Changes in microcirculation as early markers for infection in preterm infants--an observational prospective study

Effect of Kangaroo Position on microcirculation of preterm newborns: a controlled randomized clinical trial

OBJECTIVE

The objective of this study was to evaluate the effect of Kangaroo Position (KP) in microcirculation (MC) of the flexor muscles of preterm newborns.

METHOD

A controlled clinical trial was conducted in the city of Recife, Brazil, with 26 preterm children randomized in the Kangaroo Group (13) and in the Control Group (13). Assessments of blood flow, temperature, and tissue oxygen saturation (SO₂) were made at two different times and in the biceps brachii muscle and hamstrings muscle group: before the KP and after 24 h of KP. In the Control Group, the registrations were performed at the times corresponding to those of the Kangaroo Group. The mean values among the times were analyzed by paired t-test for repeated measures. The clinical trial was recorded in Clinical Trials (NCT03611088).

RESULTS

In the Kangaroo Group there was an increase in tissue temperature and blood flow at the time evaluation periods (p < 0.05). In the control group, there was no statistical difference between the recording moments hamstring muscles group, but in the biceps brachii, there was a reduction in mean blood flow (p = 0.023).

CONCLUSION

In conclusion, the KP has effects on the microcirculation of the flexor muscles of preterm newborns.

Non-invasively Measured Venous Oxygen Saturation as Early Marker of Impaired Oxygen Delivery in Preterm Neonates

INTRODUCTION

Adequate oxygen supply for preterm neonates may be defined through non-invasive measurement of venous oxygen saturation (SvO₂) and fractional oxygen extraction using near-infrared spectroscopy (NIRS). We investigated whether there was a difference in peripheral muscle SvO₂ (pSvO₂) and peripheral fractional oxygen extraction (pFOE) in preterm neonates with early inflammation/infection compared to healthy subjects during the first 72 h after birth.

MATERIALS AND METHODS

We retrospectively analyzed secondary outcome parameters of prospective observational studies, including preterm neonates at risk of infection in whom peripheral NIRS measurements were performed in combination with venous occlusions. Early neonatal inflammation/infection was diagnosed by clinical signs and laboratory parameters. Peripheral muscle tissue oxygenation index (pTOI) was measured using either NIRO 300 or NIRO 200-NX (both Hamamatsu Photonics, Japan) on the patients' lower legs. Using 20-s venous occlusions, pSvO₂ and pFOE were calculated incorporating simultaneous measurements of arterial oxygen saturation (SpO₂).

RESULTS

We analyzed measurements from 226 preterm neonates (median gestational age 33.9 weeks), 64 (28.3%) of whom were diagnosed with early neonatal inflammation/infection. During the first 24 h after birth, pSvO₂ (66.9% [62.6-69.2] vs. 69.4% [64.6-72.0]; p = 0.04) and pTOI (68.6% [65.3-71.9] vs. 71.7% [67.3-75.1]; p = 0.02) were lower in those neonates with inflammation/infection, while there was no such difference for measurements between 24-48 and 48-72 h.

DISCUSSION

NIRS measurement of pSvO₂ and pFOE is feasible and may be utilized for early detection of impaired peripheral oxygen delivery. As pTOI was also significantly lower, this parameter may serve as substitute for diminished regional oxygen supply.

Imaging of the Intestinal Microcirculation during Acute and Chronic Inflammation

Because of its unique microvascular anatomy, the intestine is particularly vulnerable to microcirculatory disturbances. During inflammation, pathological changes in blood flow, vessel integrity and capillary density result in impaired tissue oxygenation. In severe cases, these changes can progress to multiorgan failure and possibly death. Microcirculation may be evaluated in superficial tissues in patients using video microscopy devices, but these techniques do not allow the assessment of intestinal microcirculation. The gold standard for the experimental evaluation of intestinal microcirculation is intravital microscopy, a technique that allows for the in vivo examination of many pathophysiological processes including leukocyte-endothelial interactions and capillary blood flow. This review provides an overview of changes in the intestinal microcirculation in various acute and chronic inflammatory conditions. Acute conditions discussed include local infections, severe acute pancreatitis, necrotizing enterocolitis and sepsis. Inflammatory bowel disease and irritable bowel syndrome are included as examples of chronic conditions of the intestine.

COVID-19 and Microvascular Disease: Pathophysiology of SARS-CoV-2 Infection With Focus on the Renin-Angiotensin System

The recently described severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected millions of people, with thousands of fatalities. It has prompted global efforts in research, with focus on the pathophysiology of coronavirus disease-19 (COVID-19), and a rapid surge of publications. COVID-19 has been associated with a myriad of clinical manifestations, including the lungs, heart, kidneys, central nervous system, gastrointestinal system, skin, and blood coagulation abnormalities. The endothelium plays a key role in organ dysfunction associated with severe infection, and current data suggest that it is also involved in SARS-CoV-2-induced sepsis. This critical review aimed to address a possible unifying mechanism underlying the diverse complications of COVID-19: microvascular dysfunction, with emphasis on the renin-angiotensin system. In addition, research perspectives are suggested in order to expand understanding of the pathophysiology of the infection.

Relevance of Microvascular Flow Assessments in Critically Ill Neonates and Children: A Systematic Review

OBJECTIVES

Resolution of impaired microvascular flow may lag the normalization of macrocirculatory variables. The significance of microcirculatory dysfunction in critically ill children and neonates is unknown, but microcirculatory variables can be measured using Doppler or videomicroscopy imaging techniques. We outline the current understanding of the role of the microcirculation in critical illness, review methods for its assessment, and perform a systematic review of how it has been monitored in critically ill neonates and children.

DESIGN

Systematic review (PROSPERO CRD42019117993).

SETTING

Not applicable.

SUBJECTS

Not applicable.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

We systematically searched MEDLINE, EMBASE, PubMed, and Web of Science. We included studies of critically ill patients 0 to 18 years old investigating microcirculatory blood flow. Two reviewers analyzed abstracts and articles. Results were qualitatively analyzed due to study heterogeneity. A total of 2,559 abstracts met search criteria, of which 94 underwent full-text review. Of those, 36 met inclusion criteria. Seven studies investigated microcirculatory changes in critically ill children. Twenty studies investigated the microcirculatory changes in neonates with variable diagnoses compared with a diverse set of clinical endpoints. Nine studies assessed the effects of age, sex, and birth weight on microvascular flow in neonates. Across all studies, microcirculatory dysfunction was associated with poor outcomes and may not correlate with observed macrovascular function.

CONCLUSIONS

Assessment of microvascular flow in critically ill children and neonates is possible, although significant challenges remain. In many such patients, microvascular blood flow is disrupted despite medical management targeting normalized macrovascular variables. Future studies are needed to define normal pediatric microvascular flow variables and to assess the impact of patient and treatment factors on its function.

Effects of Prematurity on the Cutaneous Microcirculatory Network in the First Weeks of Life

Background: Preterm infants are at increased risk for hypertension in adolescence. Microcirculatory dysfunction has been identified as an underlying cause for cardiovascular disease. Our goal was to document the development of the cutaneous microcirculation in preterm infants during the first weeks of life and to compare it to the situation in term infants at birth. Methods: In 20 preterm infants, microcirculatory parameters were obtained prospectively by Sidestream Dark Field (SDF) Imaging at the upper inner arm once a week until discharge or 37 weeks of gestational age. A single microcirculatory measurement was obtained in 30 term infants during the first 3 days of life. Videos were blinded and analyzed with the AVA software. Results: Microcirculatory parameters in preterm infants differ significantly from term infants with a lower vessel surface (VS), a lower percentage of large and medium but higher percentage of small vessels, a higher Functional Vessel Density (FVD), and a higher Microcirculatory Flow Index (MFI). In multivariable linear regression models we could demonstrate a statistically significant association between the dependent microcirculatory variables (VS, diameter distribution, MFI) and gestational age as independent predictor variable while adjusting for postnatal days of life. Looking at the longitudinal follow-up data of preterm infants by means of a multivariable mixed-effects linear regression model adjusting for clinical variables, there is a significant decrease in FVD with increasing postnatal age, however no other significant changes in microcirculatory parameters over time. Accordingly, comparing the microcirculatory parameters of near term former preterm infants with term born neonates, we could still find significant differences with a higher FVD, lower VS and differences in vessel diameters in the former premature group. Conclusion: Infants born prematurely exhibit distinct microcirculatory alterations compared to term neonates with gestational age at birth being associated with microvascular parameters. Interestingly, this premature vascular phenotype persists even close to corrected term age. In view of the known increased cardiovascular risk of former preterm infants, our observations might have important clinical impact. The factors governing the development of the microvascular network in preterm infants and the contribution of microcirculatory changes observed here to vascular pathology in later life need to be further investigated.

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.

Vascular Endothelium in Neonatal Sepsis: Basic Mechanisms and Translational Opportunities

Neonatal sepsis remains a major health issue worldwide, especially for low-birth weight and premature infants, with a high risk of death and devastating sequelae. Apart from antibiotics and supportive care, there is an unmet need for adjunctive treatments to improve the outcomes of neonatal sepsis. Strong and long-standing research on adult patients has shown that vascular endothelium is a key player in the pathophysiology of sepsis and sepsis-associated organ failure, through a direct interaction with pathogens, leukocytes, platelets, and the effect of soluble circulating mediators, in part produced by endothelial cells themselves. Despite abundant evidence that the neonatal immune response to sepsis is distinct from that of adults, comparable knowledge on neonatal vascular endothelium is much more limited. Neonatal endothelial cells express lower amounts of adhesion molecules compared to adult ones, and present a reduced capacity to neutralize reactive oxygen species. Conversely, available evidence on biomarkers of endothelial damage in neonates is not as robust as in adult patients, and endothelium-targeted therapeutic opportunities for neonatal sepsis are almost unexplored. Here, we summarize current knowledge on the structure of neonatal vascular endothelium, its interactions with neonatal immune system and possible endothelium-targeted diagnostic and therapeutic tools for neonatal sepsis. Furthermore, we outline areas of basic and translational research worthy of further study, to shed light on the role of vascular endothelium in the context of neonatal sepsis.

Imaging sublingual microcirculatory perfusion in pediatric patients receiving procedural sedation with propofol: A pilot study

Objective

Procedural sedation with propofol is widely used in the pediatric population. A well‐known side effect of propofol is a decrease in peripheral vascular resistance resulting in hypotension, but little is known about the effects on microcirculation in humans. We aimed to evaluate the effects of propofol on the sublingual microcirculatory perfusion by continuous video imaging in pediatric patients undergoing procedural sedation.

Methods

Patients admitted to the Pediatric Intensive Care Unit for procedural sedation were recruited. Oral microcirculation was measured employing a continuous monitoring strategy with incident dark‐field illumination imaging. Measurements were obtained before and 3 minutes after propofol induction. Total and perfused vessel densities, proportion of perfused vessels, microvascular flow index, blood vessel diameter (Ø_bv), and systemic hemodynamics were analyzed.

Results

Continuous measurements were achieved in seven patients. Three minutes after propofol induction mean arterial pressure decreased (P = 0.028) and total and perfused vessel densities increased by 12% (P = 0.018) and 16% (P = 0.018), respectively. MFI was unaltered and mean Ø_bv increased but not significantly.

Conclusions

Propofol induction induces a reduction in mean arterial pressure and a rise in sublingual microvascular perfusion. The observed effects of propofol on the sublingual microcirculation may be due to a decrease in microvascular resistance.

Adaptation of the Cutaneous Microcirculation in Preterm Neonates

OBJECTIVE

Transition from fetal to neonatal circulation is characterized by multiple hemodynamic changes. The role of the microcirculation in this process is underexposed. Visualizing the cutaneous microcirculation can help us understand peripheral perfusion in a noninvasive manner.

METHODS

Cutaneous microcirculation of term and preterm infants born below 32 weeks of GA was measured in the first month of life using IDF imaging. Linear mixed modeling was used to identify clinical variables which influence the cutaneous microcirculation.

RESULTS

Sixty preterm and 33 term infants were included. TVD of preterm infants significantly decreased in the first month of life (31.7 mm/mm(2)  day 1 vs 27.9 mm/mm(2)  day 28), but remained significantly higher compared to TVD of term infants on day 1 (25.8 mm/mm(2) ). Besides postnatal age, no clinical variables were associated with TVD. Infants born SGA had significantly higher TVD values directly after birth than those born appropriate for GA (35.4 mm/mm(2) vs 31.6 mm/mm(2) ; p = 0.015).

CONCLUSIONS

TVD decreases in the first month after birth and is higher in preterm infants compared to those born term. Differences in antenatal oxygen exposure might explain the adaptation of the microcirculation.

Permissive Hypercapnia Results in Decreased Functional Vessel Density in the Skin of Extremely Low Birth Weight Infants

BACKGROUND

Ventilator-induced lung injury with subsequent bronchopulmonary dysplasia remains an important issue in the care of extremely low-birth-weight infants. Permissive hypercapnia has been proposed to reduce lung injury. Hypercapnia changes cerebral perfusion, but its influence on the peripheral microcirculation is unknown.

METHODS

Data were collected from 12 infants, who were randomized to a permissive high PCO₂ target group (HTG) or a control group (CG). Inclusion criteria were birth weight between 400 and 1,000 g, gestational age from 23 to 28 6/7 weeks, intubation during the first 24 h of life, and no malformations. The PCO₂ target range was increased stepwise in both groups for weaning and was always 15 mmHg higher in the HTG than in the CG. Skin microvascular parameters were assessed non-invasively with sidestream dark field imaging on the inner side of the right arm every 24 h during the first week of life and on the 14th day of life.

RESULTS

Infants in the HTG had significantly higher max. PCO₂ exposure, which was associated with a significantly and progressively reduced functional vessel density (FVD, p < 0.01). Moreover, there were significant differences in the diameter distribution over time, with HTG subjects having fewer small vessels but more large vessels.

CONCLUSION

High PCO₂ levels significantly impaired peripheral microcirculation in preterm infants, as shown by a decreased FVD, presumably secondary to peripheral vasoconstriction.

ISRCTN

56143743.

Videomicroscopy as a tool for investigation of the microcirculation in the newborn

The perinatal period remains a time of significant risk of death or disability. Increasing evidence suggests that this depends on microcirculatory behavior. Sidestream dark‐field orthogonal polarized light videomicroscopy (OPS) has emerged as a useful assessment of adult microcirculation but the values derived are not delineated for the newborn. We aimed to define these parameters in well term newborn infants. Demographic details were collected prospectively on 42 healthy term neonates (n = 20 females, n = 22 males). OPS videomicroscopy (Microscan) was used to view ear conch skin microcirculation at 6, 24, and 72 h of age. Stored video was analyzed by a masked observer using proprietary software. There were no significant differences between the sexes for any structural parameters at any time point. There was a significant increase over time in small vessel perfusion in female infants only (P = 0.009). A number of 6‐ and 72‐h measurements were significantly correlated, but differed from the 24‐h values. These observations confirm the utility of the ear conch for neonatal microvascular videomicroscopy. They provide a baseline for studies into the use of OPS videomicroscopy in infants. The changes observed are comparable with previous studies of term infants using these and other microvascular techniques. It is recommended that studies for examining the mature neonatal microvascular structure be delayed until 72 h of life, but studies of the physiology of cardiovascular transition should include the 24‐h time point after delivery.

Quantitative depth-resolved microcirculation imaging with optical coherence tomography angiography (Part Ι): Blood flow velocity imaging

The research goal of the microvascular network imaging with OCT angiography is to achieve depth-resolved blood flow and vessel imaging in vivo in the clinical management of patents. In this review, we review the main phenomena that have been explored in OCT to image the blood flow velocity vector and the vessels of the microcirculation within living tissues. Parameters that limit the accurate measurements of blood flow velocity are then considered. Finally, initial clinical diagnosis applications and future developments of OCT flow images are discussed.

Evaluation of sublingual microcirculation in a paediatric intensive care unit: prospective observational study about its feasibility and utility

Background

Evaluation of the microcirculation in critically ill patients is usually done by means of indirect parameters. The aim of our study was to evaluate the functional state of the microcirculation by direct visualization of sublingual microcirculation using Sidestream Dark Field Imaging, to determine the correlation between these findings and other parameters that are commonly used in the clinical practice and to assess the applicability of the systematic use of this technique in critically ill children.

Methods

A prospective observational study was carried out in a Pediatric Intensive Care Unit (PICU) of a tertiary referral hospital. All patients admitted to the PICU during a three-month period were included in the study after obtaining the informed consent from the patient. Systematic evaluation of sublingual microcirculation was done in these patients (Total Vessel Density, Proportion of Perfused Vessels, Perfused Vessel Density, De Backer Score, Microvascular Flow Index, Heterogeneity Index) within the first day of admission (T₁) and between the second and third day of admission (T₂). Other clinical, hemodynamic, and biochemical parameters were measured and registered simultaneously. When the evaluation of the microcirculation was not feasible, the reason was registered. Descriptive analysis of our findings are expressed as means, medians, standard deviations and interquartile ranges. Mann–Whitney-Wilcoxon and Fisher tests were used to compare variables between patients with and without evaluation of the microcirculation. Pearson Correlation Coefficient (ρ) was used to evaluate the correlation between microcirculatory parameters and other clinical parameters.

Results

One hundred fine patients were included during the study period. Evaluation of the microcirculation was feasible in 18 patients (17.1%). 95.2% of them were intubated. The main reason for not evaluating microcirculation was the presence of respiratory difficulty or the absence of collaboration (95.1% on T₁ and 68.9% on T₂). Evaluated patients had a higher prevalence of intubation and ECMO at admission (72.2% vs. 14.9% and 16.6% vs. 1.1%, respectively), and longer median duration of mechanical ventilation (0 vs. 6.5 days), vasoactive drugs (0 vs. 3.5 days) and length of stay (3 vs. 16.5 days) than non-evaluated patients. There was a moderate correlation between microcirculatory parameters and systolic arterial pressure, central venous pressure, serum lactate and other biochemical parameters used for motoring critically ill children.

Conclusions

Systematic evaluation of microcirculation in critically ill children is not feasible in the unstable critically ill patient, but it is feasible in stable critically ill children. Microcirculatory parameters show a moderate correlation with other parameters that are usually monitored in critically ill children.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-017-0837-5) contains supplementary material, which is available to authorized users.

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.

Impact of mode of delivery on skin microcirculation in term healthy newborns within the first day of life

BACKGROUND

Microcirculation is an important component of hemodynamic physiology. It can be assessed simply by clinical scores or by a variety of techniques including sidestream dark field (SDF) imaging and peripheral perfusion index (PI) measurements. Mode of delivery may have affects on microcirculation during transitional period. The aim of this study was to compare skin microcirculation in newborns born via vaginal delivery (VD) or cesarian section (C/S).

METHODS

Term healthy newborns not requiring NICU admission were included. Vital signs were recorded. Skin microcirculation was determined by clinical scoring including capillary refill time, skin color, warmth of extremities, by SDF imaging where capillary density and microvascular flow is determined and by PI measurements where pulsatile and nonpulsatile capillary flow is measured. Assessments were done at 30 min and 24 h of life. Results were compared between VD and C/S groups and overtime.

RESULTS

There were 12 newborns in VD group and 25 newborns in C/S group. No difference was observed in microcirculation assessments between groups. However VD group had increased hyperdynamic flow overtime.

CONCLUSION

In healthy term newborns microcirculation does not seem to be affected by mode of delivery, however results may differ in sick or preterm newborns.

Transcutaneous Microcirculatory Imaging in Preterm Neonates

Microcirculatory imaging (MI) is a relatively new research tool mainly used in the intensive care setting. MI provides a clear view of the smallest capillaries, arterioles and venules. The magnifying effect visualizes the flow pattern of erythrocytes through these vessels. It's non-invasive character makes it suitable to apply in (preterm) neonates, even in cardiorespiratory unstable patients. In adults and children, MI is mainly performed sublingually, but this is not possible in preterm infants as these cannot cooperate and the size of the probe is problematic. In preterm infants, MI is therefore performed transcutaneously. Their thin skin makes it possible to obtain high quality images of peripheral microcirculation. In this manuscript we will demonstrate the method of transcutaneous MI in preterm infants. We will focus on the different techniques and provide tips to optimize image quality. The highlights of software settings, safety and offline analysis are also addressed.

Glucosuria as an early marker of late-onset sepsis in preterms: a prospective cohort study

Background

Early and accurate diagnosis of late-onset sepsis (LONS) in preterm infants is difficult since presenting signs are subtle and non-specific. Because neonatal sepsis may be accompanied by glucose intolerance and glucosuria, we hypothesized that glucosuria may be associated with LONS in preterms, in an early stage. We aim to evaluate the association of glucosuria and late-onset neonatal sepsis (LONS) in preterm infants, in an attempt to improve early and accurate diagnosis of LONS.

Methods

We performed a prospective observational cohort study in 316 preterms (<34 weeks). We daily measured glucosuria and followed patients for occurrence of LONS, defined as clinical and blood culture-proven sepsis occurring after 72 h. Attending physicians were blinded to glucosuria results. We assessed the diagnostic value of glucosuria for clinical and blood culture-proven LONS using logistic regression analysis.

Results

Glucosuria was found in 65.8 % of 316 preterm patients, and sepsis was suspected 157 times in 123 patients. LONS was found in 47.1 % of 157 suspected episodes. The presence of glucosuria was associated with LONS (OR 2.59, 95 % CI 1.24–5.43, p = 0.012) with sensitivity 69.0 % and specificity 53.8 % (Likelihoodratio 1.49). After adjustment for gestational age, birth weight, and postnatal age, this association weakened and was no longer significant (adjusted OR 2.16; 95 % CI 0.99–1.85, p = 0.055). An increase in glucosuria 48–24 h before onset of symptoms was not associated with LONS.

Conclusion

In preterms glucosuria is associated with LONS within 24 h, however this association is too weak to be of diagnostic value.

Linear-array-based photoacoustic imaging of human microcirculation with a range of high frequency transducer probes

Photoacoustic imaging (PAI) with a linear-array-based probe can provide a convenient means of imaging the human microcirculation within its native structural context and adds functional information. PAI using a multielement linear transducer array combined with multichannel collecting system was used for in vivo volumetric imaging of the blood microcirculation, the total concentration of hemoglobin (HbT), and the hemoglobin oxygen saturation (sO₂) within human tissue. Three-dimensional (3-D) PA and ultrasound (US) volumetric scans were acquired from the forearm skin by linearly translating the transducer with a stepper motor over a region of interest, while capturing two-dimensional images using 15, 21, and 40 MHz frequency transducer probes. For the microvasculature imaging, PA images were acquired at 800- and 1064-nm wavelengths. For the HbT and sO₂ estimates, PA images were collected at 750- and 850-nm wavelengths. 3-D microcirculation, HbT, and sO₂ maps of the forearm skin were obtained from normal subjects. The linear-array-based PAI has been found promising in terms of resolution, imaging depth, and imaging speed for in vivo microcirculation imaging within human skin. We believe that a reflection type probe, similar to existing clinical US probes, is most likely to succeed in real clinical applications. Its advantages include ease of use, speed, and familiarity for radiographers and clinicians.

Peripheral blood flow monitoring in an infant with septic shock

Septic shock is associated with impaired vasoregulation, and treatment includes vasoactive drugs. Therefore, evaluation of vasoregulatory change is important. The present report describes the successful characterization of vasoregulatory change in response to a vasoactive drug during septic shock. A male infant born at 23 weeks' gestation developed septic shock. Severe hypotension developed, and treatment with colloid fluid and dopamine failed to increase blood pressure. With continuous measurement of skin blood flow using laser Doppler, noradrenaline was started. Based on changes in the blood flow, the dose was increased. At a dose of 1 μg/kg per min, skin blood flow in the foot decreased without any change in blood pressure. Subsequent blood transfusion succeeded in increasing both blood pressure and skin blood flow. It is concluded that decrease in foot blood flow reflects the vasoconstrictive effect of noradrenaline, although this finding must be validated in larger studies.

Neonatal hemodynamics: monitoring, data acquisition and analysis

Monitoring of cardiovascular function is critical to both clinical care and research as the use of sophisticated monitoring systems enable us to obtain accurate, reliable and real-time information on developmental hemodynamics in health and disease. Novel approaches to comprehensive hemodynamic monitoring and data acquisition will undoubtedly aid in developing a better understanding of developmental cardiovascular physiology in neonates. In addition, development and use of state-of-the-art, comprehensive hemodynamic monitoring systems enable the recognition of signs of cardiovascular compromise in its early stages, and provide information on the hemodynamic response to treatment in critically ill patients.

Microcirculatory changes in term newborns with suspected infection: an observational prospective study

Background. In adults severely disturbed microcirculatory flow can be observed by Orthogonal Polarized Spectral (OPS) imaging techniques during sepsis. Therefore we set out to assess for microcirculatory changes in term newborns with suspected early onset infection using OPS. Methods. OPS images were obtained prospectively from the vascular bed of the ear conch and upper arm of 47 newborns on their 1st, 2nd, and 3rd day of life. OPS sequences were analyzed semiquantitatively offline and blinded to clinical status of the infant. Flow in vessels was classified as continuous or noncontinuous flow and given as proportion of total vessels per image as in the studies in adults. Results. The proportion of vessels with continuous flow was significantly lower in the infants with infection (69% [56–81] versus 90% [87–94] (P = 0.0003)). None of the infants with infection was in shock or severely septic. Conclusion. In term neonates the microcirculatory flow is impaired in a large proportion of vessels even in mild to moderate infection. These changes can be observed at the onset of disease at the external ear, an optimal site for microcirculatory measurements in term infants.

Biomarkers and clinical tools in critically ill children: are we heading toward tailored drug therapy?

In pediatric critical care, validated biomarkers are essential for guiding drug therapy. The aim of this article is to present examples of current biomarker developments in its full breadth, including biochemical substances, physiological measurements and clinical scoring tools, with a focus on the field of circulatory, renal and neurophysiologic failure. Within each field we consecutively discuss the rationale for the selected biomarkers, studies in critically ill children, biomarker validation stage and biomarker use or potential use in drug studies and clinical drug dosing. This article demonstrates that there is paucity of properly validated biomarkers. Nevertheless, recent developments in, for instance, the field of sepsis, point us toward a future wherein, for critically ill children, drug therapy may be personalized using proteomic profiling instead of a small number of biomarkers, in order to establish a personal and dynamic disease profile.

In situ structural and microangiographic assessment of human skin lesions with high-speed OCT

We demonstrate noninvasive structural and microvascular contrast imaging of different human skin diseases in vivo using an intensity difference analysis of OCT tomograms. The high-speed swept source OCT system operates at 1310 nm with 220 kHz A-scan rate. It provides an extended focus by employing a Bessel beam. The studied lesions were two cases of dermatitis and two cases of basal cell carcinoma. The lesions show characteristic vascular patterns that are significantly different from healthy skin. In case of inflammation, vessels are dilated and perfusion is increased. In case of basal cell carcinoma, the angiogram shows a denser network of unorganized vessels with large vessels close to the skin surface. Those results indicate that assessing vascular changes yields complementary information with important insight into the metabolic demand.

In vivo imaging of the microcirculation of the volar forearm using correlation mapping optical coherence tomography (cmOCT)

Correlation mapping optical coherence tomography (cmOCT) is a recently proposed technique that extends the capabilities of OCT to enable mapping of vasculature networks. The technique is achieved as a processing step on OCT intensity images that does not require any modification to existing OCT hardware. In this paper we apply the cmOCT processing technique to in vivo human imaging of the volar forearm. We illustrate that cmOCT can produce maps of the microcirculation that clearly follow the accepted anatomical structure. We demonstrate that the technique can extract parameters such as capillary density and vessel diameter. These parameters are key clinical markers for the early changes associated with microvascular diseases. Overall the presented results show that cmOCT is a powerful new tool that generates microcirculation maps in a safe non-invasive, non-contact technique which has clear clinical applications.

Persistent low microcirculatory vessel density in nonsurvivors of sepsis in pediatric intensive care

OBJECTIVE

To investigate the time course and predictive value of microvascular alterations in children with severe sepsis.

DESIGN

Single-center, prospective observational study.

SETTING

Intensive care unit of a level III university children's hospital.

PATIENTS

Patients with septic shock, requiring the administration of fluid and vasopressor agents and/or inotropes after the correction of hypovolemia, who were intubated and ventilated, were included.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The microcirculation was assessed in the buccal mucosa, using orthogonal polarization spectral imaging, within 24 hrs after admission. Subsequent measurements were performed every 24 hrs for 3 days. The measurements were discontinued when the patient was extubated. There were no significant differences in the functional capillary density or microvascular flow index for all vessel types between survivors and nonsurvivors on day 1. In the survival group, the functional capillary density increased significantly between day 1 and day 2 from 1.7 cm/cm (0.8-3.4) to 4.3 cm/cm (2.1-6.9) (p = .001). Functional capillary density values in nonsurvivors did not change (day 1: 3.2 cm/cm [0.8-3.8]; day 2: 1.9 cm/cm [1.0-2.1]). The median functional capillary density on days 2 and 3 were significantly lower in nonsurvivors (day 2: 1.9 cm/cm [1.0 -2.1] vs. 4.3 cm/cm [2.1-6.9], p = .009; day 3: 1.8 cm/cm [1.0-2.0] vs. 4.7 cm/cm [2.1-8.6], p = .01). The microvascular flow index for all vessel types improved in survivors and did not change in nonsurvivors. Differences in microvascular flow index values between survivors and nonsurvivors were not significant.

CONCLUSION

Persistent microcirculatory alterations can be prognostic for survival in children with septic shock.

Peripheral oxygenation and management in the perinatal period

The mechanisms for the adequate provision of oxygen to the peripheral tissues are complex. They involve control of the microcirculation and peripheral blood flow, the position of the oxygen dissociation curve including the proportion of fetal and adult haemoglobin, blood gases and viscosity. Systemic blood pressure appears to have little effect, at least in the non-shocked state. The adequate delivery of oxygen (DO(2)) depends on consumption (VO(2)), which is variable. The balance between VO(2) and DO(2) is given by fractional oxygen extraction (FOE=VO(2)/DO(2)). FOE varies from organ to organ and with levels of activity. Measurements of FOE for the whole body produce a range of about 0.15-0.33, i.e. the body consumes 15-33% of oxygen transported.

Peripheral haemodynamics in newborns: best practice guidelines

Peripheral haemodynamics refers to blood flow, which determines oxygen and nutrient delivery to the tissues. Peripheral blood flow is affected by vascular resistance and blood pressure, which in turn varies with cardiac function. Arterial oxygen content depends on the blood haemoglobin concentration (Hb) and arterial pO2; tissue oxygen delivery depends on the position of the oxygen-dissociation curve, which is determined by temperature and the amount of adult or fetal haemoglobin. Methods available to study tissue perfusion include near-infrared spectroscopy, Doppler flowmetry, orthogonal polarisation spectral imaging and the peripheral perfusion index. Cardiac function, blood gases, Hb, and peripheral temperature all affect blood flow and oxygen extraction. Blood pressure appears to be less important. Other factors likely to play a role are the administration of vasoactive medications and ventilation strategies, which affect blood gases and cardiac output by changing the intrathoracic pressure.