Intrauterine transfusion combined with partial exchange transfusion for twin anemia polycythemia sequence: modeling a novel technique.

INTRODUCTION: Twin anemia-polycythemia sequence (TAPS) is a newly described disease in monochorionic twin pregnancies, characterized by large inter-twin hemoglobin differences. Optimal management for TAPS is not clear. One of the possible treatment modalities is intrauterine blood transfusion (IUT) in the donor with or without combination of partial exchange transfusion (PET) in the recipient. METHODS: We applied a computational model simulation to illustrate the mechanism of IUT with and without PET in TAPS occurring after laser surgery for twin-twin transfusion syndrome (TTTS). Model simulations were performed with the representative anastomotic pattern as observed during laser intervention, and after placental dye injection. RESULTS: The model was tested against different cases where IUT was combined with PET for the treatment of post-laser TAPS. Model simulations using the observed anastomotic pattern showed a significant reduction of hyperviscosity in the recipient after IUT/PET compared to IUT without PET. DISCUSSION: In this model simulation we show that the addition of PET to IUT reduces the severity of polycythemia in the recipient. PET may thus be important to prevent complications of hyperviscosity. CONCLUSION: This model simulation shows the beneficial effect of PET for the recipient in TAPS cases treated with IUT.

Endovenous simulated laser experiments at 940 nm and 1470 nm suggest wavelength-independent temperature profiles.

BACKGROUND: EVLA has proven to be very successful, but the optimum methods for energy delivery have still not been clarified. A better understanding of the mechanism of action may contribute to achieving a consensus on the best laser method and the most effective use of laser parameters, resulting in optimal clinical outcomes, maintaining high success rates with minimal adverse events. The aim of this study is to assess the impact of wavelength, pullback speed and power level on the endovenous temperature profile in an experimental setting. METHODS: In an experimental setting, temperature measurements were performed using thermocouples. The experimental set-up consisted of a transparent box in which a glass tube was fixed. Different laser parameters (wavelength and power) and 2 different pullback speeds (2 and 5 mm/s) were used. Thermocouples were placed at different distances from the fiber tip. Validity of the experimental setting was assessed by performing the same temperature measurements using a stripped varicose vein. The maximal temperature rise and the time span that the temperature was above collagen denaturation temperature were measured. RESULTS: The experiments showed that decreasing the pullback speed (2 mm/s) and increasing the power (up to 14 W) both cause higher maximal temperature and a longer time above the temperature for collagen denaturation. The use of different laser wavelengths (940 or 1470 nm) did not influence the temperature profile. CONCLUSION: The results of our experiments show that wavelength on its own has not been demonstrated to be an important parameter to influence the temperature profile.

Single vs. swarm detection of microparticles and exosomes by flow cytometry.

BACKGROUND: Microparticles and exosomes are cell-derived vesicles and potential biomarkers for disease. Recently, the Scientific Standardization Committee collaborative workshop of the ISTH initiated standardization of vesicle detection by flow cytometry with polystyrene beads. Because polystyrene beads have different optical properties from biological vesicles, and because the mechanisms causing the detection signal are incompletely understood, there are contradictions between expected and observed results. OBJECTIVES: To develop a model with which to relate the detection signal of a flow cytometer to the diameter of vesicles and clarify observed discrepancies. METHODS: We combined measurements of polystyrene and silica beads with an estimated refractive index of vesicles and performed Mie calculations of light scattering. RESULTS: We established the relationship between measured light scattering and the diameter of vesicles. The Megamix gating strategy proposed by the Scientific Standardization Committee selects single vesicles and cells with diameters between 800 and 2400 nm when applied on the forward-scattering detector of regular flow cytometers. Nevertheless, we demonstrated that, irrespective of the applied gating, multiple vesicles smaller than 220 nm or multiple 89-nm silica beads were counted as a single event signal at sufficiently high concentrations. CONCLUSIONS: Vesicle detection by flow cytometry is attributed to large single vesicles and swarm detection of smaller vesicles; that is, multiple vesicles are simultaneously illuminated by the laser beam and counted as a single event signal. Swarm detection allows the detection of smaller vesicles than previously thought possible, and explains the finding that flow cytometry underestimates the concentration of vesicles.

Double pass 595 nm pulsed dye laser at a 6 minute interval for the treatment of port-wine stains is not more effective than single pass.

BACKGROUND: Pulsed dye laser (PDL) is the first choice for treatment of port wine stains (PWS). However, outcome is highly variable and only a few patients achieve complete clearance. The objective of the study was to compare efficacy and safety of single pass PDL with double pass PDL at a 6 minute interval. METHODS: We conducted a randomized within-patient controlled study on PWS resistant to multiple single pass PDL treatments. In each patient two similar PWS areas were randomly allocated to PDL treatment (595 nm, 7 mm spot size, 1.5 mseconds pulse duration) using, as a control treatment, a single pass (12 J/cm(2)) or, as a new treatment, a double pass PDL (11 J/cm(2), second pass 6 minutes after the first pass). Both test areas were treated two times, 8 weeks apart. PWS clearance was assessed by two blinded dermatologists, and by color measurement (L*a*b) using reflectance spectroscopy, at 3 months follow-up. RESULTS: Sixteen out of 17 included patients completed follow-up. The mean number of treatments before inclusion was 15. Overall color assessed by spectrophotometer showed no improvement for either single or double pass PDL. Blinded Physician Global Assessment and Patient Global Assessment showed a high variability in outcome, with mostly only moderate improvement of the PWS for either single pass or double pass PDL. Furthermore, there was no significant difference in any of the outcomes between single pass and double pass PDL. CONCLUSION: At the chosen settings and after two treatment sessions, double pass PDL at a 6 minute interval does not result in improved clearance of PWS as compared to single pass treatment.

Quantification of feto-fetal transfusion rate through a single placental arterio-venous anastomosis in a monochorionic twin pregnancy.

Twin-to-twin transfusion syndrome (TTTS) is due to unbalanced inter-twin blood flow through placental vascular anastomoses. We present a TTTS-case treated with fetoscopic laser surgery that allowed us to calculate the net inter-twin blood flow. In the weeks following laser treatment, the ex-recipient developed severe fetal anemia and was treated with two intrauterine adult red cell transfusions (at 26 and 29 weeks' gestation, respectively). After birth, placental injection with color-latex identified a single residual arterio-venous anastomosis from the ex-recipient to the ex-donor. We measured the fetal and adult hemoglobin concentrations in the anemic fetus before and after both intrauterine transfusions, and in both twins at birth. On the basis of these measurements, we calculated the blood flow across the residual arterio-venous anastomosis and found it to be 5.8+/-1.5 mL/24h after the 1st transfusion and 11.4+/-2.9 mL/24h after the 2nd transfusion.

Placental characteristics of monoamniotic twin pregnancies in relation to perinatal outcome.

OBJECTIVE: To study placental characteristics in relation to perinatal outcome in 55 pairs of monochorionic monoamniotic (MA) twins. METHODS: Between January 1998 and May 2008 55 pairs of MA twins were delivered in 4 tertiary care centers and analysed for mortality, birth weight discordancy and twin-to-twin transfusion syndrome (TTTS) in relation to type of anastomoses, type and distance between cord insertions and placental sharing. Five acardiac twins, 2 conjoined twins, 4 higher order multiples and one early termination of pregnancy were excluded, leaving 43 MA placentas for analysis. Of these 43, one placenta could not be analysed for placental vascular anastomoses due to severe maceration after single intra-uterine demise leaving 42 placentas for analysis of anastomoses. RESULTS: Arterio-arterial (AA), venovenous (VV) and arteriovenous (AV) anastomoses were detected in 98%, 43% and 91% of MA placentas, respectively. Velamentous cord insertion was found in 4% of cases. Small distance between both umbilical cord insertions (<5 cm) was present in 53% of MA placentas. Overall perinatal loss rate was 22% (19/86). We found no association between mortality and type of anastomoses, type and distance between cord insertions and placental sharing. The incidence of TTTS was low (2%) and occurred in the only pregnancy with absent AA-anastomoses. CONCLUSION: Perinatal mortality in MA twins was not related to placental vascular anatomy. The almost ubiquitous presence of compensating AA-anastomoses in MA placentas appears to prevent occurrence of TTTS.

Placental characteristics of monochorionic diamniotic twin pregnancies in relation to perinatal outcome.

To study placental characteristics in relation to perinatal outcome in 150 pairs of monochorionic diamniotic (MCDA) twins. Between January 1998 and January 2007 150 pairs of MCDA twins were delivered in the University Medical Center, Utrecht, The Netherlands. Mortality, neonatal morbidity and birth weight discordancy were studied in relation to type of anastomoses, type and distance between cord insertions and placental sharing. From 14 weeks onwards, there were 45 (15.0%) perinatal deaths. We found no clear relationship between perinatal mortality and type of anastomoses, distance between cord insertions and placental sharing. Perinatal mortality was significantly increased in the presence of velamentous cord insertion (OR 3.65, 95% CI 1.83-7.28). Data concerning neonatal morbidity were similar. TTTS occurred predominantly in the presence of AV-anastomoses without compensating superficial AA-anastomoses (p=0.005) and occurred more frequently in the presence of velamentous cord insertion (OR 1.79, 95% CI 0.94-3.44). Twins with unequal shared placentas had significantly more often severe birth weight discordancy, although only in the presence of AA-anastomoses (OR 4.09, 95% CI 1.74-9.63). If AA-anastomoses were absent in the unequally shared placenta, there was no relation between severe birth weight discordancy and unequal sharing of the placenta (OR 1.06, 95% CI 0.08-13.52). In MCDA twins, placental characteristics determine perinatal outcome, occurrence of TTTS and fetal growth. Prenatal identification of these characteristics by ultrasound may alter counselling and intensity of pregnancy surveillance.

Pathology of twin placentas with special attention to monochorionic twin placentas.

The risk of perinatal morbidity and mortality in twins is 3-7 times higher than in singletons. In comparison to dichorionic twins, monochorionic twins are at increased risk for perinatal mortality and serious morbidity. In both type of twins growth discordance can occur. Discordant growth of dichorionic twins could be due to differences in placental mass or differences in placental parenchymal lesions, whereas birth weight discordancy in monochorionic twins is caused by placental vascular anastomoses. In this review the different types of complications (acardiac twins, acute and chronic twin-twin transfusion syndrome) due to different combinations of vascular anastomoses are discussed in relation to a computer model developed to gain more insight into the development of the twin-twin transfusion syndrome. The angioarchitecture of 395 monochorionic twin placentas was studied. Mortality was highest in the absence of an arterio-arterial anastomosis (42%) and lowest in the presence of an arterio-arterial anastomosis (15%). If mortality occurred, pregnancies with double mortality usually had an arterio-arterial anastomosis. If pregnancies were complicated by one death, a veno-venous anastomosis is more likely to be present. In conclusion, monochorionic twin pregnancies are a high risk pregnancy with a high chance of both mortality and morbidity; placental characteristics are a major contributor to adverse outcome in these pregnancies.

Simulated sequential laser therapy of twin-twin transfusion syndrome.

Sequential laser therapy of twin-twin transfusion syndrome (TTTS) includes laser obliteration of arteriovenous (AV) anastomoses from donor to recipient (AVDR) before obliterating AV anastomoses from recipient to donor (AVRD). This strategy allows for a beneficial intra-operative transfusion of blood from the hypervolemic recipient to the hypovolemic donor. In the present study, we sought to analyze the benefits and risks of sequential laser therapy with our computational model to aid its more widespread introduction. We simulated an equally shared placenta with an AVDR and a smaller diameter AVRD causing TTTS at 20 weeks. Laser coagulation and various volumes and directions of inter-twin transfusion were simulated at 21 weeks. A typical result is that when an AVDR is coagulated first, and 10 min later the AVRD with inner diameter of about 1 mm, an inter-twin transfusion of 25 ml may result from the recipient to the donor, based on literature data of AV flow versus diameter. This procedure causes a simulated loss of 50% of the recipient's blood volume. The opposite coagulation sequence, thus coagulating the AVRD first, 10 min later followed by the AVDR of 1 mm inner diameter, causes a loss of the donor's blood volume of 64%. In conclusion, our simulations support the concept of sequential laser therapy for TTTS and suggest directions for an improved safety and efficacy of this strategy.

Case report: twin-to-twin transfusion syndrome resulting from placental collateral artery development.

BACKGROUND: The twin-to-twin transfusion syndrome (TTTS) is a severe complication of monochorionic twin pregnancies, caused by a net inter-twin transfusion of blood from one fetus (the donor) towards the other fetus (the recipient) through placental anastomoses. TTTS is driven by unidirectional arterio-venous anastomoses, and mitigated by bidirectional arterio-arterial or veno-venous anastomoses which reduce the net inter-twin transfusion. In contrast to these accepted concepts, cases have been described paradoxically devoid of arterio-venous anastomoses but including arterio-arterial anastomoses. We hypothesized that TTTS may develop in such cases as a consequence of a stenosed chorionic artery in the recipient placenta that connects with the arterio-arterial anastomosis. CLINICAL CASES: We describe two cases of monochorionic twin placentae without arterio-venous anastomoses but with only an arterio-arterial and veno-venous anastomosis. In one case severe TTTS developed. There, the arterio-arterial anastomosis connected to a stenosed chorionic artery in the recipient placenta and showed a tortuous appearance. The other case developed uneventful. It lacked a stenosed chorionic artery and the arterio-arterial anastomosis was non-tortuous. CONCLUSION: We present evidence that the arterio-arterial anastomosis represented a functional collateral artery whose outgrowth was driven by an increased shear-stress caused by an increased flow to a lower pressure vascular bed in the placenta of the recipient. The lower arterial pressure occurred from the moment that a chorionic artery which was connected to the anastomosis developed a significant stenosis. The resulting collateral flow through the anastomosis maintained blood supply to the lower pressure placental bed, the beneficial function of collaterals, but also resulted in an increasing net inter-twin transfusion which triggered onset of severe TTTS.

Regulation of amniotic fluid volume.

Water arrives in the mammalian gestation from the maternal circulation across the placenta. It then circulates between the fetal water compartments, including the fetal body compartments, the placenta and the amniotic fluid. Amniotic fluid is created by the flow of fluid from the fetal lung and bladder. A major pathway for amniotic fluid resorption is fetal swallowing; however, in many cases the amounts of fluid produced and absorbed do not balance. A second resorption pathway, the intramembranous pathway (across the amnion to the fetal circulation), has been proposed to explain the maintenance of normal amniotic fluid volume. Amniotic fluid volume is thus a function both of the amount of water transferred to the gestation across the placental membrane, and the flux of water across the amnion. Water flux across biologic membranes may be driven by osmotic or hydrostatic forces; existing data suggest that intramembranous flow in humans is driven by the osmotic difference between the amniotic fluid and the fetal serum. The driving force for placental flow is more controversial, and both forces may be in effect. The mechanism(s) responsible for regulating water flow to and from the amniotic fluid is unknown. In other parts of the body, notably the kidney, water flux is regulated by the expression of aquaporin water channels on the cell membrane. We hypothesize that aquaporins have a role in regulating water flux across both the amnion and the placenta, and present evidence in support of this theory. Current knowledge of gestational water flow is sufficient to allow prediction of fetal outcome when water flow is abnormal, as in twin-twin transfusion syndrome. Further insight into these mechanisms may allow novel treatments for amniotic fluid volume abnormalities with resultant improvement in clinical outcome.

Amniotic fluid water dynamics.

Water arrives in the mammalian gestation from the maternal circulation across the placenta. It then circulates between the fetal water compartments, including the fetal body compartments, the placenta and the amniotic fluid. Amniotic fluid is created by the flow of fluid from the fetal lung and bladder. A major pathway for amniotic fluid resorption is fetal swallowing; however in many cases the amounts of fluid produced and absorbed do not balance. A second resorption pathway, the intramembranous pathway (across the amnion to the fetal circulation), has been proposed to explain the maintenance of normal amniotic fluid volume. Amniotic fluid volume is thus a function both of the amount of water transferred to the gestation across the placental membrane, and the flux of water across the amnion. Membrane water flux is a function of the water permeability of the membrane; available data suggests that the amnion is the structure limiting intramembranous water flow. In the placenta, the syncytiotrophoblast is likely to be responsible for limiting water flow across the placenta. In human tissues, placental trophoblast membrane permeability increases with gestational age, suggesting a mechanism for the increased water flow necessary in late gestation. Membrane water flow can be driven by both hydrostatic and osmotic forces. Changes in both osmotic/oncotic and hydrostatic forces in the placenta my alter maternal-fetal water flow. A normal amniotic fluid volume is critical for normal fetal growth and development. The study of amniotic fluid volume regulation may yield important insights into the mechanisms used by the fetus to maintain water homeostasis. Knowledge of these mechanisms may allow novel treatments for amniotic fluid volume abnormalities with resultant improvement in clinical outcome.

Significance of donor anuria differs between monoamniotic and diamniotic twin-twin transfusion syndrome.

Development of severe twin-twin transfusion syndrome (TTTS) in diamniotic-monochorionic twins includes five stages of increasing severity, i.e. recipient polyhydramnios and donor oligohydramnios, donor anuria, abnormal umbilical flow velocities in either twin, hydrops in the recipient, and intrauterine fetal death (IUFD) in either or both twins. In a severe case of TTTS in monoamniotic twins we observed donor anuria to appear after hydrops in the recipient. We conclude that donor anuria is a late and serious symptom in monoamniotic TTTS.

Laser-induced (endo)vascular photothermal effects studied by combined brightfield and fluorescence microscopy in hamster dorsal skin fold venules.

The putative features of the (endo)vascular photothermal response, characterized by laser-induced thermal denaturation of blood and vessel wall constituents, have been elucidated individually, but not simultaneously in dynamic, isolated in vivo systems. A hamster dorsal skin fold model in combination with brightfield/fluorescence intravital microscopy was used to examine the effect of laser pulse duration and blood flow velocity on the size of the thermal coagulum, its attachment behavior, and laser-mediated vasomotion. The size of the coagulum and the extent of vasoconstriction and latent vasodilation were proportional to the laser pulse duration, but pulse duration had no effect on coagulum attachment/dislodgement. Blood flow velocity exhibited no significant effect on the studied parameters. The (endo)vascular photothermal response is governed predominantly by laser energy deposition and to a marginal extent by blood flow velocity.

Colour oscillations in arterioarterial anastomoses reflect natural differences in donor and recipient oxygenation and hematocrit.

Our aim was to show that the colour difference between brighter and darker red, occasionally observed as an oscillating boundary in the recipient and donor parts of an arterioarterial anastomosis in severe twin-twin transfusion syndrome (TTTS), is a consequence of natural differences in blood oxygenation and hematocrit developing between donor and recipient twins. As method we defined a theoretical model of the placenta with dimensions from pathology examination. From literature we determined the optical absorption and scattering properties of all tissue components, and hematocrit and oxygen saturation values for donor and recipient twins. From our placental model we simulated the spectrum of back-scattered light by standard Monte Carlo photon propagation computations and calculated the colour of chorionic arterial and venous blood vessels by applying the physics theory of colour perception. Our computations demonstrate that recipient arterial blood is somewhat brighter red than donor arterial blood. The strong colour differences seen after laser coagulation of all anastomoses but the arterioarterial were explained from an angiotensin II cut-off in the recipient due to obliteration of arteriovenous anastomoses, causing a temporary increase in recipient placental perfusion and hence in blood oxygenation. In conclusion, natural differences in recipient versus donor blood oxygen saturation and hematocrit in severe TTTS explain the observed colour differences between brighter and darker red observed in the recipient and donor parts of arterioarterial anastomoses.

Efficacy of low-level laser therapy in the management of stage III decubitus ulcers: a prospective, observer-blinded multicentre randomised clinical trial.

Low-level laser therapy (LLLT) has been suggested as a promising treatment option for open wounds. In view of the absence of randomised studies with sufficiently large sample sizes, we assessed the efficacy of LLLT in the treatment of stage III decubitus ulcers. We performed a prospective, observer-blinded multicentre randomised clinical trial to assess the effect of LLLT as adjuvant to standard decubitus care. A total of 86 patients were enrolled into the study. Treatment was the prevailing consensus decubitus treatment (n=47); one group (n=39) had LLLT in addition, five times a week over a period of 6 weeks. The primary outcome measure was the absolute (mm2) and relative (%) wound size reduction at 6 weeks compared to baseline. Secondary outcome measures were the number of patients developing a stage IV ulcer during the study period, and the median change in Norton scores at 6 weeks compared to baseline. Based on the intention-to-treat principle, using last-observation-carried-forward analyses, Mann-Whitney U tests showed that the differences between the two groups in terms of absolute improvement (p=0.23) and relative improvement (p=0.42) were not significant. Because the wound size areas were non-normally distributed, we also analysed the data after logarithmic transformation of the wound size measurements. No significant difference in log(e) improvement scores between groups could be demonstrated (unpaired t-test: p=0.59). During the treatment period 11% of the patients in the control group and 8% of the patients in the LLLT group developed a stage IV decubitus ulcer (Fisher's exact test: p=0.72). The patients' Norton scores did not change during the treatment period. In this trial we found no evidence that justifies using low-level laser therapy as an adjuvant to the consensus decubitus ulcer treatment.

Monochorionic twins and twin-twin transfusion syndrome: the protective role of arterio-arterial anastomoses.

Unidirectional arterio-venous (AV) anastomoses often result in twin-twin transfusion syndrome (TTTS). Additional oppositely directed anastomoses may compensate for the circulatory imbalance and either prevent, delay the onset, or moderate the severity of TTTS. Intuitively, higher pressure gradient, oppositely-directed AV anastomoses (indicated as VA) would be expected to compensate better for TTTS than lower pressure gradient arterio-arterial (AA) anastomoses. However, clinical evidence suggests AA anastomoses compensate more efficaciously, because virtually all non-TTTS monochorionic twin placentas have AAs (84 per cent), contrary to TTTS placentas, where only 30 per cent have an AA. We sought to explain this observation by comparing the capabilities of various size VA and AA anastomoses to compensate for the effects of the primary AV. As study design we used a previously developed mathematical computer model of TTTS to determine ranges of anastomotic vascular resistances which cause varying fetal and amniotic fluid discordances. Anastomotic resistances were related with the radii of their feeding vessels, using fractal geometry modelling to mimic the placental vascular tree, and various assumptions regarding arterial blood flow. The results were as follows. An AA anastomosis of equal size as the feeding artery of an AV or VA has a significantly smaller resistance. The primary AV anastomosis may be compensated by both VA as well as AA anastomoses. However, VA transfusion adequately compensates AV flow only for a small range of VA to AV vascular radius ratios. In contrast, AA transfusion compensates the AV flow for a much wider range of AA to AV vascular radius ratios. In conclusion, the wider range of AA than VA radii for adequate compensation of the AV explains the finding that an AA protects more frequently than a VA of similar size against the manifestations of TTTS. These results may possibly allow future risk stratification of monochorionic twins by non-invasive sonographic assessment of the size and type of anastomoses.