical care for early identification of impending deterioration and to enable the initiation and titration of therapy to ensure cell survival. To date, the MC may be non-invasively monitored at the bedside using hand-held videomicroscopy, which provides useful information regarding the microcirculation. There is an increasing number of studies on the MC in neonates and pediatric patients; however, additional steps are necessary to transition MC monitoring from bench to bedside. The recently introduced concept of hemodynamic coherence describes the relationship between changes in the MC and macrocirculation. The loss of hemodynamic coherence may result in a depressed MC despite an improvement in the macrocirculation, which represents a condition associated with adverse outcomes. In the pediatric intensive care unit, the concept of hemodynamic coherence may function as a framework to develop microcirculatory measurements towards implementation in daily clinical practice.

Safety of the Manchester Triage System to Detect Critically Ill Children at the Emergency Department

OBJECTIVE

To assess the safety of the Manchester Triage System in pediatric emergency care for children who require admission to the intensive care unit (ICU).

STUDY DESIGN

Between 2006 and 2013, 50 062 consecutive emergency department visits of children younger than the age of 16 years were included. We determined the percentage of undertriage, defined as the proportion of children admitted to ICU triaged as low urgent according to the Manchester Triage System, and diagnostic performance measures, including sensitivity, specificity, and diagnostic OR. Characteristics of undertriaged patients were compared with correctly triaged patients. In a logistic regression model, risk factors for undertriage were determined.

RESULTS

In total, 238 (28.7%) of the 830 children admitted to ICU during the study period were undertriaged. Sensitivity of high Manchester Triage System urgency levels to detect ICU admission was 71% (95% CI 68%-74%) and specificity 85% (95% CI 85%-85%). Severity of illness was lower in undertriaged children than correctly triaged children admitted to ICU. Risk factors for undertriage were age <3 months, medical presenting problem, comorbidity, referral by a medical specialist or emergency medical services, and presentation during the evening or night shift.

CONCLUSION

The Manchester Triage System misclassifies a substantial number of children who require ICU admission. Modifications targeted at young children and children with a comorbid condition could possibly improve safety of the Manchester Triage System in pediatric emergency care.

Injurious mechanical ventilation causes kidney apoptosis and dysfunction during sepsis but not after intra-tracheal acid instillation: an experimental study

Background

Intratracheal aspiration and sepsis are leading causes of acute lung injury that frequently necessitate mechanical ventilation (MV), which may aggravate lung injury thereby potentially increasing the risk of acute kidney injury (AKI). We compared the effects of ventilation strategies and underlying conditions on the development of AKI.

Methods

Spraque Dawley rats were challenged by intratracheal acid instillation or 24 h of abdominal sepsis, followed by MV with a low tidal volume (LV_T) and 5 cm H₂O positive end-expiratory pressure (PEEP) or a high tidal volume (HV_T) and no PEEP, which is known to cause more lung injury after acid instillation than in sepsis. Rats were ventilated for 4 hrs and kidney function and plasma mediator levels were measured. Kidney injury was assessed by microscopy; apoptosis was quantified by TUNEL staining.

Results

During sepsis, but not after acid instillation, MV with HV_T caused more renal apoptosis than MV with LV_T. Increased plasma active plasminogen activator inhibitor-1 correlated to kidney apoptosis in the cortex and medulla. Increased apoptosis after HV_T ventilation during sepsis was associated with a 40% decrease in creatinine clearance.

Conclusions

AKI is more likely to develop after MV induced lung injury during an indirect (as in sepsis) than after a direct (as after intra-tracheal instillation) insult to the lungs, since it induces kidney apoptosis during sepsis but not after acid instillation, opposite to the lung injury it caused. Our findings thus suggest using protective ventilatory strategies in human sepsis, even in the absence of overt lung injury, to protect the kidney.

Aggravation of myocardial dysfunction by injurious mechanical ventilation in LPS-induced pneumonia in rats

BACKGROUND

Mechanical ventilation (MV) may cause ventilator-induced lung injury (VILI) and may thereby contribute to fatal multiple organ failure. We tested the hypothesis that injurious MV of lipopolysaccharide (LPS) pre-injured lungs induces myocardial inflammation and further dysfunction ex vivo, through calcium (Ca2+)-dependent mechanism.

MATERIALS AND METHODS

N = 35 male anesthetized and paralyzed male Wistar rats were randomized to intratracheal instillation of 2 mg/kg LPS or nothing and subsequent MV with lung-protective settings (low tidal volume (Vt) of 6 mL/kg and 5 cmH2O positive end-expiratory pressure (PEEP)) or injurious ventilation (high Vt of 19 mL/kg and 1 cmH2O PEEP) for 4 hours. Myocardial function ex vivo was evaluated in a Langendorff setup and Ca2+ exposure. Key mediators were determined in lung and heart at the mRNA level.

RESULTS

Instillation of LPS and high Vt MV impaired gas exchange and, particularly when combined, increased pulmonary wet/dry ratio; heat shock protein (HSP)70 mRNA expression also increased by the interaction between LPS and high Vt MV. For the heart, C-X-C motif ligand (CXCL)1 and Toll-like receptor (TLR)2 mRNA expression increased, and ventricular (LV) systolic pressure, LV developed pressure, LV +dP/dtmax and contractile responses to increasing Ca2+ exposure ex vivo decreased by LPS. High Vt ventilation aggravated the effects of LPS on myocardial inflammation and dysfunction but not on Ca2+ responses.

CONCLUSIONS

Injurious MV by high Vt aggravates the effects of intratracheal instillation of LPS on myocardial dysfunction, possibly through enhancing myocardial inflammation via pulmonary release of HSP70 stimulating cardiac TLR2, not involving Ca2+ handling and sensitivity.

High tidal volume mechanical ventilation-induced lung injury in rats is greater after acid instillation than after sepsis-induced acute lung injury, but does not increase systemic inflammation: an experimental study

BACKGROUND

To examine whether acute lung injury from direct and indirect origins differ in susceptibility to ventilator-induced lung injury (VILI) and resultant systemic inflammatory responses.

METHODS

Rats were challenged by acid instillation or 24 h of sepsis induced by cecal ligation and puncture, followed by mechanical ventilation (MV) with either a low tidal volume (Vt) of 6 mL/kg and 5 cm H2O positive end-expiratory pressure (PEEP; LVt acid, LVt sepsis) or with a high Vt of 15 mL/kg and no PEEP (HVt acid, HVt sepsis). Rats sacrificed immediately after acid instillation and non-ventilated septic animals served as controls. Hemodynamic and respiratory variables were monitored. After 4 h, lung wet to dry (W/D) weight ratios, histological lung injury and plasma mediator concentrations were measured.

RESULTS

Oxygenation and lung compliance decreased after acid instillation as compared to sepsis. Additionally, W/D weight ratios and histological lung injury scores increased after acid instillation as compared to sepsis. MV increased W/D weight ratio and lung injury score, however this effect was mainly attributable to HVt ventilation after acid instillation. Similarly, effects of HVt on oxygenation were only observed after acid instillation. HVt during sepsis did not further affect oxygenation, compliance, W/D weight ratio or lung injury score. Plasma interleukin-6 and tumour necrosis factor-α concentrations were increased after acid instillation as compared to sepsis, but plasma intercellular adhesion molecule-1 concentration increased during sepsis only. In contrast to lung injury parameters, no additional effects of HVt MV after acid instillation on plasma mediator concentrations were observed.

CONCLUSIONS

During MV more severe lung injury develops after acid instillation as compared to sepsis. HVt causes VILI after acid instillation, but not during sepsis. However, this differential effect was not observed in the systemic release of mediators.

Bench-to-bedside review: Ventilation-induced renal injury through systemic mediator release--just theory or a causal relationship?

We review the current literature on the molecular mechanisms involved in the pathogenesis of acute kidney injury induced by plasma mediators released by mechanical ventilation. A comprehensive literature search in the PubMed database was performed and articles were identified that showed increased plasma levels of mediators where the increase was solely attributable to mechanical ventilation. A subsequent search revealed articles delineating the potential effects of each mediator on the kidney or kidney cells. Limited research has focused specifically on the relationship between mechanical ventilation and acute kidney injury. Only a limited number of plasma mediators has been implicated in mechanical ventilation-associated acute kidney injury. The number of mediators released during mechanical ventilation is far greater and includes pro- and anti-inflammatory mediators, but also mediators involved in coagulation, fibrinolysis, cell adhesion, apoptosis and cell growth. The potential effects of these mediators is pleiotropic and include effects on inflammation, cell recruitment, adhesion and infiltration, apoptosis and necrosis, vasoactivity, cell proliferation, coagulation and fibrinolysis, transporter regulation, lipid metabolism and cell signaling. Most research has focused on inflammatory and chemotactic mediators. There is a great disparity of knowledge of potential effects on the kidney between different mediators. From a theoretical point of view, the systemic release of several mediators induced by mechanical ventilation may play an important role in the pathophysiology of acute kidney injury. However, evidence supporting a causal relationship is lacking for the studied mediators.

Production of endothelin-1 and reduced blood flow in the rat kidney during lung-injurious mechanical ventilation

INTRODUCTION

The mechanisms by which mechanical ventilation (MV) can injure remote organs, such as the kidney, remain poorly understood. We hypothesized that upregulation of systemic inflammation, as reflected by plasma interleukin-6 (IL-6) levels, in response to a lung-injurious ventilatory strategy, ultimately results in kidney dysfunction mediated by local endothelin-1 (ET-1) production and renal vasoconstriction.

METHODS

Healthy, male Wistar rats were randomized to 1 of 2 MV settings (n=9 per group) and ventilated for 4 h. One group had a lung-protective setting using peak inspiratory pressure of 14 cm H2O and a positive end-expiratory pressure of 5 cm H2O; the other had a lung-injurious strategy using a peak inspiratory pressure of 20 cm H2O and positive end-expiratory pressure of 2 cm H2O. Nine randomly assigned rats served as nonventilated controls. We measured venous and arterial blood pressure and cardiac output (thermodilution method), renal blood flow (RBF) using fluorescent microspheres, and calculated creatinine clearance, urine flow, and fractional sodium excretion. Histological lung damage was assessed using hematoxylin-eosin staining. Renal ET-1 and plasma ET-1 and IL-6 concentrations were measured using enzyme-linked immunosorbent assays.

RESULTS

Lung injury scores were higher after lung-injurious MV than after lung-protective ventilation or in sham controls. Lung-injurious MV resulted in significant production of renal ET-1 compared with the lung-protective and control groups. Simultaneously, RBF in the lung-injurious MV group was approximately 40% lower (P<0.05) than in the control group and 28% lower (P<0.05) than in the lung-protective group. Plasma ET-1 and IL-6 levels did not differ among the groups and systemic hemodynamics, such as cardiac output, were comparable. There was no effect on creatinine clearance, fractional sodium excretion, urine output, or kidney histology.

CONCLUSIONS

Lung-injurious MV for 4 h in healthy rats results in significant production of renal ET-1 and in decreased RBF, independent of IL-6. Decreased RBF has no observable effect on kidney function or histology.

Ventilator-induced coagulopathy in experimental Streptococcus pneumoniae pneumonia

Pneumonia, the main cause of acute lung injury, is characterised by a local pro-inflammatory response and coagulopathy. Mechanical ventilation (MV) is often required. However, MV can lead to additional injury: so-called ventilator-induced lung injury (VILI). Therefore, the current authors investigated the effect of VILI on alveolar fibrin turnover in Streptococcus pneumoniae pneumonia. Pneumonia was induced in rats, followed 48 h later by either lung-protective MV (lower tidal volumes (LV(T)) and positive end-expiratory pressure (PEEP)) or MV causing VILI (high tidal volumes (HV(T)) and zero end-expiratory pressure (ZEEP)) for 3 h. Nonventilated pneumonia rats and healthy rats served as controls. Thrombin-antithrombin complexes (TATc), as a measure for coagulation, and plasminogen activator activity, as a measure of fibrinolysis, were determined in bronchoalveolar lavage fluid (BALF) and serum. Pneumonia was characterised by local (BALF) activation of coagulation, resulting in elevated TATc levels and attenuation of fibrinolysis compared with healthy controls. LV(T)-PEEP did not influence alveolar coagulation or fibrinolysis. HV(T)-ZEEP did intensify the local procoagulant response: TATc levels rose significantly and levels of the main inhibitor of fibrinolysis, plasminogen activator inhibitor-1, increased significantly. HV(T)-ZEEP also resulted in systemic elevation of TATc compared with LV(T)-PEEP. Mechanical ventilation causing ventilator-induced lung injury increases pulmonary coagulopathy in an animal model of Streptococcus pneumoniae pneumonia and results in systemic coagulopathy.

Radiofrequency ablation in patients with primary and secondary hepatic malignancies

The aims of this study were to assess the technical effectiveness of radiofrequency (RF) ablation in patients with primary or secondary hepatic malignancies and to determine survival and complication rates. This was a retrospective analysis of prospectively collected data of patients treated with RF ablation and controlled for recurrence every 3 months by contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI). The outcome is compared with a comprehensive review of data published in recent literature. Forty-seven patients underwent 50 RF sessions for the ablation of 73 tumors. Local tumor progression was observed in 11 patients (23%). A tumor sized larger than 30 mm, a tumor load larger than 14 cm3, and a percutaneous approach were associated with a faster time to local tumor progression. At the end of a mean (+/- SD) follow-up period of 11.4 +/- 7.5 months, 39 patients (83%) were alive, including eight patients with recurrent disease. The overall cumulative survival rates at 12 and 24 months were 87% and 70%, respectively. In our center, RF ablation can be safely performed to achieve adequate local control and survival rates. Time to local tumor progression was significantly related to initial size of the tumor and tumor load.

Mechanical ventilation and acute renal failure

OBJECTIVE

To review the current literature on possible mechanisms by which mechanical ventilation may initiate or aggravate acute renal failure.

DATA SOURCE

A Medline database and references from identified articles were used to perform a literature search relating to mechanical ventilation and acute renal failure.

DATA SYNTHESIS

Acute renal failure may be initiated or aggravated by mechanical ventilation through three different mechanisms. First, strategies such as permissive hypercapnia or permissive hypoxemia may compromise renal blood flow. Second, through effects on cardiac output, mechanical ventilation affects systemic and renal hemodynamics. Third, mechanical ventilation may cause biotrauma-a pulmonary inflammatory reaction that may generate systemic release of inflammatory mediators. The harmful effects of mechanical ventilation may become more significant when a comorbidity is present. In these situations, it is more difficult to maintain normal gas exchange, and moderate arterial hypoxemia and hypercapnia are often accepted. Renal blood flow is compromised due to a decreased cardiac output as a consequence of high intrathoracic pressures. Furthermore, the effects of biotrauma are not limited to the lungs but may lead to a systemic inflammatory reaction.

CONCLUSIONS

The development of acute renal failure during mechanical ventilation likely represents a multifactorial process that may become more important in the presence of comorbidities. Development of optimal interventional strategies requires an understanding of physiologic principles and greater insight into the precise molecular and cellular mechanisms that may also play a role.

L-asparaginase-induced severe necrotizing pancreatitis successfully treated with percutaneous drainage

L-asparaginase is a key component of the antileukemic therapy in children with acute lymphoblastic leukemia (ALL). Pancreatitis has been noted to be a complication in 2-16% of patients undergoing treatment with L-asparaginase for a variety of pediatric neoplasms. Most cases of pancreatitis associated with L-asparaginase toxicity are self-limiting and respond favorably to nasogastric decompression and intravenous hyperalimentation. However, in rare instances, hemorrhagic pancreatitis or necrosis may occur. L-asparaginase-induced pancreatitis is an uncommon but potential lethal complication of the treatment of leukemia. We present a pediatric patient with leukemia and a severe, L-asparaginase-induced necrotizing pancreatitis, treated successfully with percutaneous drainage used to flush the infected necrotic parts.

Interstitial laser coagulation with temporary hepatic artery occlusion for patients with cirrhosis and irresectable hepatoma

BACKGROUND

The aim was to determine the degree of local control of hepatocellular carcinoma (HCC) in patients with cirrhotic liver disease when treated with ultrasonographically guided interstitial laser coagulation (ILC) with temporary hepatic artery occlusion.

METHODS

Sixteen patients with 24 HCC tumours were treated. Follow-up was by computed tomography or magnetic resonance imaging every 3 months.

RESULTS

Nineteen of 24 tumours showed complete necrosis immediately after treatment, and there was no tumour recurrence during follow-up (mean 14 months, median 12 months). No effect on liver function was observed after 1 week and there was no death. In 13 of the 16 patients, new HCC foci developed at other sites.

CONCLUSION

Percutaneous ILC combined with temporary hepatic artery occlusion during a single session is an effective local treatment for HCC nodules smaller than 5 cm. However, new HCC lesions develop in the majority of patients, which underscores the need for adjuvant therapy or repeated treatment in these patients.

Value of laparoscopy and laparoscopic ultrasonography in determining resectability of colorectal hepatic metastases

BACKGROUND

The aim was to assess the value of laparoscopy and laparoscopic ultrasonography (LUS) in selecting patients for resection of colorectal hepatic metastases.

METHODS

Sixty patients with potentially resectable colorectal hepatic metastases after helical computer tomography (CT) and scheduled to undergo laparoscopy and LUS were studied retrospectively. Primary outcome measurement was the number of cases in which laparoscopy and LUS resulted in a change of therapeutic approach.

RESULTS

Of the 60 patients, 59 patients were examined by LUS and/or laparoscopy. The small intestine was perforated due to adhesions in two patients, necessitating open exploration in one of them. In 17 patients (29%) the combined laparoscopic procedure yielded results prohibiting resection; another 6 patients were denied resection on other grounds. Of the 36 patients who underwent open exploration, 31 underwent resection. Combined laparoscopy and LUS predicted resectability correctly in 86% of the patient group. Compared with resection, the sensitivity of both CT and LUS to detect lesions was 91%.

DISCUSSION

Laparoscopy and LUS can avoid open exploration without resection in a substantial number of patients considered eligible for resection of colorectal hepatic metastases based on CT. LUS does not seem to detect more metastases than CT.

Inaccuracies inherent in patient-specific dual-energy X-ray absorptiometry bone mineral density measurements: comprehensive phantom-based evaluation

An extensive series of dual-energy X-ray absorptiometry (DXA) scans and dual polyenergetic X-ray simulation studies of 150 different phantom arrays were carried out to evaluate quantitatively the extent of systematic inaccuracies inherent in DXA in vivo bone mineral density (BMD). These measurements are particularly relevant to lumbar vertebral and proximal femoral sites. The phantoms were specially fabricated near perfect absorptiometric representations of bone material, red marrow (RM) and yellow marrow (YM), and extraosseous mixtures of fat (F) and lean muscle that spanned the full range of soft tissue anthropometrics encountered clinically. In each case, the DXA-measured BMD values obtained using Hologic, Lunar, and Norland densitometers were found to be virtually the same and to be in excellent agreement with the corresponding quantitative simulation study BMD results. Comparisons of the known phantom BMD values and DXA-measured BMD in each case allowed the BMD inaccuracies to be evaluated. These present findings show that these ubiquitous inaccuracies in DXA BMD methodology are of in vivo soft tissue anthropometric genesis. It is found that patient-specific DXA-measured in vivo BMD inaccuracies as high as 20% or more can be readily anticipated clinically, particularly in cases of osteopenic, osteoporotic, and elderly patients. As these inaccuracies exceed considerably DXA precision errors, they may compromise patient-specific evaluations of fracture risk and, in prospective studies, mask or exaggerate clinically significant true changes in BMD. It is concluded that the magnitudes and variability of inherent inaccuracies in DXA-measured in vivo BMD underscore the need for prudence and circumspection in interpretations and assessments of DXA-based clinical studies.

Second-Generation, Subsecond Multislice Computed-Tomography: Advancing the Role of Helical CT Pulmonary Angiography in Suspected Pulmonary Embolism

Advancements in computed tomography (CT) have led to the development of noninvasive helical CT of the pulmonary arteries as a diagnostic tool in patients with suspected pulmonary embolism (PE). The first-generation, single-slice CT scanners were capable of acquiring one 3-mm-thick imaging section per second. As a further technical evolution of helical CT, multislice CT scanners now allow simultaneous acquisition of eight slices per second. This increased imaging speed can be used to advantage by scanning the entire thorax with 1-mm-thin imaging sections during a single breath-hold. Because of the increased spatial resolution and increased robustness to motion artifacts of multislice CT, the pulmonary arteries can now be accurately depicted up to the fifth order branches. In comparison with single-slice CT, this holds the promise of better detection of small subsegmental PE and thus, increased accuracy to detect and rule out PE. A few recent management studies suggest that single-slice CT can be used as an accurate cornerstone in the diagnostic work-up of suspected PE-a concept that will be further enhanced with multislice helical CT.

[Treatment of non-resectable liver tumors with percutaneous interstitial laser coagulation while interrupting blood circulation to the liver]

OBJECTIVE

To evaluate, in patients with hepatocellular carcinoma or colorectal carcinoma disseminated to the liver, treatment with interstitial laser coagulation (ILC) during temporary occlusion of vascular inflow in the liver: feasibility, complications and initial tumour response.

DESIGN

Prospective, descriptive.

METHODS

Patients were included if their tumours were surgically irresectable and smaller than 4 cm in diameter and did not exceed a number of 3. ILC was performed under general anaesthesia, basically via a percutaneous approach. Vascular inflow was occluded during laser treatment. Twenty-four hours after ILC a triphasic spiral CT was performed to assess the result of the treatment.

RESULTS

In 10 patients 14 hepatic tumours were lasered in 12 treatment sessions (10 percutaneous and 2 at laparotomy). After 5 treatment sessions, complications were observed of which pain at the insertion site of the catheters was the most frequent. For 6 out of the 10 patients with percutaneous procedures, discharge was within 24 hours after ILC. Nine out of the 14 tumours (65%) were completely coagulated.

CONCLUSION

ILC with vascular inflow occlusion is a safe and feasible technique that can be performed during a short hospital stay. Initial tumour response is 65% and these results justify determination of duration of response in a larger group of patients.

Increased loss of trabecular but not cortical bone density, 1 year after discontinuation of 2 years hormone replacement therapy with Tibolone

OBJECTIVE

Assessment of loss of bone density (BD) 1 year after a 2-year period of hormone replacement therapy (HRT) with two doses of Tibolone as compared to placebo in early post-menopausal women.

METHODS

Sixty-four out of 84 women (1-3 years following spontaneous menopause) who completed a 2-year randomised, placebo controlled study to evaluate effects of Tibolone participated in this follow-up study. Quantitative computed tomography was used to exclusively measure trabecular BD, microdensitometry of the mid-phalangeal shaft was used for estimation of cortical BD and biochemical markers of bone metabolism were assessed, 1 year after discontinuation of Tibolone. The study group received either placebo (n = 16), 1.25 mg/day Tibolone (n = 25) or 2.5 mg/day Tibolone (n = 23).

RESULTS

Observations revealed a significantly greater decrease in trabecular BD during the post-trial year in both treatment groups compared to the placebo group (for 1.25 mg/day Tibolone, -6.0%, 95% CI -8.4 to -3.5; for 2.5 mg/day Tibolone, -10.0%, 95% CI: -12.9 to -6.9). In contrast, there was no significant difference in loss of phalangeal BD in both treatment groups compared to placebo. Biochemical markers (serum alkaline phosphatase, urinary excretion of hydroxyproline and calcium) do not suggest an increased bone turnover comparing Tibolone groups to placebo, 1 year after cessation of Tibolone.

CONCLUSION

The present study suggests an increased loss of trabecular but not cortical BD as compared to the placebo group in the first year after cessation of HRT with Tibolone in early post-menopausal women.

Vertebral dimensions: influence of X-ray technique and patient size on measurements

In this study a new reference value, "corrected vertebral dimension," is presented for vertebral height measurements. Of 68 females (age 18-88 years; mean 44.2 years) and 40 males (age 16-81 years; mean 55 years) the projected vertebral dimensions (T4-L5) were measured on lateral radiographs. In addition to this, the vertebra-to-film distances (VFD) were measured and a fixed focus-to-film distance (FFD) was used during the study. Corrected dimensions of the thoracic and lumbar vertebrae (T4-L5) were calculated using the FFD and VFD. These corrected dimensions were then used to recalculate projected vertebral dimensions at different focus-to-film distances. The applied geometric corrections were verified in a phantom study representing an in vitro situation. The results indicate that studies using different X-ray techniques for making lateral radiographs of the spine can become comparable when using corrected vertebral dimensions.

Distribution of trabecular and cortical bone related to geometry. A quantitative computed tomography study of the femoral neck

METHODS

The relation between geometry and the distribution of trabecular and cortical bone mass and density in the human femoral neck was evaluated with quantitative computed tomography (QCT). Quantitative computed tomography data were obtained from 2-mm thick computed tomography slices of 20 human femur necks in vitro. A standardized scan position in each femur was used with the smallest cross-section as reference point.

RESULTS

When trabecular bone mass (TrBM) and cortical bone mass were presented as percentage of total bone mass (ToBM), it was found that, starting at the cranial (head) side, ToBM consists of 78% TrBM. About 21% of ToBM can be found as TrBM at the caudal (trochanter) side. At the smallest cross-sectional volume TrBM is 33% of ToBM. For every 2-mm slice, an average decrease of 5% TrBM can be seen.

CONCLUSIONS

These data show that geometry and bone mass distribution are related. Whereas total bone mass remains relatively stable, the cortical and trabecular bone mass changes extensively. This implies that QCT measurements in the femoral neck depend highly on midneck positioning.

Endoanal MRI of the anal sphincter complex: correlation with cross-sectional anatomy and histology

The purpose of this study was to correlate the in vivo endoanal MRI findings of the anal sphincter with the cross-sectional anatomy and histology. Fourteen patients with rectal tumours were examined with a rigid endoanal MR coil before undergoing abdominoperineal resection. In addition, 12 cadavers were used to obtain cross-sectional anatomical sections. The images were correlated with the histology and anatomy of the resected rectal specimens as well as with the cross-sectional anatomical sections of the 12 cadavers. The findings in 8 patients, 11 rectal preparations, and 10 cadavers, could be compared. In these cases, there was an excellent correlation between endoanal MRI and the cross-sectional cadaver anatomy and histology. With endoanal MRI, all muscle layers of the anal canal wall, comprising the internal anal sphincter, longitudinal muscle, the external anal sphincter and the puborectalis muscle were clearly visible. The levator ani muscle and ligamentous attachments were also well demonstrated. The perianal anatomical spaces, containing multiple septae, were clearly visible. In conclusion, endoanal MRI is excellent for visualising the anal sphincter complex and the findings show a good correlation with the cross-sectional anatomy and histology.

Effects of two doses of tibolone on trabecular and cortical bone loss in early postmenopausal women: a two-year randomized, placebo-controlled study

The present randomized, double-blind, placebo-controlled, 2-year study is the first to evaluate the effect of 1.25 and 2.5 mg tibolone daily oral administration on trabecular and cortical bone loss in early postmenopausal women. Ninety-four healthy, normal weight, nonsmoking women participated 1-3 years following spontaneous menopause. Twenty-three subjects were randomized to the placebo group, 36 to the 1.25 mg/day tibolone group, and 35 to the 2.5 mg/day tibolone group. Bone density was assessed at 6 month intervals. Spinal trabecular bone density (BD) was measured with quantitative computed tomography. Phalangeal cortical BD was measured by radiographic absorptiometry. The 2-year change vs. baseline in the placebo group for trabecular BD was -6.4% (95% confidence interval -8.1 to -4.7). Cortical BD did not change significantly. At 24 months both tibolone groups showed a statistically significantly higher trabecular [9.4% (6.6-12.2) for the 1.25 mg group and 14.7% (11.8-17.5%) for the 2.5 mg group] and phalangeal BD [4.4% (1.5-7.4) for the 1.25 mg group and 6.8% (3.8-9.8) for the 2.5 mg group] as compared to the placebo group. After 2 years of tibolone in both regimes, trabecular and phalangeal BD was significantly higher as compared to pretreatment values. At 24 months the 2.5 mg group showed a significantly higher trabecular (p < 0.001) but not phalangeal (p = 0.064) BD compared to the 1.25 mg group. Tibolone prevents early postmenopausal bone loss by inducing an increase in trabecular and phalangeal BD.

Accuracy and the influence of marrow fat on quantitative CT and dual-energy X-ray absorptiometry measurements of the femoral neck in vitro

Bone mineral measurements with quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA) were compared with chemical analysis (ChA) to determine (1) the accuracy and (2) the influence of bone marrow fat. Total bone mass of 19 human femoral necks in vitro was determined with QCT and DXA before and after defatting. ChA consisted of defatting and decalcification of the femoral neck samples for determination of bone mineral mass (BmM) and amount of fat. The mean BmM was 4.49 g. Mean fat percentage was 37.2% (23.3%-48.5%). QCT, DXA and ChA before and after defatting were all highly correlated (r > 0.96, p < 0.0001). Before defatting the QCT values were on average 0.35 g less than BmM and the DXA values were on average 0.65 g less than BmM. After defatting, all bone mass values increased; QCT values were on average 0.30 g more than BmM and DXA values were 0.29 g less than BmM. It is concluded that bone mineral measurements of the femoral neck with QCT and DXA are highly correlated with the chemically determined bone mineral mass and that both techniques are influenced by the femoral fat content.

Skin thickness does not reflect bone mineral density in postmenopausal women

Skin and bone both contain primarily type I collagen in connective tissue matrices and are assumed to be related due to this common organic constituent. The purpose of this study was to investigate whether skin thickness measurements by ultrasound (US) could be used for screening for low bone mass. In 94 healthy, white, non-smoking women, 1-3 years postmenopause, the thickness of the skin of the left upper arm and forearm was measured by ultrasound (US). These measurements were compared with values of bone mineral density (BMD) as measured by quantitative computed tomography (QCT) of the lumbar spine and quantitative video micro-densitometry (QMD) of the hand. The correlation found between US skin thickness measurements and BMD results was of low magnitude and not significant. It is concluded that US measurements of skin thickness cannot be used to screen early postmenopausal women for low bone mass.

Determinants of lumbar bone mineral density in normal weight, non-smoking women soon after menopause. A study using clinical data and quantitative computed tomography

OBJECTIVES

Is there an influence of oral contraceptive use, parity and lactation on early postmenopausal bone mass? Is assessment of reproductive history, body weight in combination with biochemical markers of bone metabolism suitable to predict lumbar bone mass soon after menopause?

STUDY DESIGN

A cross-sectional study in 94 healthy, normal weight, non-smoking women, 1-3 years after spontaneous menopause. Bone mineral density (BMD) of the lumbar spine was measured with single energy quantitative computed tomography.

RESULTS

Multiple regression analysis showed that only total duration of lactation and alkaline phosphatase (AP) levels are independently related to trabecular BMD (P = 0.001 and P = 0.002 respectively). AP was also associated with cortical BMD (P = 0.003). Assessment of reproductive history, body mass index and biochemical markers of bone metabolism could only account for 17% of the variation of trabecular BMD observed in the study population.

CONCLUSION

This study suggests that total duration of lactation rather than parity is associated with trabecular BMD of the spine. Clinical assessment of risk factors unsuccessfully predicts lumbar BMD in healthy, early postmenopausal women.

The Dimensions and Sensitivities of Semicircular Canals

1. The dimensions of the semicircular canals of pike can be expressed as allometric functions of the body length L.

2. The equal sensitivity of pike of different sizes to rotatory stimulation can be explained as a quadratic bending of the cupula.

3. In the pike the sensitivity is of the same order of magnitude for the vertical and horizontal semicircular canals.

4. In the pike the growth rate of the volumes of duct and ampulla is the same for the horizontal semicircular canal and for the posterior semicircular canal.

5. The special growth rate of the dimensions of the horizontal semicircular canal of the ray can be explained by a quadratic bending of the cupula.

6. For equally large cupulae the sensitivity of the horizontal semicircular canal is of the same order of magnitude for twenty-three mammals, fourteen birds and one reptile as it is for the pike.

7. Within the limits of error the ‘growth rate’ of the diameter of the narrow duct is the same in mammals as in the pike.

8. At the same body mass the absolute value of the diameter of the narrow duct is smaller in mammals than in the pike by a factor of 1.69.

9. For a body mass of 1 kg the value of the enclosed area of the horizontal semicircular canal is 6 times smaller in mammals than in pike.

10. The model of the overcritically damped oscillator for the semicircular canal remains valid during growth if a quadratic bending of the cupula is assumed.