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AIM: Compared to open pyeloplasty (OP), we hypothesised that laparoscopic pyeloplasty (LP) is associated with early recovery, a shorter length of stay (LOS) and less analgesia requirement. METHODS: Between 2011 and 2016, 146 dismembered pyeloplasty cases were reviewed, of which 113 were in the OP group and 33 were in the LP group. We evaluated both groups regarding operative time, LOS, success rate, complications rate and analgesia requirement. Subgroup analysis was done for patients above the age of 5 years, and within the OP group (dorsal lumbotomy (DL) vs. loin incision (LI)). RESULTS: The success rate was 96% in the open group and 97% in the laparoscopic group. The median operative time was significantly shorter in the open group for the entire cohort (127 vs. 200 min; P < 0.05), and in children older than 5 years (n = 41, 134 vs. 225 min; P < 0.05). Other parameters were similar in both groups. The median LOS was significantly shorter (2 vs. 4 days; P < 0.05), and the median analgesia requirement was less (0.44 vs. 0.64 mg/kg morphine; P < 0.05) in the DL (n = 60) compared to LI (n = 53). CONCLUSION: Both OP and LP dismembered approaches are equally effective in treating pelvi-ureteric junction obstruction. Overall, the LOS, complications rate and analgesia requirement were not significantly different; however, the operative time was significantly longer in LP.
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Laparoscopia , Obstrução Ureteral , Criança , Humanos , Pré-Escolar , Pelve Renal/cirurgia , Resultado do Tratamento , Procedimentos Cirúrgicos Urológicos/efeitos adversos , Obstrução Ureteral/cirurgia , Obstrução Ureteral/etiologia , Dor , Estudos RetrospectivosRESUMO
AIM: Bilious vomiting (BV) in the neonatal period may herald malrotation with life-threatening volvulus. In New South Wales, contrast fluoroscopy is not available in non-tertiary paediatric centres; therefore, transfer is required. An infant with BV referred to Newborn and Paediatric Emergency Transport Service is prioritised for urgent retrieval to a surgical centre for contrast fluoroscopy and paediatric surgical review. This study analysed how many neonates with BV needed retrieval to prevent bowel loss or to save one life and to identify predictors of malrotation and/or volvulus. METHODS: All neonatal referrals (<29 days) to Newborn and Paediatric Emergency Transport Service between 31 July 2014 and 31 July 2020 with BV or aspirates were examined. Data on time of onset of BV, time of call for retrieval, vital signs, lactate level and blood glucose at referral, time of arrival at the surgical centre and outcome were analysed. RESULTS: Of 391 neonates referred with BV, 113 (28.9%) had a surgical cause and 31 (7.9%) had a time-critical malrotation and/or volvulus. All 31 neonates were well at referral with normal vital signs including three neonates who subsequently died. Lactate levels at referral (1-7.5 mmol/L) were not predictive of outcome. The odds of a time-critical diagnosis increased with every day of age (odds ratio = 1.097), heart rate >140 (P = 0.04) and decreased for each kilogram of birthweight (odds ratio 0.475; confidence interval 0.294-0.768). CONCLUSIONS: Neonates with BV require urgent referral to paediatric surgery and contrast fluoroscopy. Thirteen urgent transfers are required to preserve the bowel integrity and life in one baby.
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Volvo Intestinal , Criança , Fluoroscopia/efeitos adversos , Humanos , Lactente , Recém-Nascido , Volvo Intestinal/complicações , Volvo Intestinal/diagnóstico , Volvo Intestinal/cirurgia , Lactatos , Encaminhamento e Consulta , Vômito/diagnóstico , Vômito/etiologiaRESUMO
AIM: To report the outcome for infants with congenital diaphragmatic hernia (CDH) and identify clinical factors affecting outcome from a tertiary perinatal surgical campus where extracorporeal membrane oxygenation (ECMO) is available however rarely utilised. METHODS: A retrospective cohort study of infants with CDH born in a co-located perinatal neonatal intensive care unit (NICU) or retrieved into and managed at a surgical NICU: 2003-2018. RESULTS: One hundred and fifty-nine infants with CDH were identified. One hundred and twenty were born in the co-located hospital and 39 retrieved from outlying hospitals. Survival of all patients with CDH was 74.8%; The survival for all isolated left CDH was 89% and the survival of post-surgery was 93%. Two patients went onto ECMO and both died. Associated major congenital anomalies were seen in 13.2%. Low birthweight (< 2500 g), 5-min Apgar <5, antenatal diagnosis, right-sided diaphragmatic hernia, herniation of the liver, associated major congenital anomalies, high oxygenation index (>25) on day 1, inotrope use, inhaled nitric oxide and need for high-frequency ventilation were associated with increased mortality on univariate analysis. Neurodevelopmental follow-up was commenced in 2013. Forty-three infants were discharged and developmental data were available for 36 at 4 months (83%) and 32 at 1 year (73%). Outcomes revealed normal motor scores and expressive language with mild delay in the receptive language at 1 year. CONCLUSION: Despite the low use of ECMO, our centre's results reveal excellent survival and neurodevelopmental outcomes consistent with or better than international data.
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Oxigenação por Membrana Extracorpórea , Hérnias Diafragmáticas Congênitas , Feminino , Hérnias Diafragmáticas Congênitas/cirurgia , Humanos , Lactente , Recém-Nascido , Gravidez , Diagnóstico Pré-Natal , Estudos RetrospectivosRESUMO
BACKGROUND: Abdominal compartment syndrome after kidney transplantation in pediatric recipients is a recognized complication relating to size discrepancy requiring abdominal wall closure over a large adult allograft. In order to circumvent this problem, our center implemented use of a surgical mesh, Surgisis® (Cook Surgical, Bloomington, IN), for abdominal wall closure in very small children to increase the surface covering over the organ and prevent compression. In this article, we report on the complications encountered following the use of these mesh patches. METHODS: A retrospective case review was conducted of all pediatric kidney transplants from September 2006 to December 2018 and divided into abdominal wall closure with and without implantation of Surgisis® mesh patch. Review of clinical notes was performed to identify information with respect to clinical course and post-operative outcomes. RESULTS: A surgical mesh patch was used in 7 pediatric recipients, of which 5 (71%) presented with post-operative complications. Three recipients were found to have bowel obstruction related to the surgical patch, necessitating bowel resection in one child. In addition, three children developed large serous fluid collections between the subcutaneous layers and the surgical mesh, requiring surgical drainage in two. CONCLUSIONS: In view of these findings, we recommend close surveillance for potential complications in this cohort. Future research is needed to explore the safety of different approaches to achieve abdominal wall closure in this group.
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Parede Abdominal/cirurgia , Síndromes Compartimentais/etiologia , Transplante de Rim , Complicações Pós-Operatórias/etiologia , Telas Cirúrgicas/efeitos adversos , Técnicas de Fechamento de Ferimentos , Adolescente , Criança , Pré-Escolar , Humanos , Lactente , Estudos Retrospectivos , Adulto JovemRESUMO
BACKGROUND: Pediatric retransplantation is an accepted practice for graft failure and complications in Australasia. As 15% of children require a third transplant, this is a growing cohort with limited data in the literature. METHODS: We review nine patients from the commencement of our transplantation program in 1986 up to 2020 assessing demographics, prognosis, and outcome measures. RESULTS: Third transplant patient survival was comparative to first and second transplant patient survival at 5 years. All deaths were within the post-operative period and secondary to sepsis. Operative times and transfusion volumes were increased at third transplant (1.8 and 4.5 times compared to first transplant, respectively). Learning difficulties and psychological disturbances were prevalent (83% and 66.6%, respectively). CONCLUSIONS: While recent mortality outcomes appear comparable to undergoing a second liver transplant, third transplant operations were more complex. Neurological impairment and psychological disturbance appear to be prevalent and need to be considered in pre-transplant counseling.
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Transplante de Fígado/estatística & dados numéricos , Complicações Pós-Operatórias/cirurgia , Adolescente , Austrália , Criança , Pré-Escolar , Feminino , Rejeição de Enxerto , Sobrevivência de Enxerto , Humanos , Lactente , Masculino , Prognóstico , Reoperação/estatística & dados numéricosRESUMO
PURPOSE: Many biliary atresia (BA) patients will eventually develop liver failure even after a successful Kasai portoenterostomy. A common complication of long-term BA survivors with their native liver is problematic portal hypertension. The aim of this study was to defend the view that portosystemic shunts can delay or negate the need for transplantation in these children. METHODS: A retrospective single center review of the efficacy of portosystemic shunts in BA patients after a successful Kasai portoenterostomy was conducted. RESULTS: From 1991 to 2017, 11 patients received portosystemic shunts. Median age of Kasai operation was 48 (36-61) days. Shunts were performed at the median age of 6.2 (4.1-6.8) years. Three of these eleven patients required subsequent liver transplantation. OS at 5 and 10 years were 90.9% and 81.8%, respectively. TFS at 5 and 10 years were 90.9% and 72.7%, respectively. Long-term complications included mild encephalopathy in 2 patients, hypersplenism in 3, and cholestasis in 1. CONCLUSION: Portosystemic shunt for the treatment of portal hypertension in carefully selected BA patients is an effective option in delaying or negating the need for liver transplantation.
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Atresia Biliar/cirurgia , Hipertensão Portal/cirurgia , Derivação Portossistêmica Transjugular Intra-Hepática/métodos , Portoenterostomia Hepática/métodos , Complicações Pós-Operatórias/cirurgia , Atresia Biliar/complicações , Pré-Escolar , Feminino , Humanos , Hipertensão Portal/complicações , Masculino , Estudos Retrospectivos , Resultado do TratamentoRESUMO
BACKGROUND: Currently, there are two well-established methods of bowel lengthening in patients with short bowel syndrome (SBS)-longitudinal intestinal lengthening and tailoring (LILT) and serial transverse enteroplasty (STEP) [1-4]. Both procedures may carry a high reported morbidity and mortality of 30.2% and 14.4%, respectively [5]. We report the outcomes of a novel technique: double barrel enteroplasty (DBE) for autologous intestinal reconstruction. METHODS: We performed a retrospective review of all ten patients who underwent DBE at our institution since 2011. All patients have SBS and were dependent on parenteral nutrition (PN) at the time of surgery. Etiologies were gastroschisis (n = 4), bowel atresia (n = 3), necrotising enterocolitis (n = 1), volvulus (n = 1), and near-total intestinal aganglionosis (n = 1). Patient survival, complications, and subsequent enteral autonomy were evaluated. RESULTS: All patients are alive with normal liver function. Five children achieved enteral autonomy, while the remaining are on weaning PN. There was no bleeding, anastomotic leak, perforation, infective complications, or intestinal necrosis. No patient has required a liver and/or intestinal transplant. CONCLUSIONS: Double barrel enteroplasty is technically feasible and safe. It has similar efficacy and may have fewer complications when compared with other methods of autologous intestinal reconstruction.
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Síndrome do Intestino Curto/cirurgia , Pré-Escolar , Estudos de Coortes , Feminino , Humanos , Lactente , Intestino Delgado/cirurgia , Masculino , Complicações Pós-Operatórias/prevenção & controle , Estudos Retrospectivos , Resultado do TratamentoRESUMO
OBJECTIVE: To assess long term graft and patient survival after donor liver retransplantation in children in Australia and New Zealand during 1986-2017; to determine the factors that influence survival. DESIGN: Retrospective cohort analysis (registry data). SETTING, PARTICIPANTS: Australia and New Zealand Liver Transplant Registry data for all liver retransplantations in children (under 18 years of age), 1986-2017, in all four paediatric and six adult liver transplantation centres in the two countries. MAIN OUTCOME MEASURES: Graft and patient survival at one, 5, 10 and 15 years. RESULTS: 142 liver retransplantations were undertaken in children (59 during 1986-2000, 83 during 2001-2017). Kaplan-Meier survival analysis indicated that survival was significantly greater during 2001-2017 than 1986-2000 (P < 0.001). During 2001-2017, graft survival one year after retransplantation was 84%, at 5 years 75%, at 10 years 70%, and at 15 years 54%; patient survival was 89% at one year, 87% at 5 years, 87% at 10 years, and 71% at 15 years. Median time between transplantations was 0.2 years (IQR, 0.03-1.4 years) during 1986-2000, and 1.8 years (IQR, 0.1-6.8 years) during 2001-2017 (P = 0.002). The proportion of graft failures that involved split grafts was larger during 2001-2017 (35 of 83, 42%) than 1986-2000 (10 of 59, 17%). Graft type, cause of graft failure, and number of transplants did not influence survival following retransplantation. CONCLUSION: Survival for children following retransplantation is excellent. Graft survival is similar for split and whole grafts. Children on the liver waiting list requiring retransplantation should have the same access to donor grafts as children requiring a first transplant.
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Transplante de Fígado/mortalidade , Reoperação , Adulto , Austrália/epidemiologia , Criança , Pré-Escolar , Feminino , Seguimentos , Sobrevivência de Enxerto , Humanos , Lactente , Estimativa de Kaplan-Meier , Transplante de Fígado/métodos , Masculino , Nova Zelândia/epidemiologia , Modelos de Riscos Proporcionais , Sistema de Registros , Estudos Retrospectivos , Doadores de Tecidos , Resultado do Tratamento , Listas de EsperaRESUMO
Hepatocellular malignant neoplasm, not otherwise specified (HCN-NOS) is a provisional entity describing a subset of rare malignant pediatric liver tumors with overlapping features of hepatoblastoma and hepatocellular carcinoma. We present a case illustration of metastatic HCN-NOS successfully treated with a backbone of hepatoblastoma chemotherapy, pulmonary metastastectomy, and liver transplantation, along with a literature review of the clinical outcomes of HCN.
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Carcinoma Hepatocelular/cirurgia , Hepatoblastoma/cirurgia , Doenças do Recém-Nascido/cirurgia , Neoplasias Hepáticas/cirurgia , Transplante de Fígado , Carcinoma Hepatocelular/patologia , Hepatoblastoma/patologia , Humanos , Recém-Nascido , Doenças do Recém-Nascido/patologia , Neoplasias Hepáticas/patologia , Masculino , Metástase NeoplásicaRESUMO
Complete microscopic tumor resection is critical for successful treatment of hepatoblastoma, and this may include when liver transplantation is required. For tumors involving the IVC or PV, complete resection should include the involved IVC or PV to ensure full tumor clearance. When this is required, the venous reconstruction at transplant or post-excision can be challenging. We present the management of an 18-month-old girl with PRETEXT Stage IV (P, V, F) hepatoblastoma and IVC involvement, where native caval resection and reconstruction was required. The preoperative staging following neoadjuvant chemotherapy was POSTTEXT Stage IV (P, V, F). An orthotopic liver transplantation was performed using a left lateral segment graft from a deceased adult donor. With native hepatectomy, retrohepatic IVC resection from just above the hepatic venous confluence to just above the entry of the right adrenal vein was performed. For caval reconstruction, a venous graft from a deceased donor was used. The graft included the lower IVC with the right common iliac vein and a short stump of the left common iliac vein. The common iliac was a perfect size match for the IVC, and the three natural ostia matched the upper cava, lower cava, and the outflow from the donor left hepatic vein. The patient had an uneventful postoperative course and remains well and disease-free 2 years after transplant with continued patency of the reconstructed cava. When indicated, a donor iliac vein graft with its natural ostia should be considered in caval reconstruction for pediatric liver transplantation.
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Hepatoblastoma/cirurgia , Veia Ilíaca/transplante , Neoplasias Hepáticas/cirurgia , Transplante de Fígado/métodos , Procedimentos de Cirurgia Plástica/métodos , Veia Cava Inferior/cirurgia , Intervalo Livre de Doença , Feminino , Hepatectomia/métodos , Veias Hepáticas/cirurgia , Humanos , Lactente , Procedimentos Cirúrgicos VascularesRESUMO
BACKGROUND: The purpose of this study was to examine differences in attitudes to feeding in neonates with Gastroschisis between clinical groups and to develop a standardized feeding protocol. Confusion, inconsistencies in practice and lack of evidence could be contributing to avoidable delays in the establishment of enteral feeds resulting in lengthy requirements for central venous access, dependence on total parenteral nutrition (TPN), increased risk of sepsis, TPN related cholestasis and prolongation in length of hospital stay. METHODS: A national survey of clinicians (neonatologists, neonatal intensive care nurses and paediatric surgeons), looking after neonates with gastroschisis was undertaken to determine differences in feeding practice post repair. In addition, an audit of practice in one hospital was undertaken to examine variations in practices between clinicians. A feeding protocol was then developed using inputs from surgeons and neonatologists. RESULTS: Gastric aspirates and residuals were typically used as indicators of feed readiness and feed tolerance; however, there was very little consistency within and between clinical groups in definitions of tolerance or intolerance of feeds and in how to initiate and progress feeds. A feeding protocol with clear definition of feed readiness and a clear pathway to progression of feeds was developed to help overcome these variations in practice with the possibility that this might reduce the length of stay (LOS) and have other secondary benefits. The protocol included early introduction of enteral feeds particularly direct breast or sucking feeds. CONCLUSIONS: Wide differences in attitudes to feeding neonates post Gastroschsis repair exist and the need for a consistent protocolized approach was felt. The feeding protocol we developed requires a change of practice and further clinical trials are needed to evaluate its effectiveness.
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Atitude do Pessoal de Saúde , Nutrição Enteral , Gastrosquise/terapia , Alimentação com Mamadeira , Aleitamento Materno , Gastrosquise/cirurgia , Humanos , Recém-Nascido , Unidades de Terapia Intensiva Neonatal , Neonatologistas , Enfermeiros Neonatologistas , Nutrição Parenteral Total , Cirurgiões , Fatores de TempoRESUMO
Citation counts can identify landmark papers. The aim of this study was to identify and characterize the top-cited articles in the pediatric liver transplantation literature. A search strategy for the Scopus® database was designed for pediatric liver transplantation publications from 1945 to 2014. The 50 top-cited articles were analyzed. Author co-citation analysis was performed using VOSviewer techniques. There were 2896 articles published between 1969 and 2015. The mean citation count of the top 50 cited articles was 166 (range 95-635). There were three case reports in this top-cited list. There were 15 collaborations in this top-cited list with nine being international. The top-cited publications originated in 12 countries, with the USA and the UK contributing 31 and seven articles, respectively. There were 14 authors with four or more publications in this list. There was a single author with nine publications in the top-cited list. These top-cited papers were found in 16 journals, with three journals collectively publishing over 50% of these publications. Pediatric liver transplantation research is an evolving entity. Surgical techniques and case reports are influential articles. Collaborations at a national and international level produce highly cited articles, which are found in influential journals.
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Bibliometria , Transplante de Fígado , Pediatria , Publicações Periódicas como Assunto/estatística & dados numéricos , Autoria , Criança , HumanosRESUMO
We aimed to assess the incidence of HAT over three eras following implementation of microvascular techniques and a customized anticoagulation protocol in a predominantly cadaveric split liver transplant program. We retrospectively reviewed pediatric liver transplants performed between April 1986 and 2016 and analyzed the incidence HAT over three eras. In E1, 1986-2008, each patient received a standard dose of 5 U/kg/h of heparin and coagulation profiles normalized passively. In E2, 2008-2012, microvascular techniques were introduced. In E3, 2012-2016, in addition, a customized anticoagulation protocol was introduced which included replacement of antithrombin 3, protein C and S, and early heparinization. A total of 317 liver transplants were completed during the study period, with a median age of 31.7 months. In E1, 22% of grafts were cadaveric in situ split grafts, while the second and third eras used split grafts in 59.0% and 64.9% of cases, respectively. HAT occurred in 9.5% in the first era, 11.5% (P=.661) in the second, and dropped to 1.8% in the third era (P=.043). A routine anticoagulation protocol has significantly reduced the incidence of HAT post-liver transplantation in children in a predominantly cadaveric in situ split liver transplant program.
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Anticoagulantes/uso terapêutico , Artéria Hepática , Transplante de Fígado/métodos , Microcirurgia/métodos , Complicações Pós-Operatórias/prevenção & controle , Trombose/prevenção & controle , Procedimentos Cirúrgicos Vasculares/métodos , Criança , Pré-Escolar , Protocolos Clínicos , Terapia Combinada , Quimioterapia Combinada , Feminino , Artéria Hepática/cirurgia , Humanos , Incidência , Lactente , Masculino , Cuidados Pós-Operatórios/métodos , Complicações Pós-Operatórias/epidemiologia , Estudos Retrospectivos , Trombose/epidemiologia , Trombose/etiologia , Resultado do TratamentoRESUMO
OBJECTIVES: Most infants with biliary atresia (BA) require liver transplantation (LT) after hepatoportoenterostomy (HPE), including those who initially clear jaundice. The aim of the present study was to identify clinical and routine laboratory factors in infants with BA post-HPE that predict native liver survival at 2 years. METHODS: A retrospective cohort study was conducted in 217 patients with BA undergoing HPE in Sydney, Australia and Toronto, Canada between January 1986 and July 2009. Univariate and multivariate logistic regression using backwards-stepwise elimination identified variables at 3 months after HPE most associated with 2-year native liver survival. RESULTS: Significant variables (Pâ<â0.05) on univariate analysis included serum total bilirubin (TB) and albumin at 3 months post-HPE, bridging fibrosis or cirrhosis on initial liver biopsy, ascites of <3 months post-HPE, type 3 BA anatomy, age at HPE of >45 days, change in length z scores within 3 months of HPE, and center. On multivariate analysis, TB (Pâ<â0.0001) and albumin (Pâ=â0.02) at 3 months post-HPE, and center (Pâ=â0.0003) were independently associated with native liver survival. Receiver operating characteristic analysis revealed an optimal cut-off value of TB <74 µmol/L (4.3 mg/dL; area under the receiver operating characteristic curve 0.8990) and serum albumin level >35 g/L (3.5 mg/dL; area under the receiver operating characteristic curve 0.7633) to predict 2-year native liver survival. TB and albumin levels 3 months post-HPE defined 3 groups (1: TB ≤74 µmol/L, albumin >35 g/L; 2: TB ≤74 µmol/L, albumin ≤35 g/L; 3: TB >74 µmol/L) with distinct short- and long-term native liver survival rates (log-rank Pâ<â0.001). Length z scores 3 months post-HPE were poorer for group 2 than group 1 (-0.91 vs -0.30, Pâ=â0.0217) with similar rates of coagulopathy. CONCLUSIONS: Serum TB and albumin levels 3 months post-HPE independently predicted native liver survival in BA when controlling for center. Serum albumin level <35 g/L in infants with BA who were no longer jaundiced at 3 months post-HPE was a poor prognostic indicator. Poorer linear growth and absence of significant coagulopathy suggest a role for early aggressive nutritional therapy in this group.
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Atresia Biliar/cirurgia , Tomada de Decisão Clínica , Técnicas de Apoio para a Decisão , Doença Hepática Terminal/diagnóstico , Transplante de Fígado/estatística & dados numéricos , Portoenterostomia Hepática , Atresia Biliar/complicações , Pré-Escolar , Doença Hepática Terminal/etiologia , Doença Hepática Terminal/cirurgia , Feminino , Seguimentos , Indicadores Básicos de Saúde , Humanos , Lactente , Recém-Nascido , Modelos Logísticos , Masculino , Prognóstico , Curva ROC , Estudos Retrospectivos , Resultado do TratamentoRESUMO
A device, with MEMS sensors at its core, has been fabricated and tested for measuring low fluid pressure and slow flow rates. The motivation was to measure clinically relevant ranges of slow-moving fluids in living systems, such as the cerebrospinal fluid in the brain. For potential clinical utility, the device can be read transcutaneously by inductive coupling to MEMS capacitive sensors in circuits with resonance frequencies in the MHz range. Signal shifts for flow rates in the range of 0-42 mL/h and differential pressure levels between 0.1 and 2 kPa have been measured, because the sensitivity in the capacitance gap measurement is about 1 Å. The sensors have been used successfully to monitor simulated cerebrospinal fluid dynamics. The device does not utilize any internal power, since it is powered externally via the inductive coupling.
RESUMO
A flow sensor has been fabricated and tested that is capable of measuring the slow flow characteristic of the cerebrospinal fluid in the range from less than 4 mL/h to above 100 mL/h. This sensor is suitable for long-term implantation because it uses a wireless external spectrometer to measure passive subcutaneous components. The sensors are pressure-sensitive capacitors, in the range of 5 pF with an air gap at atmospheric pressure. Each capacitor is in series with an inductor to provide a resonant frequency that varies with flow rate. At constant flow, the system is steady with drift <0.3 mL/h over a month. At variable flow rate, VÌ , the resonant frequency, f0, which is in the 200-400 MHz range, follows a second order polynomial with respect to VÌ . For this sensor system the uncertainty in measuring f0 is 30 kHz which corresponds to a sensitivity in measuring flow of ΔVÌ = 0.6 mL/hr. Pressures up to 20 cm H2O relative to ambient pressure were also measured. An implantable twin capacitor system is proposed that can measure flow, which is fully compensated for all hydrostatic pressures. For twin capacitors, other sources of systematic variation within clinical range, such as temperature and ambient pressure, are smaller than our sensitivity and we delineate a calibration method that should maintain clinically useful accuracy over long times.